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.