Perioperative adverse events attributed to α2-adrenoceptor agonists in patients not at risk of cardiovascular events: systematic review and meta-analysis

Background: Several systematic reviews have reported the benefits of perioperative alpha 2-adrenoceptor agonist use for various conditions, but safety evidence is poorly documented. Methods: We performed a systematic review focusing on adverse events. We searched the MEDLINE, Embase, LILACS, Cochrane, and Clinical Trials Register databases for RCTs comparing the effects of alpha 2-adrenoceptor agonists and placebo during non-cardiovascular surgery under general anaesthesia, for any indication, in patients not at risk of cardiovascular events. The primary outcome was the incidence of severe adverse events during or after alpha 2-adrenoceptor agonist administration. The secondary endpoints were other adverse events. A meta-analysis was carried out on the combined data. Evidence quality was rated by the Grading of Recommendations Assessment, Development and Evaluation method. Results: We included 56 studies (4868 patients). Our review, based on moderate-quality evidence, revealed that hypotension occurred frequently during the preoperative and postoperative periods, for both clonidine and dexmedetomidine. Bradycardia was reported only with dexmedetomidine. In contrast, dexmedetomidine seemed to protect against intraoperative hypertension and tachycardia. Subgroup analysis suggested that the risk of hypotension and bradycardia persisted after cessation of treatment. Interestingly, intraoperative hypotension and postoperative bradycardia were not observed with a bolus dosage of dexmedetomidine less than 0.5 mu g kg(-1) or with continuous administration alone. Conclusions: Pooled data for the incidence of adverse events associated with use of alpha 2-adrenoceptor agonists in various perioperative contexts provide high-confidence evidence for a risk of hypotension and bradycardia, and protective effects against hypertension and tachycardia.