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

backgroundThe 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.

methodsA 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 5 ml bolus followed by a 72 h infusion at 2 ml/h was started, with patient-controlled fentanyl analgesia and oral paracetamol given on demand. Primary outcomes were fentanyl consumptions in the first 24 h, second 24 h, and third 24 h following surgery. Secondary outcomes were pain numeric rating scores, recovery outcomes and complications.

resultsTwenty-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 24 h: 61.0 vs 324.3 mcg, p < 0.001; second 24 h: 36.3 vs 119.0 mcg, p = 0.033; third 24 h: 8.8 vs 41.2, p = 0.030) when compared to placebo. Significantly lower pain scores at rest at 6 h (2.32 vs 4.0, p = 0.002), and 12 h (1.80 vs 3.08, p = 0.011) and on coughing at 6 h (4.56 vs 5.84, p = 0.019), 12 h (3.76 vs 4.96, p = 0.009), and 24 h (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.

conclusionsMcTAP block reduces postoperative fentanyl consumption and pain scores after LCS, highlighting its role as a safe and useful opioid-sparing analgesia. REGISTRATION NUMBER: TCTR20150831001 (Thai Clinical Trials Registry). Full trial protocol can be assessed at https://www.clinicaltrials.in.th/ .