This double-blind, randomized controlled trial tested whether perineural dexmedetomidine at 2 µg/kg would prolong postoperative analgesia compared with 5 mg dexamethasone when each was added to 15 mL of 0.33% bupivacaine for ultrasound-guided interscalene brachial plexus block (ISB) in patients undergoing arthroscopic shoulder surgery. The investigators hypothesized that the combination of bupivacaine with dexmedetomidine would result in longer analgesia than bupivacaine with dexamethasone.
Eligible patients scheduled for arthroscopic shoulder surgery were randomized to one of two perineural adjuvant groups during ultrasound-guided ISB: 2 µg/kg dexmedetomidine added to 15 mL of 0.33% bupivacaine, or 5 mg dexamethasone added to the same bupivacaine volume. The study was conducted in a double-blind manner. A total of 112 patients were randomized; 107 were included in the primary analysis. The full trial conduct, including randomization details, blinding procedures, and eligibility criteria, are reported in the trial manuscript; the abstract provides key outcome definitions and analysis approaches.
The primary outcome was duration of analgesia (DOA), analyzed as a time-to-event variable using Kaplan–Meier survival curves with log-rank testing. Secondary outcomes included duration of sensory block (DOS) and duration of motor block (DOM), serial postoperative pain scores evaluated with a longitudinal regression model, incidence and severity of rebound pain, postoperative opioid consumption, patient satisfaction, and adverse effects including hemodynamic events, postoperative nausea and vomiting (PONV), and sedation.
Among 107 patients included in the primary analysis, median DOA did not differ significantly between groups: 16.77 hours in the dexmedetomidine group versus 12.48 hours in the dexamethasone group (median difference in location 5.24 h; 95% CI −0.47 to 9.17; p = 0.655). Therefore, the study did not demonstrate superiority of perineural dexmedetomidine (2 µg/kg) over dexamethasone (5 mg) for prolonging overall analgesia when added to bupivacaine for ISB.
Despite similar DOA, dexmedetomidine was associated with statistically significant prolongation of block characteristics. The duration of sensory block (DOS) was longer with dexmedetomidine: mean 19.8 h versus 17.3 h for dexamethasone (mean difference 2.45 h; 95% CI 0.23 to 4.65; p = 0.031). Duration of motor block (DOM) was also longer with dexmedetomidine: median 19.9 h versus 17.8 h (median difference in location 2.23 h; 95% CI 1.02 to 3.60; p = 0.008).
Postoperative pain scores measured at 6, 12, 18, and 24 hours were reported as comparable between the two groups. The incidence and severity of rebound pain were similar. There were no reported differences in postoperative opioid consumption or patient satisfaction between perineural dexmedetomidine and dexamethasone groups in the abstract.
The dexmedetomidine group experienced higher rates of hemodynamic and sedative adverse events compared with dexamethasone. Specifically, there was a higher incidence of intraoperative hypotension in the dexmedetomidine group (risk difference 44.4%; 95% CI 30.0% to 59.9%; p < 0.001). Bradycardia was more frequent in the block room (risk difference 17.9%; p = 0.010) and intraoperatively (risk difference 27.6%; p = 0.004) for patients receiving dexmedetomidine. Postoperative sedation was also more common with dexmedetomidine (risk difference 10.9%; p = 0.027).
All reported hemodynamic events were transient and did not require intensive care admission, according to the abstract. Rates of postoperative nausea and vomiting were similar between groups.
In this randomized trial of ISB for arthroscopic shoulder surgery, perineural dexmedetomidine at 2 µg/kg did not demonstrate superiority over 5 mg dexamethasone in prolonging the duration of analgesia when added to bupivacaine. Although dexmedetomidine extended the durations of sensory and motor block by approximately 2–2.5 hours, this did not result in a longer analgesic duration. Importantly, dexmedetomidine was associated with increased rates of hypotension, bradycardia, and postoperative sedation, raising safety concerns for higher perineural doses.
These findings suggest limited clinical benefit of high-dose perineural dexmedetomidine compared with dexamethasone for this application and highlight the need to weigh incremental block prolongation against the higher incidence of hemodynamic instability and sedation.
The authors declared no competing interests. Details such as full methodological specifics, sample size calculations, and longer-term outcomes are presented in the full article; if not included in the abstract, those particulars were not reported in the source abstract.