Objective To evaluata the effect of dexmedetomidine on myocardial ischemia-reperfusion injury in the patients undergoing cardiac surgery with cardiopulmonary bypass:a meta-analysis.Methods We searched the China Integrated Knowledge Resources Database,Chinese Biomedical Database,Wanfang Database,Weipu,PubMed,Cochrane Library (from inception to July 2015) to identify randomized controlled trials involving dexmedetomidine-induced cardioprotection in the patients undergoing cardiac surgery with cardiopulmonary bypass.The following data were extracted from the trials included:the mean arterial pressure and heart rate at breast bone splitting,the spontaneous recovery of heart beat during surgery,the plasma concentrations of creatine kinase-MB and cardiac troponin I at 6,24 and 48 h after surgery,and heart rate at 24 h after surgery.Meta-analysis was conducted using the Cochrane Collaboration's RevMan 5.3 software.Results Twelve prospective randomized controlled trials involving 750 patients were included in this meta-analysis.The patients were divided into 2 groups:dexmedetomidine group (n =376)and control group (n =374).Compared with control group,the plasma caradiac troponin I concentrations at 6,24,and 48 h after surgery,and creatine kinase-MB concentrations at 6 and 24 h after surgery were significantly decreased,the mean arterial pressure and heart rate were decreased at breast bone splitting,heart rate was decreased at 24 h after surgery,and the percentage of spontaneous recovery of heart beat was increased in dexmedetomidine group (P＜0.05).Conclusion Dexmedetomidine can mitigate myocardial ischemia-reperfusion injury in the patients undergoing cardiac surgery with cardiopulmonary bypass.