1264 AFTERLOAD REDUCTION BY SODIUM NITROPRUSSIATE (SNP) IN ASPHYXIATED INFANTS WITH HYPERTENSION AND HEART FAILURE

Abstract

In adults, blood pressure is decreased by SNP due to arteriolar and venous dilating effect; however, its actions have not been established in newborn infants. To elucidate the latter, we examined the changes in heart rate, arterial and central blood pressures, echo and electrocardiograms, and pH. Tissue perfusion was evaluated using skin surface unheated PCO2 electrodes. 5 infants developed left heart failure and refractory hypertension after severe fetal distress and neonatal asphyxia and were treated with digitalis and intravenous SNP (2-6 umg/kg/hr.). Before therapy all infants had: tachycardia, cardiomegaly, pulmonary edema, high central venous and arterial blood pressures. Increased left ventricular internal diameter and LA/Ao ratio, ECG ST depression, elevated CPK-MB2 isoenzymes, acidosis and elevated skin tissue PCO2 with increased skin-arterial PO2 gradients. Hemodynamic changes observed within 20 minutes of therapy were compared to values before therapy by paired t tests. With therapy, there were no increase in heart rate, and a significant decrease in arterial and central venous blood pressures. Increases in local perfusion, tissue PO2, and arterial pH, with simultaneous decrease in skin PCO2 were observed. These data suggest that, afterload reduction with SNP in infants with post-asphyxic hypertension and acute heart failure, produces improvement of cardiac pump function, tissue perfusion and oxygenation.