Studies have shown that between one-quarter and one-half of infants undergoing cardiac surgery will suffer brain injury during surgery (the perioperative period). Some infants with congenital heart disease have neurological injury prior to cardiac surgery as a result of cyanosis, acidosis and abnormal circulation. The spectrum of neurological injury ranges from agitation and subtle disturbances in learning and new memory acquisition to visual and motor development abnormalities, seizures, stroke and encephalopathy.