Comparison of isradipine with nitroprusside for control of blood pressure following myocardial revascularization: Effects on hemodynamics, cardiac metabolism, and coronary blood flow

Abstract

The effects of isradipine (ISR) on cardiac performance, myocardial metabolism, and coronary blood flow were compared with those of sodium nitroprusside (SNP) when used to control blood pressure following myocardial revascularization. Twenty patients were randomized to receive either intravenous ISR or SNP if arterial blood pressure increased above 130 mm Hg systolic. Hemodynamic and metabolic parameters were studied using radial, pulmonary arterial, and coronary sinus catheters. Cardiac output and coronary blood flows were measured by thermodilution and blood was taken for calculation of myocardial oxygen consumption and lactate extraction. Electrocardiographic changes were recorded by Holter monitoring throughout the study. ISR and SNP both produced a satisfactory reduction in blood pressure accompanied by a decreased systemic vascular resistance ( P < 0.001). ISR infusion was associated with increases in cardiac output and stroke index ( P < 0.01), which were not apparent in the SNP group. Tachycardia occurred with SNP ( P < 0.01) but not with ISR therapy. Right and left ventricular stroke work indices and myocardial oxygen consumption were reduced with SNP. The ISR group showed unchanged myocardial oxygen consumption with increased right ventricular stroke work index. Coronary vascular resistance decreased ( P < 0.01) during ISR infusion but decreased only slightly in the SNP group. Great cardiac vein blood flow was significantly increased with ISR but not with SNP, resulting in a significant difference between the groups ( P < 0.05). Coronary sinus blood flow increased after control of blood pressure with ISR, whereas SNP was associated with a decrease in flow throughout the infusion period and one patient suffered myocardial ischemia during treatment. SNP caused reductions in mean pulmonary artery and right atrial pressures ( P < 0.05) as well as pulmonary vascular resistance ( P < 0.01), confirming SNP is a pulmonary vasodilator. Pulmonary vasodilatation was not a feature of ISR therapy. ISR appears to be a safe, effective alternative to SNP when used to control blood pressure following myocardial revascularization, and ultimately may prove to be superior.