Postoperative analgesic efficacy of modified continuous transversus abdominis plane block in laparoscopic colorectal surgery: a triple-blind randomized controlled trial

Abstract

The optimal opioid-sparing analgesic regimen following laparoscopic colorectal surgery (LCS) remains uncertain. We sought to determine the efficacy of low-dose bupivacaine infusion via surgeon-inserted modified continuous transversus abdominis plane (mcTAP) catheters after LCS. A parallel-group, placebo-controlled, randomized single-centre trial was conducted between April 2017 and February 2018. Block-of-four randomization and allocation concealment by sequentially-numbered, opaque sealed envelopes were used. Patients, surgeons and assessors were blinded. Fifty-two patients were randomized to receive either 0.2% bupivacaine or saline through mcTAP catheters. A 5ml bolus followed by a 72h infusion at 2ml/h was started, with patient-controlled fentanyl analgesia and oral paracetamol given on demand. Primary outcomes were fentanyl consumptions in the first 24h, second 24h, and third 24h following surgery. Secondary outcomes were pain numeric rating scores, recovery outcomes and complications. Twenty-five patients in the bupivacaine group and 26 in the control group were analysed. Patients in the bupivacaine group required significantly less fentanyl overall (106.1 vs 484.5 mcg, p < 0.001) and at all time points (first 24h: 61.0 vs 324.3 mcg, p < 0.001; second 24h: 36.3 vs 119.0 mcg, p = 0.033; third 24h: 8.8 vs 41.2, p = 0.030) when compared to placebo. Significantly lower pain scores at rest at 6h (2.32 vs 4.0, p = 0.002), and 12h (1.80 vs 3.08, p = 0.011) and on coughing at 6h (4.56 vs 5.84, p = 0.019), 12h (3.76 vs 4.96, p = 0.009), and 24h (3.44 vs 4.24, p = 0.049) as well as significantly lower opioid-related complications such as nausea or vomiting (9 (36%) vs 1 (4%), p =0.005) were observed in the bupivacaine group. There were no major block-related complications, and recovery outcomes were similar in both groups. McTAP block reduces postoperative fentanyl consumption and pain scores after LCS, highlighting its role as a safe and useful opioid-sparing analgesia. TCTR20150831001 (Thai Clinical Trials Registry). Full trial protocol can be assessed at https://www.clinicaltrials.in.th/ .