The Facilitatory Effects of Intravenous Dexmedetomidine on the Duration of Spinal Anesthesia: A Systematic Review and Meta-Analysis

BACKGROUND: Central mechanisms have been proposed to explain the prolongation of effect reported with the off-label use of dexmedetomidine as an adjuvant in local anesthetic admixtures. We evaluated whether IV dexmedetomidine can prolong the duration of sensory block associated with spinal anesthesia. METHODS: The authors searched MEDLINE, Embase, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials databases for randomized controlled trials investigating the facilitatory effects of IV administration of dexmedetomidine (dexmedetomidine group) compared with placebo (control group) on single-injection local anesthetic-based spinal anesthesia. Durations of sensory and motor block, sensory and motor block onset times, postoperative pain scores, time to first analgesic request, analgesic consumption, and dexmedetomidine-related side effects were evaluated. Results were combined using random effects modeling when appropriate. RESULTS: A total of 364 patients were analyzed from 7 intermediate to high-quality randomized controlled trials. When IV dexmedetomidine accompanied spinal anesthesia, sensory block duration was prolonged by at least 34% (point estimate: 38%), P < 0.00001, motor block duration was prolonged by at least 17% (point estimate: 21%), P < 0.00001, and time to first analgesic request was increased by at least 53% (point estimate: 60%), P < 0.00001. The use of dexmedetomidine was associated with a 3.7-fold increase (95% confidence interval, 1.53-8.82, P = 0.004) in transient reversible bradycardia. There was no difference in the incidence of hypotension or postoperative sedation, and none of the patients experienced respiratory depression. CONCLUSION: IV dexmedetomidine can prolong the duration of sensory block, motor block, and time to first analgesic request associated with spinal anesthesia.