High-dose dexmedetomidine versus dexamethasone supplementation to interscalene brachial plexus block in arthroscopic...

In this double-blind, randomized controlled trial, we compared the efficacy of perineural 2 µg/kg dexmedetomidine and 5 mg dexamethasone as adjuvants to bupivacaine for postoperative pain control in patients undergoing arthroscopic shoulder surgery. We hypothesized that the combination of bupivacaine with dexmedetomidine would prolong analgesia compared with dexamethasone.

One hundred twelve patients scheduled for arthroscopic shoulder surgery were randomized to receive 15 mL of 0.33% bupivacaine with either 2 µg/kg of dexmedetomidine or 5 mg of dexamethasone during ultrasound-guided interscalene brachial plexus block (ISB). The primary outcome was the duration of analgesia (DOA), analyzed as a time-to-event variable using Kaplan-Meier survival curves with log-rank testing. Secondary outcomes included the duration of sensory block (DOS) and motor block (DOM), pain scores, incidence and severity of rebound pain, opioid consumption, patient satisfaction, and adverse effects. Longitudinal pain scores were evaluated using a regression model.

Of 112 randomized patients, 107 were included in the primary analysis. Dexmedetomidine and dexamethasone produced a similar DOA (median, 16.77 vs 12.48 h; median difference in location 5.24 h, 95% CI -0.47 to 9.17; p = 0.655). The dexmedetomidine group had a significantly longer DOS (19.8 vs. 17.3 h; mean difference 2.45 h, 95% CI 0.23 to 4.65; p = 0.031) and DOM (19.9 vs. 17.8 h; median difference in location 2.23 h, 95% CI 1.02 to 3.60; p = 0.008). Postoperative pain score at 6, 12, 18, and 24 hours were comparable, as were rebound pain, postoperative nausea and vomiting (PONV), patient satisfaction, and opioid consumption. The dexmedetomidine group had a higher incidence of intraoperative hypotension (risk difference [RD] 44.4%, 95% CI 30.0% to 59.9%; p < 0.001), bradycardia in the block room (RD 17.9%; p = 0.010) and intraoperatively (RD 27.6%; p = 0.004), and postoperative sedation (RD 10.9%; p = 0.027); however, all hemodynamic events were transient and did not require intensive care admission.

Perineural dexmedetomidine (2 µg/kg) was not shown to be superior to dexamethasone (5 mg) in prolonging analgesia when added to bupivacaine for ISB in arthroscopic shoulder surgery. Although dexmedetomidine prolonged sensory and motor block duration, this did not translate into a longer DOA and was associated with higher rates of hemodynamic instability and sedation. These findings suggest limited clinical benefit and raise safety concerns regarding higher dexmedetomidine doses.