Objective To investigate the effect of different doses of dexmedetomidine on myocardial injury (in perioperative peri‐od) on cardiopulmonary bypass (CPB) in patients with rheumatic heart valve replacement surgery .Methods Patients undertook rheumatic heart valve replacement surgery with mitral stenosis were divided into three groups (n=20) in randomized and double‐blind method :control group (group C) ,dexmedetomidine 0 .3 μg/kg group (DEX1 group) ,dexmedetomidine 0 .6 μg/kg group (DEX2 group) .Central venous blood was drawn respectively before anesthesia induction (T0 ) ,2h after CPB (T1 ) ,24 h after CPB (T2 ) ,48 h after CPB (T3 ) ,72 h after CPB (T4 ) .Plasma muscle calcium protein I (cTnI) and creatine kinase (CreatineKinase MB , CK‐MB) were measured and mean arterial pressure and heart rate were recorded at each time point .Furthermore ,extubation time , ICU stay ,postoperative inotropic score 24 h after operation ,drainage 24 h after operation ,cardio auto‐resuscitation rates and ad‐verse cardiovascular events were recorded .Results Compared with T0 ,HR was significantly lower in the T1 time point in DEX2 group .Compared with group C ,HR ,plasma CK‐MB ,inotropic score 24 h after operation and cardiovascular adverse events was sig‐nificantly reduced in the T1 time points in DEX1 group (P<0 .05) ,but the heart auto‐resuscitation rate did not significantly im‐proved .HR at T1 ,plasma CK‐MB values at T1 and T2 ,and plasma cTnI values at T2 -T4 were significantly reduced ;the heart re‐suscitation significantly increased ,myocardial contraction power ratings 24 h after operation and the incidence of cardiovascular e‐vents was significantly lower in DEX2 group (P<0 .05) .The extubation time ,ICU stay time and drainage 24 h after operation did not change significantly in both groups .Conclusion Dexmedetomidine has a protective effect on perioperative myocardial injury in patients with rheumatic heart valve replacement surgery ,and the effect would be better when the dexmedetomidine was infused at 0 .6 μg · kg -1 · h-1 after a loading dose of 0 .6 μg/Kg continuously .%目的：比较不同剂量右美托咪定对心肺转流（C PB ）风心瓣膜置换术患者围术期心肌损伤的影响。方法随机、双盲将择期风心二尖瓣狭窄瓣膜置换术患者分为3组：对照组（C组）、低剂量右美托咪定组（DEX1组）、高剂量右美托咪定组（DEX2组）。3组患者分别于全身麻醉诱导前（T0）、CPB后2 h（T1）、CPB后24 h（T2）、CPB后48 h（T3）、CPB后72 h（T4）抽取患者中心静脉血，监测各时点血浆肌钙蛋白I（cTnI）、肌酸激酶同工酶（CK‐MB）水平、平均动脉压（MAP）和心率（HR）的变化。并记录气管导管拔除时间、IC U停留时间、术后24 h时心肌收缩力评分、术后24 h引流量、心脏自动复跳及心血管不良事件发生的情况。结果与T0相比，DEX2组 HR在T1时间点明显降低。与C组相比，DEX1组在T1时间点HR、血浆CK‐MB明显降低，术后24 h时心肌收缩力评分和心血管不良事件发生率显著降低（P＜0．05），但心脏自动复跳率没有明显改善；DEX2组在T1时间点HR显著减少，在T1和T2时间点血浆CK‐MB值明显降低，在T2～ T4时间点血浆cTnI值显著减少，心脏自动复跳率明显增加，术后24 h时心肌收缩力评分和心血管不良事件发生率明显降低（P＜0．05）；DEX1组和DEX2组的气管导管拔除时间、ICU停留时间和术后24 h引流量没有明显变化。结论右美托咪定对风心瓣膜置换术患者围术期心肌损伤具有保护作用，负荷量0．6μg／kg继之以0．6μg·kg －1·h－1输注的给药方法更佳。
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