Comparison of phenoxybenzamine to sodium nitroprusside in infants undergoing surgery

Objectives: The purpose of this study was to compare the effects of a direct-acting arterial dilator, sodium nitroprusside, to an a-adrenergic receptor blocker, phenoxybenzamine, in infants with congenital heart defects undergoing cardiac repairs on cardiopulmonary bypass. Design: A prospective, multicenter, observational study. Setting: Tertiary care center. Participants: Sixty infants scheduled for elective congenital cardiac surgery repair requiring cardiopulmonary bypass. Interventions: Patients received either sodium nitroprusside 2 to 5 mug/kg/min infusion intraoperatively and in the intensive care unit (n = 30 patients) or received phenoxybenzamine 1 mg/kg slowly intravenously at the onset of cardiopulmonary bypass (n = 30 patients). Measurement and Main Results: Despite similar mean arterial pressures during cardiopulmonary bypass in both groups, infants who received phenoxybenzamine had a significantly higher flow compared with those who received sodium nitroprusside (180 +/- 4.8 v 73 +/- 5.12 mL/kg/min, p < 0.0001). Base deficit was significantly larger in the sodium nitroprusside group compared with the phenoxybenzamine group intraoperatively and postoperatively (3.4 +/- 0.5 v 1.3 +/- 0.5 mEq/L, p < 0.05). The core-to-peripheral temperature gradient was significantly larger in the sodium nitroprusside group compared with the phenoxybenzamine group intra- and postoperatively at all points studied. In the intensive care unit, the left atrial pressure was significantly higher in the sodium nitroprusside group compared with the phenoxybenzamine group (9 +/- 0.4 v 7 +/- 0.4 mmHg, p less than or equal to 0.0005). Conclusion: The use of phenoxybenzamine can maintain organ perfusion on cardiopulmonary bypass and improve peripheral circulation as shown by less base deficit and smaller temperature gradients intraoperatively and in the intensive care unit better than nitroprusside. (C) 2005 Elsevier Inc. All rights reserved.