Comparison between ultrasound-guided transversus abdominis plane and conventional ilioinguinal/iliohypogastric nerve blocks for day-case open inguinal hernia repair

Background. Transversus abdominis plane (TAP) block has been reported to provide effective analgesia after lower abdominal surgery, but there are few data comparing ilioinguinal/iliohypogastric nerve (IHN) block with ultrasound-guided TAP block in patients undergoing inguinal hernia repair. Methods. Two hundred and seventy-three patients undergoing day-case open inguinal hernia repair with a mesh were randomly allocated to receive either ultrasound-guided TAP block or blind IHN block with levobupivacaine 0.5%, before surgery. Patients were monitored for visual analogue scale (VAS) scores at rest (in the post-anaesthesia care unit, and at 4 and 12 h) and at rest and during movement (at 24, 48 h, 3 and 6 months). Pain at 6 months was also assessed using the DN4 questionnaire for neuropathic pain. Results. Median VAS pain scores at rest were lower in the ultrasound-guided TAP group at 4 h (11 vs 15, P = 0.04), at 12 h (20 vs 30, P = 0.0014), and at 24 h (29 vs 33, P = 0.013). Pain after the first 24 h, at 3 and 6 months after surgery, and DN4 scores were similar in both groups (P = NS). The proportion of patients with VAS >40 mm on movement at 6 months was comparable {18.2% [ 95% CI (12.2-26.1%)] vs 22.4% (15.8-30.6%) in the TAP and IHN groups, respectively, P = 0.8}. Postoperative morphine requirements were lower during the first 24 h in the TAP block group (P = 0.03). Conclusions. Ultrasound-guided TAP block provided better pain control than 'blind' IHN block after inguinal hernia repair but did not prevent the occurrence of chronic pain.