Effect of Antibiotic Choice On ReNal Outcomes (ACORN)
Phase: PHASE4
Conditions: Sepsis, AKI, Neurotoxicity
Sponsor: Vanderbilt University Medical Center

Supplementary Appendix 
Study Protocol and Statistical Analysis Plan 
Trial: 
Antibiotic Choice On ReNal outcomes (ACORN) trial 
Manuscript: 
Effect of Cefepime versus Piperacillin-tazobactam in Adults Hospitalized with 
Acute Infection: A Randomized Clinical Trial 
ClinicalTrials.gov: 
NCT05094154 
Authors: 
Edward T. Qian; Jonathan D. Casey; Adam Wright; Li Wang; Matthew S. Shotwell; 
Justin K. Siemann; Mary Lynn Dear; Joanna L. Stollings; Brad D. Lloyd; Tanya 
Marvi; Kevin P. Seitz; George E. Nelson; Patty W. Wright; Edward D. Siew; Bradley 
M. Dennis; Jesse O. Wrenn; Jonathan W. Andereck; Jin H. Han; Wesley H. Self; 
Matthew W. Semler; Todd W. Rice for the Vanderbilt Center for Learning 
Healthcare and the Pragmatic Critical Care Research Group 
This Supplementary Appendix contains the following items: 
 
1) Initial Protocol [dated 10/19/2021] 
2) Final Protocol [dated 7/27/2022] 
3) Summary of changes to Study Protocol 
4) Original Statistical Analysis Plan [submitted 7/27/2022] 
5) Final Statistical Analysis Plan [published BMJ Open 3/10/2023] 
6) Summary of changes to the Statistical Analysis Plan 
 

1 
 
Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
 
Study Principal Investigators:  
Edward Qian, MD, Fellow, Department of Medicine, Division of Allergy, Pulmonary, and Critical Care 
Medicine 
 
Co-investigators 
 
Todd Rice, MD, MSc, Associate Professor, Department of Medicine, Division of Allergy, Pulmonary, 
and Critical Care Medicine; Director, Medical ICU; Director, Vanderbilt Human Research Protections 
Program 
 
Matthew Semler, MD, MSc, Assistant Professor, Department of Medicine, Division of Allergy, 
Pulmonary, and Critical Care Medicine 
 
Jonathan Casey, MD, MSc, Assistant Professor, Department of Medicine, Division of Allergy, 
Pulmonary, and Critical Care Medicine 
 
Christopher Lindsell, PhD, Professor, Department of Biostatistics 
 
Wes Self, MD, MPH, Associate Professor, Department of Emergency Medicine 
 
Edward Siew, MD, MSc, Associate Professor, Department of Medicine, Division of Nephrology and 
Hypertension  
 
George Nelson, MD, MPH, Assistant Professor, Department of Medicine, Division of Infectious 
Diseases; Director, Antimicrobial Stewardship Program; Associate Hospital Epidemiologist 
 
Joanna Stollings, PharmD, FCCP, FCCM, BCPS, BCCCP, Department of Pharmacy Services 
 
Li Wang, MS, Department of Biostatistics 
 
 
 
 
Submission Date: 10/19/2021 
 
 
 
 
 
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
 
Study Schema 
1.0 Study Summary ................................................................................................................................. 4 
2.0 Background ....................................................................................................................................... 5 
2.1 Anti-Pseudomonal Cephalosporins as Part of an Empiric Broad Spectrum Regimen ....................... 6 
2.2 Anti-Pseudomonal Penicillins as Part of an Empiric Broad Spectrum Regimen .............................. 6 
2.3 Acute Kidney Injury during Critical Illness .................................................................................... 6 
2.4 Prior Evidence of the Effect of Antibiotic Choice on Acute Kidney Injury ..................................... 6 
2.5 Rationale for a Trial of Anti-Pseudomonal Cephalosporins vs Anti-Pseudomonal Penicillins ......... 7 
3.0 Rationale, Aims, and Hypotheses ....................................................................................................... 7 
4.0 Study Description .............................................................................................................................. 7 
5.0 Inclusion/Exclusion Criteria ............................................................................................................... 8 
5.1 
Inclusion Criteria: .................................................................................................................... 8 
5.2 Exclusion Criteria: ......................................................................................................................... 8 
6.0 Enrollment/Randomization ................................................................................................................ 8 
6.1 Study Sites: .................................................................................................................................... 8 
6.2 Study Population:........................................................................................................................... 8 
6.3 Enrollment: .................................................................................................................................... 8 
6.4 Consent: ...................................................................................................................................... 10 
6.5 Randomization: ............................................................................................................................ 10 
7.0 Study Procedures ............................................................................................................................. 10 
7.1 Electronic Health Record (EHR) Based Screening for Eligible Patients ........................................ 11 
7.2 Antibiotic Ordering after Randomization...................................................................................... 11 
7.3 EHR-Based Tool to Capture Data on Antibiotic Modification and Adverse Events ....................... 11 
7.4 Duration of the Intervention ......................................................................................................... 12 
7. 5 Blinding: ..................................................................................................................................... 12 
8.0 Data Collection: ............................................................................................................................... 12 
8.1 In-Hospital Outcomes: ................................................................................................................. 12 
8.2 Baseline data: .............................................................................................................................. 13 
8.3 Data from enrollment to hospital discharge: ................................................................................. 13 
8.4 Outcome Data: ............................................................................................................................. 14 
9.0 Risks and Benefits ........................................................................................................................... 14 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
10.0 Statistical Considerations ............................................................................................................... 15 
11.0 Reporting of Adverse Events or Unanticipated Problems ................................................................ 17 
12.0 Privacy/Confidentiality Issues ........................................................................................................ 20 
13.0 Follow-up and Record Retention .................................................................................................... 20 
14.0 Data and Safety Monitoring Board (DSMB)................................................................................... 20 
15.0 References ..................................................................................................................................... 21 
 
 
 
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
 
1.0 Study Summary 
Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Background: Sepsis is one of the most common causes of acute illness and death in the United States. 
Early, empiric broad-spectrum antibiotics are a mainstay of sepsis treatment. Two classes of antibiotics 
with activity against Pseudomonas, anti-pseudomonal cephalosporins and anti-pseudomonal penicillins, 
are commonly used for acutely ill adults with sepsis in current practice. Recent observational studies, 
however, have raised concern that anti-pseudomonal penicillins may cause renal toxicity. Anti-
pseudomonal cephalosporins, by comparison, may be associated with a risk of neurotoxicity.  Rigorous, 
prospective data regarding the comparative effectiveness and toxicity of these two classes of medications 
among acutely ill patients are lacking. We propose a randomized trial comparing the impact of anti-
pseudomonal cephalosporins and anti-pseudomonal penicillins on renal outcomes of acutely ill patients. 
Primary Aim: 
- 
To compare the effect of anti-pseudomonal cephalosporins versus anti-pseudomonal penicillins on the 
incidence of acute kidney injury among acutely ill patients 
Primary Hypothesis: 
- 
Among acutely ill patients with sepsis, use of anti-pseudomonal cephalosporins will decrease the 
incidence of acute kidney injury (AKI), compared to anti-pseudomonal penicillins. 
Inclusion Criteria: 
1. Age ≥ 18 years old 
2. Located in a participating emergency department or medical intensive care unit  
3. Less than 12 hours from presentation to study hospital 
4. Treating clinician initiating an order for an anti-pseudomonal cephalosporin or anti-pseudomonal 
penicillin  
Exclusion Criteria: 
1. Known receipt of > 1 dose of an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin 
during the last 7 days 
2. Current documented allergy to cephalosporins or penicillin 
3. Known to be a prisoner 
4. Treating clinicians feel that either an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin 
is required or contraindicated for the optimal treatment of the patient, including for more directed 
antibiotic therapy against known prior resistant infections or suspected sepsis with an associated 
central nervous system infection  
Consent: 
- 
Given that both anti-pseudomonal cephalosporins and anti-pseudomonal penicillins are routinely used 
in usual care, the lack of established risk or benefit with either treatment group, the impracticability of 
obtaining informed consent prior to initiating antibiotics for acutely ill patients, a waiver of informed 
consent will be requested. 
Randomization: 
- 
Using a best-practices advisor embedded within the electronic health record, patients meeting all 
inclusion criteria and no exclusion criteria will be randomized in a 1:1 ratio to receive an anti-
pseudomonal cephalosporin (treating clinicians’ choice of cefepime or ceftazidime) or anti-
pseudomonal penicillin. 
Study Interventions: 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
- 
Anti-pseudomonal cephalosporin group: patients assigned to the anti-pseudomonal cephalosporin 
group will receive the treating clinicians’ choice of either cefepime or ceftazidime.   
- 
Anti-pseudomonal penicillin group: patients assigned to the anti-pseudomonal penicillin group will 
receive piperacillin-tazobactam or ticarcillin-clavulanate.  
- 
For patients in both groups, treating clinicians will determine the dose and duration of the assigned 
antibiotic class.  An EHR-based advisor will alert treating clinicians of group assignment and collect 
data regarding any adverse events and the reason for modification or discontinuation of antibiotics in 
the 7 days after randomization 
Primary Efficacy Outcome: 
- 
The primary outcome will be the highest stage of acute kidney injury (AKI) between enrollment and 
14 days after enrollment.  Stage of AKI will be defined by Kidney Disease: Improving Global 
Outcomes (KDIGO) AKI creatinine criteria.  Death will be classified as worse than the highest stage 
of AKI.  The outcome will be defined using the following 5-value ordinal scale ranging from the 
lowest value (0 = alive without having experienced AKI) to the highest value (4 = died). 
o 0 = No AKI 
o 1 = Stage 1 AKI (Creatinine increase by 1.5-1.9 times baseline OR increase by >= 0.3 
mg/dL) 
o 2 = Stage 2 AKI (Creatinine increase by 2.0-2.9 times baseline) 
o 3 = Stage 3 AKI (Creatinine increase by >= 3.0 times baseline OR increase to >= 4.0 mg/dL 
OR New RRT) 
o 4 = Death  
 
Exploratory Outcomes: 
- 
Exploratory Renal Outcomes: acute kidney injury of stage 2 or higher as defined in the KDIGO 
criteria for creatinine level, new receipt of renal-replacement therapy, days alive and free of renal-
replacement therapy during the 28 days after enrollment, the highest creatinine level during the 28 
days after enrollment, the change from baseline to the highest creatinine level, the final creatinine 
level, and dialysis dependence at hospital discharge. 
- 
Exploratory Neurologic Outcomes: Glasgow Coma Scale score during the 14 days after enrollment, 
neurologic component of SOFA score, Coma and Delirium Free Days in 14 days after enrollment 
- 
Exploratory Clinical Outcomes: ICU-free days, ventilator-free days, vasopressor-free days, 
interaction between patients admitted to the ICU vs ward 
 
Sample Size Considerations: 
- 
Using data obtained from 820 patients during the creation and testing of the enrollment advisor, we 
measured the distribution of outcomes expected among patients in the anti-pseudomonal penicillin 
group.  We calculated that enrolling 2,050 patients would provide 80% power at an alpha of 0.05 to 
detect an odds ratio for highest stage of AKI of 0.65. 
 
2.0 Background 
Sepsis is a common condition associated with high mortality and morbidity1. Antibiotics are an integral 
component of the management of patients with sepsis2. Each hour delay in antibiotic administration in 
sepsis is associated with an increase in mortality3. Clinical guidelines recommend early management 
bundles, including early broad-spectrum antibiotics, for patients with presumed sepsis in the emergency 
department and intensive care unit2,4. Since the specific organism causing an infection is rarely known at 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
clinical presentation, empiric broad-spectrum antibiotics are commonly prescribed5. For patients at risk 
for resistant organisms, the most common regimens include vancomycin (to cover gram-positive 
organisms including methicillin-resistant Staphylococcus aureus) and an anti-pseudomonal cephalosporin 
or anti-pseudomonal penicillin (to cover gram-negative organisms including Pseudomonas).  
 
2.1 Anti-Pseudomonal Cephalosporins as Part of an Empiric Broad Spectrum Regimen 
Cephalosporins are beta-lactam antibiotics that act by inhibiting the synthesis of the peptidoglycan layer 
of bacterial cell walls. They are commonly used for a variety of infections including empiric broad 
spectrum coverage for sepsis, suspected nosocomial infections, and meningitis.  Several cephalosporins 
have anti-pseudomonal activity, including cefepime, a fourth-generation cephalosporin, and ceftazidime, 
a third-generation cephalosporin.  Anti-pseudomonal cephalosporins have replaced anti-pseudomonal 
penicillins as the preferred agent for empiric antibiotic regimens based on observational evidence that 
anti-cephalosporins are associated with a lower incidence of AKI6.  However, others have argued against 
this approach given the lack of randomized trials comparing the relative efficacy and safety of the two 
agents as well as observational data suggesting that cephalosporins may be associated with neuro-
toxicity7–9. 
 
2.2 Anti-Pseudomonal Penicillins as Part of an Empiric Broad Spectrum Regimen 
Penicillins are also beta-lactam anti-biotics with similar mechanisms of action to cephalosporins. Anti-
pseudomonal penicillins, such as piperacillin, ureidopenicillin, and ticarcillin are typically administered 
with a beta-lactamase inhibitor such as tazobactam or clavulanate. In the United States the most 
commonly used anti-pseudomonal penicillins are piperacillin-tazobactam and ticarcillin-clavulanate. 
Anti-pseudomonal penicillins are the preferred agents for empiric broad spectrum coverage at many 
centers, and piperacillin-tazobactam, specifically, has the added benefit of treating anaerobic organisms.  
Conversely, penicillins do not cover meningitis due to poor central nervous system penetration.   
 
2.3 Acute Kidney Injury during Critical Illness 
Acute Kidney Injury (AKI) is a common complication of ICU admission. AKI is associated with a six to 
eight fold increase in mortality in ICU populations, 10,11 is therefore a common target of critical care trials. 
There are many potential contributors to AKI in critical illness including isotonic fluids12, IV contrast 
administration, medication toxicities13, and acute illnesses like sepsis.  Sepsis is the most common cause 
of AKI and accounts for 40-50% of AKI in the intensive care unit (ICU)14,15. As the primary treatment for 
the underlying cause of sepsis, antibiotics are a critical treatment for acutely ill patients, but antibiotics 
may cause renal injury, and renally-cleared antibiotics may reach supratherapeutic levels in the setting of 
AKI.  
 
2.4 Prior Evidence of the Effect of Antibiotic Choice on Acute Kidney Injury 
Vancomycin has long been associated with AKI16,17. Recently, a number of retrospective observational 
analyses have examined a potential association between the concurrent administration of vancomycin and 
piperacillin-tazobactam and the development of AKI, compared with vancomycin alone18–21. These data, 
however, are likely to be confounded by indication bias and studies evaluating whether piperacillin-
tazobactam causes more AKI than other anti-pseudomonal antibiotics have been inconclusive.18,22–30.  
Studies that limited their analyses to the first 72 hours of treatment (when antibiotic choices are empiric 
and not yet tailored based on microbiologic data), have not shown any association between piperacillin-
tazobactam and kidney injury31.   

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
 
Based on this preliminary, observational data, however, some institutions have elected to change their 
preferred broad spectrum antibiotic regimens from one including an anti-pseudomonal to one including an 
anti-pseudomonal cephalosporins.   
 
2.5 Rationale for a Trial of Anti-Pseudomonal Cephalosporins vs Anti-Pseudomonal 
Penicillins 
Tens of thousands of patients each year receive either anti-pseudomonal cephalosporins and penicillins, 
but no randomized trials have ever compared their relative effectiveness or safety.  Each class of 
medications has been hypothesized to have toxicities that may be relevant for acutely ill patients. Because 
the relationship between antibiotic choice (anti-pseudomonal cephalosporins or anti-pseudomonal 
penicillins) and clinically relevant outcomes, such as AKI, are unknown, clinical trial data is urgently 
needed.  Rigorous high-quality evidence that anti-pseudomonal cephalosporins, compared to anti-
pseudomonal penicillins, decreases, increases or has no impact on the risk of AKI would have the 
potential to change the care received by thousands of acutely ill adults each year. 
 
To address this knowledge gap, we will conduct a prospective, randomized trial of acutely ill adults 
undergoing initiation of empiric antibiotics in the ED or ICU, comparing anti-pseudomonal 
cephalosporins vs anti-pseudomonal penicillins with regard to renal outcomes.  
3.0 Rationale, Aims, and Hypotheses 
In order to determine the effect of an anti-pseudomonal cephalosporin, compared to an anti-pseudomonal 
penicillin, on the incidence of acute kidney injury among acutely ill patients, a randomized trial is needed. 
Study Aims: 
- 
Primary: 
o To compare the effect of anti-pseudomonal cephalosporins versus anti-pseudomonal 
penicillins on the incidence of acute kidney injury among acutely ill patients 
- 
Secondary: 
o To compare the effect of anti-pseudomonal cephalosporins vs anti-pseudomonal penicillins 
on in-hospital mortality, ICU length of stay, and ventilator days 
Study Hypotheses 
- 
Primary Hypothesis: 
o The use of anti-pseudomonal cephalosporins, compared to the use of anti-pseudomonal 
penicillins, will decrease the incidence of acute kidney injury among acutely ill adults   
 
4.0 Study Description 
In order to address the aims outlined above, we propose a randomized trial evaluating the impact of anti-
pseudomonal cephalosporins versus anti-pseudomonal penicillins in the treatment of sepsis in acutely ill 
adults. Patients admitted to a study unit who are deemed by their clinical team to require empiric broad 
spectrum antibiotics and fulfill inclusion criteria without meeting exclusion criteria will be enrolled and 
randomly assigned to an anti-pseudomonal cephalosporin vs an anti-pseudomonal penicillin.  
Randomization, group assignment and delivery of the intervention will occur within the electronic health 
record (details in section 7). All other decisions regarding treatment will remain at the discretion of the 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
treating provider.  Data will be collected prospectively from the medical record to determine the effect of 
the assigned interventions on procedural, physiologic, and clinical outcomes. 
 
5.0 Inclusion/Exclusion Criteria 
 
5.1 Inclusion Criteria: 
1. Age ≥ 18 years old 
2. Located in a participating emergency department or medical intensive care unit  
3. Less than 12 hours from presentation to study hospital 
4. Treating clinician initiating an order for an anti-pseudomonal cephalosporin or anti-pseudomonal 
penicillin  
5.2 Exclusion Criteria: 
1. Known receipt of > 1 dose of an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin 
during the last 7 days 
2. Current documented allergy to cephalosporins or penicillin 
3. Known to be a prisoner 
4. Treating clinicians feel that either an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin 
is required or contraindicated for the optimal treatment of the patient, including for more directed 
antibiotic therapy against known prior resistant infections or suspected sepsis with an associated 
central nervous system infection   
6.0 Enrollment/Randomization 
6.1 Study Sites: 
Emergency Department and Medical Intensive Care Unit at Vanderbilt University Medical Center 
 
6.2 Study Population:  
All adults with sepsis located in a participating unit for whom the treating clinician orders either an anti-
pseudomonal cephalosporins or anti-pseudomonal penicillin within 12 hours of hospital presentation 
unless determined to meet an exclusion criteria. All eligible patients will be included and there will be no 
selection based on gender, race, weight or other clinical factors.  
 
6.3 Enrollment:  
At the time that a treating clinician in a participating emergency department or medical intensive care unit 
initiates an order for an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin for a patient who 
meets all inclusion criteria, an advisor within the electronic health record (details in section 7) will prompt 
treating clinicians to record whether the patient meets any exclusion criteria.  Patients not meeting any 
exclusion criteria will be enrolled and randomized.  For patients who are determined to be ineligible, the 
advisor will track the number and reasons for exclusion.  The time of randomization will be defined as 
“time zero” on “study day 0.”  
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
 
  
Figure 6: Enrollment Schema – When a treating clinician orders an anti-pseudomonal 
cephalosporin or anti-pseudomonal penicillin, tools within the electronic health record (details in 
section 7) will evaluate if the patient meets inclusion criteria (order placed within 12 hours of 
hospital presentation, age ≥ 18, and located in a participating unit), and the presence of 
documented allergy to penicillin or cephalosporins (an exclusion criteria).  If the patient has not 
been previously enrolled in the trial during the index hospitalization, appears to meet all inclusion 
criteria, does not have a documented allergy to penicillin or cephalosporins, an ordering advisor 
will prompt the clinician to determine whether the patient meets any exclusion criteria. If the 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
treating clinician confirms that the patient does meet an exclusion criterion, the patient will be 
enrolled and randomized.  The ordering advisor will track all exclusions. 
 
6.4 Consent:  
Anti-pseudomonal cephalosporins and anti-pseudomonal penicillins are routinely used in the care of 
acutely ill patients with sepsis in the emergency department and intensive care units at Vanderbilt 
University Medical Center.  Currently, choice of empiric gram-negative coverage is based primarily on 
provider preference as there are no large randomized trials or evidence-based guidelines to support the 
choice of one empiric anti-pseudomonal therapy for sepsis over another.  The concept of a randomized 
trial comparing anti-pseudomonal cephalosporins versus anti-pseudomonal penicillins has been discussed 
with the leaders of emergency department and intensive care units and representation from the infectious 
diseases and nephrology programs who agree that clinical equipoise exists regarding the choice of empiric 
anti-pseudomonal therapy for acutely ill adults with sepsis. 
 
Because the interventions studied (1) are used as a part of routine care, (2) are interventions the patient 
would be exposed to even if not participating in the study, (3) have no prior high-quality data to suggest 
the superiority of one approach over the other, and (4) are equivalent options from the perspective of the 
treating provider (otherwise the patient is excluded), we feel the study presents minimal risk. 
 
In addition to the minimal risk posed by the study, obtaining informed consent prior to participation 
would not be feasible or practicable.  Sepsis is a medical emergency.  Each hour of delay in the initiation 
of antibiotics for acutely ill patients with sepsis increases mortality by about 7%.  For patients presenting 
with sepsis to the participating units, the average time between initiation of an order for an anti-
pseudomonal antibiotic and its administration to the patient is 28 minutes.  Obtaining prospective written 
informed consent during this interval is impracticable and risks delaying antibiotic administration.  
Moreover, acutely ill patients with sepsis are commonly delirious or unconscious, and a legally authorized 
representative (LAR) is not consistently present at the time of initiation of antibiotics.  Because the trial 
determines choice of the initial anti-pseudomonal antibiotic, but defers decisions regarding subsequent 
doses of antibiotics (e.g., duration of therapy, escalation, de-escalation) to treating clinicians, the primary 
study procedure will be completed within 1 hour of meeting eligibility criteria. 
 
 
Because the study presents minimal risk, would not adversely affect the welfare or privacy rights of the 
participant, and consent would be impracticable, we will request a waiver of informed consent. 
 
6.5 Randomization:  
A series of study group assignments will be generated by computerized randomization in a 1:1 ratio of 
intervention to control.  Study group assignment will remain concealed to study personnel and treatment 
team until after the study team has confirmed that the patient does not meet any exclusion criteria and the 
patient has been enrolled.   Following randomization, treating clinicians will be notified via the ordering 
advisor. 
 
7.0 Study Procedures 
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
7.1 Electronic Health Record (EHR) Based Screening for Eligible Patients 
For the duration of the study, when a provider initiates an order for the administration of an intravenous 
anti-pseudomonal cephalosporin or anti-pseudomonal penicillin, a software application in the EHR will 
assess if the patient is eligible for the study. The application will assess that the patient meets all the 
inclusion criteria (located in study unit, age ≥ 18, in the hospital for less than 12 hours, and has not been 
previously enrolled during the hospitalization) and none of the exclusion criteria (current documented 
allergy to cephalosporin or penicillin class antibiotics, more than one prior administration of study 
antibiotics during the last 7 days). If the above criteria are met, an order advisor (Figure 7) will: 1) Inform 
the provider of the study, 2) solicit the presence of contraindications to either study drug, 3) (if patient 
meets all eligibility criteria) enroll and randomize the patient. If there are contraindications which were 
not established electronically, the advisor will ask the provider to select the reason. 
 
 
Figure 7: Order advisor informing providers of the study and soliciting other exclusion criteria 
 
7.2 Antibiotic Ordering after Randomization 
Once the participant is enrolled and randomized, the ordering advisor will guide the provider to the order 
one of the assigned study antibiotics. Dose, frequency, and duration will be at the discretion of treating 
clinicians and not affected by the advisor. 
 
7.3 EHR-Based Tool to Capture Data on Antibiotic Modification and Adverse Events  
In the 7 days after enrollment, if a clinician attempts the discontinue the study-related antibiotic order, an 
EHR-based advisor will remind the clinician of the treatment arm and if the treating clinician chooses to 
discontinue the antibiotic from the assigned group, the clinician will be asked for the rationale: 
- 
Antibiotic tailoring (escalation or de-escalation) based on microbiologic data 
- 
Undocumented or newly apparent allergy to either penicillins or cephalosporins 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
- 
Treating clinicians feel that either anti-pseudomonal cephalosporins or anti-pseudomonal penicillins 
are superior in the optimal treatment of the patient (provide reason why) 
- 
Other (provider input rationale) 
- 
Antibiotic induced adverse event 
 
Data provided by the treating clinicians will be used for prospective safety monitoring and adverse event 
reporting. 
 
7.4 Duration of the Intervention 
Patients will be allocated to the anti-pseudomonal cephalosporin or anti-pseudomonal penicillin groups 
which will determine their initial antibiotic choice only. All further antibiotic decisions including, but not 
limited to, duration of antibiotics, changing based on new clinical or microbiological data, and switching 
between classes of anti-pseudomonal antibiotics will be left to the discretion of the treating team. 
 
As described above, an EHR-based advisor will alert treating clinicians to group assignment and collect 
data for monitor for adverse events occurring in the seven days after randomization.  The advisor will not 
impede the ability to change classes of antibiotic and will be used primarily for safety monitoring.  
 
7. 5 Blinding:  
It would be impractical to pursue blinding for the study. The medicines involved in this study are given at 
different doses with varying volumes of IV infusion. They are also given on different schedules varying 
as widely as 4 times a day to once daily. Furthermore, these dosing variations are impacted by renal 
function. Given the nature of the study intervention, patients, clinicians, and investigators will not be 
blinded to group assignment.   
 
8.0 Data Collection: 
 
8.1 In-Hospital Outcomes:  
Primary Efficacy Outcome: Acute Kidney Injury Score between randomization and day 14. The acute 
kidney injury score is an ordinal outcome containing the stages of AKI as defined by KDIGO creatinine 
criteria, new renal replacement therapy (RRT), and death: 
 
0 = No AKI 
1 = Stage 1 AKI (Creatinine increase by 1.5-1.9 times baseline OR increase by >= 0.3 mg/dL) 
2 = Stage 2 AKI (Creatinine increase by 2.0-2.9 times baseline) 
3 = Stage 3 AKI (Creatinine increase by >= 3.0 times baseline OR increase to >= 4.0 mg/dL OR 
New RRT) 
4 = Death  
 
Death is defined as in-hospital mortality from any cause prior to hospital discharge, censored at 14 days. 
New RRT is defined as receipt of RRT at any point between ICU admission and hospital discharge, 
censored at 14 days.  Baseline creatinine level will be determined by using a previously described 
hierarchical approach in which creatinine values obtained during the year before hospitalization are given 
priority over in-hospital measurements obtained before antibiotic administration. When no pre-enrollment 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
measurements are available, the baseline creatinine level is estimated with a previously described three-
variable formula32,33. It is important to note that those patients with End-Stage Renal Disease (ESRD) 
would only be eligible to meet the “Death” component of the primary outcome. 
 
Justification for the Primary Efficacy Outcome 
This outcome is 1) validated for electronic assessment, 2) uses outcome thresholds for renal dysfunction 
defined by international nephrology organizations, 3) incorporates patient-centered outcomes (new RRT 
and death) that would be missed by a purely laboratory-based outcome, and 4) uses a hierarchal approach 
to analysis that counts rare but important patient-centered outcomes (new RRT, death) as worse than 
purely laboratory-based measures (stage 2 AKI).  
 
Exploratory Outcomes:  
- 
Exploratory Renal Outcomes: acute kidney injury of stage 2 or higher as defined in the KDIGO 
criteria for creatinine level within 14 days, acute kidney injury of stage 2 or higher as defined in the 
KDIGO criteria for creatinine level within 28 days, new receipt of renal-replacement therapy at 28 
days, new receipt of renal-replacement therapy at 14 days, days alive and free of renal-replacement 
therapy during the 28 days after enrollment, days alive and free of renal-replacement therapy during 
the 14 days after enrollment, the highest creatinine level during the 28 days after enrollment, the 
change from baseline to the highest creatinine level, and the final creatinine level before hospital 
discharge. 
- 
Exploratory Neurologic Outcomes: Glasgow Coma Scale (GCS) score during the 28 days after 
enrollment, neurologic component of SOFA score, Coma and Delirium Free Days in 28 days after 
enrollment 
- 
Exploratory Clinical Outcomes: ICU-free days, ventilator-free days, vasopressor-free days, 28-day 
mortality, 14-day mortality, interaction between outcomes of patients admitted to the ICU vs wards 
 
8.2 Baseline data:  
Age, gender, height, weight, body mass index, race, APACHE II score, active medical problems at the 
time of admission, active comorbidities, comorbidities and medications known to increase risk of kidney 
or neurologic injury at enrollment (receipt of IV contrast in the previous 24 hours, receipt of ACE 
inhibitor or Angiotensin Receptor Blocker in the previous 24 hours), mean arterial pressure and 
vasopressor use prior to antibiotic receipt, analgesia and sedation use prior to antibiotic receipt (propofol, 
dexmedetomidine, fentanyl, hydromorphone, ketamine), pH, PaO2, PaCO2, respiratory rate, heart rate, 
oxygen saturation, temperature, lactic acid, elements of a basic metabolic panel (Na, K, Cl, HCO3, BUN, 
Creatinine, Glucose), magnesium, elements of a complete blood count (white blood cell count, 
hemoglobin, hematocrit, platelets), Confusion Assessment Method – ICU (CAM-ICU), Richmond 
Agitation Sedation Score (RASS), mechanical ventilation status and variables related to ventilation 
(FiO2, PEEP, respiratory rate, tidal volume), on renal replacement therapy prior to receipt of antibiotics, 
admission to ICU vs ward 
 
 
8.3 Data from enrollment to hospital discharge:  
Mean arterial pressure and vasopressor use, pH, PaO2, PaCO2, respiratory rate, heart rate, oxygen 
saturation, temperature, lactic acid, elements of a basic metabolic panel (Na, K, Cl, HCO3, BUN, 
Creatinine, Glucose), magnesium, elements of a complete blood count (white blood cell count, 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
hemoglobin, hematocrit, platelets), all microbiologic culture data (blood, urine, respiratory, wound, 
surgical, aspirate, body fluid), CAM-ICU, RASS, mechanical ventilation status and variables related to 
ventilation (FiO2, PEEP, respiratory rate, tidal volume), new-start renal replacement therapy, medications 
known to increase risk of kidney injury (receipt of IV contrast ACE inhibitor or Angiotensin Receptor 
Blocker, NSAIDs, trimethoprim-sulfamethoxazole, acyclovir, amphotericin B, diuretics), medications 
known to increase risk of neurologic injury (metronidazole, benzodiazepines, barbiturates, opiate pain 
medicines, typical and atypical anti-psychotics, propofol, dexmedetomidine, ketamine, corticosteroids), 
days spent in ICU, days spent in the hospital, date of intubation and extubation, date of death 
 
8.4 Outcome Data:  
Primary Outcome: All creatinine values from presentation to day 14, creatinine values prior to 
hospitalization, and dates and times of the following events, if applicable: presentation to the hospital, 
receipt of new renal replacement therapy, admission to the hospital, discharge from the hospital, death 
 
Exploratory Renal Outcomes: All creatinine values from presentation to hospital discharge, creatinine 
values prior to hospitalization, and the dates and times of the following events, if applicable: presentation 
to the hospital, receipt of new renal replacement therapy, admission to the hospital, discharge from the 
hospital, death 
 
Exploratory Neurologic Outcomes: All RASS values/dates/times from presentation to day 28, all CAM-
ICU values/dates/time from presentation to day 28, all GCS values/dates/times from presentation to day 
28 
 
Exploratory Clinical Outcomes: Date and time of the following events, if applicable: presentation to the 
hospital, admission to the hospital, admission to the ICU, transfer from the ICU, discharge from the 
hospital, receipt of mechanical ventilation, discontinuation of mechanical ventilation, receipt of 
vasopressors, discontinuation of vasopressors, death 
 
9.0 Risks and Benefits 
In patients for whom the treating team has decided empiric broad spectrum antibiotics are required for the 
treatment of sepsis, there are currently no established risks or benefits to using anti-pseudomonal 
cephalosporins or anti-pseudomonal penicillins as empiric gram negative coverage.  At this time, there is 
no reason to believe that participation in this study would expose patients to greater medical risks or 
benefits than those experienced by acutely ill patients requiring antibiotics as a part of routine care.  The 
greater benefit of the study would be to society in the form of improved understanding of safe and 
effective empiric antibiotic selection for acutely ill patients with sepsis. 
 
A potential risk to patients participating in this study involves the collection of protected health 
information (PHI).  In order to limit the associated risks, the minimum amount of PHI necessary for study 
conduct will be collected.  After collection, the data will be stored in a secure online database (REDCap) 
only accessible by the investigators.  After publication, a de-identified database will be generated to 
protect participant privacy. 
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
10.0 Statistical Considerations 
 
Sample size considerations 
Using data captured during the development and testing of the enrollment advisor (trial intervention) from 
820 patients who would have been eligible for ACORN, we estimated the distribution of the primary 
outcome in the anti-pseudomonal penicillin group.  A total of 61.2% of patients did not experience AKI 
or death, 4.9% had Stage I AKI, 4.3% had Stage II AKI, 8.0% had Stage III AKI or new RRT, and 21.5% 
died within 30 days of ICU admission. We calculated that obtaining 80% power at an alpha of 0.05 to 
detect an odds ratio of 0.65 for patients assigned to anti-pseudomonal cephalosporins would require a 
sample size of 2010. Assuming missing data for 40 patients, or < 5%, we plan to enroll 2050 patients. 
 
Sample size re-estimation 
At the planned interim analysis after 1025 patients, or roughly half of the intended enrollment, the DSMB 
will evaluate the distribution of the primary outcome in the anti-pseudomonal penicillin group. If required 
by the observed distribution of the primary outcome in the anti-pseudomonal penicillin group, the DSMB 
may recommend that the investigators increase the total sample size of the trial to maintain 80% power 
and an alpha of 0.05 to detect an odds ratio of 0.65. 
 
Statistical Analysis: 
Analysis principles 
- 
Primary analysis will be conducted on an intention-to-treat basis (patients with protocol violations are 
analyzed per the assigned treatment arm). 
- 
All hypothesis tests will be two sided, with an α of 0.05 unless otherwise specified. 
- 
All analyses will be unadjusted unless otherwise specified. 
- 
Pre-specified analyses of heterogeny of treatment effect based on baseline variables will be performed 
irrespective of treatment efficacy. 
 
Trial profile:  
We will present a Consolidated Standards of Reporting Trials diagram to detail the movement of patients 
through the study. This diagram will include total number of patients meeting inclusion criteria, number 
excluded and reason for exclusion, number enrolled and randomized in the study, number followed, and 
number analyzed. 
 
Baseline Characteristics:  
To assess randomization success, we will summarize in Table 1 the distribution of baseline variables 
across the study arms. Categorical variables will be reported as frequencies and percentages and 
continuous variables as either means with SDs or medians with interquartile ranges. Variables reported 
will include Demographics (age, gender, race, BMI, co-morbidities); Indication for antibiotics; Severity 
of Illness (APACHE II score); Acute Kidney Injury at enrollment; Delirium at enrollment 
 
Primary Efficacy Outcome Analysis: 
We will compare the primary outcome, the AKI ordinal outcome, between patients randomized to the 
anti-pseudomonal cephalosporins versus anti-pseudomonal penicillins groups. It is important to note that 
those patients with End-Stage Renal Disease (ESRD) would only be eligible to meet the “Death” 
component of the primary outcome. 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
 
The main analysis will be an intention-to-treat comparison of the primary outcome between the anti-
pseudomonal cephalosporin and anti-pseudomonal penicillin groups. To do this, we will use an 
unadjusted, proportional odds model with group assignment (anti-pseudomonal cephalosporin, anti-
pseudomonal penicillin) as the independent variable.  For the purposes of declaring a statistically 
significant difference between groups in the primary endpoint, we will consider a two-sided P value of 
0.05 as significant. 
 
Secondary Analyses of the Primary Outcome 
To account for potential confounders, we will develop an adjusted proportional odds regression model 
with the AKI ordinal outcome score (primary outcome) as the dependent variable and independent 
covariate of groups assignment, and relevant confounders (age, baseline creatinine, gender, mechanical 
ventilation at enrollment, receipt of inotropes at enrollment, AKI at enrollment, presence of CKD, 
admission location). 
 
Secondary Analyses: 
Analysis of Secondary and Exploratory Outcomes 
We will conduct an intention-to-treat comparison of all secondary and exploratory outcomes between 
patients randomized to anti-pseudomonal cephalosporins and patients randomized to anti-pseudomonal 
penicillins. Continuous outcomes will be compared with the Mann-Whitney U test and categorical 
variables with the chi-square test or Fischer’s exact test, as appropriate. 
 
Heterogeny of Treatment Effect 
We will examine the effect of group assignment on the primary outcome relative to a set of pre-specified 
baseline variables.  These variables will be prespecified as part of a formal statistical analysis plan 
completed and made public prior to the completion of enrollment.  A formal test of interaction will be 
used to evaluate for effect modification. 
 
Presentation of Statistics 
Continuous variables will be described as mean and standard deviation or median and interquartile range 
or bootstrapped 95% confidence intervals as appropriate.  Categorical variables will be given as number 
and percentage.  All between-group comparisons with continuous variables will be performed using 
Mann-Whitney U tests; categorical variables will be compared with chi-square testing or Fisher’s exact 
test as appropriate. 
 
Interim Analysis 
We will plan for the DSMB to conduct a single interim analysis for efficacy and safety at the anticipated 
halfway point of the trial, after enrollment of 1025 patients.  The stopping boundary for efficacy will be 
met if the P value for the difference between groups in the primary outcome is 0.001 or less.  Use of the 
conservative Haybittle-Peto boundary (P < 0.001) will allow the final analysis to be performed using an 
unchanged level of significance (P = 0.05).  Given the minimal risk nature of the study and current use of 
both interventions as a part of usual care, there will be no stopping boundary for futility.  At the interim 
analysis, the DSMB will also monitor the distribution of the AKI ordinal outcome within the anti-
pseudomonal penicillin group and may propose to increase the planned sample size to maintain the pre-
planned power to detect an odds ratio of 0.65.  
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
11.0 Reporting of Adverse Events or Unanticipated Problems 
Assuring patient safety is an essential component of this protocol. All medications used in this trial are 
approved by the Food and Drug Administration and used in clinical practice with an established safety 
profile. This protocol further ensures safety of its participants through: 
a) Exclusion criteria designed to prevent enrollment of patients likely to experience adverse events 
from the study antibiotics; 
b) Systematic collection of safety outcomes relevant to the use of anti-pseudomonal cephalosporins 
and anti-pseudomonal penicillins in this setting; 
c) Structured monitoring, assessment, recording, and reporting of adverse events. 
 
11.1 Adverse Event Definitions 
Adverse Event – An adverse event will be defined as any untoward or unfavorable medical 
occurrence in a human subject temporally associated with the subject’s participation in the research, 
whether or not considered related to the subject’s participation in the research.  Any adverse event 
occurring during the research will be classified according to the following characteristics: 
 
● Seriousness – An adverse event will be considered “serious” if it: 
o Results in death; 
o Is life-threatening (defined as placing the patient at immediate risk of death); 
o Results in inpatient hospitalization or prolongation of existing hospitalization;  
o Results in a persistent or significant disability or incapacity; 
o Results in a congenital anomaly or birth defect; or  
o Based upon appropriate medical judgment, may jeopardize the patient’s health and may 
require medical or surgical intervention to prevent one of the other outcomes listed in this 
definition. 
 
● Unexpectedness – An adverse event will be considered “unexpected” if the nature, severity, or 
frequency is neither consistent with: 
o The known or foreseeable risk of adverse events associated with the procedures involved 
in the research that are described in the protocol-related documents, such as the IRB-
approved research protocol; nor 
o The expected natural progression of any underlying disease, disorder, or condition of the 
subject experiencing the adverse event and the subject’s predisposing risk factor profile 
for the adverse event. 
 
● Relatedness – The strength of the relationship of an adverse event to a study intervention or 
study procedure will be defined as follows:  
o Definitely Related: The adverse event follows (1) a reasonable, temporal sequence from a 
study procedure AND (2) cannot be explained by the known characteristics of the 
patient’s clinical state or other therapies AND (3) evaluation of the patient’s clinical state 
indicates to the investigator that the experience is definitely related to study procedures.  
o Probably or Possibly Related: The adverse event meets some but not all of the above 
criteria for “Definitely Related”. 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
o Probably Not Related: The adverse event occurred while the patient was on the study but 
can reasonably be explained by the known characteristics of the patient’s clinical state or 
other therapies.  
o Definitely Not Related: The adverse event is definitely produced by the patient’s clinical 
state or by other modes of therapy administered to the patient.  
o Uncertain Relationship: The adverse event does not fit in any of the above categories. 
 
11.2 Monitoring for Adverse Events 
The time interval during which patients will be monitored for the occurrence of adverse events begins at 
randomization and ends at the first of hospital discharge or 28 days.  Adverse events occurring before 
randomization or after hospital discharge or 28 days will not be collected. In this trial, enrollment, 
randomization, intervention delivery, monitoring for safety and adverse events and outcome assessment 
will all take place within the electronic health record.  As described an EHR-based advisor will 
continuously monitor for discontinuation of study drug and require that clinicians identify reason for 
discontinuation.  Every time a study drug is discontinued, investigators will be notified in real-time 
using an automated lists within the EHR.  Investigators will investigate and adjudicate potential adverse  
as close as feasible to 24 hours after initial report by treating clinicians.  Investigators will assess any 
potential adverse events for whether the adverse event meets the criteria for recording and reporting 
outlined below. 
 
11.3 Recording and Reporting Adverse Events 
The following types of adverse events will be recorded and reported: 
● Adverse events that are Serious and Definitely Related, Probably or Possibly Related, or of 
Uncertain Relationship. 
● Adverse events that are Unexpected and Definitely Related, Probably or Possibly Related, or of 
Uncertain Relationship. 
 
Adverse events that do not meet the above criteria will not be recorded or reported.  Adverse events that 
the investigator assesses to meet the above criteria for recording and reporting will be entered into the 
adverse event electronic case report form in the trial database.  The investigator will record a 
preliminary assessment of each characteristic for the adverse event, including seriousness, 
unexpectedness, and relatedness.  For any adverse event that is serious AND unexpected, and 
definitely related, probably or possibly related, or of uncertain relationship, the investigator will report 
the adverse event to the principal investigator within 24 hours of the investigator becoming aware of 
the adverse event.  For any other adverse event requiring recording and reporting, the investigator will 
report the adverse event to the principal investigator within 72 hours of the investigator becoming 
aware of the adverse event.  The principal investigator will make the final determination regarding each 
characteristic for the adverse event, including seriousness, expectedness, and relatedness.   
 
For adverse events that meet the above criteria for recording and reporting, the coordinating center will 
notify the DSMB, the IRB, and the sponsor in accordance with the following reporting plan: 
Characteristics of the Adverse Event 
Reporting Period 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
Fatal or life-threatening (and therefore serious), 
unexpected, and definitely related, probably or 
possibility related, or of uncertain relationship. 
Report to the DSMB, IRB, and sponsor 
within 7 days after notification of the 
event. 
Serious but non-fatal and non-life-threatening, 
unexpected, and definitely related, probably or 
possibly related, or of uncertain relationship. 
Report to DSMB, IRB, and sponsor within 
15 days of notification of the event. 
All other adverse events meeting criteria for 
recording and reporting. 
Report to DSMB in regularly scheduled 
DSMB safety reports. 
The investigator will distribute the written summary of the DSMB’s periodic review of reported adverse 
events to the IRB in accordance with NIH guidelines: (http://grants.nih.gov/grants/guide/notice-
files/not99-107.html). 
 
11.4 Clinical Outcomes that may be Exempt from Adverse Event Recording and Reporting 
In this study of critically ill patients at high risk for death and other adverse outcomes due to their 
underlying critical illness, clinical outcomes, including death and organ dysfunction, will be 
systematically collected and analyzed for all patients. The primary, secondary, and exploratory 
outcomes will be recorded and reported as clinical outcomes and not as adverse events unless treating 
clinicians or site investigators believe the event is Definitely Related or Probably or Possibly Related to 
the study intervention or study procedures.  This approach – considering death and organ dysfunction as 
clinical outcomes rather than adverse events and systemically collecting these clinical outcomes for 
analysis – is common in ICU trials. This approach ensures comprehensive data on death and organ 
dysfunction for all patients, rather than relying on sporadic adverse event reporting to identify these 
important events.  The following events are examples of study-specific clinical outcomes that would not 
be recorded and reported as adverse events unless treating clinicians or site investigators believe the 
event was Definitely Related or Probably or Possibly Related to the study intervention or study 
procedures: 
● Death (all deaths occurring prior to hospital discharge or 28 days will be recorded); 
● Organ dysfunction 
o Circulatory failure, including hypotension, cardiac arrest or shock with or without 
receipt of vasopressors; 
o Acute renal failure 
o Delirium or coma 
● Duration of mechanical ventilation; 
● Duration of ICU admission; 
● Duration of hospitalization 
 
Note: A study-specific clinical outcome may also qualify as a reportable adverse event.  For example, 
anaphylaxis that the investigator considers Definitely Related to an anti-pseudomonal penicillin would 
be both recorded as a study-specific clinical outcome and reported as a Serious and Definitely Related 
Adverse Event. 
  
11.5 Unanticipated Problems involving Risks to Subjects or Others 
Investigators must also report to the principal investigator Unanticipated Problems Involving Risks to 
Subjects or Others (“Unanticipated Problems”), regardless of severity, associated with study procedures 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
within 24 hours of the investigator becoming aware of the Unanticipated Problem. An Unanticipated 
Problem is defined as any incident, experience, or outcome that meets all of the following criteria:  
● Unexpected (in terms of nature, severity, or frequency) given (a) the research procedures that 
are described in the protocol-related documents, such as the IRB-approved research protocol; 
and (b) the characteristics of the subject population being studied; AND 
● Definitely Related or Probably or Possibly Related to participation in the research (as defined 
above in the section on characteristics of adverse events); AND  
● Suggests that the research places subjects or others at a greater risk of harm (including 
physical, psychological, economic, or social harm) than was previously known or recognized.  
Upon becoming aware of any event that may represent an Unanticipated Problem, the investigator will 
assess whether the event represents an Unanticipated Problem by applying the criteria described above.  
If the investigator determines that the event represents an Unanticipated Problem, the investigator will 
record the Unanticipated Problem in the Unanticipated Problem electronic case report form in the trial 
database.  The investigators will obtain information about the Unanticipated Problem and report the 
Unanticipated Problem to the DSMB, IRB, and sponsor within 15 days of becoming aware of the 
Unanticipated Problem. 
 
12.0 Privacy/Confidentiality Issues 
At no time during the course of this study, its analysis, or its publication will patient identities be revealed 
in any manner. The minimum necessary data containing patient or provider identities will be collected. As 
quickly as feasible, all data collected will be uploaded into a password-protected computerized database 
maintained within a secure, web-based application for building and managing online databases 
(REDCap), or stored on secure servers with user-level access control. All patients will be assigned a 
unique study number for use in the computerized database. At the time of publication all identifiers will 
be removed. 
 
13.0 Follow-up and Record Retention 
Patients will be followed after enrollment for 28 days or until hospital discharge, whichever occurs first.  
Data collected from the medical record will be entered into the secure online database REDCap. All data 
will be maintained in the secure online database REDCap until the time of study publication.  At the time 
of publication, a de-identified version of the database will be generated. 
14.0 Data and Safety Monitoring Board (DSMB) 
The principal role of the DSMB is to assure the safety of patients in the trial. They will regularly monitor 
data from this trial, review and assess the performance of its operations, and make recommendations to 
the steering committee and sponsor with respect to:  
- 
Participant safety and risk/benefit ratio of study procedures and interventions 
- 
Protocol amendments (with specific attention to study population, intervention, and study procedures) 
- 
Adherence to the protocol requirements 
- 
Completeness, quality, and planned analysis of data  
- 
Ancillary study burden on participants and main study  
- 
Possible early termination of the trial because of new external information, early attainment of study 
objectives, safety concerns, or inadequate performance 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
The DSMB will consist of members with expertise in critical care medicine, infectious disease, 
biostatistics, and clinical trials. Appointment of all members is contingent upon the absence of any 
conflicts of interest. All the members of the DSMB are voting members. The Principal Investigator and 
unblinded study biostatistician will be responsible for the preparation of all DSMB and adverse event 
reports. The DSMB will develop a charter and review the protocol and patient notification forms during 
its first meeting. Subsequent DSMB meetings will be scheduled in accordance with the DSMB Charter 
with the assistance of the Principal Investigator. The DSMB will have the ability to recommend that the 
trial end, be modified, or continued unchanged. 
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Primary Investigator: Edward Qian, MD 
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Primary Investigator: Edward Qian, MD 
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prognosis of vancomycin monotherapy and combination therapy with beta-lactams in the intensive 
care unit. PloS One. 2019;14(6):e0217908. doi:10.1371/journal.pone.0217908 
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30.  Luther MK, Timbrook TT, Caffrey AR, Dosa D, Lodise TP, LaPlante KL. Vancomycin Plus 
Piperacillin-Tazobactam and Acute Kidney Injury in Adults: A Systematic Review and Meta-
Analysis. Crit Care Med. 2018;46(1):12-20. doi:10.1097/CCM.0000000000002769 
31.  Schreier DJ, Kashani KB, Sakhuja A, et al. Incidence of Acute Kidney Injury Among Critically Ill 
Patients With Brief Empiric Use of Antipseudomonal β-Lactams With Vancomycin. Clin Infect Dis 
Off Publ Infect Dis Soc Am. 2019;68(9):1456-1462. doi:10.1093/cid/ciy724 
32.  Závada J, Hoste E, Cartin-Ceba R, et al. A comparison of three methods to estimate baseline 
creatinine for RIFLE classification. Nephrol Dial Transplant. 2010;25(12):3911-3918. 
doi:10.1093/ndt/gfp766 
33.  Semler MW, Rice TW, Shaw AD, et al. Identification of Major Adverse Kidney Events Within the 
Electronic Health Record. J Med Syst. 2016;40(7):167. doi:10.1007/s10916-016-0528-z 
 

1 
 
Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
 
Study Principal Investigators:  
Edward Qian, MD, Fellow, Department of Medicine, Division of Allergy, Pulmonary, and Critical Care 
Medicine 
 
Co-investigators 
 
Todd Rice, MD, MSc, Associate Professor, Department of Medicine, Division of Allergy, Pulmonary, 
and Critical Care Medicine; Director, Medical ICU; Director, Vanderbilt Human Research Protections 
Program 
 
Matthew Semler, MD, MSc, Assistant Professor, Department of Medicine, Division of Allergy, 
Pulmonary, and Critical Care Medicine 
 
Jonathan Casey, MD, MSc, Assistant Professor, Department of Medicine, Division of Allergy, 
Pulmonary, and Critical Care Medicine 
 
Christopher Lindsell, PhD, Professor, Department of Biostatistics 
 
Wes Self, MD, MPH, Associate Professor, Department of Emergency Medicine 
 
Edward Siew, MD, MSc, Associate Professor, Department of Medicine, Division of Nephrology and 
Hypertension  
 
George Nelson, MD, MPH, Assistant Professor, Department of Medicine, Division of Infectious 
Diseases; Director, Antimicrobial Stewardship Program; Associate Hospital Epidemiologist 
 
Joanna Stollings, PharmD, FCCP, FCCM, BCPS, BCCCP, Department of Pharmacy Services 
 
Li Wang, MS, Department of Biostatistics 
 
 
 
Date: 7/27/2022 
 
 
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
 
Study Schema 
1.0 
Study Summary ........................................................................................................................... 3 
2.0 Background ....................................................................................................................................... 5 
2.1 Anti-Pseudomonal Cephalosporins as Part of an Empiric Broad Spectrum Regimen ....................... 5 
2.2 Anti-Pseudomonal Penicillins as Part of an Empiric Broad Spectrum Regimen .............................. 6 
2.3 Acute Kidney Injury during Critical Illness .................................................................................... 6 
2.4 Prior Evidence of the Effect of Antibiotic Choice on Acute Kidney Injury ..................................... 6 
2.5 Rationale for a Trial of Anti-Pseudomonal Cephalosporins vs Anti-Pseudomonal Penicillins ......... 6 
3.0 Rationale, Aims, and Hypotheses ....................................................................................................... 7 
4.0 Study Description .............................................................................................................................. 7 
5.0 Inclusion/Exclusion Criteria ............................................................................................................... 7 
5.1 
Inclusion Criteria: .................................................................................................................... 7 
5.2 Exclusion Criteria: ......................................................................................................................... 8 
6.0 Enrollment/Randomization ................................................................................................................ 8 
6.1 Study Sites: .................................................................................................................................... 8 
6.2 Study Population:........................................................................................................................... 8 
6.3 Enrollment: .................................................................................................................................... 8 
6.4 Consent: ...................................................................................................................................... 10 
6.5 Randomization: ............................................................................................................................ 10 
7.0 Study Procedures ............................................................................................................................. 10 
7.1 Electronic Health Record (EHR) Based Screening for Eligible Patients ........................................ 11 
7.2 Antibiotic Ordering after Randomization...................................................................................... 11 
7.3 EHR-Based Tool to Capture Data on Antibiotic Modification and Adverse Events ....................... 11 
7.4 Duration of the Intervention ......................................................................................................... 12 
7. 5 Blinding: ..................................................................................................................................... 12 
8.0 Data Collection: ............................................................................................................................... 12 
8.1 In-Hospital Outcomes: ................................................................................................................. 12 
8.2 Baseline data: .............................................................................................................................. 14 
8.3 Data from enrollment to hospital discharge: ................................................................................. 14 
8.4 Outcome Data: ............................................................................................................................. 14 
9.0 Risks and Benefits ........................................................................................................................... 14 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
10.0 Statistical Considerations ............................................................................................................... 15 
11.0 Reporting of Adverse Events or Unanticipated Problems ................................................................ 17 
11.1 Adverse Event Definitions .......................................................................................................... 17 
11.2 Monitoring for Adverse Events ................................................................................................... 18 
11.3 Recording and Reporting Adverse Events ................................................................................... 18 
11.4 Clinical Outcomes that may be Exempt from Adverse Event Recording and Reporting ............... 19 
11.5 Unanticipated Problems involving Risks to Subjects or Others .................................................... 20 
12.0 Privacy/Confidentiality Issues ........................................................................................................ 20 
13.0 Follow-up and Record Retention .................................................................................................... 21 
14.0 Data and Safety Monitoring Board (DSMB)................................................................................... 21 
15.0 References ..................................................................................................................................... 21 
 
 
1.0 Study Summary 
Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Background: Sepsis is one of the most common causes of acute illness and death in the United States. 
Early, empiric broad-spectrum antibiotics are a mainstay of sepsis treatment. Two classes of antibiotics 
with activity against Pseudomonas, anti-pseudomonal cephalosporins and anti-pseudomonal penicillins, 
are commonly used for acutely ill adults with sepsis in current practice. Recent observational studies, 
however, have raised concern that anti-pseudomonal penicillins may cause renal toxicity. Anti-
pseudomonal cephalosporins, by comparison, may be associated with a risk of neurotoxicity.  Rigorous, 
prospective data regarding the comparative effectiveness and toxicity of these two classes of medications 
among acutely ill patients are lacking. We propose a randomized trial comparing the impact of anti-
pseudomonal cephalosporins and anti-pseudomonal penicillins on renal outcomes of acutely ill patients. 
Primary Aim: 
- 
To compare the effect of anti-pseudomonal cephalosporins versus anti-pseudomonal penicillins on the 
incidence of acute kidney injury among acutely ill patients 
Primary Hypothesis: 
- 
Among acutely ill patients with sepsis, use of anti-pseudomonal cephalosporins will decrease the 
incidence of acute kidney injury (AKI), compared to anti-pseudomonal penicillins. 
Inclusion Criteria: 
1. Age ≥ 18 years old 
2. Located in a participating emergency department or medical intensive care unit  
3. Less than 12 hours from presentation to study hospital 
4. Treating clinician initiating an order for an anti-pseudomonal cephalosporin or anti-pseudomonal 
penicillin  
Exclusion Criteria: 
1. Known receipt of > 1 dose of an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin 
during the last 7 days 
2. Current documented allergy to cephalosporins or penicillin 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
3. Known to be a prisoner 
4. Treating clinicians feel that either an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin 
is required or contraindicated for the optimal treatment of the patient, including for more directed 
antibiotic therapy against known prior resistant infections or suspected sepsis with an associated 
central nervous system infection  
Consent: 
- 
Given that both anti-pseudomonal cephalosporins and anti-pseudomonal penicillins are routinely used 
in usual care, the lack of established risk or benefit with either treatment group, the impracticability of 
obtaining informed consent prior to initiating antibiotics for acutely ill patients, a waiver of informed 
consent will be requested. 
Randomization: 
- 
Using a best-practices advisor embedded within the electronic health record, patients meeting all 
inclusion criteria and no exclusion criteria will be randomized in a 1:1 ratio to receive an anti-
pseudomonal cephalosporin (treating clinicians’ choice of cefepime or ceftazidime) or anti-
pseudomonal penicillin. 
Study Interventions: 
- 
Anti-pseudomonal cephalosporin group: patients assigned to the anti-pseudomonal cephalosporin 
group will receive the treating clinicians’ choice of either cefepime or ceftazidime.   
- 
Anti-pseudomonal penicillin group: patients assigned to the anti-pseudomonal penicillin group will 
receive piperacillin-tazobactam or ticarcillin-clavulanate.  
- 
For patients in both groups, treating clinicians will determine the dose and duration of the assigned 
antibiotic class.  An EHR-based advisor will alert treating clinicians of group assignment and collect 
data regarding any adverse events and the reason for modification or discontinuation of antibiotics in 
the 7 days after randomization 
Primary Efficacy Outcome: 
- 
The primary outcome will be the highest stage of acute kidney injury (AKI) between enrollment and 
14 days after enrollment.  Stage of AKI will be defined by Kidney Disease: Improving Global 
Outcomes (KDIGO) AKI creatinine criteria.  Death will be classified as worse than the highest stage 
of AKI.  The outcome will be defined using the following 5-value ordinal scale ranging from the 
lowest value (0 = alive without having experienced AKI) to the highest value (4 = died). 
o 0 = No AKI 
o 1 = Stage 1 AKI (Creatinine increase by 1.5-1.9 times baseline OR increase by >= 0.3 
mg/dL) 
o 2 = Stage 2 AKI (Creatinine increase by 2.0-2.9 times baseline) 
o 3 = Stage 3 AKI (Creatinine increase by >= 3.0 times baseline OR increase to >= 4.0 mg/dL 
OR New RRT) 
o 4 = Death  
Secondary Outcomes: 
- 
Secondary Renal Outcome: Major Adverse Kidney Events within 14 days (MAKE14): Composite 
outcome of death within 14 days, new renal replacement therapy within 14 days, or stage 2 or higher 
AKI at day 14. 
- 
Secondary Neurologic Outcome:  The number of days alive and free of coma and delirium in the 14 
days after enrollment (Delirium and Coma-Free Days to day 14). 
 
Exploratory Outcomes: 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
- 
Exploratory Renal Outcomes: Major Adverse Kidney Events within 28 days (MAKE28), highest 
stage of AKI or death between randomization and day 7, stage 2 or higher acute kidney injury as 
defined in the KDIGO criteria for creatinine level within 14 and 28 days after enrollment, new receipt 
of renal-replacement therapy within 14 and 28 days after enrollment, days alive and free of renal-
replacement therapy during the 14 and 28 days after enrollment, the highest creatinine level within 28 
days after enrollment, the change from pre-illness creatinine to the highest creatinine level with 28 
days after enrollment, the final creatinine level before hospital discharge at 28 days, and ongoing 
receipt of renal replacement therapy at hospital discharge or 28 days, nephrology consultation. 
- 
Exploratory Neurologic Outcomes: Worst Glasgow Coma Scale score during the 7, 14, and 28 days 
after enrollment, Delirium and Coma Free Days in 28 days after enrollment 
- 
Exploratory Clinical Outcomes: ICU-free days, hospital-free days, ventilator-free days, vasopressor-
free days, 28-day mortality, 14-day mortality, disposition of patients admitted from the ED (ward vs 
ICU), escalation of antibiotics defined by subsequent receipt of meropenem, meropenem-
vaborbactam, imipenem, imipenem-relebactam, cefiderocol, ceftazidime-avibactam, ceftolozane-
tazobactam, tigecycline, amikacin, tobramycin, gentamicin 
 
Sample Size Considerations: 
- 
Our original sample size was calculated from 820 patients during the creation and testing of the 
enrollment advisor, where we measured the distribution of outcomes expected among patients in the 
anti-pseudomonal penicillin group.  We calculated that enrolling 2,050 patients would provide 80% 
power at an alpha of 0.05 to detect an odds ratio for highest stage of AKI of 0.65. 
 
Near the midpoint of the trial, we determined that about 75% of our patients received concurrent 
vancomycin, a key subgroup of interest. We increased the sample size to 2,500 patients to estimate 
the enrollment of the original sample size (2,050) in the subgroup of patients receiving concurrent 
vancomycin. 
 
2.0 Background 
Sepsis is a common condition associated with high mortality and morbidity1. Antibiotics are an integral 
component of the management of patients with sepsis2. Each hour delay in antibiotic administration in 
sepsis is associated with an increase in mortality3. Clinical guidelines recommend early management 
bundles, including early broad-spectrum antibiotics, for patients with presumed sepsis in the emergency 
department and intensive care unit2,4. Since the specific organism causing an infection is rarely known at 
clinical presentation, empiric broad-spectrum antibiotics are commonly prescribed5. For patients at risk 
for resistant organisms, the most common regimens include vancomycin (to cover gram-positive 
organisms including methicillin-resistant Staphylococcus aureus) and an anti-pseudomonal cephalosporin 
or anti-pseudomonal penicillin (to cover gram-negative organisms including Pseudomonas).  
 
2.1 Anti-Pseudomonal Cephalosporins as Part of an Empiric Broad Spectrum Regimen 
Cephalosporins are beta-lactam antibiotics that act by inhibiting the synthesis of the peptidoglycan layer 
of bacterial cell walls. They are commonly used for a variety of infections including empiric broad 
spectrum coverage for sepsis, suspected nosocomial infections, and meningitis.  Several cephalosporins 
have anti-pseudomonal activity, including cefepime, a fourth-generation cephalosporin, and ceftazidime, 
a third-generation cephalosporin.  Anti-pseudomonal cephalosporins have replaced anti-pseudomonal 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
penicillins as the preferred agent for empiric antibiotic regimens based on observational evidence that 
anti-cephalosporins are associated with a lower incidence of AKI6.  However, others have argued against 
this approach given the lack of randomized trials comparing the relative efficacy and safety of the two 
agents as well as observational data suggesting that cephalosporins may be associated with neuro-
toxicity7–9. 
 
2.2 Anti-Pseudomonal Penicillins as Part of an Empiric Broad Spectrum Regimen 
Penicillins are also beta-lactam anti-biotics with similar mechanisms of action to cephalosporins. Anti-
pseudomonal penicillins, such as piperacillin, ureidopenicillin, and ticarcillin are typically administered 
with a beta-lactamase inhibitor such as tazobactam or clavulanate. In the United States the most 
commonly used anti-pseudomonal penicillins are piperacillin-tazobactam and ticarcillin-clavulanate. 
Anti-pseudomonal penicillins are the preferred agents for empiric broad spectrum coverage at many 
centers, and piperacillin-tazobactam, specifically, has the added benefit of treating anaerobic organisms.  
Conversely, penicillins do not cover meningitis due to poor central nervous system penetration.   
 
2.3 Acute Kidney Injury during Critical Illness 
Acute Kidney Injury (AKI) is a common complication of ICU admission. AKI is associated with a six to 
eight fold increase in mortality in ICU populations, 10,11 is therefore a common target of critical care trials. 
There are many potential contributors to AKI in critical illness including isotonic fluids12, IV contrast 
administration, medication toxicities13, and acute illnesses like sepsis.  Sepsis is the most common cause 
of AKI and accounts for 40-50% of AKI in the intensive care unit (ICU)14,15. As the primary treatment for 
the underlying cause of sepsis, antibiotics are a critical treatment for acutely ill patients, but antibiotics 
may cause renal injury, and renally-cleared antibiotics may reach supratherapeutic levels in the setting of 
AKI.  
 
2.4 Prior Evidence of the Effect of Antibiotic Choice on Acute Kidney Injury 
Vancomycin has long been associated with AKI16,17. Recently, a number of retrospective observational 
analyses have examined a potential association between the concurrent administration of vancomycin and 
piperacillin-tazobactam and the development of AKI, compared with vancomycin alone18–21. These data, 
however, are likely to be confounded by indication bias and studies evaluating whether piperacillin-
tazobactam causes more AKI than other anti-pseudomonal antibiotics have been inconclusive.18,22–30.  
Studies that limited their analyses to the first 72 hours of treatment (when antibiotic choices are empiric 
and not yet tailored based on microbiologic data), have not shown any association between piperacillin-
tazobactam and kidney injury31.   
 
Based on this preliminary, observational data, however, some institutions have elected to change their 
preferred broad spectrum antibiotic regimens from one including an anti-pseudomonal to one including an 
anti-pseudomonal cephalosporins.   
 
2.5 Rationale for a Trial of Anti-Pseudomonal Cephalosporins vs Anti-Pseudomonal 
Penicillins 
Tens of thousands of patients each year receive either anti-pseudomonal cephalosporins and penicillins, 
but no randomized trials have ever compared their relative effectiveness or safety.  Each class of 
medications has been hypothesized to have toxicities that may be relevant for acutely ill patients. Because 
the relationship between antibiotic choice (anti-pseudomonal cephalosporins or anti-pseudomonal 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
penicillins) and clinically relevant outcomes, such as AKI, are unknown, clinical trial data is urgently 
needed.  Rigorous high-quality evidence that anti-pseudomonal cephalosporins, compared to anti-
pseudomonal penicillins, decreases, increases or has no impact on the risk of AKI would have the 
potential to change the care received by thousands of acutely ill adults each year. 
 
To address this knowledge gap, we will conduct a prospective, randomized trial of acutely ill adults 
undergoing initiation of empiric antibiotics in the ED or ICU, comparing anti-pseudomonal 
cephalosporins vs anti-pseudomonal penicillins with regard to renal outcomes.  
3.0 Rationale, Aims, and Hypotheses 
In order to determine the effect of an anti-pseudomonal cephalosporin, compared to an anti-pseudomonal 
penicillin, on the incidence of acute kidney injury among acutely ill patients, a randomized trial is needed. 
Study Aims: 
- 
Primary: 
o To compare the effect of anti-pseudomonal cephalosporins versus anti-pseudomonal 
penicillins on the incidence of acute kidney injury among acutely ill patients 
- 
Secondary: 
o To compare the effect of anti-pseudomonal cephalosporins vs anti-pseudomonal penicillins 
on in-hospital mortality, ICU length of stay, and ventilator days 
Study Hypotheses 
- 
Primary Hypothesis: 
o The use of anti-pseudomonal cephalosporins, compared to the use of anti-pseudomonal 
penicillins, will decrease the incidence of acute kidney injury among acutely ill adults   
 
4.0 Study Description 
In order to address the aims outlined above, we propose a randomized trial evaluating the impact of anti-
pseudomonal cephalosporins versus anti-pseudomonal penicillins in the treatment of sepsis in acutely ill 
adults. Patients admitted to a study unit who are deemed by their clinical team to require empiric broad 
spectrum antibiotics and fulfill inclusion criteria without meeting exclusion criteria will be enrolled and 
randomly assigned to an anti-pseudomonal cephalosporin vs an anti-pseudomonal penicillin.  
Randomization, group assignment and delivery of the intervention will occur within the electronic health 
record (details in section 7). All other decisions regarding treatment will remain at the discretion of the 
treating provider.  Data will be collected prospectively from the medical record to determine the effect of 
the assigned interventions on procedural, physiologic, and clinical outcomes. 
 
5.0 Inclusion/Exclusion Criteria 
 
5.1 Inclusion Criteria: 
1. Age ≥ 18 years old 
2. Located in a participating emergency department or medical intensive care unit  
3. Less than 12 hours from presentation to study hospital 
4. Treating clinician initiating an order for an anti-pseudomonal cephalosporin or anti-pseudomonal 
penicillin  

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
5.2 Exclusion Criteria: 
1. Known receipt of > 1 dose of an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin 
during the last 7 days 
2. Current documented allergy to cephalosporins or penicillin 
3. Known to be a prisoner 
4. Treating clinicians feel that either an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin 
is required or contraindicated for the optimal treatment of the patient, including for more directed 
antibiotic therapy against known prior resistant infections or suspected sepsis with an associated 
central nervous system infection   
6.0 Enrollment/Randomization 
6.1 Study Sites: 
Emergency Department and Medical Intensive Care Unit at Vanderbilt University Medical Center 
 
6.2 Study Population:  
All adults with sepsis located in a participating unit for whom the treating clinician orders either an anti-
pseudomonal cephalosporins or anti-pseudomonal penicillin within 12 hours of hospital presentation 
unless determined to meet an exclusion criteria. All eligible patients will be included and there will be no 
selection based on gender, race, weight or other clinical factors.  
 
6.3 Enrollment:  
At the time that a treating clinician in a participating emergency department or medical intensive care unit 
initiates an order for an anti-pseudomonal cephalosporin or anti-pseudomonal penicillin for a patient who 
meets all inclusion criteria, an advisor within the electronic health record (details in section 7) will prompt 
treating clinicians to record whether the patient meets any exclusion criteria.  Patients not meeting any 
exclusion criteria will be enrolled and randomized.  For patients who are determined to be ineligible, the 
advisor will track the number and reasons for exclusion.  The time of randomization will be defined as 
“time zero” on “study day 0.”  
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
 
  
Figure 6: Enrollment Schema – When a treating clinician orders an anti-pseudomonal 
cephalosporin or anti-pseudomonal penicillin, tools within the electronic health record (details in 
section 7) will evaluate if the patient meets inclusion criteria (order placed within 12 hours of 
hospital presentation, age ≥ 18, and located in a participating unit), and the presence of 
documented allergy to penicillin or cephalosporins (an exclusion criteria).  If the patient has not 
been previously enrolled in the trial during the index hospitalization, appears to meet all inclusion 
criteria, does not have a documented allergy to penicillin or cephalosporins, an ordering advisor 
will prompt the clinician to determine whether the patient meets any exclusion criteria. If the 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
treating clinician confirms that the patient does meet an exclusion criterion, the patient will be 
enrolled and randomized.  The ordering advisor will track all exclusions. 
 
6.4 Consent:  
Anti-pseudomonal cephalosporins and anti-pseudomonal penicillins are routinely used in the care of 
acutely ill patients with sepsis in the emergency department and intensive care units at Vanderbilt 
University Medical Center.  Currently, choice of empiric gram-negative coverage is based primarily on 
provider preference as there are no large randomized trials or evidence-based guidelines to support the 
choice of one empiric anti-pseudomonal therapy for sepsis over another.  The concept of a randomized 
trial comparing anti-pseudomonal cephalosporins versus anti-pseudomonal penicillins has been discussed 
with the leaders of emergency department and intensive care units and representation from the infectious 
diseases and nephrology programs who agree that clinical equipoise exists regarding the choice of empiric 
anti-pseudomonal therapy for acutely ill adults with sepsis. 
 
Because the interventions studied (1) are used as a part of routine care, (2) are interventions the patient 
would be exposed to even if not participating in the study, (3) have no prior high-quality data to suggest 
the superiority of one approach over the other, and (4) are equivalent options from the perspective of the 
treating provider (otherwise the patient is excluded), we feel the study presents minimal risk. 
 
In addition to the minimal risk posed by the study, obtaining informed consent prior to participation 
would not be feasible or practicable.  Sepsis is a medical emergency.  Each hour of delay in the initiation 
of antibiotics for acutely ill patients with sepsis increases mortality by about 7%.  For patients presenting 
with sepsis to the participating units, the average time between initiation of an order for an anti-
pseudomonal antibiotic and its administration to the patient is 28 minutes.  Obtaining prospective written 
informed consent during this interval is impracticable and risks delaying antibiotic administration.  
Moreover, acutely ill patients with sepsis are commonly delirious or unconscious, and a legally authorized 
representative (LAR) is not consistently present at the time of initiation of antibiotics.  Because the trial 
determines choice of the initial anti-pseudomonal antibiotic, but defers decisions regarding subsequent 
doses of antibiotics (e.g., duration of therapy, escalation, de-escalation) to treating clinicians, the primary 
study procedure will be completed within 1 hour of meeting eligibility criteria. 
 
 
Because the study presents minimal risk, would not adversely affect the welfare or privacy rights of the 
participant, and consent would be impracticable, we will request a waiver of informed consent. 
 
6.5 Randomization:  
A series of study group assignments will be generated by computerized randomization in a 1:1 ratio of 
intervention to control.  Study group assignment will remain concealed to study personnel and treatment 
team until after the study team has confirmed that the patient does not meet any exclusion criteria and the 
patient has been enrolled.   Following randomization, treating clinicians will be notified via the ordering 
advisor. 
 
7.0 Study Procedures 
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
7.1 Electronic Health Record (EHR) Based Screening for Eligible Patients 
For the duration of the study, when a provider initiates an order for the administration of an intravenous 
anti-pseudomonal cephalosporin or anti-pseudomonal penicillin, a software application in the EHR will 
assess if the patient is eligible for the study. The application will assess that the patient meets all the 
inclusion criteria (located in study unit, age ≥ 18, in the hospital for less than 12 hours, and has not been 
previously enrolled during the hospitalization) and none of the exclusion criteria (current documented 
allergy to cephalosporin or penicillin class antibiotics, more than one prior administration of study 
antibiotics during the last 7 days). If the above criteria are met, an order advisor (Figure 7) will: 1) Inform 
the provider of the study, 2) solicit the presence of contraindications to either study drug, 3) (if patient 
meets all eligibility criteria) enroll and randomize the patient. If there are contraindications which were 
not established electronically, the advisor will ask the provider to select the reason. 
 
 
Figure 7: Order advisor informing providers of the study and soliciting other exclusion criteria 
 
7.2 Antibiotic Ordering after Randomization 
Once the participant is enrolled and randomized, the ordering advisor will guide the provider to the order 
one of the assigned study antibiotics. Dose, frequency, and duration will be at the discretion of treating 
clinicians and not affected by the advisor. 
 
7.3 EHR-Based Tool to Capture Data on Antibiotic Modification and Adverse Events  
In the 7 days after enrollment, if a clinician attempts the discontinue the study-related antibiotic order, an 
EHR-based advisor will remind the clinician of the treatment arm and if the treating clinician chooses to 
discontinue the antibiotic from the assigned group, the clinician will be asked for the rationale: 
- 
Antibiotic tailoring (escalation or de-escalation) based on microbiologic data 
- 
Undocumented or newly apparent allergy to either penicillins or cephalosporins 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
- 
Treating clinicians feel that either anti-pseudomonal cephalosporins or anti-pseudomonal penicillins 
are superior in the optimal treatment of the patient (provide reason why) 
- 
Other (provider input rationale) 
- 
Antibiotic induced adverse event 
 
Data provided by the treating clinicians will be used for prospective safety monitoring and adverse event 
reporting. 
 
7.4 Duration of the Intervention 
Patients will be allocated to the anti-pseudomonal cephalosporin or anti-pseudomonal penicillin groups 
which will determine their initial antibiotic choice only. All further antibiotic decisions including, but not 
limited to, duration of antibiotics, changing based on new clinical or microbiological data, and switching 
between classes of anti-pseudomonal antibiotics will be left to the discretion of the treating team. 
 
As described above, an EHR-based advisor will alert treating clinicians to group assignment and collect 
data for monitor for adverse events occurring in the seven days after randomization.  The advisor will not 
impede the ability to change classes of antibiotic and will be used primarily for safety monitoring.  
 
7. 5 Blinding:  
It would be impractical to pursue blinding for the study. The medicines involved in this study are given at 
different doses with varying volumes of IV infusion. They are also given on different schedules varying 
as widely as 4 times a day to once daily. Furthermore, these dosing variations are impacted by renal 
function. Given the nature of the study intervention, patients, clinicians, and investigators will not be 
blinded to group assignment.   
 
8.0 Data Collection: 
 
8.1 In-Hospital Outcomes:  
Primary Efficacy Outcome: Acute Kidney Injury Score between randomization and day 14. The acute 
kidney injury score is an ordinal outcome containing the stages of AKI as defined by KDIGO creatinine 
criteria, new renal replacement therapy (RRT), and death: 
 
0 = No AKI 
1 = Stage 1 AKI (Creatinine increase by 1.5-1.9 times baseline OR increase by >= 0.3 mg/dL) 
2 = Stage 2 AKI (Creatinine increase by 2.0-2.9 times baseline) 
3 = Stage 3 AKI (Creatinine increase by >= 3.0 times baseline OR increase to >= 4.0 mg/dL OR 
New RRT) 
4 = Death  
 
“Baseline” creatinine values are defined as the lowest prior creatinine values from three different 
timepoints: the pre-illness creatinine value, the peri-enrollment creatinine value, and the lowest prior on-
study creatinine value. Death is defined as in-hospital mortality from any cause prior to hospital 
discharge, censored at 14 days. New RRT is defined as receipt of RRT at any point between ICU 
admission and hospital discharge, censored at 14 days.   

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
 
Pre-illness creatinine level will be determined by using a previously described hierarchical approach in 
which creatinine values obtained during the year before hospitalization are given priority over in-hospital 
measurements obtained before antibiotic administration. When no pre-enrollment measurements are 
available, the pre-illness creatinine level is estimated with a previously described three-variable 
formula32,33. It is important to note that those patients with End-Stage Renal Disease (ESRD) would only 
be eligible to meet the “Death” component of the primary outcome. 
Patients’ peri-enrollment creatinine will be defined hierarchically using the creatinine value closest to 
enrollment in: (first) the 24 hours prior to enrollment, if available, and (second) the six hours after 
enrollment (if no value is available prior to enrollment).  Prevalent AKI, or AKI that is present on 
admission and unrelated to the study intervention, will be defined by comparing the peri-enrollment 
creatinine to the pre-illness creatinine.  
On-study creatinine will be defined as any creatinine value occurring after both the time of enrollment 
and the time of the peri-enrollment creatinine value. On-study creatinine values will be used to identify 
incident AKI and calculate the stage of AKI for the primary outcome.   
 
Justification for the Primary Efficacy Outcome 
This outcome is 1) validated for electronic assessment, 2) uses outcome thresholds for renal dysfunction 
defined by international nephrology organizations, 3) incorporates patient-centered outcomes (new RRT 
and death) that would be missed by a purely laboratory-based outcome, and 4) uses a hierarchal approach 
to analysis that counts rare but important patient-centered outcomes (new RRT, death) as worse than 
purely laboratory-based measures (stage 2 AKI).  
 
Secondary Outcomes: 
- 
Secondary Renal Outcome: Major Adverse Kidney Events within 14 days (MAKE14): Composite 
outcome of death within 14 days, new renal replacement therapy within 14 days, or stage 2 or higher 
AKI at day 14. 
- 
Secondary Neurologic Outcome:  The number of days alive and free of coma and delirium in the 14 
days after enrollment (Delirium and Coma-Free Days to day 14). 
 
Exploratory Outcomes:  
- 
Exploratory Renal Outcomes: Major Adverse Kidney Events within 28 days (MAKE28), highest 
stage of AKI or death between randomization and day 7, stage 2 or higher acute kidney injury as 
defined in the KDIGO criteria for creatinine level within 14 and 28 days after enrollment, new receipt 
of renal-replacement therapy within 14 and 28 days after enrollment, days alive and free of renal-
replacement therapy during the 14 and 28 days after enrollment, the highest creatinine level within 28 
days after enrollment, the change from pre-illness creatinine to the highest creatinine level with 28 
days after enrollment, the final creatinine level before hospital discharge at 28 days, and ongoing 
receipt of renal replacement therapy at hospital discharge or 28 days, nephrology consultation. 
- 
Exploratory Neurologic Outcomes: Worst Glasgow Coma Scale score during the 7, 14, and 28 days 
after enrollment, Delirium and Coma Free Days in 28 days after enrollment 
- 
Exploratory Clinical Outcomes: ICU-free days, hospital-free days, ventilator-free days, vasopressor-
free days, 28-day mortality, 14-day mortality, disposition of patients admitted from the ED (ward vs 
ICU), escalation of antibiotics defined by subsequent receipt of meropenem, meropenem-

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
vaborbactam, imipenem, imipenem-relebactam, cefiderocol, ceftazidime-avibactam, ceftolozane-
tazobactam, tigecycline, amikacin, tobramycin, gentamicin 
 
8.2 Baseline data:  
Age, sex, height, weight, body mass index, race, SOFA score, active medical problems at the time of 
admission, active comorbidities, comorbidities and medications known to increase risk of kidney or 
neurologic injury at enrollment, mean arterial pressure and vasopressor use prior to antibiotic receipt, 
analgesia and sedation use prior to antibiotic receipt, presence of sepsis define by Sepsis-3 criteria, 
transplant recipient status, presumed source of infection, on renal replacement therapy prior to receipt of 
antibiotics, admission to ICU vs ward 
 
 
8.3 Data from enrollment to hospital discharge:  
Mean arterial pressure and vasopressor use, pH, PaO2, PaCO2, respiratory rate, heart rate, oxygen 
saturation, temperature, lactic acid, elements of a basic metabolic panel, magnesium, elements of a 
complete blood count, all microbiologic culture data, CAM-ICU, RASS, GCS mechanical ventilation 
status and variables related to ventilation, nephrology consultation, new-start renal replacement therapy, 
indications for new renal replacement therapy among patients who received new renal replacement 
therapy, medications known to increase risk of kidney injury, medications known to increase risk of 
neurologic injury, days spent in ICU, days spent in the hospital, date of intubation and extubation, date of 
death 
 
8.4 Outcome Data:  
Primary Outcome: All creatinine values from presentation to day 14, creatinine values prior to 
hospitalization, and dates and times of the following events, if applicable: presentation to the hospital, 
receipt of new renal replacement therapy, admission to the hospital, discharge from the hospital, death 
 
Exploratory Renal Outcomes: All creatinine values from presentation to hospital discharge, creatinine 
values prior to hospitalization, and the dates and times of the following events, if applicable: presentation 
to the hospital, receipt of new renal replacement therapy, admission to the hospital, discharge from the 
hospital, death, nephrology consultation 
 
Exploratory Neurologic Outcomes: All RASS values/dates/times from presentation to day 28, all CAM-
ICU values/dates/time from presentation to day 28, all GCS values/dates/times from presentation to day 
28 
 
Exploratory Clinical Outcomes: Date and time of the following events, if applicable: presentation to the 
hospital, admission to the hospital, admission to the ICU, transfer from the ICU, discharge from the 
hospital, receipt of mechanical ventilation, discontinuation of mechanical ventilation, receipt of 
vasopressors, discontinuation of vasopressors, death, antibiotic receipt 
 
9.0 Risks and Benefits 
In patients for whom the treating team has decided empiric broad spectrum antibiotics are required for the 
treatment of sepsis, there are currently no established risks or benefits to using anti-pseudomonal 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
cephalosporins or anti-pseudomonal penicillins as empiric gram negative coverage.  At this time, there is 
no reason to believe that participation in this study would expose patients to greater medical risks or 
benefits than those experienced by acutely ill patients requiring antibiotics as a part of routine care.  The 
greater benefit of the study would be to society in the form of improved understanding of safe and 
effective empiric antibiotic selection for acutely ill patients with sepsis. 
 
A potential risk to patients participating in this study involves the collection of protected health 
information (PHI).  In order to limit the associated risks, the minimum amount of PHI necessary for study 
conduct will be collected.  After collection, the data will be stored in a secure online database (REDCap) 
only accessible by the investigators.  After publication, a de-identified database will be generated to 
protect participant privacy. 
 
10.0 Statistical Considerations 
 
Sample size considerations 
Using data captured during the development and testing of the enrollment advisor (trial intervention) from 
820 patients who would have been eligible for ACORN, we estimated the distribution of the primary 
outcome in the anti-pseudomonal penicillin group.  A total of 61.2% of patients did not experience AKI 
or death, 4.9% had Stage I AKI, 4.3% had Stage II AKI, 8.0% had Stage III AKI or new RRT, and 21.5% 
died within 30 days of ICU admission. We calculated that obtaining 80% power at an alpha of 0.05 to 
detect an odds ratio of 0.65 for patients assigned to anti-pseudomonal cephalosporins would require a 
sample size of 2010. Assuming missing data for 40 patients, or < 5%, we planned to enroll 2050 patients. 
 
Sample size re-estimation 
At the planned interim analysis after 1025 patients, or roughly half of the intended enrollment, the DSMB 
will evaluate the distribution of the primary outcome in the anti-pseudomonal penicillin group. If required 
by the observed distribution of the primary outcome in the anti-pseudomonal penicillin group, the DSMB 
may recommend that the investigators increase the total sample size of the trial to maintain 80% power 
and an alpha of 0.05 to detect an odds ratio of 0.65. 
 
Near the midpoint of the trial, we determined that about 75% of the total population received concurrent 
vancomycin, an important subgroup of interest. We increased the sample size from the original 2,050 
patients to 2,500 patients to estimate the original sample size in the subgroup of the receipt of concurrent 
vancomycin. Given our faster than expected enrollment, the trial is estimated to complete at the originally 
proposed endpoint. This would provide 92% power to detect and OR of 0.75 at an alpha of 0.05 in the 
primary analysis cohort. This was presented to the DSMB at the interim analysis who agreed with the 
sample size increase. 
 
Statistical Analysis: 
Analysis principles 
- 
Primary analysis will be conducted on an intention-to-treat basis (patients with protocol violations are 
analyzed per the assigned treatment arm). 
- 
All hypothesis tests will be two sided, with an α of 0.05 unless otherwise specified. 
- 
All analyses will be unadjusted unless otherwise specified. 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
- 
Pre-specified analyses of heterogeny of treatment effect based on baseline variables will be performed 
irrespective of treatment efficacy. 
 
Trial profile:  
We will present a Consolidated Standards of Reporting Trials diagram to detail the movement of patients 
through the study. This diagram will include total number of patients meeting inclusion criteria, number 
excluded and reason for exclusion, number enrolled and randomized in the study, number followed, and 
number analyzed. 
 
Baseline Characteristics:  
To assess randomization success, we will summarize in Table 1 the distribution of baseline variables 
across the study arms. Categorical variables will be reported as frequencies and percentages and 
continuous variables as either means with SDs or medians with interquartile ranges. Variables reported 
will include Demographics (age, gender, race, BMI, co-morbidities); Indication for antibiotics; Severity 
of Illness (APACHE II score); Acute Kidney Injury at enrollment; Delirium at enrollment 
 
Primary Efficacy Outcome Analysis: 
We will compare the primary outcome, the AKI ordinal outcome, between patients randomized to the 
anti-pseudomonal cephalosporins versus anti-pseudomonal penicillins groups. It is important to note that 
those patients with End-Stage Renal Disease (ESRD) would only be eligible to meet the “Death” 
component of the primary outcome. 
 
The main analysis will be an intention-to-treat comparison of the primary outcome between the anti-
pseudomonal cephalosporin and anti-pseudomonal penicillin groups who received at least one dose of a 
study drug. To do this, we will use an unadjusted, proportional odds model with group assignment (anti-
pseudomonal cephalosporin, anti-pseudomonal penicillin) as the independent variable.  For the purposes 
of declaring a statistically significant difference between groups in the primary endpoint, we will consider 
a two-sided P value of 0.05 as significant. 
 
Secondary Analyses of the Primary Outcome 
To account for potential confounders, we will develop an adjusted proportional odds regression model 
with the AKI ordinal outcome score (primary outcome) as the dependent variable and independent 
covariate of groups assignment, and relevant confounders (age, peri-enrollment creatinine, sex, 
mechanical ventilation prior to enrollment, receipt of inotropes prior to enrollment, receipt of RRT prior 
to enrollment, SOFA score, presumed source of infection, enrollment location). 
 
Secondary Analyses: 
Analysis of Secondary and Exploratory Outcomes 
We will conduct an intention-to-treat comparison of all secondary and exploratory outcomes between 
patients randomized to anti-pseudomonal cephalosporins and patients randomized to anti-pseudomonal 
penicillins. Continuous outcomes will be compared with the Mann-Whitney U test and categorical 
variables with the chi-square test or Fischer’s exact test, as appropriate. 
 
Heterogeny of Treatment Effect 
We will examine the effect of group assignment on the primary outcome relative to a set of pre-specified 
baseline variables.  These variables will be prespecified as part of a formal statistical analysis plan 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
completed and made public prior to the completion of enrollment.  A formal test of interaction will be 
used to evaluate for effect modification. 
 
Presentation of Statistics 
Continuous variables will be described as mean and standard deviation or median and interquartile range 
or bootstrapped 95% confidence intervals as appropriate.  Categorical variables will be given as number 
and percentage.  All between-group comparisons with continuous variables will be performed using 
Mann-Whitney U tests; categorical variables will be compared with chi-square testing or Fisher’s exact 
test as appropriate. 
 
Interim Analysis 
We will plan for the DSMB to conduct a single interim analysis for efficacy and safety at the anticipated 
halfway point of the trial, after enrollment of 1025 patients.  The stopping boundary for efficacy will be 
met if the P value for the difference between groups in the primary outcome is 0.001 or less.  Use of the 
conservative Haybittle-Peto boundary (P < 0.001) will allow the final analysis to be performed using an 
unchanged level of significance (P = 0.05).  Given the minimal risk nature of the study and current use of 
both interventions as a part of usual care, there will be no stopping boundary for futility.  At the interim 
analysis, the DSMB will also monitor the distribution of the AKI ordinal outcome within the anti-
pseudomonal penicillin group and may propose to increase the planned sample size to maintain the pre-
planned power to detect an odds ratio of 0.65.  
 
11.0 Reporting of Adverse Events or Unanticipated Problems 
Assuring patient safety is an essential component of this protocol. All medications used in this trial are 
approved by the Food and Drug Administration and used in clinical practice with an established safety 
profile. This protocol further ensures safety of its participants through: 
a) Exclusion criteria designed to prevent enrollment of patients likely to experience adverse events 
from the study antibiotics; 
b) Systematic collection of safety outcomes relevant to the use of anti-pseudomonal cephalosporins 
and anti-pseudomonal penicillins in this setting; 
c) Structured monitoring, assessment, recording, and reporting of adverse events. 
 
11.1 Adverse Event Definitions 
Adverse Event – An adverse event will be defined as any untoward or unfavorable medical 
occurrence in a human subject temporally associated with the subject’s participation in the research, 
whether or not considered related to the subject’s participation in the research.  Any adverse event 
occurring during the research will be classified according to the following characteristics: 
 
● Seriousness – An adverse event will be considered “serious” if it: 
o Results in death; 
o Is life-threatening (defined as placing the patient at immediate risk of death); 
o Results in inpatient hospitalization or prolongation of existing hospitalization;  
o Results in a persistent or significant disability or incapacity; 
o Results in a congenital anomaly or birth defect; or  

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
o Based upon appropriate medical judgment, may jeopardize the patient’s health and may 
require medical or surgical intervention to prevent one of the other outcomes listed in this 
definition. 
 
● Unexpectedness – An adverse event will be considered “unexpected” if the nature, severity, or 
frequency is neither consistent with: 
o The known or foreseeable risk of adverse events associated with the procedures involved 
in the research that are described in the protocol-related documents, such as the IRB-
approved research protocol; nor 
o The expected natural progression of any underlying disease, disorder, or condition of the 
subject experiencing the adverse event and the subject’s predisposing risk factor profile 
for the adverse event. 
 
● Relatedness – The strength of the relationship of an adverse event to a study intervention or 
study procedure will be defined as follows:  
o Definitely Related: The adverse event follows (1) a reasonable, temporal sequence from a 
study procedure AND (2) cannot be explained by the known characteristics of the 
patient’s clinical state or other therapies AND (3) evaluation of the patient’s clinical state 
indicates to the investigator that the experience is definitely related to study procedures.  
o Probably or Possibly Related: The adverse event meets some but not all of the above 
criteria for “Definitely Related”. 
o Probably Not Related: The adverse event occurred while the patient was on the study but 
can reasonably be explained by the known characteristics of the patient’s clinical state or 
other therapies.  
o Definitely Not Related: The adverse event is definitely produced by the patient’s clinical 
state or by other modes of therapy administered to the patient.  
o Uncertain Relationship: The adverse event does not fit in any of the above categories. 
 
11.2 Monitoring for Adverse Events 
The time interval during which patients will be monitored for the occurrence of adverse events begins at 
randomization and ends at the first of hospital discharge or 28 days.  Adverse events occurring before 
randomization or after hospital discharge or 28 days will not be collected. In this trial, enrollment, 
randomization, intervention delivery, monitoring for safety and adverse events and outcome assessment 
will all take place within the electronic health record.  As described an EHR-based advisor will 
continuously monitor for discontinuation of study drug and require that clinicians identify reason for 
discontinuation.  Every time a study drug is discontinued, investigators will be notified in real-time 
using an automated lists within the EHR.  Investigators will investigate and adjudicate potential adverse  
as close as feasible to 24 hours after initial report by treating clinicians.  Investigators will assess any 
potential adverse events for whether the adverse event meets the criteria for recording and reporting 
outlined below. 
 
11.3 Recording and Reporting Adverse Events 
The following types of adverse events will be recorded and reported: 
● Adverse events that are Serious and Definitely Related, Probably or Possibly Related, or of 
Uncertain Relationship. 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
● Adverse events that are Unexpected and Definitely Related, Probably or Possibly Related, or of 
Uncertain Relationship. 
 
Adverse events that do not meet the above criteria will not be recorded or reported.  Adverse events that 
the investigator assesses to meet the above criteria for recording and reporting will be entered into the 
adverse event electronic case report form in the trial database.  The investigator will record a 
preliminary assessment of each characteristic for the adverse event, including seriousness, 
unexpectedness, and relatedness.  For any adverse event that is serious AND unexpected, and 
definitely related, probably or possibly related, or of uncertain relationship, the investigator will report 
the adverse event to the principal investigator within 24 hours of the investigator becoming aware of 
the adverse event.  For any other adverse event requiring recording and reporting, the investigator will 
report the adverse event to the principal investigator within 72 hours of the investigator becoming 
aware of the adverse event.  The principal investigator will make the final determination regarding each 
characteristic for the adverse event, including seriousness, expectedness, and relatedness.   
 
For adverse events that meet the above criteria for recording and reporting, the coordinating center will 
notify the DSMB, the IRB, and the sponsor in accordance with the following reporting plan: 
Characteristics of the Adverse Event 
Reporting Period 
Fatal or life-threatening (and therefore serious), 
unexpected, and definitely related, probably or 
possibility related, or of uncertain relationship. 
Report to the DSMB, IRB, and sponsor 
within 7 days after notification of the 
event. 
Serious but non-fatal and non-life-threatening, 
unexpected, and definitely related, probably or 
possibly related, or of uncertain relationship. 
Report to DSMB, IRB, and sponsor within 
15 days of notification of the event. 
All other adverse events meeting criteria for 
recording and reporting. 
Report to DSMB in regularly scheduled 
DSMB safety reports. 
The investigator will distribute the written summary of the DSMB’s periodic review of reported adverse 
events to the IRB in accordance with NIH guidelines: (http://grants.nih.gov/grants/guide/notice-
files/not99-107.html). 
 
11.4 Clinical Outcomes that may be Exempt from Adverse Event Recording and Reporting 
In this study of critically ill patients at high risk for death and other adverse outcomes due to their 
underlying critical illness, clinical outcomes, including death and organ dysfunction, will be 
systematically collected and analyzed for all patients. The primary, secondary, and exploratory 
outcomes will be recorded and reported as clinical outcomes and not as adverse events unless treating 
clinicians or site investigators believe the event is Definitely Related or Probably or Possibly Related to 
the study intervention or study procedures.  This approach – considering death and organ dysfunction as 
clinical outcomes rather than adverse events and systemically collecting these clinical outcomes for 
analysis – is common in ICU trials. This approach ensures comprehensive data on death and organ 
dysfunction for all patients, rather than relying on sporadic adverse event reporting to identify these 
important events.  The following events are examples of study-specific clinical outcomes that would not 
be recorded and reported as adverse events unless treating clinicians or site investigators believe the 
event was Definitely Related or Probably or Possibly Related to the study intervention or study 
procedures: 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
● Death (all deaths occurring prior to hospital discharge or 28 days will be recorded); 
● Organ dysfunction 
o Circulatory failure, including hypotension, cardiac arrest or shock with or without 
receipt of vasopressors; 
o Acute renal failure 
o Delirium or coma 
● Duration of mechanical ventilation; 
● Duration of ICU admission; 
● Duration of hospitalization 
 
Note: A study-specific clinical outcome may also qualify as a reportable adverse event.  For example, 
anaphylaxis that the investigator considers Definitely Related to an anti-pseudomonal penicillin would 
be both recorded as a study-specific clinical outcome and reported as a Serious and Definitely Related 
Adverse Event. 
  
11.5 Unanticipated Problems involving Risks to Subjects or Others 
Investigators must also report to the principal investigator Unanticipated Problems Involving Risks to 
Subjects or Others (“Unanticipated Problems”), regardless of severity, associated with study procedures 
within 24 hours of the investigator becoming aware of the Unanticipated Problem. An Unanticipated 
Problem is defined as any incident, experience, or outcome that meets all of the following criteria:  
● Unexpected (in terms of nature, severity, or frequency) given (a) the research procedures that 
are described in the protocol-related documents, such as the IRB-approved research protocol; 
and (b) the characteristics of the subject population being studied; AND 
● Definitely Related or Probably or Possibly Related to participation in the research (as defined 
above in the section on characteristics of adverse events); AND  
● Suggests that the research places subjects or others at a greater risk of harm (including 
physical, psychological, economic, or social harm) than was previously known or recognized.  
Upon becoming aware of any event that may represent an Unanticipated Problem, the investigator will 
assess whether the event represents an Unanticipated Problem by applying the criteria described above.  
If the investigator determines that the event represents an Unanticipated Problem, the investigator will 
record the Unanticipated Problem in the Unanticipated Problem electronic case report form in the trial 
database.  The investigators will obtain information about the Unanticipated Problem and report the 
Unanticipated Problem to the DSMB, IRB, and sponsor within 15 days of becoming aware of the 
Unanticipated Problem. 
 
12.0 Privacy/Confidentiality Issues 
At no time during the course of this study, its analysis, or its publication will patient identities be revealed 
in any manner. The minimum necessary data containing patient or provider identities will be collected. As 
quickly as feasible, all data collected will be uploaded into a password-protected computerized database 
maintained within a secure, web-based application for building and managing online databases 
(REDCap), or stored on secure servers with user-level access control. All patients will be assigned a 
unique study number for use in the computerized database. At the time of publication all identifiers will 
be removed. 
 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
13.0 Follow-up and Record Retention 
Patients will be followed after enrollment for 28 days or until hospital discharge, whichever occurs first.  
Data collected from the medical record will be entered into the secure online database REDCap. All data 
will be maintained in the secure online database REDCap until the time of study publication.  At the time 
of publication, a de-identified version of the database will be generated. 
14.0 Data and Safety Monitoring Board (DSMB) 
The principal role of the DSMB is to assure the safety of patients in the trial. They will regularly monitor 
data from this trial, review and assess the performance of its operations, and make recommendations to 
the steering committee and sponsor with respect to:  
- 
Participant safety and risk/benefit ratio of study procedures and interventions 
- 
Protocol amendments (with specific attention to study population, intervention, and study procedures) 
- 
Adherence to the protocol requirements 
- 
Completeness, quality, and planned analysis of data  
- 
Ancillary study burden on participants and main study  
- 
Possible early termination of the trial because of new external information, early attainment of study 
objectives, safety concerns, or inadequate performance 
The DSMB will consist of members with expertise in critical care medicine, infectious disease, 
biostatistics, and clinical trials. Appointment of all members is contingent upon the absence of any 
conflicts of interest. All the members of the DSMB are voting members. The Principal Investigator and 
unblinded study biostatistician will be responsible for the preparation of all DSMB and adverse event 
reports. The DSMB will develop a charter and review the protocol and patient notification forms during 
its first meeting. Subsequent DSMB meetings will be scheduled in accordance with the DSMB Charter 
with the assistance of the Principal Investigator. The DSMB will have the ability to recommend that the 
trial end, be modified, or continued unchanged. 
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Management of Sepsis and Septic Shock: 2016. Intensive Care Med. 2017;43(3):304-377. 
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3.  Liu VX, Fielding-Singh V, Greene JD, et al. The Timing of Early Antibiotics and Hospital Mortality 
in Sepsis. Am J Respir Crit Care Med. 2017;196(7):856-863. doi:10.1164/rccm.201609-1848OC 
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with sepsis bundles and mortality: a systematic review and meta-analysis of observational studies. 
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prescription for adults with pneumonia in the emergency department. BMC Pulm Med. 2020;20. 
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Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
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Injury in Critically Ill Patients Receiving Vancomycin with Concomitant Piperacillin-Tazobactam, 
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19.  Rutter WC, Burgess DR, Talbert JC, Burgess DS. Acute kidney injury in patients treated with 
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Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
20.  Long B, April MD. Are Patients Receiving the Combination of Vancomycin and Piperacillin-
Tazobactam at Higher Risk for Acute Renal Injury? Ann Emerg Med. 2018;72(4):467-469. 
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21.  Carreno J, Smiraglia T, Hunter C, Tobin E, Lomaestro B. Comparative incidence and excess risk of 
acute kidney injury in hospitalised patients receiving vancomycin and piperacillin/tazobactam in 
combination or as monotherapy. Int J Antimicrob Agents. 2018;52(5):643-650. 
doi:10.1016/j.ijantimicag.2018.08.001 
22.  Downes KJ, Cowden C, Laskin BL, et al. Association of Acute Kidney Injury With Concomitant 
Vancomycin and Piperacillin/Tazobactam Treatment Among Hospitalized Children. JAMA Pediatr. 
2017;171(12):e173219. doi:10.1001/jamapediatrics.2017.3219 
23.  Buhlinger KM, Fuller KA, Faircloth CB, Wallace JR. Effect of concomitant vancomycin and 
piperacillin-tazobactam on frequency of acute kidney injury in pediatric patients. Am J Health-Syst 
Pharm AJHP Off J Am Soc Health-Syst Pharm. 2019;76(16):1204-1210. doi:10.1093/ajhp/zxz125 
24.  O’Callaghan K, Hay K, Lavana J, McNamara JF. Acute kidney injury with combination vancomycin 
and piperacillin-tazobactam therapy in the ICU: A retrospective cohort study. Int J Antimicrob 
Agents. Published online May 12, 2020:106010. doi:10.1016/j.ijantimicag.2020.106010 
25.  Hammond DA, Smith MN, Painter JT, Meena NK, Lusardi K. Comparative Incidence of Acute 
Kidney Injury in Critically Ill Patients Receiving Vancomycin with Concomitant Piperacillin-
Tazobactam or Cefepime: A Retrospective Cohort Study. Pharmacotherapy. 2016;36(5):463-471. 
doi:10.1002/phar.1738 
26.  Kang S, Park J, Yu YM, Park MS, Han E, Chang MJ. Comparison of acute kidney injury and clinical 
prognosis of vancomycin monotherapy and combination therapy with beta-lactams in the intensive 
care unit. PloS One. 2019;14(6):e0217908. doi:10.1371/journal.pone.0217908 
27.  Buckley MS, Hartsock NC, Berry AJ, et al. Comparison of acute kidney injury risk associated with 
vancomycin and concomitant piperacillin/tazobactam or cefepime in the intensive care unit. J Crit 
Care. 2018;48:32-38. doi:10.1016/j.jcrc.2018.08.007 
28.  Hammond DA, Smith MN, Li C, Hayes SM, Lusardi K, Bookstaver PB. Systematic Review and 
Meta-Analysis of Acute Kidney Injury Associated with Concomitant Vancomycin and 
Piperacillin/tazobactam. Clin Infect Dis Off Publ Infect Dis Soc Am. 2017;64(5):666-674. 
doi:10.1093/cid/ciw811 
29.  Molina KC, Barletta JF, Hall ST, Yazdani C, Huang V. The Risk of Acute Kidney Injury in Critically 
Ill Patients Receiving Concomitant Vancomycin With Piperacillin-Tazobactam or Cefepime. J 
Intensive Care Med. Published online February 10, 2019:885066619828290. 
doi:10.1177/0885066619828290 
30.  Luther MK, Timbrook TT, Caffrey AR, Dosa D, Lodise TP, LaPlante KL. Vancomycin Plus 
Piperacillin-Tazobactam and Acute Kidney Injury in Adults: A Systematic Review and Meta-
Analysis. Crit Care Med. 2018;46(1):12-20. doi:10.1097/CCM.0000000000002769 

Study Protocol 
Full Study Title: Effect of Antibiotic Choice On ReNal Outcomes (ACORN) 
Primary Investigator: Edward Qian, MD 
31.  Schreier DJ, Kashani KB, Sakhuja A, et al. Incidence of Acute Kidney Injury Among Critically Ill 
Patients With Brief Empiric Use of Antipseudomonal β-Lactams With Vancomycin. Clin Infect Dis 
Off Publ Infect Dis Soc Am. 2019;68(9):1456-1462. doi:10.1093/cid/ciy724 
32.  Závada J, Hoste E, Cartin-Ceba R, et al. A comparison of three methods to estimate baseline 
creatinine for RIFLE classification. Nephrol Dial Transplant. 2010;25(12):3911-3918. 
doi:10.1093/ndt/gfp766 
33.  Semler MW, Rice TW, Shaw AD, et al. Identification of Major Adverse Kidney Events Within the 
Electronic Health Record. J Med Syst. 2016;40(7):167. doi:10.1007/s10916-016-0528-z 
 

Antibiotic Choice On ReNal outcomes (ACORN) trial 
Study Protocol Revision Sequence 
10/19/2021 
Original Protocol, version 1.0 
11/10/2021 
First patient enrolled 
2/11/2021 
Amendment to Study Protocol, version 1.1  
 
Exploratory outcomes were updated to match clinicaltrials.gov (with addition of 
disposition from the Emergency Department). 
 
Secondary outcome definitions were revised for clarity and internal inconsistencies 
in outcomes were resolved. 
 
7/27/2022 
Amendment to Study Protocol, version 1.2 
 
Sample size was increased to 2,500 at the time of the interim analysis to ensure 
sufficient patients in the subgroup receiving vancomycin at baseline. 
 
Protocol revision also included changes to match the pre-specified statistical 
analysis plan: 
1. Approach to calculation of baseline creatinine was clarified. 
2. Clarified outcome windows for existing exploratory outcomes. 
3. Inclusion of additional exploratory outcomes: 
a. 7- day and 28-day renal and neurologic outcomes 
b. Escalation of antibiotics 
c. Hospital-free days 
d. Nephrology consultation 
4. Changed the covariables included in the adjusted analysis of the primary 
outcome (a secondary analysis) to include enrollment SOFA score, 
presumed source of infection, and receipt of kidney replacement therapy 
at enrollment. 
5. Clarified the definition of the primary analytic population 
10/7/2022 
Enrollment complete 
 

 
1
Protocol and statistical analysis plan for the Antibiotic Choice On ReNal 
outcomes (ACORN) randomized clinical trial  
 
Edward T. Qian, MD1; Jonathan D. Casey, MD, MSc1; Adam Wright, PhD2; Li Wang, 
MS3; Justin K. Siemann, PhD4; Mary Lynn Dear, PhD4; Joanna L. Stollings, PharmD5; 
Brad Lloyd, BS6; Kevin P. Seitz, MD, MSc1; George Nelson, MD, MPH7; Patty Wright, 
MD7; Edward D. Siew, MD, MSc8; Brad Dennis, MD9; Jesse O. Wrenn, MD, PhD6; 
Jonathan W. Andereck MD, MBA6; Wesley H. Self, MD, MPH6; Matthew W. Semler, 
MD, MSc1*; Todd W. Rice, MD, MSc1* for the Vanderbilt Learning Healthcare System 
Platform Investigators#. 
 
* These authors contributed equally. 
# A complete list of the members of the Vanderbilt Learning Healthcare System Platform 
Investigators is provided in the Supplement 
 
Affiliations: 
1 Vanderbilt University Medical Center, Department of Medicine, Division of Allergy, 
Pulmonary and Critical Care Medicine; 
2 Vanderbilt University Medical Center, Department of Bioinformatics 
3 Vanderbilt University School of Medicine, Department of Biostatistics 
4 Vanderbilt University Medical Center, Vanderbilt Institute for Clinical and Translational 
Research 
5 Vanderbilt University Medical Center, Department of Pharmaceutical Services 
6 Vanderbilt University Medical Center, Department of Emergency Medicine. 
7 Vanderbilt University Medical Center, Department of Medicine, Division of Infectious 
Disease 
8 Vanderbilt University Medical Center, Department of Medicine, Division of Nephrology 
and Hypertension 
9 Vanderbilt University Medical Center, Department of Surgery 
 
 
Corresponding Author:  
Edward T. Qian, MD 
 
Email: 
edward.t.qian@vumc.org 
 
Address: 
T-1218 MCN 
1161 21st Ave S. 
Nashville, TN  37232-2650 
 
 

 
2
Telephone: 
301-219-2350 
 
Key words for indexing: Antibacterial Agents, Sepsis, Acute Kidney Injury, Delirium 
 
Subject Descriptor Number: 4.4 Clinical Trials in Critical Care Medicine 
Manuscript Word Count (body only): 4038/4000 
Date: 7/26/2022 
Version: 1 
 
 

 
3
Abstract:  
Introduction: Antibiotics are time-critical in the management of sepsis. When infectious 
organisms are unknown, patients are treated with empiric antibiotics to include 
coverage for gram-negative organisms, such as anti-pseudomonal cephalosporins and 
penicillins. However, in observational studies some anti-pseudomonal cephalosporins 
(e.g. cefepime) is associated with neurologic dysfunction while the most common anti-
pseudomonal penicillin (piperacillin-tazobactam) is associated with acute kidney injury. 
No randomized control trials have compared these regimens. This manuscript describes 
the protocol and analysis plan for a trial designed to compare the effects of anti-
pseudomonal cephalosporins and anti-pseudomonal penicillins among acutely ill 
patients receiving empiric antibiotics.  
 
Methods and Analysis:  
The Antibiotic Choice On ReNal outcomes (ACORN) trial is a prospective, single-center, 
non-blinded randomized trial being conducted at Vanderbilt University Medical Center. 
The trial will enroll 2,500 acutely ill adults receiving gram-negative coverage for 
treatment of infection. Eligible patients are randomized 1:1 to receive cefepime or 
piperacillin-tazobactam upon first order entry of a broad-spectrum antibiotic covering 
gram-negative organisms. The primary outcome is the highest stage of acute kidney 
injury and death occurring between enrollment and 14 days after enrollment. This will be 
compared between patients randomized to cefepime and randomized to piperacillin-
tazobactam using an unadjusted proportional odds regression model. The secondary 
outcomes are Major Adverse Kidney Events through day 14 and number of days alive 
and free of delirium and coma in 14 days after enrollment. Enrollment began on 
November 10, 2021 and is expected to be completed in December 2022. 
 
Ethics and Dissemination: 
The trial was approved by the Vanderbilt University Medical Center institutional review 
board with a waiver of informed consent. Results will be submitted in a peer-reviewed 
journal and presented at scientific conferences. 
 

 
4
Trial Registration:  
This trial was registered with ClinicalTrials.gov (NCT05094154) on October 26, 2021, 
prior to enrollment of the first patient on November 10, 2021. 
 
 

 
5
Strengths and Limitations: 
 
● This ongoing pragmatic trial will compare the effects of cefepime vs piperacillin-
tazobactam on acute kidney injury and death among acutely ill adults receiving 
gram-negative antibiotic therapy in the Emergency Department or Intensive Care 
Unit.  
● Strengths: Broad eligibility criteria, inclusion of a range of indications for antibiotic 
therapy, and use of the electronic health record to screen for eligible patients and 
facilitate delivery of the assigned intervention will increase the external validity of 
the findings 
● Limitations: After concealed randomization, patients, clinicians, and investigators 
are unblinded to study group assignment. Because urine output is not 
systematically available across all care, the outcome of AKI is based on 
creatinine measurements. 
 
 

 
6
Introduction: 
 
Antibiotics are necessary for management of patients with sepsis1 but can cause 
unintended adverse effects on organ function2. Since specific organisms causing 
infection is often unknown, empiric broad-spectrum antibiotics are commonly 
prescribed. For patients at risk for resistant organisms, common regimens include gram-
positive coverage (i.e. vancomycin) and gram-negative coverage with an anti-
pseudomonal cephalosporin or penicillin, predominantly cefepime or piperacillin-
tazobactam1. 
 
Because the medications are considered to have comparable anti-pseudomonal 
activity, discussion surrounding choice has focused on adverse effects. Some 
observational studies have reported an association between receipt of piperacillin-
tazobactam and acute kidney injury (AKI)3,4, particularly among patients receiving 
vancomycin5–7.  Other studies have shown no relationship between piperacillin-
tazobactam and AKI8,9. AKI is common during hospitalization10, and there are many 
potential contributors including isotonic fluids11,12, medications, and acute illnesses like 
sepsis13,14.  
Similarly, an association between cephalosporins and neurotoxicity manifesting 
as delirium and coma has been observed.15–17  Delirium, acute brain dysfunction 
characterized by fluctuations in mental status, inattention, altered consciousness, and 
disorganized thinking,18 is also a common complication of hospitalization. In Intensive 
Care Unit (ICU) populations, delirium is predictive of mortality, prolonged length of stay, 
and long-term cognitive impairment19,20. The incidence of cephalosporin-induced 
neurotoxicity is unknown but has been reported to increase in-hospital mortality21. 
 
A randomized controlled trial would overcome limitations of observational data, 
but none are known to exist22.  Rigorous, high-quality evidence assessing risk of AKI 
and neurotoxicity after exposure to anti-pseudomonal antibiotics would have potential to 
change care received by thousands of acutely ill adults annually. To address the lack of 
available evidence, we are conducting a prospective, randomized trial comparing anti-
pseudomonal cephalosporins and anti-pseudomonal penicillins among acutely ill adults 
in the Emergency Department (ED) or ICU.  
 

 
7
Methods and Analysis: 
This manuscript was written in accordance with Standard Protocol Items: 
Recommendations for Interventional Trials (SPIRIT) guidelines (Table 1, Supplement 
1)23. The Learning Healthcare System (LHS) Platform at Vanderbilt University Medical 
Center conducts research studies using a unique model that leverages pragmatic, 
randomized, controlled clinical trials embedded within usual care24. The LHS Platform is 
composed of stakeholders from across the enterprise and supports projects in both the 
pediatric and adult inpatient and outpatient settings (Supplement 2). LHS Platform 
studies focus on comparative effectiveness, implementation science, and programmatic 
evaluation approaches25,26. 
 
Study Design 
The Antibiotic Choice On ReNal outcomes (ACORN) trial is a pragmatic, single-
center, unblinded, parallel-group, randomized trial comparing anti-pseudomonal 
cephalosporins to anti-pseudomonal penicillins among acutely ill adults receiving gram-
negative antibiotics in the ED and ICU. At this center, the predominant anti-
pseudomonal cephalosporin is cefepime and the predominant anti-pseudomonal 
penicillin is piperacillin-tazobactam. The primary outcome is highest stage of AKI or 
death in 14 days. The trial protocol was approved by the institutional review board at 
Vanderbilt University Medical Center and registered prior to initiation of enrollment 
(NCT05094154). An independent data and safety monitoring board (DSMB) monitors 
the progress and safety of the trial. 
 
 
 
 
 
 
 
 
 

 
8
 
 
STUDY PERIOD 
 
Eligibility 
Screen 
Randomization 
& 
Allocation 
Post-allocation 
Final Outcome  
Assessment 
TIMEPOINT Order entry for 
CEF or PTZ 
EHR enrollment 
advisor 
7 days after 
enrollment 
14 days after 
enrollment 
Discharge or 28 days 
after enrollment 
ENROLLMENT: 
 
X 
 
 
 
EHR-based inclusion 
criteria screening 
X 
 
 
 
 
Manual screening for 
exclusion criteria by 
treating clinicians 
X 
 
 
 
 
Allocation 
 
X 
 
 
 
INTERVENTIONS: 
 
 
Cefepime 
 
X 
X 
 
 
Piperacillin-
tazobactam 
 
X 
X 
 
 
ASSESSMENTS: 
 
 
Baseline variables 
X 
X 
 
 
 
Adverse events 
 
X 
X 
X 
 
X 
Primary and 
secondary outcome  
 
X 
X 
X 
 
Exploratory 
outcomes 
 
 
X 
X 
X 
 
Table 1. Standard Protocol Items: Recommendations for Interventional Trials (SPIRIT) 
checklist. Enrollment, interventions, and assessments. CEF, Cefepime; PTZ, 
piperacillin-tazobactam; EHR, Electronic health record; 
 
 
 

 
9
Study Population 
Inclusion criteria: 
1. Age ≥ 18 years old 
2. Located in a participating ED or ICU 
3. Less than 12 hours between presentation to study hospital 
4. Treating clinician initiating an order for an anti-pseudomonal cephalosporin or 
anti-pseudomonal penicillin 
 
Exclusion criteria: 
1. Known receipt of > 1 dose of an anti-pseudomonal cephalosporin or anti-
pseudomonal penicillin during the last 7 days 
2. Current documented allergy to cephalosporins or penicillin 
3. Known to be a prisoner 
4. Treating clinicians feel that either an anti-pseudomonal cephalosporin or anti-
pseudomonal penicillin is required or contraindicated for the optimal treatment of 
the patient, including for more directed antibiotic therapy against known prior 
resistant infections or suspected sepsis with an associated central nervous 
system infection 
 
Screening and Enrollment 
When a treating clinician in a participating ED or ICU initiates an order for 
cefepime or piperacillin-tazobactam for a patient who meets all inclusion criteria, a 
clinical decision support (CDS) tool will 1) inform the provider of the study, 2) query the 
provider regarding the presence of any exclusion criteria, and if none are present, 3) 
enroll and randomize the patient. For patients who meet an exclusion criterion, the 
reason is recorded (Fig. 1).  
 
Analysis population 
The primary goal is the exploration of uncommon safety effects, therefore the 
population for primary analysis will include all patients who were randomized and 
received at least one dose of either study drug in the 168 hours (7 days) after 

 
10
randomization. A sensitivity analysis will include all patients randomized, including those 
who never received either cefepime or piperacillin/tazobactam. 
 
Randomization and Treatment Allocation 
Study group assignments are generated by computerized randomization in a 1:1 
ratio of intervention to control.  Study group assignment will remain concealed until the 
team has confirmed the patient does not meet any exclusion criteria and the patient has 
been enrolled. The CDS tool will advise the clinician of group assignment following 
randomization. 
 
Study Interventions 
For patients assigned to cefepime, the CDS tool will guide providers to 
intravenous cefepime. For patients assigned to piperacillin-tazobactam, the CDS tool 
will guide providers to intravenous piperacillin-tazobactam. The CDS tool will display a 
standardized table of dose by glomerular filtration rate, but decisions regarding dose, 
frequency, and duration will be the treating clinician’s discretion.  
In the 168 hours (7 days) following enrollment, any new order for cefepime or 
piperacillin-tazobactam will open a CDS tool, which displays group assignment and 
allows clinicians to (re)order the assigned antibiotic or provide a reason for ordering the 
non-assigned antibiotic. Similarly, if the assigned antibiotic is discontinued, the CDS tool 
will solicit a rationale for discontinuation, including antibiotic tailoring, newly apparent 
allergy to either cephalosporins or penicillins, or clinician preference. 
 
The CDS tool influences only the choice of the initial anti-pseudomonal antibiotic. 
Treating clinicians determine concurrent administration of other antibiotics (e.g., 
vancomycin, metronidazole), duration of therapy, escalation, de-escalation, approach to 
source control, and use of culture and laboratory data to modify antibiotic therapy. 
 
Data Collection 
 
Trial personnel will monitor for adverse events daily and will record the following 
data elements at the time of enrollment by manual review of the health record 
(Supplement 3 and 4): 

 
11
- 
Presence of sepsis, defined by Sepsis-3 criteria27 
- 
Transplant recipient status 
- 
Receipt of renal replacement therapy (RRT) prior to enrollment 
- 
Presumed source of infection organized into groups based on previously 
published data28 
 
All other data will be obtained using electronic exports from the health record. The 
following variables are collected: 
1. Collected at baseline: Age, sex, height, weight, body mass index, race, 
Sequential Organ Failure Assessment (SOFA) score, active medical problems at 
the time of admission, active comorbidities, comorbidities and medications known 
to increase risk of kidney or neurologic injury at enrollment, mean arterial 
pressure and vasopressor use prior to antibiotic receipt, analgesia and sedation 
use prior to antibiotic receipt, admission to ICU vs ward 
2. Collected from randomization to hospital discharge: Mean arterial pressure and 
vasopressor use, pH, PaO2, PaCO2, respiratory rate, heart rate, oxygen 
saturation, temperature, lactic acid, elements of a basic metabolic panel, 
magnesium, elements of a complete blood count, antibiotic receipt, all 
microbiologic culture data, Confusion Assessment Method for the ICU (CAM-
ICU), Richmond Agitation Sedation Score (RASS), Glasgow Coma Scale (GCS), 
mechanical ventilation status and variables related to ventilation, nephrology 
consultation, receipt of new RRT, indications for new RRT among patients who 
received new RRT, medications known to increase risk of kidney injury, 
medications known to increase risk of neurologic injury, admitting team, date of 
admission, days spent in the ICU, days spent in the hospital, date of intubation(s) 
and extubation(s), date of discharge, and date of death. 
 
Primary Outcome 
The primary outcome will be a combination of the highest stage of AKI and death 
between randomization and day 14.  The stages of AKI are defined using creatinine 

 
12
measurements and the “Kidney Disease: Improving Global Outcomes (KDIGO)”29 
criteria.  The score will range from 0 (best value) to 4 (worst value): 
0 = No AKI 
1 = Stage 1 AKI (Creatinine increased by 1.5-1.9 times baseline OR increase by 
>= 0.3 mg/dL) 
2 = Stage 2 AKI (Creatinine increased by 2.0-2.9 times baseline) 
3 = Stage 3 AKI (Creatinine increased by >= 3.0 times baseline OR increase to 
>= 4.0 mg/dL OR New RRT) 
4 = Death 
 
“Baseline” creatinine values are defined as the lowest prior creatinine values 
from three different timepoints: the pre-illness creatinine value, the peri-enrollment 
creatinine value, and the lowest prior on-study creatinine value as defined below. Death 
is defined as mortality from any cause occurring prior to or on the end of study day 14, 
censored at hospital discharge.  RRT is defined as receipt of RRT at any point between 
randomization and the end of study day 14, censored at hospital discharge. Patients 
who are receiving RRT prior to enrollment can only experience values of 0 (patient did 
not die) or 4 (patient died) because they are ineligible to experience changes in 
creatinine or new receipt of RRT that define levels 1 through 3.  
Patients’ pre-illness creatinine will be defined as the lowest serum creatinine 
between 12 months and 24 hours prior to enrollment. For patients for whom a value is 
unavailable, a pre-illness creatinine value will be estimated using a previously-described 
three-variable formula [creatinine = 0.74 − 0.2 (if female) + 0.08 (if African American) + 
0.003 × age (in years)]30. There are no validated estimations of creatinine without race 
but we will evaluate the effect of social constructs by fitting models both with and 
without race in a sensitivity analysis. 
Patients’ peri-enrollment creatinine will be defined hierarchically using the 
creatinine value closest to enrollment in: (first) the 24 hours prior to enrollment, if 
available, and (second) the six hours after enrollment (if no value is available prior to 
enrollment).  Prevalent AKI, or AKI that is present on admission and unrelated to the 

 
13
study intervention, will be defined by comparing the peri-enrollment creatinine to the 
pre-illness creatinine.  
On-study creatinine will be defined as any creatinine value occurring after both 
the time of enrollment and the time of the peri-enrollment creatinine value. On-study 
creatinine values will be used to identify incident AKI and calculate the stage of AKI for 
the primary outcome.   
The primary outcome will be calculated as follows: 
• Patients who survive without new RRT and do not experience an on-study 
creatinine value that is at least 0.3 mg/dL higher than the peri-enrollment 
value or any preceding on-study value, and whose on-study creatinine is 
never more than 1.5 times the peri-enrollment value or any preceding on-
study value, will be considered not to have experienced incident AKI and 
will receive a value of 0 for the primary outcome. 
• Among patients who survive and experience AKI (have on-study 
creatinine value that is at 1.5 times or at least 0.3 mg/dL higher than the 
peri-enrollment value or any preceding on-study value), the score for the 
primary outcome will be determined by the stage of AKI and classified as 
follows: 
a. A value of 1 if the highest on-study creatinine after qualifying for 
AKI is less than 2.0 times the lowest of the pre-illness creatinine 
value, the peri-enrollment creatinine value, and the lowest prior on-
study creatinine value (baseline creatinine); 
b. A value of 2 if the highest on-study creatinine after qualifying for 
AKI is at least 2.0 times and less than 3.0 times the lowest of the 
pre-illness creatinine value, the peri-enrollment creatinine value, 
and the lowest prior on-study creatinine value (baseline creatinine); 
and 
c. A value of 3 if the highest on-study creatinine after qualifying for 
AKI is at least 3.0 times the lowest of the pre-illness creatinine 
value, the peri-enrollment creatinine value, and the lowest prior on-

 
14
study creatinine value (baseline creatinine), with a maximum 
creatinine above 4 mg/dL, or receive new RRT 
• Patients who die will receive a value of 4  
 
The mechanisms and extent of AKI with antibiotic exposure are not well understood.  
The primary outcome window of 14 days was chosen as it was felt to capture the period 
most likely to be affected by controlling antibiotics choice for 168 hours (7 days). 
 
Secondary Outcomes 
We have prespecified two secondary outcomes. Major Adverse Kidney Events 
within 14 days (MAKE14), is the composite outcome of death within 14 days, new RRT 
within 14 days, or stage 2 or higher AKI at day 14, according to KDIGO creatinine 
criteria. The second is number of days alive and free of delirium and coma in the 14 
days after enrollment (Delirium and Coma-Free Days to day 14). Delirium is defined as 
a positive assessment on the CAM-ICU31 and coma is defined as a RASS of -4 or -532 
at any point during that study day. 
 
Exploratory Outcomes 
- 
Exploratory Renal Outcomes 
o Major Adverse Kidney Events within 28 days (MAKE28) 
o Highest stage of AKI or death between randomization and day 7 
o Stage 2 or higher AKI as defined in the KDIGO criteria for creatinine level 
within 14 days and 28 days after enrollment 
o New receipt of RRT within 14 days and 28 days after enrollment 
o Days alive and free of RRT during 14 days and 28 days after enrollment 
o Highest creatinine level within 28 days after enrollment 
o Change from pre-illness creatinine to the highest creatinine level within 28 
days after enrollment 
o Final creatinine level before hospital discharge at 28 days 
o Ongoing receipt of RRT at hospital discharge or 28 days 
o Nephrology consultation 

 
15
- 
Exploratory Neurologic Outcomes 
o Worst GCS score during the 7 days, 14 days, and 28 days after 
enrollment 
o Delirium and Coma-Free Days in the 28 days after enrollment 
- 
Exploratory Clinical Outcomes 
o ICU-free, Hospital-free, Ventilator-free, and Vasopressor-free days in the 
28 days after enrollment 
o 14-day mortality 
o 28-day mortality 
o Disposition of patients admitted from the ED (ward vs ICU) 
o Escalation of antibiotics defined by subsequent receipt of meropenem, 
meropenem-vaborbactam, imipenem, imipenem-relebactam, cefiderocol, 
ceftazidime-avibactam, ceftolozane-tazobactam, tigecycline, amikacin, 
tobramycin, gentamicin. 
Definition of Supportive Therapy-Free days is available in Supplement section 5.  
 
DSMB and Interim Analysis 
A DSMB composed of experts in critical care medicine, infectious disease, and 
biostatistics has overseen the design of the trial and is monitoring its conduct 
(Supplement 6). The DSMB conducted a single interim analysis, prepared by the study 
biostatistician, at the anticipated halfway point of the trial after enrollment of 1025 
patients. The meeting was held on July 14, 2022, and the DSMB recommended 
continuing the trial to completion without alteration.  The stopping boundary for efficacy 
was prespecified as p-value for the difference between groups in the primary outcome 
of 0.001 or less.  Given current use of both interventions as a part of usual care, there 
was no stopping boundary for futility. Use of a conservative Haybittle-Peto boundary for 
efficacy will allow the final analysis to be performed using an unchanged level of 
significance (P = 0.05).  The DSMB retains the authority to recommend stopping the trial 
at any point, request additional data or interim analyses, or request modifications of 
study protocol to protect patient safety. 
 

 
16
Sample Size Estimation 
As specified in the initial trial protocol, at the time of the single, planned interim 
analysis the DSMB oversaw a re-estimation of the planned sample size.  Because [1] 
concurrent receipt of vancomycin has been hypothesized to be in the proposed 
mechanistic pathway between receipt of an anti-pseudomonal penicillin and AKI and [2] 
approximately 75% of patients in the trial concurrently receive vancomycin, the sample 
size was increased by 25% from 2,050 to 2,500 patients. The increase in sample size 
ensures the number of patients receiving concurrent vancomycin will be approximately 
2,050, consistent with the original sample size estimation.  Assuming a two-sided alpha 
of 0.05 and a distribution of the primary outcome with approximately 70% of patients 
experiencing no AKI, 10% of patients experiencing stage I AKI, 7% of patients 
experiencing stage II AKI, 7% of patients experiencing stage III AKI, and 6% of patients 
experiencing death, we calculated that enrollment of a total of 2,500 patients would 
provide 92% statistical power to detect an odds ratio of 0.75 in the primary analysis. 
 
Statistical Analysis Principles 
Analyses will be conducted following reproducible research principles using R (R 
Foundation for Statistical Computing, Vienna, Austria)33. Continuous variables will be 
reported as mean ± SD or median and IQR; categorical variables will be reported as 
frequencies and proportions. As a randomized controlled trial, there will be no 
comparison of baseline characteristics. A two-sided p-value of < 0.05 will be used to 
indicate statistical significance; with just one primary outcome, no adjustment for 
multiplicity will be made. Two secondary outcomes are specified, one safety outcome 
for each treatment regimen. Since hypothesized safety concerns are independent, we 
will not adjust our secondary outcomes for multiplicity. For all other outcomes, emphasis 
will be placed on magnitude of differences between groups rather than statistical 
significance.  
 
Main Analysis of the Primary Outcome 
The main analysis will be an unadjusted, intention-to-treat comparison of the 
primary outcome between patients randomized to receive anti-pseudomonal 

 
17
cephalosporins versus anti-pseudomonal penicillins who received at least one dose of a 
study drug using a proportional odds regression model. The unadjusted common odds 
ratio (cOR) with confidence intervals will be the primary treatment effect. If departures 
from the proportionality assumption are observed, then a partially proportional odds 
model will be constructed. 
 
Secondary Analyses of the Primary Outcome 
Multivariable modeling to account for covariates 
To account for participants’ baseline status, we will include covariates in the 
proportional odds regression model. The following prespecified baseline covariates will 
be considered: age; sex; peri-enrollment creatinine; receipt of RRT prior to enrollment; 
receipt of vasopressors; receipt of mechanical ventilation; SOFA score; presumed 
source of infection; enrollment location (ED vs ICU).  Source of infection will be 
categorized as: lung, intra-abdominal (perforated viscus, ischemic bowel, 
cholecystitis/cholangitis, peritonitis/abscess/small bowel obstruction, Clostridium difficile 
colitis, spontaneous bacterial peritonitis, pancreatitis, enterocolitis/diverticulitis, other 
intra-abdominal infections), urinary (pyelonephritis, obstructive urinary tract infection), 
skin and soft tissue (cellulitis/abscess/necrotizing fasciitis/decubitus ulcer, surgical site 
infection), other (bone/joint, primary blood stream infection, intravascular catheter, 
disseminated infection, central nervous system infection, endocarditis, other), and 
unknown. 
 
Effect Modification 
We will test the interaction between the treatment effect of anti-pseudomonal 
cephalosporins vs anti-pseudomonal penicillins and baseline variables expected to 
modify effects of treatments on the outcomes. The effect modifiers will be tested one by 
one by including both the main effect and the interaction term in the adjusted model. 
Because this study is not formally designed or powered to test for interaction, a less 
conservative two-sided p value for the interaction term will be used, with values less 
than 0.10 considered suggestive of potential interaction and values less than 0.05 
considered conclusive evidence. The following variables will be considered: 

 
18
1. Location at randomization (ED vs ICU) 
2. Presence of sepsis (meeting Sepsis-3 criteria) at randomization 
3. Receipt of vancomycin (defined as an order for vancomycin in the 12 hours 
before or 6 hours after randomization)  
4. Source of infection 
5. AKI at randomization 
6. CKD at randomization 
7. Neutropenia at randomization 
8. Admitting team (medicine vs surgical) 
 
Sensitivity Analyses of the Primary Outcome 
To assess robustness of findings, the main analysis of the primary outcome will 
be repeated in several alternative populations. First, we will include all patients who 
were identified by the CDS tool as meeting eligibility criteria, regardless of receipt of any 
doses of anti-pseudomonal cephalosporins or anti-pseudomonal penicillins. Second, 
many patients are initiated on antibiotics in the acute setting, which are stopped as a 
more likely cause for their illness becomes known (e.g. pulmonary embolism). We will 
repeat the main analysis restricted to the subset of patients that received more than 2 
days (48 hours) of anti-pseudomonal therapy. Third, because race is a social construct, 
we will repeat the main analysis with those whose pre-illness creatinine was estimated 
by an equation without race as a factor. Fourth, to avoid uncertainty around the 
calculations of pre-illness creatinine, we will repeat the main analysis excluding patients 
with calculated pre-illness creatinine values. Because group assignment might influence 
recovery from prevalent AKI in a way that could affect calculations of the primary 
outcome, we will recalculate the primary outcome as a repeated measure assessed 
daily from randomization to day 14 using only the pre-illness creatinine as the baseline 
creatinine. 
 
Analysis of the Secondary Outcomes 
Analysis of secondary outcomes will follow a similar framework to the primary 
analysis, with a systematic assessment of unadjusted models, adjusted models using 

 
19
the same set of covariates. The secondary outcome of MAKE14 will be compared 
between groups using a logistic regression model. Delirium and coma-free days to day 
14 will be compared between groups using a proportional odds regression model, and 
will include the additional covariate of coma on enrollment for the adjusted model. 
Delirium and coma free days to day 14 will be assessed for effect modification using the 
same approach as the primary outcome replacing receipt of vancomycin with baseline 
coma.  
 
Analyses of Exploratory Outcomes 
Exploratory outcomes will proceed using unadjusted analyses only, with 
presentation of effect sizes and confidence intervals as well as p-values. Continuous 
outcomes will be compared with the Mann-Whitney U test and difference in medians 
reported. For categorical variables, groups will be compared with the chi-square test or 
Fischer’s exact test as appropriate and results will be expressed as a difference in 
proportions or odds ratios, each with 95% confidence intervals.  
 
Handling of Missing Data 
In the case that a patient is enrolled, never receives RRT, and is discharged alive 
without having a creatinine value measured following enrollment, the patient will be 
assumed to have no AKI. When data are missing for secondary or exploratory 
outcomes, complete-case analysis, excluding cases where data for the analyzed 
outcome are missing, will be performed. There will be no imputation of missing data for 
these outcomes. In adjusted analyses, missing data for covariates will be imputed using 
multiple imputations. 
 
Trial status 
The ACORN trial is currently enrolling and started enrollment on November 10, 
2021. 
 
 
 

 
20
Ethics and Dissemination 
Waiver of Informed Consent 
Acutely ill patients for whom the provider is ordering broad-spectrum antibiotics in 
the ED or ICU are at significant risk for morbidity and mortality from their underlying 
illness. Most patients receiving empiric gram-negative antibiotics in routine clinical care 
receive either anti-pseudomonal cephalosporins or anti-pseudomonal penicillins. Any 
benefits or risks of these two approaches are experienced by patients receiving gram 
negative antibiotics in clinical care, outside the context of research. As a requirement for 
enrollment in the ACORN trial, the patient’s treating clinician must have made the 
decision to order either anti-pseudomonal cephalosporins or anti-pseudomonal 
penicillins as part of routine clinical care and affirmed that either would be a safe and 
reasonable approach for the patient (otherwise the patient is excluded). Therefore, 
making the decision between the two approaches randomly through study group 
assignment rather than by a provider who thinks either approach is safe and reasonable 
for the patient was proposed to pose no more than minimal incremental risk. 
Obtaining informed consent for participation in the study would be impracticable. 
Receipt of antibiotics in sepsis is time sensitive. Each hour delay in antibiotics in 
patients with sepsis is associated with an increase in mortality34. Attempting to obtain 
prospective written informed consent from patients presenting to the ED or ICU during 
the interval between the placement of an order for empiric antibiotics and their 
administration risks delaying antibiotic delivery.  Moreover, acutely ill patients with 
sepsis are commonly delirious or unconscious, and a legally authorized representative 
is not consistently present at the time of initiation of antibiotics.  Because the trial 
determines only the choice of the initial anti-pseudomonal antibiotic and defers 
decisions regarding subsequent doses of antibiotics (e.g., duration of therapy, 
escalation, de-escalation) to treating clinicians, enrollment, trial group assignment, and 
the primary study procedure (administration of the assigned antibiotic) commonly occurs 
within 1 hour of meeting eligibility criteria.  
Because the study was expected to pose minimal risk and prospective informed 
consent was considered to be impracticable, a waiver of informed consent was 
requested and granted from the Vanderbilt University Medical Center IRB.  

 
21
Protocol Changes 
ClinicalTrials.Gov will be updated with any amendments to the protocol as per 
SPIRIT guidelines (Supplement 7).  
 
Dissemination Plan 
Trial results will be submitted to a peer-reviewed journal for consideration of 
publication and will be presented at one or more scientific conferences. Data will be 
made available following publication (Supplement 8). 
 
Conclusion 
To allow for a clearer and more objective interpretation of trial results, this 
description delineates the ACORN trial methods and analysis prior to the conclusion of 
enrollment. 
 
 

 
22
Contributors: All study authors approved the final version of this manuscript. Study 
concept and design: E.T.Q., J.D.C., A.W., L.W., J.L.S., G.N., P.W., E.D.S., J.O.W., 
J.W.A., W.H.S., M.W.S., T.W.R.; Acquisition of data: E.T.Q., B.L., K.P.S.; Drafting of the 
manuscript: E.T.Q., J.D.C., M.W.S., T.W.R.; Critical revision of the manuscript for 
important intellectual content: E.T.Q., J.D.C., A.W., L.W., J.K.S., M.L.D, J.L.S., B.L., 
K.P.S., G.N., P.W., E.D.S., B.D., J.O.W., J.W.A., W.H.S., M.W.S., T.W.R.; Study 
supervision: M.W.S., T.W.R.  
 
Funding:  The project described was supported by the VICTR Learning Healthcare 
System Platform under CTSA award No. UL1 TR002243 from the National Center for 
Advancing Translational Sciences. It contents are solely the responsibility of the authors 
and do not necessarily represent official views of the National Center for Advancing 
Translational Sciences or the National Institutes of Health. E.T.Q. was supported by the 
National Heart, Lung, and Blood Institute award No. T32HL087738. J.D.C. was 
supported in part by the NHLBI (K23HL153584). M.W.S. was supported in part by the 
NHLBI (K23HL143053). E.D.S. was supported by the Vanderbilt O’Brien Kidney Center 
P30-DK114809 for service provided through the Clinical and Translational Research 
Core. The funding institutions had no role in (1) conception, design, or conduct of the 
study, (2) collection, management, analysis, interpretation, or presentation of the data, 
or (3) preparation, review, or approval of the manuscript.   
 
Competing Interests and Financial Disclosures:  None 
 
Patient and Public Involvement: Patients or the public were not involved in the 
design, or conduct, or reporting, or dissemination plans of our research 
 
 
 
 

 
23
Figure 1. Electronic health record-based enrollment advisor 
 
 
 

 
24
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1
Qian ET, et al. BMJ Open 2023;13:e066995. doi:10.1136/bmjopen-2022-066995
Open access
Protocol and statistical analysis plan for 
the Antibiotic Choice On ReNal outcomes 
(ACORN) randomised clinical trial
Edward Tang Qian  ‍ ‍ ,1 Jonathan D Casey,1 Adam Wright,2 Li Wang,3 
Justin Siemann,4 Mary Lynn Dear,4 Joanna Stollings,5 Bradley Daniel Lloyd,6 
Kevin Seitz,1 George Nelson,7 Patty Wright,7 Edward D Siew,8 Bradley Dennis,9 
Jesse Wrenn,6 Jonathan Andereck,6 Wesley H Self,6 Matthew W Semler  ‍ ‍ ,1 
Todd W Rice,1 Vanderbilt Learning Healthcare System Platform Investigators
To cite: Qian ET, Casey JD, 
Wright A, et al.  Protocol and 
statistical analysis plan for the 
Antibiotic Choice On ReNal 
outcomes (ACORN) randomised 
clinical trial. BMJ Open 
2023;13:e066995. doi:10.1136/
bmjopen-2022-066995
	
►Prepublication history and 
additional supplemental material 
for this paper are available 
online. To view these files, 
please visit the journal online 
(http://dx.doi.org/10.1136/​
bmjopen-2022-066995).
MWS and TWR contributed 
equally.
Received 27 July 2022
Accepted 02 March 2023
For numbered affiliations see 
end of article.
Correspondence to
Dr Edward Tang Qian;  
​edward.​t.​qian@​vumc.​org
Protocol
© Author(s) (or their 
employer(s)) 2023. Re-­use 
permitted under CC BY-­NC. No 
commercial re-­use. See rights 
and permissions. Published by 
BMJ.
ABSTRACT
Introduction  Antibiotics are time-­critical in the 
management of sepsis. When infectious organisms 
are unknown, patients are treated with empiric 
antibiotics to include coverage for gram-­negative 
organisms, such as antipseudomonal cephalosporins 
and penicillins. However, in observational studies, 
some antipseudomonal cephalosporins (eg, cefepime) 
are associated with neurologic dysfunction while 
the most common antipseudomonal penicillin 
(piperacillin–tazobactam) is associated with acute 
kidney injury (AKI). No randomised control trials 
have compared these regimens. This manuscript 
describes the protocol and analysis plan for a trial 
designed to compare the effects of antipseudomonal 
cephalosporins and antipseudomonal penicillins 
among acutely ill patients receiving empiric 
antibiotics.
Methods and analysis  The Antibiotic Choice On 
ReNal outcomes trial is a prospective, single-­centre, 
non-­blinded randomised trial being conducted 
at Vanderbilt University Medical Center. The trial 
will enrol 2500 acutely ill adults receiving gram-­
negative coverage for treatment of infection. Eligible 
patients are randomised 1:1 to receive cefepime 
or piperacillin–tazobactam on first order entry of a 
broad-­spectrum antibiotic covering gram-­negative 
organisms. The primary outcome is the highest stage 
of AKI and death occurring between enrolment and 14 
days after enrolment. This will be compared between 
patients randomised to cefepime and randomised 
to piperacillin–tazobactam using an unadjusted 
proportional odds regression model. The secondary 
outcomes are major adverse kidney events through 
day 14 and number of days alive and free of delirium 
and coma in 14 days after enrolment. Enrolment 
began on 10 November 2021 and is expected to be 
completed in December 2022.
Ethics and dissemination  The trial was approved by 
the Vanderbilt University Medical Center institutional 
review board (IRB#210591) with a waiver of informed 
consent. Results will be submitted to a peer-­reviewed 
journal and presented at scientific conferences.
Trial registration number  NCT05094154.
INTRODUCTION
Antibiotics are necessary for the management 
of patients with sepsis,1 but can cause unin-
tended adverse effects on organ function.2 
Since specific organisms causing infection 
are often unknown, empiric broad-­spectrum 
antibiotics are commonly prescribed. For 
patients at risk for resistant organisms, 
common regimens include gram-­positive 
coverage (ie, vancomycin) and gram-­negative 
coverage with an antipseudomonal cephalo-
sporin or penicillin, predominantly cefepime 
or piperacillin–tazobactam.1
No prospective randomised trials have 
compared the efficacy of cefepime versus 
piperacillin–tazobactam head to head. When 
administered empirically in clinical prac-
tice, both antibiotics are commonly consid-
ered to have comparable activity against 
gram-­negative organisms, including Pseudo-
monas, although cefepime does not cover 
anaerobic organisms and piperacillin–tazo-
bactam does. Whether coverage of anaerobic 
STRENGTHS AND LIMITATIONS OF THIS STUDY
	
⇒This ongoing pragmatic trial will compare the ef-
fects of cefepime versus piperacillin–tazobactam on 
acute kidney injury (AKI) and death among acutely 
ill adults receiving gram-­negative antibiotic therapy 
in the emergency department or intensive care unit.
	
⇒Strengths: Broad eligibility criteria, inclusion of a 
range of indications for antibiotic therapy and use 
of the electronic health record to screen for eligible 
patients and facilitate delivery of the assigned in-
tervention will increase the external validity of the 
findings.
	
⇒Limitations: After concealed randomisation, pa-
tients, clinicians and investigators are unblinded to 
study group assignment. Because urine output is 
not systematically available across all care, the out-
come of AKI is based on creatinine measurements.
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Qian ET, et al. BMJ Open 2023;13:e066995. doi:10.1136/bmjopen-2022-066995
Open access
organisms in acutely ill patients is associated with higher3 
mortality, lower4–7 mortality or no difference in mortality 
is uncertain.
In the absence of evidence that efficacy differs between 
cefepime 
and 
piperacillin–tazobactam, 
discussion 
surrounding the choice between the two has focused on 
adverse effects. Some observational studies have reported 
an association between receipt of piperacillin–tazobactam 
and acute kidney injury (AKI),8 9 particularly among 
patients receiving vancomycin.10–12 Other studies have 
shown no relationship between piperacillin–tazobactam 
and AKI.13 14 Adverse kidney events are common during 
hospitalisation,15 and there are many potential contribu-
tors including isotonic fluids,16 17 medications and acute 
illnesses such as sepsis.18 19
Similarly, an association between cephalosporins and 
neurotoxicity manifesting as delirium and coma has been 
observed.20–22 Delirium, acute brain dysfunction char-
acterised by fluctuations in mental status, inattention, 
altered consciousness and disorganised thinking,23 is also 
a common complication of hospitalisation. In intensive 
care unit (ICU) populations, delirium is predictive of 
mortality, prolonged length of stay and long-­term cogni-
tive impairment.24 25 The incidence of cephalosporin-­
induced neurotoxicity is unknown but has been reported 
to increase in-­hospital mortality.26
A randomised controlled trial would overcome limita-
tions of observational data, but none is known to exist.27 
Rigorous, high-­quality evidence assessing the risk of AKI 
and neurotoxicity after exposure to antipseudomonal 
antibiotics would have the potential to change care 
received by thousands of acutely ill adults annually. To 
address the lack of available evidence, we are conducting 
a prospective, randomised trial comparing antipseudo-
monal cephalosporins and antipseudomonal penicillins 
among acutely ill adults in the emergency department 
(ED) or ICU.
METHODS AND ANALYSIS
This manuscript was written in accordance with Stan-
dard Protocol Items: Recommendations for Inter-
ventional Trials (SPIRIT) guidelines (table  1, online 
supplemental file 1).28 The Learning Healthcare System 
(LHS) Platform at Vanderbilt University Medical Center 
conducts research studies using a unique model that 
leverages pragmatic, randomised, controlled clinical 
trials embedded within usual care.29 The LHS Platform is 
composed of stakeholders from across the enterprise and 
supports projects in both the paediatric and adult inpa-
tient and outpatient settings (online supplemental file 2). 
LHS Platform studies focus on comparative effectiveness, 
implementation science and programmatic evaluation 
approaches.30 31
Study design
The Antibiotic Choice On ReNal outcomes (ACORN) 
trial is a pragmatic, single-­centre, unblinded, parallel-­
group, randomised trial comparing antipseudomonal 
cephalosporins to antipseudomonal penicillins among 
acutely ill adults receiving gram-­negative antibiotics in the 
ED and ICU. At this centre, the predominant antipseudo-
monal cephalosporin is cefepime and the predominant 
antipseudomonal penicillin is piperacillin–tazobactam. 
The primary outcome is the highest stage of AKI or 
death in 14 days. The trial protocol was approved by 
Table 1  Standard Protocol Items: Recommendations for Interventional Trials checklist
Study period
Eligibility
screen
Randomisation
and allocation
Post allocation
Final outcome
assessment
Timepoint
Order entry for 
CEF or PTZ
EHR enrolment 
advisor
7 days after 
enrolment
14 days after 
enrolment
Discharge or 28 days 
after enrolment
Enrolment:
X
EHR-­based inclusion criteria screening
X
Manual screening for exclusion criteria by 
treating clinicians
X
Allocation
X
Interventions:
Cefepime
X
X
Piperacillin–tazobactam
X
X
Assessments:
Baseline variables
X
X
Adverse events
X
X
X
X
Primary and secondary outcomes
X
X
X
Exploratory outcomes
X
X
X
Enrolment, interventions and assessments.
CEF, cefepime; EHR, electronic health record; PTZ, piperacillin–tazobactam.
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Qian ET, et al. BMJ Open 2023;13:e066995. doi:10.1136/bmjopen-2022-066995
Open access
the institutional review board at Vanderbilt University 
Medical Center and registered prior to initiation of enrol-
ment (NCT05094154). An independent data and safety 
monitoring board (DSMB) monitors the progress and 
safety of the trial.
Patient and public involvement
Patients or the public were not involved in the design, 
or conduct, or reporting, or dissemination plans of our 
research. Patient and community representatives partici-
pated in the steering committee for the LHS in which the 
trial was conducted.
Study population
Inclusion criteria
1.	 Age≥18 years old.
2.	 Located in a participating ED or ICU.
3.	 Less than 12 hours between presentation to study hos-
pital.
4.	 Treating clinician initiating an order for an antipseudo-
monal cephalosporin or antipseudomonal penicillin.
Exclusion criteria
1.	 Known receipt of >1 dose of an antipseudomonal ceph-
alosporin or antipseudomonal penicillin during the 
last 7 days.
2.	 Current documented allergy to cephalosporins or pen-
icillin.
3.	 Known to be a prisoner.
4.	 Treating clinicians feel that either an antipseudomon-
al cephalosporin or antipseudomonal penicillin is re-
quired or contraindicated for the optimal treatment 
of the patient, including for more directed antibiotic 
therapy against known prior resistant infections or sus-
pected sepsis with an associated central nervous system 
infection.
Screening and enrolment
When a treating clinician in a participating ED or ICU 
initiates an order for cefepime or piperacillin–tazo-
bactam for a patient who meets all inclusion criteria, a 
clinical decision support (CDS) tool will (1) inform the 
provider of the study, (2) query the provider regarding 
the presence of any exclusion criteria, and if none 
is present, (3) enrol and randomise the patient. For 
patients who meet an exclusion criterion, the reason is 
recorded (figure 1).
Analysis population
The primary goal is the exploration of uncommon safety 
effects, therefore the population for primary analysis will 
include all patients who were randomised and received at 
least one dose of either study drug in the 168 hours (7 days) 
after randomisation. A sensitivity analysis will include all 
patients randomised, including those who never received 
either cefepime or piperacillin/tazobactam.
Randomisation and treatment allocation
Study group assignments are generated by computerised 
randomisation in a 1:1 ratio of intervention to control. 
Study group assignment will remain concealed until 
the team has confirmed the patient does not meet any 
exclusion criteria and the patient has been enrolled. The 
CDS tool will advise the clinician of group assignment 
following randomisation.
Figure 1  Electronic health record-­based enrolment advisor. ACORN, Antibiotic Choice On ReNal outcomes. D5W - Dextrose 
5% in Water; IVPB - Intravenous Piggyback; PCN - penicillin
 on July 6, 2023 by guest. Protected by copyright.
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Study interventions
For patients assigned to cefepime, the CDS tool will 
guide providers to intravenous cefepime. For patients 
assigned to piperacillin–tazobactam, the CDS tool will 
guide providers to intravenous piperacillin–tazobactam. 
The CDS tool will display a standardised table of dose by 
glomerular filtration rate, but decisions regarding dose, 
frequency and duration will be the treating clinician’s 
discretion.
In the 168 hours (7 days) following enrolment, any new 
order for cefepime or piperacillin–tazobactam will open 
a CDS tool, which displays group assignment and allows 
clinicians to (re)order the assigned antibiotic or provide 
a reason for ordering the non-­assigned antibiotic. Simi-
larly, if the assigned antibiotic is discontinued, the CDS 
tool will solicit a rationale for discontinuation, including 
antibiotic tailoring, newly apparent allergy to either ceph-
alosporins or penicillins, or clinician preference.
The CDS tool influences only the choice of the initial 
antipseudomonal antibiotic. Treating clinicians to deter-
mine concurrent administration of other antibiotics (eg, 
vancomycin, metronidazole), duration of therapy, escala-
tion, de-­escalation, approach to source control and use of 
culture and laboratory data to modify antibiotic therapy.
Data collection
Trial personnel will monitor for adverse events daily and 
will record the following data elements at the time of 
enrolment by manual review of the health record (online 
supplemental files 3 and 4):
	
►Presence of sepsis, defined by Sepsis-­3 criteria.32
	
►Transplant recipient status.
	
►Receipt of renal replacement therapy (RRT) prior to 
enrolment.
	
►Presumed source of infection organised into groups 
based on previously published data.33
All other data will be obtained using electronic exports 
from the health record. The following variables are 
collected:
1.	 Collected at baseline: age, sex, height, weight, body 
mass index, race, Sequential Organ Failure Assessment 
(SOFA) Score, active medical problems at the time of 
admission, active comorbidities, comorbidities and 
medications known to increase risk of kidney or neuro-
logic injury at enrolment, mean arterial pressure and 
vasopressor use prior to antibiotic receipt, analgesia 
and sedation use prior to antibiotic receipt, admission 
to ICU versus ward.
2.	 Collected from randomisation to hospital discharge: 
mean arterial pressure and vasopressor use, pH, PaO2, 
PaCO2, respiratory rate, heart rate, oxygen saturation, 
temperature, lactic acid, elements of a basic metabol-
ic panel, magnesium, elements of a complete blood 
count, antibiotic receipt, all microbiologic culture data, 
Clostridium difficile testing results, Confusion Assessment 
Method for the ICU (CAM-­ICU), Richmond Agitation 
Sedation Score (RASS), Glasgow Coma Scale (GCS), 
mechanical ventilation status and variables related to 
ventilation, nephrology consultation, receipt of new 
RRT, indications for new RRT among patients who re-
ceived new RRT, medications known to increase risk of 
kidney injury, medications known to increase risk of 
neurologic injury, admitting team, date of admission, 
days spent in the ICU, days spent in the hospital, date 
of intubation(s) and extubation(s), date of discharge 
and date of death.
Primary outcome
The primary outcome will be a combination of the 
highest stage of AKI and death between randomisation 
and day 14. The stages of AKI are defined using creati-
nine measurements and the ‘Kidney Disease: Improving 
Global Outcomes (KDIGO)’34 criteria. The score will 
range from 0 (best value) to 4 (worst value):
0=No AKI.
1=Stage 1 AKI (creatinine increased by 1.5–1.9 times 
baseline or increase by ≥0.3 mg/dL).
2=Stage 2 AKI (creatinine increased by 2.0–2.9 times 
baseline).
3=Stage 3 AKI (creatinine increased by ≥3.0 times base-
line or increase to ≥4.0 mg/dL or new RRT).
4=Death.
‘Baseline’ creatinine values are defined as the lowest 
prior creatinine values from three different timepoints: 
the preillness creatinine value, the perienrolment creati-
nine value and the lowest prior on-­study creatinine value 
as defined below. Death is defined as mortality from any 
cause occurring prior to or on the end of study day 14, 
censored at hospital discharge. RRT is defined as receipt 
of RRT at any point between randomisation and the end 
of study day 14, censored at hospital discharge. Patients 
who are receiving RRT prior to enrolment can only expe-
rience values of 0 (patient did not die) or 4 (patient 
died) because they are ineligible to experience changes 
in creatinine or new receipt of RRT that define levels 1 
through 3.
Patients’ preillness creatinine will be defined as the 
lowest serum creatinine between 12 months and 24 hours 
prior to enrolment. For patients for whom a value is 
unavailable, a preillness creatinine value will be estimated 
using a previously described three-­variable formula 
(creatinine=0.74–0.2 (if female)+0.08 (if African Ameri-
can)+0.003×age (in years)).35 There are no validated esti-
mations of creatinine without race but we will evaluate 
the effect of social constructs by fitting models both with 
and without race in a sensitivity analysis.
Patients’ perienrolment creatinine will be defined hier-
archically using the creatinine value closest to enrolment 
in: (first) the 24 hours prior to enrolment, if available, 
and (second) the 6 hours after enrolment (if no value is 
available prior to enrolment). The prevalent AKI, or AKI 
that is present on admission and unrelated to the study 
intervention, will be defined by comparing the perienrol-
ment creatinine to the preillness creatinine.
On-­study creatinine will be defined as any creatinine 
value occurring after both the time of enrolment and 
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the time of the perienrolment creatinine value. On-­study 
creatinine values will be used to identify incident AKI and 
calculate the stage of AKI for the primary outcome.
The primary outcome will be calculated as follows:
	
►Patients who survive without new RRT and do not 
experience an on-­study creatinine value that is at 
least 0.3 mg/dL higher than the perienrolment value 
or any preceding on-­study value, and whose on-­study 
creatinine is never more than 1.5 times the perienrol-
ment value or any preceding on-­study value, will be 
considered not to have experienced incident AKI and 
will receive a value of 0 for the primary outcome.
	
►Among patients who survive and experience AKI 
(have on-­study creatinine value that is at 1.5 times 
or at least 0.3 mg/dL higher than the perienrolment 
value or any preceding on-­study value), the score for 
the primary outcome will be determined by the stage 
of AKI and classified as follows:
a.	 A value of 1 if the highest on-­study creatinine after 
qualifying for AKI is less than 2 times the lowest of 
the preillness creatinine value, the perienrolment 
creatinine value and the lowest prior on-­study 
creatinine value (baseline creatinine).
b.	A value of 2 if the highest on-­study creatinine 
after qualifying for AKI is at least 2 times and less 
than 3 times the lowest of the preillness creatinine 
value, the perienrolment creatinine value and the 
lowest prior on-­study creatinine value (baseline 
creatinine).
c.	 A value of 3 if the highest on-­study creatinine after 
qualifying for AKI is at least 3 times the lowest of 
the preillness creatinine value, the perienrolment 
creatinine value and the lowest prior on-­study 
creatinine value (baseline creatinine), with a 
maximum creatinine above 4 mg/dL, or receive 
new RRT.
	
►Patients who die will receive a value of 4.
The mechanisms and extent of AKI with antibiotic 
exposure are not well understood. The primary outcome 
window of 14 days was chosen as it was felt to capture the 
period most likely to be affected by controlling antibiotics 
choice for 168 hours (7 days).
Secondary outcomes
We have prespecified two secondary outcomes. Major 
adverse kidney events within 14 days (MAKE14) is 
the composite outcome of death within 14 days, new 
RRT within 14 days or stage 2 or higher AKI at day 14, 
according to KDIGO creatinine criteria. The second is 
number of days alive and free of delirium and coma in 
the 14 days after enrolment (delirium and coma-­free days 
to day 14). Delirium is defined as a positive assessment on 
the CAM-­ICU36 and coma is defined as an RASS of −4 or 
−537 at any point during that study day.
Exploratory outcomes
	
►Exploratory renal outcomes.
	–
Major adverse kidney events within 28 days 
(MAKE28).
	–
Highest stage of AKI or death between randomisa-
tion and day 7.
	–
Stage 2 or higher AKI as defined in the KDIGO cri-
teria for creatinine level within 14 days and 28 days 
after enrolment.
	–
New receipt of RRT within 14 days and 28 days after 
enrolment.
	–
Days alive and free of RRT during 14 days and 28 
days after enrolment.
	–
Highest creatinine level within 28 days after 
enrolment.
	–
Change from preillness creatinine to the highest 
creatinine level within 28 days after enrolment.
	–
Final creatinine level before hospital discharge at 
28 days.
	–
Ongoing receipt of RRT at hospital discharge or 
28 days.
	–
Nephrology consultation.
	
►Exploratory neurologic outcomes.
	–
Worst GCS Score during the 7, 14 and 28 days after 
enrolment.
	–
Delirium and coma-­free days in the 28 days after 
enrolment.
	
►Exploratory clinical outcomes.
	–
ICU-­free, 
hospital-­free, 
ventilator-­free 
and 
vasopressor-­free days in the 28 days after enrolment.
	–
14-­day mortality.
	–
28-­day mortality.
	–
Disposition of patients admitted from the ED (ward 
vs ICU).
	–
Escalation of antibiotics defined by subsequent re-
ceipt of meropenem, meropenem–vaborbactam, 
imipenem, imipenem–relebactam, cefiderocol, 
ceftazidime–avibactam, 
ceftolozane–tazobactam, 
tigecycline, amikacin, tobramycin, gentamicin.
Definition of supportive therapy-­free days is available in 
online supplemental section 5.
DSMB and interim analysis
A DSMB composed of experts in critical care medicine, 
infectious disease and biostatistics has overseen the 
design of the trial and is monitoring its conduct (online 
supplemental file 6). The DSMB conducted a single 
interim analysis, prepared by the study biostatistician, 
at the anticipated halfway point of the trial after enrol-
ment of 1025 patients. The meeting was held on 14 July 
2022, and the DSMB recommended continuing the trial 
to completion without alteration. The stopping boundary 
for efficacy was prespecified as p value for the difference 
between groups in the primary outcome of 0.001 or less. 
Given current use of both interventions as a part of usual 
care, there was no stopping boundary for futility. The 
use of a conservative Haybittle-­Peto boundary for effi-
cacy will allow the final analysis to be performed using 
an unchanged level of significance (p=0.05). The DSMB 
retains the authority to recommend stopping the trial at 
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any point, request additional data or interim analyses, 
or request modifications of the study protocol to protect 
patient safety.
Sample size estimation
As specified in the initial trial protocol, at the time of the 
single, planned interim analysis the DSMB oversaw a re-­es-
timation of the planned sample size. Because (1) concur-
rent receipt of vancomycin has been hypothesised to be 
in the proposed mechanistic pathway between receipt of 
an antipseudomonal penicillin and AKI and (2) approx-
imately 75% of patients in the trial concurrently receive 
vancomycin, the sample size was increased by 25% from 
2050 to 2500 patients. The increase in sample size ensures 
the number of patients receiving concurrent vancomycin 
will be approximately 2050, consistent with the orig-
inal sample size estimation. Assuming a two-­sided alpha 
of 0.05 and a distribution of the primary outcome with 
approximately 70% of patients experiencing no AKI, 10% 
of patients experiencing stage 1 AKI, 7% of patients expe-
riencing stage 2 AKI, 7% of patients experiencing stage 
3 AKI and 6% of patients experiencing death, we calcu-
lated that enrolment of a total of 2500 patients would 
provide 92% statistical power to detect an OR of 0.75 in 
the primary analysis.
Statistical analysis principles
Analyses will be conducted following reproducible 
research principles using R (R Foundation for Statistical 
Computing, Vienna, Austria).38 Continuous variables will 
be reported as mean±SD or median and IQR; categorical 
variables will be reported as frequencies and proportions. 
As a randomised controlled trial, there will be no compar-
ison of baseline characteristics. A two-­sided p value of 
<0.05 will be used to indicate statistical significance; with 
just one primary outcome, no adjustment for multiplicity 
will be made. Two secondary outcomes are specified, 
one safety outcome for each treatment regimen. Since 
hypothesised safety concerns are independent, we will 
not adjust our secondary outcomes for multiplicity. For 
all other outcomes, emphasis will be placed on the magni-
tude of differences between groups rather than statistical 
significance.
Main analysis of the primary outcome
The main analysis will be an unadjusted, intention-­to-­treat 
comparison of the primary outcome between patients 
randomised to receive antipseudomonal cephalosporins 
versus antipseudomonal penicillins who received at least 
one dose of a study drug using a proportional odds regres-
sion model. The unadjusted common OR with CIs will 
be the primary treatment effect. If departures from the 
proportionality assumption are observed, then a partially 
proportional odds model will be constructed.
Secondary analyses of the primary outcome
Multivariable modelling to account for covariates
To account for participants’ baseline status, we will 
include covariates in the proportional odds regression 
model. The following prespecified baseline covariates 
will be considered: age; sex; perienrolment creatinine; 
receipt of RRT prior to enrolment; receipt of vasopres-
sors; receipt of mechanical ventilation; SOFA Score; 
presumed source of infection; enrolment location (ED 
vs ICU). Source of infection will be categorised as: lung, 
intra-­abdominal (perforated viscus, ischaemic bowel, 
cholecystitis/cholangitis, peritonitis/abscess/small bowel 
obstruction, Clostridium difficile colitis, spontaneous bacte-
rial peritonitis, pancreatitis, enterocolitis/diverticulitis, 
other intra-­abdominal infections), urinary (pyelone-
phritis, obstructive urinary tract infection), skin and soft 
tissue (cellulitis/abscess/necrotizing fasciitis/decubitus 
ulcer, surgical site infection), other (bone/joint, primary 
blood stream infection, intravascular catheter, dissemi-
nated infection, central nervous system infection, endo-
carditis, other) and unknown.
Effect modification
We will test the interaction between the treatment effect 
of antipseudomonal cephalosporins versus antipseu-
domonal penicillins and baseline variables expected to 
modify the effects of treatments on the outcomes. The 
effect modifiers will be tested one by one by including both 
the main effect and the interaction term in the adjusted 
model. Because this study is not formally designed or 
powered to test for interaction, a less conservative two-­
sided p value for the interaction term will be used, with 
values less than 0.10 considered suggestive of potential 
interaction and values less than 0.05 considered conclu-
sive evidence. The following variables will be considered:
1.	 Location at randomisation (ED vs ICU).
2.	 Presence of sepsis (meeting Sepsis-­3 criteria) at rando-
misation.
3.	 Receipt of vancomycin (defined as an order for vanco-
mycin in the 12 hours before or 6 hours after rando-
misation).
4.	 Source of infection.
5.	 AKI at randomisation.
6.	 CKD at randomisation.
7.	 Neutropenia at randomisation.
8.	 Admitting team (medicine vs surgical).
Sensitivity analyses of the primary outcome
To assess robustness of findings, the main analysis of the 
primary outcome will be repeated in several alternative popu-
lations. First, we will include all patients who were identified 
by the CDS tool as meeting eligibility criteria, regardless of 
receipt of any doses of antipseudomonal cephalosporins or 
antipseudomonal penicillins. Second, many patients are initi-
ated on antibiotics in the acute setting, which are stopped as a 
more likely cause for their illness becomes known (eg, pulmo-
nary embolism). We will repeat the main analysis restricted 
to the subset of patients that received more than 2 days (48 
hours) of antipseudomonal therapy. Third, because race is 
a social construct, we will repeat the main analysis with those 
whose preillness creatinine was estimated by an equation 
without race as a factor. Fourth, to avoid uncertainty around 
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the calculations of preillness creatinine, we will repeat the 
main analysis excluding patients with calculated preillness 
creatinine values. Because group assignment might influ-
ence recovery from prevalent AKI in a way that could affect 
calculations of the primary outcome, we will recalculate the 
primary outcome as a repeated measure assessed daily from 
randomisation to day 14 using only the preillness creatinine 
as the baseline creatinine.
Analysis of the secondary outcomes
Analysis of secondary outcomes will follow a similar frame-
work to the primary analysis, with a systematic assessment 
of unadjusted models, adjusted models using the same set 
of covariates. The secondary outcome of MAKE14 will be 
compared between groups using a logistic regression model. 
Delirium and coma-­free days to day 14 will be compared 
between groups using a proportional odds regression model, 
and will include the additional covariate of coma on enrol-
ment for the adjusted model. Delirium and coma free days 
to day 14 will be assessed for effect modification using the 
same approach as the primary outcome replacing receipt of 
vancomycin with baseline coma.
Analyses of exploratory outcomes
Exploratory outcomes will proceed using unadjusted 
analyses only, with presentation of effect sizes and CIs as 
well as p values. Continuous outcomes will be compared 
with the Mann-­Whitney U test and the difference in 
medians reported. For categorical variables, groups will 
be compared with the χ2 test or Fischer’s exact test as 
appropriate and results will be expressed as a difference 
in proportions or ORs, each with 95% CIs.
Handling of missing data
In the case that a patient is enrolled, never receives 
RRT and is discharged alive without having a creatinine 
value measured following enrolment, the patient will 
be assumed to have no AKI. When data are missing for 
secondary or exploratory outcomes, complete-­case anal-
ysis, excluding cases where data for the analysed outcome 
are missing, will be performed. There will be no impu-
tation of missing data for these outcomes. In adjusted 
analyses, missing data for covariates will be imputed using 
multiple imputations.
Trial status
The ACORN trial is currently enrolling and started enrol-
ment on 10 November 2021.
Ethics and dissemination
Waiver of informed consent
Acutely ill patients for whom the provider is ordering 
broad-­spectrum antibiotics in the ED or ICU are at 
significant risk for morbidity and mortality from their 
underlying illness. Most patients receiving empiric 
gram-­negative antibiotics in routine clinical care receive 
either antipseudomonal cephalosporins or antipseu-
domonal penicillins. Any benefits or risks of these 
two approaches are experienced by patients receiving 
gram-­negative antibiotics in clinical care, outside the 
context of research. As a requirement for enrolment in 
the ACORN trial, the patient’s treating clinician must 
have made the decision to order either antipseudomonal 
cephalosporins or antipseudomonal penicillins as part of 
routine clinical care and affirmed that either would be a 
safe and reasonable approach for the patient (otherwise 
the patient is excluded). Therefore, making the decision 
between the two approaches randomly through study 
group assignment rather than by a provider who thinks 
either approach is safe and reasonable for the patient was 
proposed to pose no more than minimal incremental risk.
Obtaining informed consent for participation in the study 
would be impracticable. Receipt of antibiotics in sepsis is time 
sensitive. Each hour delay in antibiotics in patients with sepsis 
is associated with an increase in mortality.39 Attempting to 
obtain prospective written informed consent from patients 
presenting to the ED or ICU during the interval between 
the placement of an order for empiric antibiotics and their 
administration risks delaying antibiotic delivery. Moreover, 
acutely ill patients with sepsis are commonly delirious or 
unconscious, and a legally authorised representative is not 
consistently present at the time of initiation of antibiotics. 
Because the trial determines only the choice of the initial 
antipseudomonal antibiotic and defers decisions regarding 
subsequent doses of antibiotics (eg, duration of therapy, esca-
lation, de-­escalation) to treating clinicians, enrolment, trial 
group assignment and the primary study procedure (admin-
istration of the assigned antibiotic) commonly occurs within 
1 hour of meeting eligibility criteria.
Because the study was expected to pose minimal risk and 
prospective informed consent was considered to be imprac-
ticable, a waiver of informed consent was requested and 
granted from the Vanderbilt University Medical Center IRB.
Protocol changes
ClinicalTrials.Gov will be updated with any amendments to 
the protocol as per SPIRIT guidelines (online supplemental 
file 7).
Dissemination plan
Trial results will be submitted to a peer-­reviewed journal for 
consideration of publication and will be presented at one 
or more scientific conferences. Data will be made available 
following publication (online supplemental file 8).
CONCLUSION
To allow for a clearer and more objective interpretation 
of trial results, this description delineates the ACORN 
trial methods and analysis prior to the conclusion of 
enrolment.
Author affiliations
1Division of Allergy, Pulmonary, and Critical Care Medicine, Vanderbilt University 
Medical Center, Nashville, Tennessee, USA
2Department of Biomedical Informatics, Vanderbilt University Medical Center, 
Nashville, Tennessee, USA
3Department of Biostatistics, Vanderbilt University School of Medicine, Nashville, 
Tennessee, USA
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4Vanderbilt Institute for Clinical and Translational Research, Vanderbilt University 
Medical Center, Nashville, Tennessee, USA
5Department of Pharmaceutical Services, Vanderbilt University Medical Center, 
Nashville, Tennessee, USA
6Department of Emergency Medicine, Vanderbilt University Medical Center, 
Nashville, Tennessee, USA
7Division of Infectious Disease, Vanderbilt University Medical Center, Nashville, 
Tennessee, USA
8Division of Nephrology and Hypertension, Vanderbilt University Medical Center, 
Nashville, Tennessee, USA
9Department of Surgery, Vanderbilt University Medical Center, Nashville, Tennessee, 
USA
Twitter Edward Tang Qian @edqain, Bradley Daniel Lloyd @BradLloydVFL and 
Bradley Dennis @TraumaDawg
Collaborators  A complete list of the members of the Vanderbilt Learning 
Healthcare System Platform Investigators is provided in the online supplemental 
file 1.
Contributors  All study authors approved the final version of this manuscript. Study 
concept and design: ETQ, JDC, AW, LW, JStollings, GN, PW, EDS, JW, JA, WHS, MWS 
and TWR. Acquisition of data: ETQ, BDL and KS. Drafting of the manuscript: ETQ, 
JDC, MWS and TWR. Critical revision of the manuscript for important intellectual 
content: ETQ, JDC, AW, LW, JSiemann, MLD, JStollings, BDL, KS, GN, PW, EDS, BD, 
JW, JA, WHS, MWS and TWR. Study supervision: MWS and TWR.
Funding  The project described was supported by the VICTR Learning Healthcare 
System Platform under CTSA, award No. UL1 TR002243, from the National Center 
for Advancing Translational Sciences. It contents are solely the responsibility of 
the authors and do not necessarily represent the official views of the National 
Center for Advancing Translational Sciences or the National Institutes of Health. 
ETQ was supported by the National Heart, Lung, and Blood Institute, award No. 
T32HL087738. JDC was supported in part by the NHLBI (K23HL153584). MWS 
was supported in part by the NHLBI (K23HL143053). EDS was supported by the 
Vanderbilt O’Brien Kidney Center P30-­DK114809 for service provided through the 
Clinical and Translational Research Core. The funding institutions had no role in (1) 
conception, design, or conduct of the study, (2) collection, management, analysis, 
interpretation, or presentation of the data or (3) preparation, review or approval of 
the manuscript.
Competing interests  None declared.
Patient and public involvement  Patients and/or the public were not involved in 
the design, or conduct, or reporting, or dissemination plans of this research.
Patient consent for publication  Not applicable.
Provenance and peer review  Not commissioned; externally peer reviewed.
Supplemental material  This content has been supplied by the author(s). It has 
not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been 
peer-­reviewed. Any opinions or recommendations discussed are solely those 
of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and 
responsibility arising from any reliance placed on the content. Where the content 
includes any translated material, BMJ does not warrant the accuracy and reliability 
of the translations (including but not limited to local regulations, clinical guidelines, 
terminology, drug names and drug dosages), and is not responsible for any error 
and/or omissions arising from translation and adaptation or otherwise.
Open access  This is an open access article distributed in accordance with the 
Creative Commons Attribution Non Commercial (CC BY-­NC 4.0) license, which 
permits others to distribute, remix, adapt, build upon this work non-­commercially, 
and license their derivative works on different terms, provided the original work is 
properly cited, appropriate credit is given, any changes made indicated, and the use 
is non-­commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
ORCID iDs
Edward Tang Qian http://orcid.org/0000-0002-1092-3533
Matthew W Semler http://orcid.org/0000-0002-7664-8263
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Antibiotic Choice On ReNal outcomes (ACORN) trial 
Statistical Analysis Plan Revision Sequence 
7/27/2022 
Original Statistical Analysis Plan complete and submitted for review at BMJ Open 
10/7/2022 
Enrollment Complete 
3/10/2023 
Statistical Analysis Plan Published in BMJ Open 
 
Qian ET, Casey JD, Wright A, et al. Protocol and statistical analysis plan for the 
Antibiotic Choice On ReNal outcomes (ACORN) randomised clinical trial. BMJ Open. 
2023;13(3):e066995. Published 2023 Mar 10. doi:10.1136/bmjopen-2022-066995 
 
 
* No changes occurred to the Statistical Analysis Plan from initial submission to publication