Analgesic duration of interscalene block after outpatient arthroscopic shoulder surgery with intravenous dexamethasone, intravenous dexmedetomidine, or their combination: a randomized-controlled trial.

PURPOSE Both intravenous dexamethasone and dexmedetomidine prolong the analgesic duration of interscalene blocks (ISB) after arthroscopic shoulder surgery. This study compared their relative effectiveness and the benefit of their use in combination. METHODS This single-centre, double-blinded, parallel three-group superiority trial randomized 198 adult patients undergoing ambulatory arthroscopic shoulder surgery. Patients received preoperative ISB with 30 mL 0.5% bupivacaine and 50 µg dexmedetomidine or 4 mg dexamethasone or both of these agents as intravenous adjuncts. The primary outcome was analgesic block duration. Secondary outcomes included the quality of recovery 15 score (range: 0-150) on day 1 and postoperative neurologic symptoms in the surgical arm. RESULTS Block durations (n = 195) with dexamethasone (median [range], 24.5 [2.0-339.5] hr) and both adjuncts (24.0 [1.5-157.0] hr) were prolonged compared with dexmedetomidine (16.0 [1.5-154.0] hr). When analyzed by linear regression after an unplanned log transformation because of right-skewed data, the corresponding prolongations of block duration were 59% (95% confidence interval [CI], 28 to 97) and 46% (95% CI, 18 to 80), respectively (both P < 0.001). The combined adjuncts were not superior to dexamethasone alone (-8%; 95% CI, -26 to 14; P = 0.42). Median [IQR] quality of recovery 15 scores (n = 197) were significantly different only between dexamethasone (126 [79-149]) and dexmedetomidine (118.5 [41-150], P = 0.004), but by an amount less than the 8-point minimum clinically important difference. CONCLUSION Dexamethasone is superior to dexmedetomidine as an intravenous adjunct for prolongation of bupivacaine-based ISB analgesic duration. There was no additional benefit to using both adjuncts in combination. TRIAL REGISTRATION www.clinicaltrials.gov (NCT03270033); registered 1 September 2017.