Perineural and Systemic Dexamethasone and Ulnar Nerve Block Duration. A Randomized, Blinded, Placebo-controlled Trial in Healthy Volunteers

Background: We hypothesized that both perineural and systemic dexamethasone as adjuncts to bupivacaine increase the duration of an ulnar nerve block compared with bupivacaine alone, and that systemic dexamethasone is non-inferior to perineural dexamethasone.

Methods: We performed bilateral ulnar nerve blocks with 3 ml bupivacaine 5 mg/ml in 16 healthy volunteers on two trial days. According to randomization, subjects received adjunct treatment with 1 ml dexamethasone 4 mg/ml + 1 ml of saline (perineural condition) in one arm and 2 ml saline in the other arm (systemic condition, through absorption and redistribution of the contralaterally administered perineural dexamethasone) on one trial day; and 2 ml of saline in one arm (placebo condition) and 2 ml of lidocaine in the other arm (lidocaine condition) on the other trial day. The primary outcome was the duration of the sensory nerve block assessed by temperature discrimination.

Results: Mean sensory block duration was 706 ± 94 minutes for the perineural condition, 677 ± 112 minutes for the systemic condition, and 640 ± 121 minutes for the placebo condition. The duration of the sensory nerve block was greater with perineural dexamethasone versus placebo (mean difference (MD) 66 minutes (95% CI 23 to 108). Block duration was similar between systemic dexamethasone and placebo (MD 36 minutes; 95% CI -30 to 103).

Conclusions: Perineural dexamethasone as an adjunct to bupivacaine in healthy volunteers resulted in a greater duration of an ulnar nerve block when compared with placebo. Systemic dexamethasone resulted in a similar duration as placebo.