Perineural versus intravenous dexmedetomidine as an adjuvant for ilioinguinal/iliohypogastric nerve block in open inguinal hernia repair: a randomised controlled trial.

PURPOSE: Dexmedetomidine is widely added to peripheral nerve blocks, but whether the perineural or intravenous route provides better analgesia-and at what haemodynamic cost-is unclear in inguinal hernia repair. We compared the two routes as adjuncts to an ilioinguinal/iliohypogastric (II/IH) nerve block.

METHODS

This single-centre, triple-blind randomised controlled trial enrolled 90 adults (ASA I-III) undergoing elective open inguinal hernia repair. All received an ultrasound-guided II/IH block (0.5% bupivacaine with epinephrine, 20 mL) and standardised tumescent local anaesthesia, and were randomised 1:1:1 to perineural dexmedetomidine 1 µg/kg (DexLA), intravenous dexmedetomidine 1 µg/kg over 10 min (DexIV), or placebo (Control). The primary outcome was movement-evoked visual analogue scale (VAS, 0-100) pain at 6 h, analysed by intention-to-treat.

RESULTS

Movement VAS at 6 h was lower with perineural dexmedetomidine (DexLA 10.3 ± 10.3) than DexIV (20.0 ± 17.4) or Control (22.0 ± 20.6; overall p = 0.018): DexLA versus Control - 11.7 (95% CI - 21.9 to - 1.4; p = 0.022), whereas DexIV did not differ from Control (p = 0.888). This reduction reached the established minimum clinically important difference of approximately 10 points, although pain was low overall. Time to first opioid was similar (p = 0.723). Bradycardia was more frequent with DexIV (20.0%) than DexLA (3.3%) or Control (6.7%; DexIV vs DexLA p = 0.040); hypotension occurred in 43.3%, 40.0% and 20.0% (p = 0.151).

CONCLUSION

Perineural-but not intravenous-dexmedetomidine produced a clinically relevant reduction in early movement-evoked pain, whereas intravenous dexmedetomidine added bradycardia without analgesic benefit. If dexmedetomidine is used in this setting, the perineural route is preferable.

TRIAL REGISTRATION: Thai Clinical Trials Registry TCTR20220208002; registered 7 February 2022.