Effect of Isoproterenol, l -Norepinephrine, and Intraaortic Counterpulsation on Hemodynamics and Myocardial Metabolism in Shock following Acute Myocardial Infarction

Abstract

The effects of isoproterenol, l-norepinephrine, and intraaortic counterpulsation on hemodynamics and myocardial metabolism were evaluated in shock due to acute myocardial infarction. Before treatment, the cardiac index was markedly reduced, averaging 1.35 liters/min/m². Mean aortic pressures ranged from 40 to 65 mm Hg. Decreases in coronary blood flow (mean, 68 ml/100 g/min) and in myocardial oxygen consumption (mean, 8.11 ml/100 g/min) were associated with abnormally high myocardial oxygen extractions (mean, 78%) and with lactate production (mean, 9%). Isoproterenol increased cardiac index 63% and heart rate 26%. Coronary blood flow rose an average of 12 ml/100 g/min in the face of decreased diastolic aortic pressure. Rate of myocardial lactate production increased. l-Norepinephrine increased mean aortic pressure and coronary blood flow an average of 21 mm Hg and 27 ml/100 g/min. Mean myocardial oxygen consumption rose 2.24 ml/100 g/min. While myocardial lactate production shifted to extraction (mean, 12%), myocardial oxygen extraction remained abnormally high (mean, 73%). Cardiac index did not change. Intraaortic counterpulsation increased mean aortic pressure and coronary blood flow an average of 15 mm Hg and 23 ml/100 g/min. Myocardial oxygen consumption remained essentially unchanged. Both myocardial lactate and oxygen extraction improved toward normal values (15 and 61%). Cardiac index increased an average of 0.45 liters/min/m².