Comparison of chronic and acute effects of morphine sulfate on cardiovascular function

Circulatory effects of morphine sulfate on supine anesthetized dogs were investigated to define acute and chronic effects of this drug upon cardiovascular function. Right atrial injection of morphine produced a sustained fall of systemic pressure, cardiac output and heart rate without a significant change in systemic resistance. The mechanism of its efficacy in treatment of acute pulmonary edema may be due to two major factors: (1) peripheral venous pooling of blood resulting in pulmonary decongestion which appears to be a short-lasting effect, and (2) a sustained decrease in left ventricular minute work with no apparent change in myocardial contractility, as demonstrated in this study. N-allylnormorphine abolished the morphineinduced bradycardia but not the reduced cardiac output and systemic pressure.