Patients born with heart defects often undergo surgical procedures on a heart lung machine. With improvements in medical and surgical management, their survival has significantly improved, but their brain insult has not been paid much attention. This study is to determine the relationship between specific proteins in the blood and brain injury in patients less than 18-year-old undergoing heart surgery.

Inclusion Criteria:

• less than 18 years old
• undergoing cardiac surgery with cardiopulmonary bypass at Boston Children's Hospital

Exclusion Criteria:

• undergoing an emergent procedure and do not have more than 1 hour ahead of time to review the consent
• patient in a moribund condition American Society of Anesthesiology (ASA 5)
• patient with a hematological and/or oncological disease
• Jehovah witnesses
• patient on preoperative mechanical ventilation

Patients less than 18 years old undergoing a cardiac surgical procedure at Boston Children's Hospital with cardiopulmonary bypass.