Advances in minimally invasive surgery have reduced postoperative morbidity and enhanced
recovery. Despite increased use of minimally invasive techniques, postoperative pain remains
a challenging aspect of surgical treatment of colorectal diseases and is typically treated
with multimodal analgesia, yet the backbone of analgesia continues to be opioid therapy. As
analgesics, opioids are effective but fraught with side effects, including delay in return of
bowel function, sedation, and potential for dependency.
Minimally invasive colorectal surgery has dramatically improved postoperative outcomes,
resulting in significantly shorter length of stay, pain, and overall cost. Despite the
advances in multimodal analgesia and enhanced-recovery pathways, the optimal strategy for
perioperative analgesia has not yet been defined, and there may be a role for expanded use of
regional anesthesia in minimally invasive surgery.
Regional anesthesia, specifically the transversus abdominis plane block, has been shown to
reduce postoperative pain and opioid requirements even in the context of minimally invasive
surgery. Surgeon-performed, laparoscopically placed TAP blocks are equivalent, or perhaps
superior, to ultrasound-guided TAP blocks . Long-acting local anesthetics, specifically
liposomal bupivacaine, have been shown to prolong the effect of TAP blocks over non-liposomal
bupivacaine , and has also suggested a reduced length of stay and less overall cost, despite
the high cost of the formulation. These findings suggest improved outcomes can be expected if
a longer block is achieved.
Liposomal bupivacaine is not available and Canada and is very costly. Regional anesthetic
supplemented with dexamethasone, a potent corticosteroid, has shown improved efficacy and
prolonged duration of anesthetic in other regional anesthetic techniques. The investigators
hypothesize that addition of dexamethasone to bupivacaine can prolong the duration of block
to be similar to that achieved with liposomal bupivacaine, but at a much lower cost.
Ample evidence exists validating TAP block as an effective adjunct to minimally invasive
surgery. Robust data also support the additional benefit of dexamethasone in regional
anesthesia. No studies have been published specifically assessing any benefit of combining
dexamethasone with local anesthetic to improve the TAP block, and none can be found
registered at clinicaltrials.gov. This will be the first such trial to evaluate a promising
technique that could reduce postoperative pain and opioid requirements. If found to be
effective, this technique would profoundly impact surgical practice around the world.
The investigators propose a multi-centre randomized, single-blinded, controlled trial,
enrolling 60 patients. Royal University Hospital in Saskatoon, Saskatchewan will be the
primary site, with potential to include at least one additional site. Planning is currently
underway to run a second trial site at St. Paul's Hospital, Vancouver, British Columbia. The
study investigators maintain a collaborative research relationship with the Division of
Colorectal Surgery at the University of British Columbia, and there is potential to leverage
this relationship to increase the power and relevance of the trial.
Patients older than 18 years scheduled to undergo elective or urgent inpatient minimally
invasive colorectal resection will be recruited. The type and site of extraction incision
will be at the surgeon's preference. Exclusion criteria include conversion to laparotomy,
perforated viscus, peritonitis, acute diverticulitis, death within 72 hours, and preoperative
opioid use. The primary outcome will be total opioid consumption in the first 48 hours after
surgery. Secondary outcomes will be time in the PACU and length of stay in hospital. A
computer-generated random number table will be used to randomize patients to receive either
conventional TAP (n=30) or TAP-DEX (n=30). Allocation will be performed in a 1:1 ratio. Group
allocation will be revealed to the operating surgeon in order to administer the correct
solution, but blinded to patient and study investigators, PACU staff, and ward staff.
Trial participants will undergo their planned procedures as clinically indicated. Eligible
procedures include laparoscopic low anterior resection, anterior resection, and segmental
colectomy.
At completion of the surgery, patients will undergo surgeon-placed laparoscopic TAP blocks
using 1mL/kg of 0.25% bupivacaine with epinephrine 1:200,000, placed at two locations per
side along the anterior axillary line between the costal margin and the iliac crest. The
dexamethasone group will have 16mg dexamethasone added to the solution. Intravenous
dexamethasone will not be given for prevention of postoperative nausea and vomiting. General
anesthetic technique will be at the preference of the anesthesiologist.
Statistical Analysis
Data collection: A blinded, centralized, third-party research assistant will carry out data
collection. Postoperative opioid consumption will be quantified through chart review as well
as assessment of PCA usage 48 hours following the operation. Recording the doses of opioids
administered in the medication administration record (MAR) is standard practice by PACU
nursing staff at the study institution. PCA pumps automatically document cumulative opioids
administered and can easily be checked at the bedside. Data will be entered and recorded into
an encrypted Microsoft Excel spreadsheet.
The study intends to enroll a sample size of 60 patients, with 30 patients in each group,
using a power of 80% and alpha set at 5%, to detect a detect a difference of 25%
(delta=-0.25) under a normal distribution. Given that the standard deviation of 1 is 0.341
under a normal distribution, the sample size was calculated using a 'power of two means" test
with a commercially available software (STATA ®). This same sample size, and power
calculation, has been used in several trials before . There is an anticipated reduction from
32mg hydromorphone equivalents in the TAP group to less than 25mg in the TAP-DEX group. Thus,
the investigators are confident that enrolling 60 patients will be sufficient to detect at
least a 25% difference.
Primary outcome: The primary outcome will be total opioid use, in morphine equivalents, in
the post-anesthetic recovery unit and the first 48 hours after surgery, Opioid equivalents
will be calculated using http://opioidcalculator.practicalpainmanagement.com/conversion.php.
Secondary Outcome: Secondary outcomes will include time of stay in the PACU and length of
stay in hospital.
An interim analysis will be performed after 50% enrolment for evaluation of superiority of
either treatment.