In this single-center, prospective, randomized study, hemodilution to a HCT level of 35% versus 25% will be compared with respect to neurodevelopmental outcome and early postoperative course in infants with congenital heart disease. The first aim of this study will test the hypothesis that hemodilution to a HCT level of 35%, compared to a level of 25%, will be associated with superior central nervous system protection. The primary outcome variable will be developmental outcome at age 1 year, assessed using the Bayley Scales of Infant Development. Secondary outcome variables include the following: 1) tissue release of S-100 protein as a measure of cerebral cellular injury; 2) cerebral hemodynamics and oxygenation, determined by near infrared spectroscopy (NIRS); 3) intrinsic cerebral vasoregulation, measured by NIRS and transcranial Doppler; and 4) at age 1 year, neurologic examination, the MacArthur inventory, and structural and volumetric findings of magnetic resonance imaging (MRI).