Single Blinded Randomized Trial of Transversus Abdominis Plane Block Using Liposomal Bupivacaine in Metabolic and Bariatric Surgery Patients
Phase: PHASE1
Conditions: Morbid Obesity, Bariatric Surgery Candidate
Sponsor: Wake Forest University Health Sciences

TAP Block Study
NCT05537883
IRB Approval Date:  07AUG2023

Bariatric Exparel TAP Block Study 
Date: 8/4/2023 
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Study Title: Single Blinded Randomized Trial of Transversus Abdominis Plane Block Using 
Liposomal Bupivacaine in Metabolic and Bariatric Surgery Patients 
Principal Investigator: Selwan Barbat 
Co-Investigators: Paul Chandler, Elizabeth Santone 
Sponsor or funding source: Wake Forest University Health Sciences 
Background, Rationale, and Context 
The transversus abdominis plane (TAP) block was described in 2007 using an ultrasound 
to inject local anesthetic between the internal oblique and transversus abdominis muscles where 
the sensory nerves of the abdominal wall travel [1]. The TAP block can also be performed by the 
surgeon with laparoscopic guidance. TAP block has been shown to provide analgesia after ab-
dominal surgery, decreasing opioid use, and is widely accepted into practice [2]. TAP block has 
become a cornerstone in enhanced recovery after surgery programs, as well as part of multi-
modal analgesia, and opioid reducing efforts nationwide. A recent meta-analysis of Randomized 
Controlled Trials (RCT) comparing TAP block with bupivacaine or ropivacaine to no TAP block 
in bariatric surgery showed reduced postoperative nausea and vomiting and time to ambulation 
[3]. Liposomal bupivacaine compared to plain bupivacaine has been touted to provide a longer 
duration of analgesia (up to 72 hours) by slowly releasing the anesthetic agent into local tissue. A 
recent systematic review comparing liposomal bupivacaine to conventional local anesthetic 
agents in regional anesthesia, including TAP blocks, showed conflicting results so no definitive 
conclusions could be made [4]. It is unclear if liposomal bupivacaine is superior to plain bupiva-
caine for TAP blocks in bariatric surgery. Our study would be the first RCT comparing laparo-
scopic TAP block with liposomal bupivacaine vs plain bupivacaine in a bariatric surgery popula-
tion.  
Objectives 
Compared to only Bupivacaine administered via TAP block, we will investigate the anal-
gesia effects to patients undergoing metabolic and bariatric surgery receiving TAP block with a 
Liposomal Bupivacaine mixture.     
Primary Objective: To determine if patients undergoing metabolic and bariatric surgery 
receiving TAP block with a Liposomal Bupivacaine results in pain scores, as measured by visual 
analogic scale (VAS), that are equivalent compared to patients receiving TAP block with Bupi-
vacaine only.  
Primary Hypothesis: 
1) Lower values of the outcome variable VAS are desirable, and the hypothesis
is listed below –

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Hypothesis 1. 1  
𝐻𝐻0: 
 𝜇𝜇𝐸𝐸−𝜇𝜇𝑆𝑆  ≥𝛿𝛿  (Study group is different compared to the active 
control group      by 𝛿𝛿 or more) 
𝐻𝐻1: 
 𝜇𝜇𝐸𝐸−𝜇𝜇𝑆𝑆  < 𝛿𝛿 (Study group is equivalent to the active control when 
difference is within prespecified 𝛿𝛿) 
Where 𝜇𝜇𝐸𝐸, 𝜇𝜇𝑆𝑆  are the population means for the outcome VAS measured at 24 
hours after surgery for the study group (E) and the standard (S) active group, re-
spectively  
𝛿𝛿 is non-inferiority margin, specified in advance based on clinical judgement. 
Based on our clinical experience, 𝛿𝛿 = 1.5 
Secondary Objectives: Compared to TAP block with Bupivacaine only, we will compare 
opioid consumption, and other effect differences to patients undergoing metabolic and bariatric 
surgery receiving TAP block with Liposomal Bupivacaine.     
Secondary Hypotheses 
Hypothesis 2.1 – Patients undergoing metabolic and bariatric surgery receiving 
TAP block with Liposomal Bupivacaine results in less opioid consumption before hospi-
tal discharge /during the first 48 hours postoperatively as measured in morphine equiva-
lents (mg) compared to patients receiving simply TAP block with Bupivacaine only.  
Hypothesis 2.2 - Patients undergoing metabolic and bariatric surgery receiving 
TAP block with Liposomal Bupivacaine results in pain score as measured by visual ana-
logic scale (VAS) at 12 hours after surgery that are equivalent compared to patients re-
ceiving TAP block with Bupivacaine only.  
Exploratory objectives: We will explore other effects, including pain score at 48 hours, 
and 72 hours after surgery, total opioid consumption required post op during their one-week post 
op visit as measured in morphine equivalences. 
Methods and Measures 
Design 
This study is a 2-arm parallel single blinded randomized equivalency, single-cen-
ter, clinical trial.  Patients will be blinded to type of TAP block used.  
Setting 
This study will take place at Atrium Health, an academic medical center. 
Subjects selection criteria 

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Inclusion Criteria 
To be eligible for enrollment in this study, participants must meet all the following 
criteria: 
1. Adult, age > 18 years 
2. Participants who can give written informed consent and willing to comply with all 
stud-related procedures. 
3. Patients undergoing primary sleeve gastrectomy or roux-en-y gastric bypass 
Exclusion Criteria 
1. Patients undergoing duodenal switch procedures 
2. Patients undergoing concomitant hiatal hernia repair or ventral hernia repair or 
cholecystectomy at time of primary metabolic surgery 
3. Patients with chronic opioid use 
Sample Size 
The number of patients required in each group is determined from a power analysis based 
on primary hypothesis.  
In this study, based on our clinical experience, we assume standard deviation for each 
group is 3, the margin of equivalence is 1.5 on NRS, and the true difference between the two 
groups is 0 on the NRS. Group sample size of 88 from each group achieves 90% power to detect 
our prespecified equivalence margins, with alpha of 0.05.  Assuming a 20% dropout or with-
drawal based upon previous experience, 106 subjects per group will be required.   
 
Interventions and Interactions 
 
There will be two groups: (1) active control and (2) study group. Active control group pa-
tients receive TAP block with a Bupivacaine only mixture, containing 50 mL 0.5% Bupivacaine, 
and 100 mL normal saline solution. Study group patients will receive TAP block with a Liposo-
mal Bupivacaine mixture, containing 20 mL Liposomal Bupivacaine, 30 mL 0.5% Bupivacaine, 
and 100 mL normal saline solution. TAP block technique will be standardized using subcostal as 
well as anterior axillary line as landmarks, injecting down to level of T10, using laparoscopic-
guided approach. TAP block will be administered at the start of every case, after the first port is 
placed upon laparoscopy. Type of anesthesia administered will also be standardized including 
the use of narcotics, lidocaine, inhalational anesthesia and Ketamine. 
 
Randomization schedules will be generated by SAS 9.4 (SAS Institute Inc., Cary, NC) by 
using a masked block randomization procedure. Eligible patients will be randomized with a 1:1 
ratio between the 2 groups of patients receiving TAP block Exparel mixture or simply bupiva-
caine administered via TAP block. Research Electronic Data Capture (REDCap) randomization 

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module will be used to manage randomization and allocate treatment groups. The allocation se-
quence will be concealed with application of the REDCap.  
 
Outcome Measure(s) 
Primary Outcome measures 
1. Pain score at 24 hours post-operative, using visual analogue scale (VAS), ranging 
from 1 to 10. One indicates no pain, and 10 indicates the worst pain one could image. 
Secondary Outcome Measures 
1. Pain scores at 12 hours, 48 hours, and 72 hours post-operatively.  
2. Morphine milligram equivalences consumed during hospital stay 
3. Morphine milligram equivalences prescribed and consumed as measured at one week 
follow up clinic visit 
4. Post-operative nausea and vomiting (PONV) measured by a numerical score (1: no 
nausea or vomiting, 2: some nausea no vomiting, 3: nausea and vomiting) 
5. Length of stay in hours 
6. Patient satisfaction score 
These parameters will be scored via SeamlessMD on a phone application, as well as pa-
per and pen on a standardized reporting form for patients less comfortable using technology. 
Data will also be collected from patient electronic charts.  
 
Analytical Plan 
 
Equivalency test with priori specified non-inferiority region will be used to assess pri-
mary outcome variables. 
Descriptive statistics (mean, range, percentage, median, etc.) will be used to assess the quality 
and accuracy of the administrative and clinical data. Means with standard deviations or medians 
with interquartile range (IQR) will be reported for continuous variables and percentages for cate-
gorical variables. Missing data will be evaluated prior to data modeling. General linear regres-
sion, or other generalized linear regression models will be used to compare the outcomes be-
tween the two groups with both univariate or multivariate analyses. Potential confounders will be 
identified with univariate analysis. For univariate analyses, a Student’s t-test or Wilcoxon two-
sample test will be used for continuous variables, and chi-square test for categorical variables 
against the primary and secondary outcomes. Both unadjusted and adjusted odds ratio (OR) with 

Bariatric Exparel TAP Block Study  
 
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corresponding 95% confidence interval (CI) will be reported. Two-tailed p values will be calcu-
lated for all tests, and p< 0.05 is considered statistically significant. All data will be analyzed us-
ing Statistical Analysis Software, version 9.4 (SAS Institute Inc., Cary, NC). 
There are no plans for interim data analyses. Analyses will be conducted according to per-proto-
col (PP) principle. 
 
Human Subjects Protection 
Subject Recruitment Methods 
Patients who are scheduled for sleeve gastrectomy or roux-en-y gastric bypass will be identified 
and recruited for the study at the Atrium Health Weight Management clinics during their pre-
operative visit. The bariatric surgeons and bariatric surgery fellows will do the recruiting, and pa-
tients will be contacted directly face to face during the preoperative visit about the study. Patients 
will also receive a written flyer containing information about the study during the preoperative 
visit. As all qualifying patients will be informed about the study during the preoperative visit, ac-
cess to participation among women and minorities will depend on how many of these patients 
undergo sleeve gastrectomy or roux-en-y gastric bypass at our institution. Subject’s privacy will 
be protected by storing records of Protected Health Information in locked facilities or password 
protected computers. Data will be stored on a password protected computer of the investigator 
and in a password protected RedCap database. 
 
Informed Consent 
Signed informed consent will be obtained from each subject. The investigators as well as the 
other bariatric surgeons and bariatric surgery fellows will obtain informed consent at the Atrium 
Health Weight Management clinics during the preoperative visit. 
 
Confidentiality and Privacy 
Confidentiality will be protected by collecting only information needed to assess study out-
comes, minimizing to the fullest extent possible the collection of any information that could di-
rectly identify subjects, and maintaining all study information in a secure manner. To help ensure 
subject privacy and confidentiality, only a unique study identifier will appear on the data collec-
tion form. Any collected patient identifying information corresponding to the unique study iden-
tifier will be maintained on a linkage file, store separately from the data. The linkage file will be 
kept secure, with access limited to designated study personnel. Following data collection subject 
identifying information will be destroyed (state the anticipated time the data will be destroyed, 
e.g. three years after closure of the study, and the method of destruction), consistent with data 
validation and study design, producing an anonymous analytical data set. Data access will be 
limited to study staff. Data and records will be kept locked and secured, with any computer data 

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password protected. No reference to any individual participant will appear in reports, presenta-
tions, or publications that may arise from the study. 
 
Data and Safety Monitoring 
The principal investigator will be responsible for the overall monitoring of the data and safety of 
study participants. The principal investigator will be assisted by other members of the study staff. 
 
Reporting of Unanticipated Problems, Adverse Events or Deviations 
Any unanticipated problems, serious and unexpected adverse events, deviations or protocol 
changes will be promptly reported by the principal investigator or designated member of the re-
search team to the IRB and sponsor or appropriate government agency if appropriate. 
 
References: 
1. McDonnell JG, O’Donnell BD, Farrell T, et al. Transversus abdominis plane block: a cadav-
eric and radiological evaluation. Reg Anesth Pain Med. 2007;32:399–404  
2. Mukhtar K, Singh S. Transversus abdominis plane block for laparoscopic surgery. Br J 
Anaesth. 2009;102:143–4.  
3. Hytham K.S. Hamid, Amjed Y. Ahmed, Alan A. Saber, Sameh H. Emile, Mohamed Ibrahim, 
Jaime Ruiz-Tovar. Transversus abdominis plane block using a short-acting local anesthetic re-
duces pain and opioid consumption after laparoscopic bariatric surgery: a meta-analysis, Surgery 
for Obesity and Related Diseases. Volume 16, Issue 9. 2020, Pages 1349-1357  
4. Jin Z, Ding O, Islam A, Li R, Lin J. Comparison of liposomal bupivacaine and conventional 
local anesthetic agents in regional anesthesia: A systematic review. Anesth and Analg. 2021; 132 
(6): 1626-34. 
 
Appendix 
1. Consent form 
2. Copy of Seamless MD Daily Health Check surveys 
 
 
 
 

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