Hemodynamic Predictors of Myocardial Ischemia during Halothane Anesthesia for Coronary-Artery Revascularization

Abstract

The authors undertook a prospective study of 30 patients undergoing halothane anesthesia for coronary-artery revascularization to ascertain which clinically monitored hemodynamic variables--or combination of variables--associated with myocardial oxygen supply and demand best predict myocardial ischemia. Simultaneous recordings of electrocardiogram (lead II and V5), systemic, central venous, pulmonary artery, and pulmonary artery occluded pressures were analyzed for correlation with ischemic episodes. Ischemia occurred with significant increases (P less than 0.0001) in heart rate, central venous pressure, and pulmonary artery occlusion pressure and with significant decreases (P less than 0.0001) in systolic and mean arterial blood pressure and in coronary perfusion pressure (mean arterial minus pulmonary artery occluded pressure). There was no correlation between ischemia and either hypertension (systolic blood pressures up to 200 mmHg) or the rate-pressure product. Systemic systolic blood pressure, systemic mean arterial blood pressure, and coronary perfusion pressure as single determinants were the most useful to monitor in avoiding myocardial ischemia. A combination of systemic arterial blood pressure (systolic or mean) and filling pressure (central venous or pulmonary artery occluded) was generally as useful but not more so than the preceding single variables in avoiding ischemia. Rate-pressure product was not of value in this regard. Patients were divided into three groups according to preoperative left ventricular (LV) function to determine whether pulmonary artery occluded pressure (PAOP) was more useful than central venous pressure (CVP) as either a predictor of ischemia or an index of cardiac filling: normal LV function (Group I), moderately abnormal LV function (Group II), and markedly abnormal LV function (Group III). PAOP offered no advantage over CVP for either purpose, except in some Group III patients.