Effects of Volatile Anesthetics on the Coronary Circulation in Chronically Instrumented Dogs
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Although it had been generally assumed that the potent inhalation anesthetics could directly relax vascular smooth muscle including coronary,1–3 there had been few published accounts of the direct effects of anesthetics on the coronary vasculature. The initial experiments concerning the effect of volatile anesthetics on the coronary circulation suggested that the metabolic depression produced by the potent inhalation anesthetics overrode the direct vasodilating effects, resulting in a dose-dependent decrease in coronary blood flow without appreciable effect on calculated coronary vascular resistance.4–8 However, the study in humans by Reiz and colleagues challenged this universal effect of inhalation anesthetics9 and subsequent studies in animals under controlled conditions have shown that isoflurane is indeed a coronary vasodilator even in the chronically instrumented intact animal.10–13 Since coronary vasodilation can produce deleterious redistribution of myocardial perfusion especially in collateralized hearts,14 there has been great interest in this coronary vasodilating effect of isoflurane. Although Buffington demonstrated that isoflurane can produce this maldistribution of myocardial perfusion under carefully defined conditions,15 others have disputed his contention.16,17 Part of the controversy has stemmed from a question about the magnitude of the coronary vasodilation produced by isoflurane. With the advent of two new inhalation anesthetics, sevoflurane and the isoflurane analog desflurane, it seemed appropriate and necessary to compare the coronary dynamic effects of the new anesthetics with isoflurane.
KeywordsCoronary Blood Flow Volatile Anesthetic Coronary Circulation Coronary Vasodilation Inhalation Anesthetic
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