Alpha₂‐receptor agonists as adjuvants for brachial plexus nerve blocks—A systematic review with meta‐analyses

Abstract

Background:We review the efficacy and safety of dexmedetomidine and clonidine as perineural or systemic adjuvants for brachial plexus blocks (BPB). Methods:We included randomised controlled trials on upper limb surgery with BPBs in adults, comparing dexmedetomidine with clonidine or either drug with placebo.The primary outcome was duration of analgesia. Secondary outcomes included adverse and serious adverse events. The review was conducted using Cochrane standards, trial sequential analyses (TSA) and Grading of Recommendations Assessment, Development and Evaluation (GRADE). Results: We included 101 trials with 6248 patients. Overall, duration of analgesia was prolonged with both clonidine (176 min [TSA adj. 95% CI: 118, 205, p < .00001; 33 trials]) and dexmedetomidine (292 min [TSA adj. 95% CI: 245 329, p < .00001; 53 trials]), but was longer for dexmedetomidine than clonidine (205 min [TSA adj. 95% CI: 157, 254, p < .00001; 19 trials]). Compared with placebo, dexmedetomidine was associated with bradycardia (RR 4.2 [95% CI 2.2, 8.3]), and both clonidine (RR 4.5 [95% CI 1.1, 18.3]) and dexmedetomidine (RR 3.9 [95% CI 2.0, 7.5]) were associated with hypotension. Serious adverse events were mostly related to block technique. GRADErated quality of evidence was low or very low. Conclusion:Alpha2-receptor agonists used as adjuvants for BPBs lead to a prolonged duration of analgesia, with dexmedetomidine as the most efficient. Alpha2-receptor agonists were associated with increased risk of cardiovascular adverse events. The quality of evidence was low to very low.

Thoracic transversus plane block as part of a multimodal analgesia plan in a cat undergoing sternotomy

“…Alpha2‐receptor agonists used as adjuvants for nerve blockage have shown to prolong the duration of analgesia, with dexmedetomidine being the most efficient 29 . However, alpha2‐receptor agonists have been associated with increased risk of cardiovascular adverse events in brachial plexus blockage in humans 30 …”

SP49 Adjuvants or dexamethasone as multimodal analgesics at high doses?

“…In the studies directly comparing the two a 2 -agonists, dexmedetomidine prolonged analgesia by approximately three hours. 14 Of note, both a 2 -agonists were associated with a concurrent fourfold increase in the relative risk for hypotension, in addition, dexmedetomidine also increased the relative risk for bradycardia requiring medical intervention by a fourfold. 14 Dexamethasone Dexamethasone increases time to first request of analgesics by 8.7 hours (95% CI: 6.6 to 10.8) compared with placebo.…”

“…14 Of note, both a 2 -agonists were associated with a concurrent fourfold increase in the relative risk for hypotension, in addition, dexmedetomidine also increased the relative risk for bradycardia requiring medical intervention by a fourfold. 14 Dexamethasone Dexamethasone increases time to first request of analgesics by 8.7 hours (95% CI: 6.6 to 10.8) compared with placebo. 12 In comparison, the meta-analyses comparing the two a 2 -agonists to placebo have shown that dexmedetomidine prolongs analgesia by about five hours and clonidine by about three hours.…”

“…12-13 a 2 -adrenergic agonists Clonidine prolongs sensory and motor block, and increases the time to first analgesia compared with placebo, but to a lesser degree than dexmedetomidine. 12,[14][15] Recent meta-analyses have shown that compared with placebo, dexmedetomidine prolonged a brachial plexus block by 292 minutes (95% CI: 245 to 329) and clonidine by 176 minutes (95% CI: 118 to 205). In the studies directly comparing the two a 2 -agonists, dexmedetomidine prolonged analgesia by approximately three hours.…”

“…12 In comparison, the meta-analyses comparing the two a 2 -agonists to placebo have shown that dexmedetomidine prolongs analgesia by about five hours and clonidine by about three hours. 12,14 A recent systematic review by Albrecht et al 13 only retrieved one study directly comparing dexamethasone to dexmedetomidine, reporting that dexamethasone prolongs analgesic duration by about 2 hours. 16 Because of the scarcity of direct comparisons, Albrecht et al performed an indirect comparison between perineural dexamethasone and perineural dexmedetomidine, finding that dexamethasone significantly prolongs the duration of analgesia by a mean difference of 148 minutes (95% CI: 37 to 259 minutes).…”