Adding dexmedetomidine to dexamethasone does not prolong analgesia in upper limb surgery

BACKGROUND: Intravenous dexamethasone and dexmedetomidine are two adjuncts to local anaesthetics used independently to prolong analgesia after peripheral nerve block. This randomised, controlled, triple-blind trial tested the hypothesis that the combination of i.v. dexamethasone and dexmedetomidine would provide superior analgesia than i.v. dexamethasone alone as an adjunct in patients undergoing upper limb surgery with a supraclavicular brachial plexus block. METHODS: We randomised 100 participants to receive either dexamethasone 0.15 mg kg i.v. (Dexa group) or a combination of dexamethasone 0.15 mg kg and dexmedetomidine 1 μg kg i.v. (Dexa-Dexme group). The primary outcome was the duration of analgesia measured from the time of block procedure with a mix of mepivacaine 0.5% and ropivacaine 0.25% to first oral opioid intake. Secondary outcomes included duration of sensory and motor blocks, pain scores at rest and on movement, cumulative oral morphine consumption at 48 h, and incidence of hypotension episodes and bradycardia. RESULTS: The mean (sd) duration of analgesia was 621 (334) min in the Dexa group and 690 (544) min in the Dexa-Dexme group (P=0.47). Similarly, there were no significant differences in the secondary outcomes. CONCLUSIONS: The combination of i.v. dexamethasone and dexmedetomidine does not provide superior analgesia than i.v. dexamethasone alone after supraclavicular brachial plexus block. CLINICAL TRIAL REGISTRATION: NCT05389852.