The association between the cutaneous sensory block area, the surgical incision’s location, and the block’s analgesic efficacy: a post hoc sensitivity analysis of data from a controlled randomised multicentre trial

Background: Transversus abdominis plane blocks are widely used, but the association between the cutaneous sensory block area and the analgesic effect is still debated. We aimed to determine the relationship between the cutaneous sensory block area, the surgical incision’s location, and the block’s analgesic efficacy. Methods: A sensitivity analysis of data from a multicentre, patient-, clinician-, investigator-blinded, placebo- and active-controlled, 3-arm randomised clinical trial. Patients undergoing minimally invasive colon surgery were included from four hospitals across Denmark between January 2021 and February 2024. In this sensitivity analysis, we used our previously collected data of the cutaneous sensory block area to examine the efficacy of two different approaches to the transversus abdominis plane block, as compared to each other and placebo based on incision location. The primary outcome was total morphine dose equivalents administered in the first 24 h after minimally invasive surgery in patients receiving either a Pfannenstiel or a supraumbilical transverse incision. Results: We found that the subcostal dual laparoscopic-assisted transversus abdominis plane block was superior to both the ultrasound-guided posterior transversus abdominis plane block and placebo in patients with a Pfannenstiel incision with an absolute difference of − 8.9 mg (95% CI, − 16.5 to − 1.3 mg; p = 0.02) and − 10.3 mg (95% CI, − 17.0 to − 3.6 mg; p < 0.01) morphine dose equivalents, respectively. No difference was found for the supraumbilical transverse incision. Patient-reported outcome measures favoured the laparoscopic-assisted block, with an absolute difference of 13 (95% CI, 1.7–24.3; p = 0.025) in the Quality of Recovery-15 score compared to placebo. Conclusion: The effect of the transversus abdominis plane block seems to be independent of the distribution of the cutaneous sensory block area of the approach. The laparoscopic-assisted subcostal transversus abdominis plane block reduced postoperative pain with a high QoR-15 score.