Influence of Desflurane on Regional Distribution of Coronary Blood Flow in a Chronically Instrumented Canine Model of Multivessel Coronary Artery Obstruction

Abstract

The influence of desflurane on myocardial perfusion measured by a microsphere technique during a total occlusion of the left anterior descending coronary artery and concomitant moderate or severe stenosis of the left circumflex coronary artery was evaluated in chronically instrumented dogs. Hemodynamics, regional contractile function, and myocardial blood flow were measured during the conscious state and after anesthesia with desflurane (8.2%-9.2% and 12.5%-12.7%) with and without control of arterial pressure. Total left anterior descending occlusion produced in combination with a left circumflex coronary artery stenosis significantly (P less than 0.05) increased heart rate and left ventricular end diastolic pressure in the absence of desflurane anesthesia. Desflurane, administered only in the presence of left anterior descending occlusion and left circumflex stenosis, significantly (P less than 0.05) decreased mean arterial pressure, left ventricular systolic pressure, and left ventricular positive dP/dt50 without change in heart rate. Blood flow to the subendocardium of normal myocardium was reduced during the high concentration of desflurane (P less than 0.05), but perfusion of the subepicardium and midmyocardium was maintained at conscious levels. When the left circumflex stenosis was of moderate severity, only blood flow to the subendocardium distal to the stenosis was reduced by desflurane (P less than 0.05). In the presence of a severe stenosis, perfusion was decreased in the subepicardium, midmyocardium, and subendocardium of the stenotic zone (P less than 0.05). During the reduction in arterial pressure produced by desflurane, collateral blood flow in the left anterior descending region was reduced in dogs with either a moderate or severe left circumflex stenosis (P less than 0.05). When arterial pressure and heart rate conditions observed in the postocclusion conscious state were restored during the high concentration of desflurane, myocardial blood flow in all regions returned to those levels present in the conscious state (P less than 0.05). Ratios of flow between occluded and normal zones were decreased when hypotension produced by desflurane was uncontrolled, but when arterial pressure and heart rate were adjusted to conscious postocclusion levels using partial thoracic aorta occlusion and atrial pacing, the ratio remained at conscious control levels regardless of the degree of left circumflex stenosis severity (P less than 0.05). Results of this investigation indicate that desflurane does not redistribute blood flow away from collateral-dependent myocardium to other regions via a "coronary steal" mechanism in a chronically instrumented canine model of multivessel coronary artery disease.