Intravenous dexmedetomidine as addition to dexamethasone adjunct for interscalene brachial plexus block for postoperative analgesia after arthroscopic shoulder surgery

BACKGROUND The co-administration of intravenous dexamethasone and dexmedetomidine is reported to prolong the duration of analgesia after single-shot interscalene brachial plexus block. The most effective dose with minimal side effects remains undetermined. OBJECTIVES To evaluate the difference in time to first analgesic request in patients receiving different doses of intravenous dexmedetomidine after an interscalene brachial plexus block undergoing arthroscopic shoulder surgery. DESIGN A double-blind, randomised controlled study. SETTING A single-centre study from November 2021 to December 2023. PATIENTS Two hundred and eighteen patients undergoing arthroscopic shoulder surgery were included. INTERVENTIONS Patients were randomly assigned to one of four groups using blocked randomisation: intravenous 0.9% saline (group 1) or intravenous dexmedetomidine: 1.0 (group 2), 1.5 (group 3) and 2.0 (group 4) μg kg −1 . MAIN OUTCOME MEASURES The primary outcome was the time to first analgesic request in hours. RESULTS There was no significant difference in the time to first analgesic request: group 1 (18.8 ± 6.3 h), group 2 (18.7 ± 5.1 h), group 3 (17.7 ± 5.6 h) and group 4 (19.5 ± 5.0 h). There was no significant difference in postoperative nausea and vomiting, patient satisfaction and quality of sleep in the first 24 h. There were significant differences in the incidences of intra-operative hypotension and bradycardia between the control group and all the dexmedetomidine groups combined; however, this study was not powered for this analysis. The time to extubation was statistically significantly higher in group 4 with a prolonged time to extubation (>14 min) when the duration of surgery was shorter (OR 0.98, 95% CI 0.96 to 0.99). CONCLUSIONS Administering high doses of intravenous dexmedetomidine may not yield additional analgesic benefits after single-shot interscalene brachial plexus block while potentially increasing haemodynamic risks and prolonging time to extubation. TRIAL REGISTRATION EudraCT 2021-004686-12