Gilbert M, Roberts S L, Mori M, Blomberg R, Tinker J H
Department of Anesthesia, University of Iowa College of Medicine, Iowa City.
Anesthesiology. 1988 Feb;68(2):243-53. doi: 10.1097/00000542-198802000-00011.
To assess the dose-response effects of isoflurane and halothane anesthesia on hemodynamics and coronary artery reactivity, the authors studied myocardial hyperemic responses following brief single artery flow arrests in 21 open chest, isocapnic swine in which arterial blood pressures and cardiac outputs were recorded. A specially designed Doppler probe was used to measure the peak and time course of coronary blood flow velocity in the left anterior descending coronary artery (LAD) after 15-s LAD occlusions. The ratio of peak velocity of blood flow to resting velocity (coronary reserve), relative repayment of flow debt, and duration of hyperemic responses were studied. Surgery was performed at MAC end-tidal concentrations ([Et]isoflurane = 1.45%. [Et]halothane = 1.25%) of isoflurane (n = 7) or halothane (n = 7), and recordings were made after 15-min steady state [Et]agent at 0.5, 1, 1.25, 1.5, 1.75, 2 MAC, and further 0.5 MAC increments until the demise of each animal. To compare coronary reactivity at similar coronary pressures, an aortic snare was used to elevate arterial pressures in a third group of halothane anesthesized pigs (n = 7) to those in the previously studied isoflurane group at each MAC level. There were three major differences between halothane and isoflurane. First, cardiac depression (reduction in arterial pressure, cardiac output, and stroke volume) was less with isoflurane compared with halothane anesthesia. Second, with halothane anesthesia, there was a marked decrease in coronary reactivity independent of coronary perfusion pressures with marked, dose-dependent reductions in both coronary reserve and relative flow repayment. During isoflurane anesthesia, coronary reactivity and coronary reserve was well preserved within physiologic limits up to 1.75 MAC [Et]. Third, halothane anesthesized pigs died in cardiac collapse at much lower agent concentrations than with isoflurane (no animals survived 1.75 MAC halothane, whereas all animals survived 2.5 MAC isoflurane). Therefore, pigs anesthesized with isoflurane had greater coronary reserve, better preserved cardiac function, and greater tolerance to increasing agent concentration than pigs anesthesized with halothane.
为评估异氟烷和氟烷麻醉对血流动力学及冠状动脉反应性的剂量 - 反应效应，作者对21只开胸、等碳酸血症猪进行了研究，这些猪在短暂单动脉血流阻断后记录动脉血压和心输出量，研究心肌充血反应。使用专门设计的多普勒探头测量左前降支冠状动脉（LAD）闭塞15秒后冠状动脉血流速度的峰值和时间过程。研究了血流峰值速度与静息速度之比（冠状动脉储备）、血流亏欠的相对偿还以及充血反应的持续时间。手术在异氟烷（n = 7）或氟烷（n = 7）的MAC呼气末浓度（[Et]异氟烷 = 1.45%，[Et]氟烷 = 1.25%）下进行，在0.5、1、1.25、1.5、1.75、2 MAC的15分钟稳态[Et]麻醉剂后进行记录，并以0.5 MAC的增量进一步记录，直至每只动物死亡。为比较相似冠状动脉压力下的冠状动脉反应性，在第三组氟烷麻醉猪（n = 7）中使用主动脉圈套将动脉血压升高至先前研究的异氟烷组在每个MAC水平时的血压。氟烷和异氟烷之间存在三个主要差异。首先，与氟烷麻醉相比，异氟烷麻醉时心脏抑制（动脉压、心输出量和每搏量降低）较轻。其次，在氟烷麻醉下，冠状动脉反应性显著降低，与冠状动脉灌注压力无关，冠状动脉储备和相对血流偿还均有显著的剂量依赖性降低。在异氟烷麻醉期间，冠状动脉反应性和冠状动脉储备在高达1.75 MAC [Et]的生理范围内得到良好保留。第三，氟烷麻醉的猪在比异氟烷低得多的麻醉剂浓度下死于心脏衰竭（没有动物在1.75 MAC氟烷下存活，而所有动物在2.5 MAC异氟烷下存活）。因此，与氟烷麻醉的猪相比，异氟烷麻醉的猪具有更大的冠状动脉储备、更好的心脏功能保留以及对麻醉剂浓度增加的更大耐受性。
