Mechanisms of Myocardial Ischemia During Anesthesia

Abstract

Careful monitoring and control of systemic blood pressure and heart rate still seem to be the most effective means of avoiding perioperative myocardial ischemia. In a comparison of the predicitive value for ischemia of the commonly measured hemodynamic variables, Lieberman and co-workers (1) found the systolic blood pressure to have the highest predicitive value of positive tests (79%) and the highest efficiency (84%). In comparison, an elevated pulmonary capillary wedge pressure had an efficiency to predict ischemia of 55% only. These authors found the combination of decreased systolic blood pressure (more than 30% below the awake value or less than 90 mm Hg) and tachycardia to be the variables most commonly associated with ischemia. These findings are partly in contrast with those obtained by Slogoff and Keats (2). They found that perioperative ischemia correlated with tachycardia and hypertension rather than hypotension. More intriguing in this study was that more than half the ischemic episodes were temporally unassociated with hemodynamic abnormalities. This suggests that other mechanisms for ischemia than those generally recognized, may be active during anesthesia and surgery.