右美托咪定对家兔窦房结和房室结功能的影响

Effects of dexmedetomidine on rabbit sinus node and atrioventricular node

目的研究不同剂量右美托咪定对家兔窦房结和房室结功能的影响。方法健康雄性新西兰大白兔24只,体重1.5~2.8kg,按随机数字表分为三组（n=8）：对照组（C组）,以12ml/kg速度持续泵注生理盐水;造成心动过缓最低剂量组（D1组）,负荷量10μg/kg,持续泵注量5μg·kg-1·h-1;6倍剂量组（D2组）,负荷量60μg/kg,持续泵注量30μg·kg-1·h-1。麻醉家兔,分离右侧股动脉并置管,实时监测MAP和HR。右侧颈外静脉置入起搏电极,深度位于上腔静脉下段和右心房交界处,通过程控刺激的方法获取窦房结、房室结的功能指标。于右美托咪定泵注前（T0）、右美托咪定持续泵注后20~30min（T1）、50~60min（T2）测量窦房结恢复时间（SNRT）、校正窦房结恢复时间（CSNRT）、窦房结总恢复时间（TRT）,和房室结前传功能2∶1点。结果 C组各时点SNRT、CSNRT、TRT和2∶1点差异均无统计学意义。与T0时比较,T1、T2时D1组和D2组SNRT、CSNRT和TRT明显延长,T1时D1组和D2组2∶1点明显缩短,T2时D2组2∶1点明显缩短（P〈0.05）。与T1时比较,T2时D1组SNRT、CSNRT和TRT明显缩短,2∶1点明显延长（P〈0.05）。与C组比较,T1、T2时D1组和D2组SNRT、CSNRT和TRT明显延长,T1时D1组和D2组2∶1点明显缩短,T2时D2组2∶1点明显缩短（P〈0.05）。与D1组比较,T1、T2时D2组SNRT、CSNRT和TRT明显延长,2∶1点明显缩短（P〈0.05）。结论 10μg/kg负荷剂量右美托咪定泵注结束后对家兔窦房结和房室结功能抑制较显著,并在短时间内有所恢复（≤1h）,而60μg/kg负荷量抑制效应更明显,并持续抑制窦房结和房室结功能。

Objective To investigate the effects of different doses of dexmedetomidine（Dex）on rabbit sinus node and atrioventricular node.Methods A total of 24 healthy male rabbits weighing1.5-2.8kg,were divided into 3groups randomly according to random number table（n=8）.Group C（control）,critical dosage of Dex causing sinus bradycardia D1（loading dose of Dex was 10μg/kg,continual pumping dose was 5μg·kg-1·h-1）,six times of critical dosage of Dex causing sinus bradycardia D2（loading dose of Dex was 60μg/kg,continual pumping dose was 30μg·kg-1·h-1）.Rabbits were anesthetized,the right femoral artery was separated and catheterized followed by realtime monitoring of arterial blood pressure.Right external jugular vein was searched and separated,bipolar stimulating electrode were inserted to the junction of superior vena cava and right atrium,the index of sinus node and atrioventricular node were observed by means of programmed stimulation.Sinus node recovery time（SNRT）,corrected sinus node recovery time（CSNRT）,total recovery time（TRT）,and atrioventricular node 2∶1point were recorded before Dex infusion（T0）,15-20 min after infusion of Dex（T1）and 50-60 min after perfusion of Dex（T2）.Results SNRT,CSNRT,TRT and2∶1point had no statistical significance.Compared with T0,SNRT,CSNRT and CSNRT were significantly prolonged at T1 and T2.2∶1point in group D1 and D2was shortened obviously at T1 than that at T2（P〈0.05）.SNRT,CSNRT and TRT of group D1 at T2 were significantly prolonged,2∶1piont was shortened compared with T1（P〈0.05）.SNRT,CSNRT and TRT of group D1 and D2were prolonged both at T1 and T2than those of group C.2∶1point was shortened in group D1 and D2at T1 than that in group C（P〈0.05）.Compared with group D1,SNRT,CSNRT and TRT of group D2 at T1and T2 were prolonged,2∶1point was shortened obviously（P〈0.05）.Conclusion Load capacity of 10μg/kg Dex apparently inhibits the function of rabbit sinus node and atrioventricular node,which is partially recovered within a short time（≤1h）.The inhibiting effect is more continously and remarkably in load capacity of 60μg/kg Dex.