Correlation of plasma catecholamines, renal function, and the effects of Dibenzyline on cardiac patients undergoing corrective surgery

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 alpha-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 microg/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<or=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.

Postoperative management in patients with complex congenital heart disease

Life-threatening problems occur in the neonate and infant after cardiac surgery because of the interplay of diminished cardiac output (CO), increased metabolic demand, inflammatory responses to cardiopulmonary bypass, and maladaptive responses to stress. Therefore, the postoperative management of patients with complex congenital heart defects is directed at optimization of oxygen delivery to maintain end-organ function and promote wound healing. Traditionally, assessment of circulation in the postoperative congenital heart patient has depended on indirect assessment of CO using parameters such as blood pressure, pulses, capillary refill, and urine output. Because of the limitations of indirect and observer-dependent assessment of CO, we rely on objective measures of tissue oxygen levels for the complex postoperative patient. We have found that continuous monitoring of the mixed venous saturation (SvO2) allows for identification of acute changes in systemic oxygen delivery and frequently precedes other indicators of decreased CO. The postoperative patient can be expected to have a period of decreasing CO, and the need for intervention should be anticipated because critical low output syndrome will develop in a subset of patients. Strategies for postoperative care are developed based on the diagnosis and procedure, but optimizing SvO2 is a consistent goal. A uniform approach to airway maintenance, vascular access, and drug infusions, all universal concerns during the perioperative period, minimizes the potential for these predictable and necessary interventions to result in morbidity or mortality. Management of the postoperative single ventricle patient targets stabilization of the systemic vascular resistance through the use of vasodilators to improve systemic perfusion and simplify ventilator management. Management of any individual patient should be driven by objective analysis of available data and must include efforts to re-evaluate the treatment plan as well as to identify unanticipated problems.