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Myocardial protective effects of thoracic epidural anesthesia with ropivacaine during acute myocardial ischemia reperfusion

李刚  许永广  刘慧贞  王萍

LI Gang，XU Yongguang，LIU Huizhen，et al1 Department of Anesthesiology，Shandong Provincial Hospital，Jinan 250021

Abstract

　　Objective：To evaluate the myocardial protective effects of thoracic epidural anesthesia（TEA）with 0.5% ropivacaine during acute myocardial ischemia－reperfusion.

　　Methods：Eighteen healthy hybrid dogs were randomly divided into three groups：ropivacaine group（group Ⅰ），bupivacaine group（group Ⅱa）and normal saline group（group Ⅱb）. Anesthesia was induced and maintained with intravenous anesthesia and ventilation was mechanically controlled1 Epidural catheter was placed at T627 and 0.5% ropivacaine，0.5% bupivacaine or normal saline 12ml was administered epidurally. 15min after epidural administration of local anesthetics or normal saline，the anterior descending branch of left coronary artery was temporarilly occluded for 45min. Blood samples were taken from right atrium and assayed for cardiac troponin T（cTnT）before epidural administration and 6h after reperfusion. Myocardial tissues of left ventricular infarction area were examined by electron microscopy.

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　　Results：Plasma cTnT levels were comparable（P<0.05ng/L）in the three groups before epidural administration but increased significantly in 4 dogs of each group 6h after reperfusion. The difference between group Ⅰand group Ⅱb was significant（P<0.05）. Electron microscope examination of the infarct myocardium showed that myocardial fibers were regularly arranged with normal mitochondria in group Ⅰ；the intercellular spaces were enlarged with unclear nuclar membrane and near normal mitochondria in groupⅡa；the myocardial fibers were irregularly arranged with a number of vacuoles and no normal sarcomere structure was seen in the cytoplasm in group Ⅱb.

　　Conclusions：TEA with 0.5% ropivacaine can afford effective protection against acute myocardial ischemia－reperfusion injury and the effect is better than TEA with bupivacaine at the same concentration.

　　Key Words：Anesthesia，epidural；Myocardial reperfusion injury；Troponin T；Ropivacaine

　　临床上胸段硬膜外阻滞（TEA）治疗心肌缺血在国内外已有尝试，但对预防和治疗急性心肌缺血/再灌注损伤尚未见系统的报道。本研究旨在探讨罗哌卡因行TEA治疗对急性心肌缺血/再灌注损伤的保护作用。

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结　果

　　各组动物一般资料无统计学差异。Ⅰ组及Ⅱa组在硬膜外给药后动脉压及心率均有所下降，但与Ⅱb组相比其差异无统计学意义。三组动物在阻断及开放冠状动脉前后心电图的变化相似。

　　给药前各组血浆cTnT浓度均<0.05ng/L。开放后6h，cTnT浓度<0.05ng/L：三组中各有2只；0.05～0.1ng/L：Ⅰ组4只，Ⅱa组2只，Ⅱb组0只；>0.1ng/L：Ⅰ组0只，Ⅱa组2只，Ⅱb组4只，Ⅰ组与Ⅱb组比较有显著性差异（P<0.05）。

　　开放后6h的梗塞区心肌组织的电镜学观察，Ⅰ组心肌肌纤维排列完整、规律，线粒体未见异常（图1），Ⅱa组肌纤维间隙增宽，核膜模糊，线粒体基本正常（图2），Ⅱb组肌纤维排列极度紊乱，正常肌节结构消失，区域内出现大量空泡区（图3）。

讨　论

　　TEA心肌保护的作用机制有：⑴降低心率及心脏前后负荷，减少心脏做功，降低氧耗；⑵扩张病变冠脉，重新分配冠脉血流，增加缺血区/非缺血区、心内膜/心外膜血流比，增加缺血区氧供；⑶抑制缺血及手术所致的应激反应，减少神经内分泌反应，从而减少应激所致的心肌耗能增加；⑷减少因疼痛等所致的心脏做功增多^[1－3]。罗哌卡因是一种纯左旋式同分异构体长效酰胺类局麻药，与布比卡因比具有对心血管系统和中枢神经系统毒性低，在低浓度时对感觉神经和运动神经阻滞分离等特点^[4]。本研究心肌组织的电镜检查结果显示，Ⅰ组及Ⅱa组心肌细胞的损伤程度低于Ⅱb组，且Ⅰ组心肌细胞损伤程度最轻。说明TEA对急性心肌缺血/再灌注损伤具有保护作用，同时说明0.5%罗哌卡因的效果优于相同浓度的布比卡因，这可能与罗哌卡因对心肌钠离子通道阻滞较弱、对线粒体能量代谢干扰较小、对细胞内cAMP生成抑制较轻等因素有关^[5]。

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　　本实验结果证实，0.5%罗哌卡因胸段硬膜外阻滞，对犬急性心肌缺血/再灌注损伤具有明显的保护作用，其效果优于相同浓度的布比卡因，这还有待于在临床研究中进一步验证。

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