Conditions: Inflammation Platelet Dysfunction
Keywords: Cardiopulmonary Bypass Infant Nitric Oxide Thrombocytopenia Blood Platelets
Allocation: RANDOMIZED | Intervention model: PARALLEL
Enrollment: 40
Healthy volunteers: no

Brief summary:
Open heart surgery requires the use of a cardiopulmonary bypass (CPB) circuit. As blood flows across the artificial surfaces of the CPB circuit, platelets are activated and consumed. This activation results in a profound inflammatory reaction and need for transfusion. This reaction is intensified in younger, smaller patients undergoing longer, more complex open heart surgery. Nitric oxide is naturally released by vascular endothelial surfaces and acts as a signaling molecule which prevents platelet activation. The investigators hypothesize that the addition of the nitric oxide to the sweep gas of the oxygenator during cardiopulmonary bypass surgery will replace this natural endothelial function and thus prevent platelet activation and consumption. The investigators plan to test this hypothesis with a pilot double blinded, randomized trial of 40 patients less than a year of age undergoing cardiac surgery requiring CPB.

Detailed description:
Open heart surgery requires the use of a CPB circuit. As blood flows across the artificial surfaces of the CPB circuit, platelets are consumed (1). The investigators recently completed a prospective observational trial of neonates undergoing cardiac surgery requiring CPB. In this trial the investigators demonstrated a dramatic decrease in platelet count from baseline to intraoperatively. The platelet count rebounded with transfusion and normalized by the time of admission to the cardiac intensive care unit (CICU). Despite prophylactic transfusion of blood products to all patients, 41% experienced excessive postoperative bleeding (defined in terms of chest tube output and need for reoperation).

Further investigation by Dr. Debra Newman in her lab at the Blood Research Institute delineated the platelet defect associated with CPB in the neonates more clearly. Dr. Newman found a significant decrease in the platelet responsiveness to thrombin receptor activating protein (TRAP), thromboxane A2 analog (U46619), and collagen-related peptide (CRP). Further analysis revealed that the effect of CPB on platelet responsiveness to TRAP and U46619 is likely dependent on its effect on platelet count, whereas CPB affects platelet responsiveness to CRP independently of platelet count.

In children, postoperative blood loss and transfusion of blood products has been shown to contribute significantly to the morbidity and mortality of surgeries that require CPB (2, 3). In addition to the need for blood product replacement, the activation of platelets contributes to the intense inflammatory reaction seen in surgeries requiring CPB (4). Patients with a less intense inflammatory response post-operatively generally do better with less morbidity (5).

The oxygenator membrane surface of the CPB pump is a large contributor to the surface area of CPB circuit. As a major contributor to the surface area of the circuit and the location of the gas interface, the oxygenator is a significant contributor to the hemostatic and inflammatory stimulus of CPB. Advances in oxygenator technology have modified the surface to prevent interaction with the blood, but no artificial surface has been found to be as inert as the natural endothelium of the vasculature (5).

A major mechanism by which endothelial surfaces inhibit activation of platelets is by producing nitric oxide (6). Nitric oxide is lipophilic and traverses cellular membranes where it acts on intracellular signaling pathways in platelets to prevent platelet activation and aggregation (7). The artificial surface of the CPB pump does not produce nitric oxide and hence is devoid of this potent inhibitor of platelet activation.

In multiple experimental ex-vivo models of CPB, the addition of nitric oxide to the sweep gas of the oxygenator resulted in preserved platelet counts, preserved platelet function, and decreased markers of platelet activation (8-11).

Multiple clinical trials of nitric oxide administration during CPB have shown positive results. Chung et al. showed in a group of 41 adults undergoing coronary artery surgery requiring CPB that the addition of nitric oxide to the oxygenator resulted in a preservation of platelet numbers, a decrease in markers of platelet activation, and less post-operative blood loss (12). Checchia et al. investigated the effect of nitric oxide in a group of sixteen infants undergoing repair of tetralogy of Fallot and found the patients treated with nitric oxide had an improvement in clinical outcomes of length of stay in the intensive care unit and number of hours requiring mechanical ventilation (13). James et al. showed a 50% decrease in the incidence of low cardiac output syndrome in a randomized trial of 198 children. The effect was most profound in the younger children and those undergoing the most complex repairs (14). These patients are also the ones demonstrated to have the most intense inflammatory reaction postoperatively (15).

Despite these promising studies, several questions remain. The mechanism of platelet preservation has not been delineated. The collaboration between clinicians at Children's Hospital of Wisconsin and Dr. Newman at the Blood Center of Wisconsin has been established and has experience in investigating the effects of CPB on platelets in infants. This collaboration is poised to help define the mechanism of nitric oxide in preserving platelet function during CPB in infants. All studies to date have been single center and underpowered to investigate clinical outcomes of interest such as mortality and length of hospital stay. Dr. Niebler has begun to assemble a multi-center study team. Local data is necessary to help guide the power calculation in determining the sample size for this larger study and to demonstrate the capabilities of the local institution in leading a trial of this magnitude.

Arms:
arm 1: 20 ppm of Nitric Oxide delivered to the oxygenator via the INOmax device for the duration of the cardiopulmonary bypass time arm 2: INOmax device attached to the oxygenator, but no gas is delivered through the device

Interventions: intervention 1: Nitric Oxide intervention 2: Placebo intervention 3: INOmax
Intervention descriptions: intervention 1: 20 ppm of Nitric Oxide gas delivered to the oxygenator for the duration of cardiopulmonary bypass intervention 2: INOmax device connected to oxygenator, but no gas is delivered intervention 3: All patients will have the INOmax device connected to the oxygenator

Protocol document:
Prot_SAP_000.pdf: 
Title: Nitric Oxide Administration During Pediatric Cardiopulmonary 
Bypass Surgery to Prevent Platelet Activation 
 
NCT03455218 
Unique Protocol ID 1111115-1NO in CPB 001 
 
 
Study Protocol and Statistical Analysis Plan 
 
Document Date: 5/19/2020 
 
 
 


Protocol 
To complete the aims and objectives of this project we are planning a pilot randomized, double 
blinded, placebo controlled clinical trial of nitric oxide added to the sweep gas of the oxygenator 
during cardiac surgery requiring CPB in infants.   
Inclusion Criteria: Infants less than one year of age undergoing cardiac surgery with the use of 
cardiopulmonary bypass.   
Exclusion Criteria:  Prior surgery requiring CPB within the same hospitalization, pre-operative 
need for ECMO or mechanical circulatory support, known hypersensitivity to nitric oxide, 
known hemostatic or thrombotic disorder that results in an altered transfusion/anticoagulation 
protocol 
Equitable subject selection:  All patients will be considered for eligibility that meet the 
inclusion/exclusion criteria regardless of race, gender, or ethnic background.  Non-English 
speaking patients will be considered for inclusion if a suitable consent form can be approved 
prior to their surgical procedure.  A Spanish language short form will be submitted along with 
the initial study as we anticipate some eligible subjects will be Spanish speaking only.  Other 
languages encountered in eligible patients will be considered on an individual basis and if a 
suitable consent form can be drafted and approved prior to the patient’s surgical date, they will 
be considered for enrolment.    
Sample Size: 40 patients equally distributed amongst the treatment and placebo groups 
Power Calculation: using 0.05 as type 1 error tolerance and previous data from neonatal CPB 
studies, a minimum sample size of 12 patients is necessary to detect a difference of a change in 
platelet count (Specific Aim 1) of 50 with a power of 91%.  
Sample size justification:  In order to maximize the ability to estimate a sample size for a larger 
multi-institutional trial (Specific Aim 2) we need to maximize the number of patients enrolled 
within this local pilot trial.  Approximately 120 infants annually meet the inclusion/exclusion 
requirements annually at CHW.  Given experience with prior interventional studies in this 
population, we anticipate a consent rate of approximately 33%.  Therefore we anticipate being 
able to enroll 40 patients into this trial within one year. 
Randomization: Stratified to insure the number of patients with Society of Thoracic Surgery 
(STS) Mortality Class 1-3 and 4-5 surgeries are equally distributed.  
Justification for stratification of randomization:  The complexity of congenital cardiac surgery is 
known to significantly impact morbidity and mortality (16).  In order to insure an equal 
distribution of patients with this known confounder among groups we will stratify the 
randomization to insure an equal distribution to active and placebo groups.    
Recruitment: The PI and co-investigators have access to the cardiac surgical scheduling 
coordinators.  We will be in contact with them and browse the list of scheduled surgical patients 
at the weekly surgical conference.  The PI and co-investigators are also active clinicians within 
the cardiac intensive care unit and will be looking for eligible patients amongst the census of the 
intensive care unit within the normal course of their clinical duties.  No fliers or published 
materials will be used.  If the patient has an identified primary cardiologist at the time they are 
deemed to be eligible, we will contact them prior to approaching the patient/family to answer any 
questions they would have.   


Treatment:  A minimum sweep gas flow of 2.5 L/min will be used in all patients with CO2 added 
to maintain PaCO2 35-40 mmHg. All patients will have an INOmax DSIR device in line with the 
sweep gas.  Nitric oxide at a dose of 20 ppm will be added to the sweep gas of the treatment 
group from the initiation to the conclusion of CPB.  The placebo group will not receive nitric 
oxide but will be connected to the INOmax DSIR device.   
The INOmax DSIR  device and nitric oxide will be supplied by Mallinckrodt Pharmaceuticals. A 
letter indicating this support from Mallinckrodt is included in the package.         
Blinding:  All care providers involved in the clinical care of the patient will be blinded to 
treatment group (and methemoglobin levels) for 30 days post-operatively or hospital discharge 
(whichever is later).  A single study staff (perfusionist or respiratory care practitioner) will be 
responsible for nitric oxide delivery according to the randomization scheme outlined above. 
Study Measurements (Primary objectives in bold):   
Aim 1:  
Baseline and at conclusion of cardiac repair/prior to transfusion: Change in platelet count, 
platelet response to TRAP, U46619, and CRP (to be done at the Blood Research Institute) 
Aim 2: 
30 day (all cause) mortality, length of hospital stay post-operatively, transfusion volumes of 
platelets and pRBCs, total number of transfused products, length of mechanical ventilation post-
operatively, vasoactive infusion score (highest within the first 24 hours post-operatively), need 
for ECMO within 48 hours post-operatively, and total hospital cost.    
Aim 3: 
Baseline, at conclusion of CPB, and upon arrival to ICU: Methemoglobin levels 
 
 


Statistical Analysis Plan 
A redcap database will be created to collect all data fields and insure data integrity.  Statistical 
support will be through a qualified statistician from the Clinical and Translational Science 
Institute of Southeast Wisconsin, Dr. Chiang-Ching Huang.  We plan to compare continuous 
variables such as change in platelet count; platelet response to TRAP, U46619, and CRP; length 
of stay; length of mechanical ventilation; transfusion volumes; total hospital cost; and 
methemoglobin levels with either a Mann Whitney test or t-test.  A chi-square analysis will be 
used for dichotomous variables such as mortality and need for ECMO.  Multivariate or 
regression analysis will be done as needed to control for significant cofounders such as surgical 
complexity scoring, age, gender, race, ethnicity, weight, and presence of known genetic disorder.