Fujita S, Tsuchida H, Kanaya N, Kokita N, Kawamata M, Namiki A, Ichihara K
Department of Anesthesiology, Sapporo Medical College, Japan.
J Cardiothorac Vasc Anesth. 1996 Dec;10(7):903-8. doi: 10.1016/s1053-0770(96)80054-1.
Thoracic epidural anesthesia (TEA) has been reported to alleviate ischemic damage to the myocardium. Endothelin, an endothelium-derived peptide and a potent coronary vasoconstrictor, may contribute to poor cardiac perfusion and ischemia. The objective was to examine regional myocardial metabolism during ischemia caused by intracoronary injection of endothelin with and without TEA.
The three experimental groups and three treatments were randomized.
All studies were conducted in a university research laboratory.
Thirty anesthetized dogs comprised the study groups.
Study animals were divided into three groups of 10 animals each identified as normal saline (NS); TEA; and TEA + blood pressure controlled (TEA + BPC). The NS group had 0.5 mL/kg of normal saline injected into the T4-5 epidural space. The TEA group had 0.5 mL/kg of saline containing 1% lidocaine injected into the T4-5 space. The TEA + BPC group had blood pressure and heart rate maintained at pre-epidural injection values by partially occluding the descending aorta and by atrial pacing. Endothelin (15 pmol/kg) was bolus injected into the left anterior descending (LAD) artery of each heart. Systolic and diastolic blood pressure, heart rate, and LAD coronary blood flow (CBF) were monitored. Three minutes after injection of endothelin, myocardial tissue was sampled from the distribution of the LAD artery and from the control, left circumflex (LCx) artery. ATP, ADP, AMP, lactate, and pyruvate were measured by enzymatic methods.
It was found that in each group endothelin consistently decreased LAD CBF, but the decrease was less in the TEA + BPC group. In the tissue distribution of the LAD, the levels of ATP and energy charge potential were lower, and the level of lactate was higher in the NS group than in the TEA or the TEA + BPC groups (p < 0.01).
These results confirm that (1) endothelin injected into the LAD artery decreases CBF and causes selective myocardial ischemia in a fashion similar to intravascular stenosis of the LAD rather than to mechanical occlusion and (2) TEA, with or without pressure support, lessens the degree of regional ischemia induced by injection of endothelin in the LAD.
据报道，胸段硬膜外麻醉（TEA）可减轻心肌的缺血性损伤。内皮素是一种内皮源性肽，是一种强力的冠状动脉血管收缩剂，可能导致心脏灌注不良和缺血。目的是研究在冠状动脉内注射内皮素且有或无TEA的情况下局部心肌代谢情况。
将三个实验组和三种处理进行随机分组。
所有研究均在大学研究实验室进行。
30只麻醉犬组成研究组。
研究动物分为三组，每组10只，分别为生理盐水组（NS）；TEA组；TEA + 血压控制组（TEA + BPC）。NS组在T4 - 5硬膜外间隙注射0.5 mL/kg生理盐水。TEA组在T4 - 5间隙注射0.5 mL/kg含1%利多卡因的生理盐水。TEA + BPC组通过部分阻断降主动脉和心房起搏将血压和心率维持在硬膜外注射前的值。将内皮素（15 pmol/kg）推注到每只心脏的左前降支（LAD）动脉中。监测收缩压、舒张压、心率和LAD冠状动脉血流量（CBF）。注射内皮素三分钟后，从LAD动脉分布区域以及对照左旋支（LCx）动脉采集心肌组织样本。通过酶法测量三磷酸腺苷（ATP）、二磷酸腺苷（ADP）、一磷酸腺苷（AMP）、乳酸和丙酮酸。
发现每组内皮素均持续降低LAD CBF，但TEA + BPC组降低幅度较小。在LAD的组织分布中，NS组的ATP水平和能量电荷电位较低，乳酸水平高于TEA组或TEA + BPC组（p < 0.01）。
这些结果证实：（1）向LAD动脉注射内皮素会降低CBF，并以类似于LAD血管内狭窄而非机械性阻塞的方式导致选择性心肌缺血；（2）无论有无压力支持，TEA均可减轻LAD内注射内皮素所诱导的局部缺血程度。
