低温联合右美托咪定对兔心肌单相动作电位的影响

Effects of hypothermia combined with dexmedetomidine on myocardial monophasic action potentials in isolated rabbit hearts

目的 探讨低温联合右美托咪定对兔心肌单相动作电位的影响.方法 成年家兔,体重2.0～ 2.5 kg,制备Langendorff离体心脏灌注模型,取模型制备成功的心脏18个,采用随机数字表法分为3组（n=6）：正常对照组（C组）、低温组（H组）和低温＋右美托咪定组（HD组）.C组继续灌注37℃K-H液60 min,H组灌注32℃K-H液60 min,HD组灌注含右美托咪定25 ng/ml的32℃K-H液60 min.于平衡灌注末、灌注K-H液15、30和60 min时记录HR和3层心肌单相动作电位,计算单相动作电位复极50％的时程（MAPD50）、单相动作电位复极90％的时程（MAPD90）、单向动作电位振幅（MAPA）和最大去极化速度（Vmax）.结果 与C组比较,H组及HD组灌注K-H液各时点HR减慢,MAPD50、MAPD90延长（P＜0.05）.H组及HD组各时点HR、MAPD50和MAPD90比较差异无统计学意义（P＞0.05）.3组各时点MAPA和V…比较差异无统计学意义（P＞0.05）.结论 低温联合右美托咪定可延长兔心肌复极时程,且右美托咪定对低温导致的兔心肌单相动作电位改变无影响.

Objective To investigate the effects of hypothermia combined with dexmedetomidine on myocardial monophasic action potentials （MAPs） in isolated rabbit hearts.Methods Adult rabbits,weighing 2.0-2.5 kg,were heparinized and anesthetized with pentobarbital sodium 30 mg/kg.Their hearts were rapidly removed and retrogradely perfused in a Langendorff apparatus at 37 ℃.Eighteen hearts were randomly divided into 3 groups （n =6 each） using a random number table：control group （group C）,hypothermia group （group H）,and hypothermia＋dexmedetomidine group （group HD）.The hearts were continuously perfused for 60 min with 37 ℃ K-H solution in group C,with 32 ℃ K-H solution in group H,or with 32 ℃ K-H solution containing dexmedetomidine 25 ng/ml in group HD.At the end of equilibration （T0） and at 15,30 and 60 min of perfusion with K-H solution,HR and MAPs of left ventricular epicardium,mid-myocardium and endocardium were recorded.MAP duration at 50％ repolarization （MAPD50） and at 90％ repolarization （MAPD90）,monophasic action potential amplitude （MAPA） and maximal velocity （Vmax） were calculated.Results Compared with group C,HR was significantly decreased,and MAPD50 and MAPD90 were prolonged at each time of perfusion with K-H solution in H and HD groups.There was no significant difference in HR,MAPD50 and MAPD90 between H group and HD group.There was no significant difference in MAPA and Vmax between the three groups.Conclusion Hypothermia combined with dexmedetomidine can lead to prolongation of myocardial repolarization,and dexmedetomidine exerts no effect on hypothermia-induced change in MAPs in isolated rabbit hearts.