Transversus abdominis plane block in minimally invasive colon surgery: a multicenter three-arm randomized controlled superiority and non-inferiority clinical trial

Background and objectives: The transversus abdominis plane (TAP) block is the most widely used abdominal field block in colorectal surgery with a postoperative enhanced recovery pathway. We aimed to determine whether the laparoscopic-assisted and ultrasound-guided TAP (US-TAP) blocks provide superior pain relief compared with placebo. We separately investigated whether the laparoscopic-assisted technique was non-inferior to the ultrasound-guided technique in providing pain relief, with a non-inferiority margin of 10 mg morphine dose equivalents.

Methods: 340 patients undergoing elective minimally invasive colon surgery were randomly allocated to one of three groups: (1) US-TAP block, (2) laparoscopic-assisted TAP (L-TAP) block, or (3) placebo. Superiority and non-inferiority were tested for the primary outcome: 24-hour postoperative morphine equivalent consumption. Secondary outcomes, including patient-reported quality of recovery, were included in the superiority analysis.

Results: 127 patients were included in each block group and 86 in the placebo group. The US-TAP block was no different from placebo at -1.4 mg morphine (97.5% CI -6.8 to 4.0 mg; p=0.55). The L-TAP block was superior to placebo at -5.9 mg morphine (97.5% CI -11.3 to -0.5 mg; p=0.01) and non-inferior to the US-TAP block at -4.5 mg morphine (98.75% CI -10.0 to 1.1 mg).

Conclusion: The L-TAP block was superior to placebo and non-inferior to the US-TAP block. However, neither met our predetermined estimate of the minimal clinically important difference of 10 mg morphine.

Trial registration number: NCT04311099.