Comparative evaluation of pre-emptive analgesic efficacy of Posterior Transversus Abdominis Plane block with Fascia Transversalis Plane Block in adult patients undergoing unilateral inguinal hernia repair: A prospective, randomized, single-blind, two-arm parallel study.

Introduction: Abdominal wall blocks, in conjunction with multimodal analgesia, have demonstrated efficacy in providing post-operative analgesia, reducing opioid requirements in patients undergoing inguinal hernia repair. The inguinal region is primarily innervated by the ilioinguinal nerve (IIN) and iliohypogastric nerve (IIH). Posterior transverse abdominis plane block (pTAP) and fascia transversalis plane block (TFP) have been observed to reliably block IIN and IIH. We hypothesized that posterior TAP block (pTAP) owing to its potential paravertebral spread will provide better post-operative analgesia than TFP block in patients undergoing unilateral open inguinal hernia repair.

Methods: This prospective, randomized, single-blind, two-arm parallel study was conducted over a duration of one year for which sixty patients undergoing unilateral open inguinal hernia repair under spinal anesthesia were enrolled. They were equally and randomly assigned to receive either preoperative pTAP block or TFP block. The primary aim of the study was to compare median static and dynamic NRS scores during a 24-hour period, with the secondary aim to compare the number of patients who required rescue analgesics in each group.

Results: All enrolled patients completed the study. Results showed no statistically significant difference in median static NRS scores between Group pTAP and Group TFP at the designated time of observation during the 24-hour period [1.2 (0.4-1.60 vs. 1 (0.6-1)]. Group pTAP reported a higher median dynamic NRS scores during the 24-hour period [2.6 (1.2-3) v/s 2 (1.6-2.4); P < 0.035], although this difference was clinically insignificant. The mean time to request for the first rescue analgesia was comparable (11.7 h v/s 12 h; P = 0.99). In all the patients of both groups, loss of pinprick and cold touch sensation was observed at T10, T12, and L1 dermatomal levels. However, sensory assessment at T6 and T8 levels showed variability between the two groups (P > 0.05).

Conclusion: In conjunction with background analgesia and the use of dexamethasone as an adjuvant, both blocks (pTAP and TFP) were observed to be equally effective for post-operative pain relief with similar patient satisfaction scores.