Opioid sparing effect of intravenous dexmedetomidine in orthopaedic surgery: a retrospective analysis

BACKGROUND: Dexmedetomidine is a highly selective alpha-2 receptor agonist without any effect on the GABA receptor. It provides an excellent sedative and analgesic profile with few side effects. We report our experience with dexmedetomidine use during orthopaedic surgery under locoregional anaesthesia to ensure adequate sedation and optimal postoperative pain control. METHODS: In this retrospective analysis, we included 128 patients who underwent orthopaedic surgery between January 2019 and December 2021. All patients received the same local anaesthetic dose of 20 ml of ropivacaine 0.375% + mepivacaine 0.5% for axillary and supraclavicular block and 35 ml of ropivacaine 0.375% + mepivacaine 0.5% for triple nerve block (femoral, obturator and sciatic nerve). The cohort was divided into two groups based on sedation drugs used during surgery (dexmedetomidine, or group D, vs midazolam, or group M). All patients received postoperative 24-h analgesia consisting of 60 mg of ketorolac, 200 mg of tramadol and 4 mg of ondansetron. The primary outcome measured how many patients in the two groups required an analgesic rescue dose of pethidine and the time to first pethidine administration. To reduce confounding, we included patients in two groups with non-statistically different demo-anamnestic parameters and who received the same dose of intraoperative local anaesthetic and postoperative analgesia. RESULTS: The number of patients in group D who did not require a rescue dose of analgesia was significantly greater than in group M (49 vs 11, p < 0.001). Time-to-first postoperative opioid administration did not show a fundamental difference between the two groups under examination (523.75 ± 131.55 min vs 564 ± 117.84 min). Total opioid consumption was higher in the M group than in the D group (3529.8 ± 30.36 μg vs 1864.8 ± 31.59 μg, p 0.075), with a mean opioid consumption significantly higher in the M group than in the D group (26.26 ± 42.8 μg vs 69.21 ± 46.1 μg, p < 0.001): D group received 62.06% less opioid than M group. CONCLUSIONS: The continuous infusion of dexmedetomidine during orthopaedic surgery performed under locoregional anaesthesia has been shown to increase the analgesic effect of local anaesthetics and reduce the consumption of major opioids in the postoperative period. Dexmedetomidine offers a unique ability to supply sedation and analgesia without respiratory depression, having a wide safety margin and an excellent sedative capacity. It does not increase the rate of postoperative complications.