Exploring the Additive or Synergistic Effects of the Systemic and Perineural Routes of Dexamethasone as Adjuncts to Supraclavicular Block: A Randomized Controlled Trial

Background: Both perineural and intravenous dexamethasone have been proposed as effective adjuncts that prolong the duration of peripheral nerve blocks. The authors sought to explore whether combining systemic with perineural dexamethasone yields any additive or synergistic effect on the characteristics and analgesic effects of peripheral nerve blocks. Methods: Adult patients having distal radius open reduction and internal fixation and/or carpometacarpal arthroplasty under supraclavicular block were randomized to intravenous dexamethasone, a combination of perineural plus intravenous dexamethasone, or no dexamethasone (control). Sensory block duration was set as the primary outcome. Secondary outcomes included motor block duration; postoperative rebound pain scores as well as worst pain at 8, 16, 24, 32, 40, and 48 h; opioid consumption at 0 to 24 and 25 to 48 h; incidence of nausea/vomiting; and presence of burning sensation in the blocked limb at 24 and 48 h. The null hypothesis was lack of difference in sensory block duration between the three groups. Results: A total of 104 patients were included in the analysis (intravenous dexamethasone, 37; intravenous plus perineural dexamethasone, 34; control, 33). Compared to intravenous dexamethasone alone, adding perineural dexamethasone did not yield any incremental benefits in any of the outcomes examined. The mean ± SD of sensory block duration was 21.3 ± 7.3 h in the intravenous dexamethasone group, 20.6 ± 6.1 h in the perineural plus intravenous group, and 16.8 ± 6.8 h in the control group. The mean difference (95% CI) of sensory block duration was significantly prolonged by 4.5 h (95% CI, 1.3 to 7.7; P = 0.006) in the intravenous dexamethasone group and 3.8 h (95% CI, 0.8 to 6.8; P = 0.015) in the perineural plus intravenous dexamethasone group compared to control; however, no difference was observed when the two dexamethasone groups were compared to each other (0.7 h [95% CI, –2.5 to 3.9]; P = 0.670). Compared to control, both intravenous and intravenous plus perineural dexamethasone similarly reduced 24-h pain scores and opioid consumption and decreased incidence of rebound pain. Conclusions: The authors’ findings suggest that intravenous dexamethasone alone is sufficient to improve analgesic outcomes for patients receiving supraclavicular block for upper extremity surgery. Combining the intravenous and perineural dexamethasone routes does not yield an additive or synergistic effect on the characteristics and analgesic effects of supraclavicular block.