The staged surgical pathway to treat children with single ventricle heart defects culminates with the Fontan operation. In this procedure, systemic venous return is rerouted directly to the pulmonary arteries, which serves to separate the systemic and pulmonary circulations. Following this operation, deoxygenated blood flows passively from the body through the lungs without a pumping chamber. Although mortality following the Fontan operation is now uncommon, early postoperative morbidity including prolonged postoperative chest tube drainage and hospitalization remains significant. The efficacy of empiric inotropic, vasodilator and neurohumoral-inhibitory therapies in the perioperative period is unknown and practice varies widely between centers.