The investigators propose a randomized double-blind trial comparing TAP blocks with
liposomal bupivacaine, plain bupivacaine, and placebo in patients having elective
abdominal surgery.
After eligibility is confirmed, patients will receive complete information about the
study both verbally and in writing. Informed consent will be obtained from the patients
prior to randomization and study-specific procedures.
Randomization will be based on computer-generated codes and use random-sized blocks.
Allocations will be concealed until the morning of surgery where they will be provided by
a web-based system. Randomization will be stratified by study site and chronic opioid
use, defined by opioid use for more than 30 consecutive days within three preoperative
months, at a daily dose of 15 mg or more of morphine or equivalent. Randomization will
also be stratified according to anticipated type of surgery (open vs.
laparoscopic-assisted). Clinicians doing the blocks will not be involved in data
collection and all the evaluators will be blinded to group allocations.
All blocks will be performed preoperatively or after induction of anesthesia by attending
anesthesiologists or regional anesthesia fellows who are experienced in TAP blocks.
Premedication will be administered at the discretion of the attending anesthesiologist
and standard monitors will be used. Patients will be given 1 g oral acetaminophen an hour
before surgery, and an additional 500 mg every 6 hours for 72 hours after surgery
starting with oral intake.
Patients will be randomly assigned to: 1) 4-quadrant TAP block with liposomal
bupivacaine; 2) 4-quadrant TAP block with plain bupivacaine; or, 3) placebo (normal
saline). An in-plane ultrasound will be guide TAP blocks. Two subcostal injections will
be applied by placing the probe midline and then moving lateral along the subcostal
margin identifying area between the rectus abdominis sheath and the transversus abdominis
muscle. The lateral two TAP block injections will be applied in the midaxillary line
between the thoracic cage and iliac crest between external oblique and transversus
abdominis muscles. Once the target area is positioned, the following injections will be
given, based on randomization:
Liposomal bupivacaine. 40 ml of plain bupivacaine 0.25% will be mixed with 20 ml
liposomal bupivacaine and 20 ml of saline. 20 ml of the mix will be injected at each
location of the 4-quadrant TAP block.
Plain bupivacaine group. 50 ml of plain bupivacaine 0.5% will be combined with 30 ml of
normal saline making a total of 80 ml. 20 ml will be injected at each location of the
4-quadrant TAP block.
Placebo group; patients will receive total of 80 ml of normal saline, injected 20 ml in
each of the four-quadrant sites.
General anesthesia will be induced using propofol or etomidate, fentanyl, and rocuronium
to facilitate intubation. Anesthesia will be maintained with sevoflurane or isoflurane,
along with opioids and muscle relaxants as clinically indicated. However, intraoperative
analgesic use will be limited to fentanyl, a short-acting opioid.
Postoperatively, patients will be given intravenous patient-controlled analgesia and
nurses will be free to give additional opioid as clinically indicated. Hydromorphone will
be the default drug, but fentanyl will be substituted if necessary. Clinicians blinded to
trial drug will adjust analgesic management as necessary in an effort to keep verbal
response pain scores (details below) <4 points on a 0-10 scale, with 10 being worst pain.
When patients no longer need PCA, they will be switched to as-needed hydromorphone or
fentanyl.
A single dose of dexamethasone (4-8 mg) will be permitted for PONV prophylaxis, and
inhaled steroids will be permitted as necessary to treat reactive airway disease. The use
of non-steroidal anti-inflammatory drugs and gabapentinoids will be allowed as part of
the ERAS approach (enhanced recovery after surgery) according to hospital's clinical
practice. Other opioid-sparing medications such as ketamine and lidocaine patches will
not be permitted through the initial 72 postoperative hours.
Patients will be allowed to receive prophylactic anti-emetic (first choice ondansetron)
intraoperatively based on the risk assessment for nausea and vomiting. Postoperative
anti-emetics for symptomatic treatment will also be allowed; again ondansetron will be
the first choice.