Effect of ultrasound-guided ilioinguinal-iliohypogastric nerve block on chronic pain in patients undergoing open inguinal hernia surgery under spinal anesthesia: a randomized double-blind study

Background: Pre-operative ilioinguinal-iliohypogastric nerve block (II-IHNB) has a proven role in lessening acute postoperative pain and opioid consumption following hernia repair. However, its role in preventing post-herniorrhaphy groin pain (PHGP) is still unknown. The current study aims to assess pre-operative II-IHNB's impact on PHGP three and six months after open inguinal hernia repair under spinal anesthesia. Methods: Seventy patients posted for inguinal hernia surgery were randomly allocated into group A (received ultrasound-guided II-IHNB with 10 mL of 0.5% ropivacaine and 4 mg [1 mL] dexamethasone) and group B (received ultrasound-guided II-IHNB with 11 mL of 0.9% normal saline). The time to first analgesic request, pain scores, opioid consumption, DN4 score, and PHGP at 3 and 6 months were analyzed using appropriate statistical tests. Results: The numerical pain rating scale at movement in group A was significantly reduced at all the time intervals of 3, 6, 12, and 24 hours compared to group B. Total opioid usage was lower in group A (3.71 mg [3.90]) versus group B (12.14 mg [4.90]) with a mean difference of -8.43 mg (95% CI -10.54, -6.32), P < 0.001. The time required for the first rescue analgesic was significantly longer in group A (360 min [180-360]) versus (180 min [180-360]) in group B (P < 0.001). However, there was no difference in the incidence of PHGP at three and six months between the two groups. Conclusions: Pre-operative ultrasound-guided II-IHNB reduces postoperative analgesic requirement but does not reduce the incidence of chronic PHGP following hernia surgery at 6 months.