Erector Spinae Plane Block versus Transversus Abdominis Plane Block for Robotic Inguinal Hernia Repair: A Blinded, Active-Controlled, Randomized Trial

Background: Regional anesthetic nerve blocks are widely used in the treatment of pain after outpatient surgery to reduce opioid consumption. Erector spinae plane (ESP) block is a recently described technique with promising results in different scenarios. Objectives: To compare ESP block efficacy with the commonly used transversus abdominis plane (TAP) block in patients undergoing robot-assisted inguinal hernia repair. Study Design: This was a randomized, blinded, active controlled, superiority trial with 2 parallel groups. The study was approved by the local ethics committee. Registration took place on www. clinicaltrials.gov with the identifier NCT04750512. Setting: Adults undergoing robotic inguinal hernia repair were recruited between January 2021 and April 2022 in a single referral center of southern Switzerland. Methods: To ensure blinding, the study employed a "double dummy" design, where all patients underwent both TAP and ESP blocks, but only one block was therapeutically active. The therapeutic block contained ropivacaine 0.2%, while the other infiltration contained placebo. The therapeutic intervention varied between groups, with one group receiving the TAP block as the active treatment and the other group receiving the ESP block as the active treatment. Computer generated 1:1 randomization determined allocation, which took place immediately prior to the intervention. As a result, blinding included patients, anesthesia, and surgery providers, outcome assessors and statistical analysts. The main outcome measure was the highest reported pain score on a Visual Analog Scale (VAS) during the 6 hours following the end of general anesthesia. Secondary outcomes included pain scores at set intervals, analgesic consumption, and complications. Results: A total of 50 patients (25 per arm) were enrolled and included in the analysis. The study found no significant difference in the mean maximal VAS scores between the 2 groups (TAP block 22.2, ESP block 20, difference 2.2, 95% CI is-12.1 to 16.5). Secondary endpoints, including VAS pain scores at different time points, use of rescue analgesics, time to first walk, duration of stay, and frequency of adverse events, did not show any significant differences between the 2 groups. However, post-hoc analysis suggested a more stable effect over time for the ESP block compared to the TAP block. Limitations: The main limitation is a higher variance in VAS scores than expected in the power calculations. Conclusions: ESP block was not superior to TAP block in the treatment of post-operative pain among patients undergoing robotic inguinal hernia repair.