Critical care after surgery for congenital cardiac disease
The neonatal myocardium is less compliant than that of the older child, less tolerant of increases in afterload, and less responsive to increases in preload. A predictable decrease in cardiac index typically occurs 6 to 12 hours after separation from cardiopulmonary bypass, but milrinone administration during the early postoperative period may attenuate this phenomenon. Patients with postoperative low cardiac output require careful evaluation for unanticipated residual lesions. Patients with restrictive physiology from hypertrophy and diastolic dysfunction of the right ventricle may require high right-sided filling pressures to achieve adequate cardiac output, making them prone to hepatic congestion, anasarca, pleural effusions, and ascites. Inhaled nitric oxide plays an important role in the management of postoperative pulmonary hypertension in the cardiac intensive care unit. Hypoxemia after bidirectional cavopulmonary anastomosis generally is a sign of decreased pulmonary blood flow related to reduced cardiac output. Liberation from positive-pressure mechanical ventilation should be accomplished as soon as feasible, particularly in patients after a cavopulmonary anastomosis (bidirectional Glenn) or Fontan operation because spontaneous breathing improves pulmonary blood flow, arterial oxygen saturation, and ventricular preload. Ventricular ectopy and elevated atrial pressures after the arterial switch operation should raise suspicion of myocardial ischemia from insufficient coronary blood flow. Postoperative care of the patient with hypoplastic left heart syndrome after stage I palliation (Norwood procedure) may require delicate balancing of the pulmonary and systemic blood flows. A high arterial oxygen saturation denotes excessive pulmonary blood flow and in patients with impaired ventricular output is generally accompanied by inadequate systemic blood flow, acidosis, and end-organ dysfunction..
