Effect Of Perioperative Alpha-2 Agonists On Postoperative Nausea And Vomiting: A Systematic Review And Meta-analysis

[Background]Postoperative nausea and vomiting(PONV)is a disturbing problem for patients after surgery.The incidence of PONV is reported to be over 30%,which reaches over80% in patients having three or more risk factors.Although usually self-limited and nonfatal,PONV can lead to rare but serious consequences,including aspiration,suture dehiscence,esophageal rupture,electrolyte imbalances,and subcutaneous emphysema.PONV also prolonges length of stay in the postanesthesia care unit(PACU),raises the dissatisfaction of patients,and brings an increase of hospitalization expense and extension of hospitalization time.The alpha-2 adrenergic receptor agonists have been used for decades to treat common medical conditions and have been used as an anesthesia adjuvant,which produce diverse responses,including sedation,analgesia,and sympatholytic.However,it is still controversial whether it can reduce the incidence of PONV.[Methods]The investigators selected and analyzed randomized controlled trials published on Pubmed,EMBASE,and Cochrane database.Two reviewers independently abstracted the data.We included all published randomized controlled trials involving adult patients undergoing non-cardiac surgery under general anesthesia with American Society of Anesthesiologists Physical Status ? ~?,who received systemic(intravenous,intramuscular,subcutaneous,oral)alpha-2 agonists pre,per or postoperative,testing its effects,compared with placebo or no treatment.The Review Manager computer program Version 5.2 was used for performing statistical analyses.[Results]After screening,17 randomized controlled clinical trials with 1325 patients were included.There was a significant decrease in the incidence of twenty-four-hour PONV,RR(95% confidence interval)of 0.54(0.45 to 0.65).The number needed to treat(NNT)was 6.5(4.3 to 13.1).Twenty-four hours postoperative opioid consumption was decreased by alpha-2 agonists from this meta-analysis,the weighted mean difference was-6.95mg(-12.76 to-1.14).There was also a decrease in the incidence of postoperative shivering,RR(95% CI)of 0.17(0.09 to 0.34).Adverse effects of systemic alpha-2 agonists include bradycardia and hypotension.There was no differece in intraoperative bradycardia and hypotension between alpha-2 agonist and control groups,but the incidence of intraoperative bradycardia tend to increase.[Conclusion]Perioperative systemic alpha-2 agonists decrease the incidence of PONV and postoperative opioid consumption,as well as the incidence of postoperative shivering.Thus,it can be used as an anesthesia adjuvant.