As the survival of infants and children with all forms of congenital heart defects has dramatically improved over the last three decades, the focus of care has now shifted toward reducing short and long-term morbidity. The field of perioperative care is rapidly evolving with nearly simultaneous advances in surgical techniques and adjunctive therapies, respiratory care, intensive care technology and monitoring, pharmacologic research and development, and computing and electronics. Despite these advances, there remains a predictable fall in cardiac output after cardiopulmonary bypass (CPB)

particularly in the neonate and young infant. This chapter will mostly focus on early identification and aggressive treatment of the ‘‘low cardiac output syndrome’’ (LCOS) peculiar to these patients.