Cardiac pathology is a major risk for brain injury and neurodevelopmental deficit. The most common cause of cardiac pathology is congenital heart defects (CHD) about 4-8/1000 live births a year. The most common etiology of the brain insult is hypoxic ischemic injury (HII) as result of hemodynamic instability in the perioperative period. Similar insults in adults with cardiac arrest or infants with neonatal asphyxia, was successfully treated with hypothermia, initiated within 6 hours after the event. Although, hypothermia is most likely an effective treatment for HII in children with cardiac anomaly, it also carries a risk for bleeding or infection of the surgical wound. In this randomized control trial, hypothermia treatment will be compared to normothermia treatment of patients in the pediatric cardiac intensive care unit (PCICU) following severe HII in the PCICU or operating room. The effect will be quantified by MRI, serum biomarkers of brain injury, amplitude integrated EEG, neurological evaluation coagulation and infection evaluation in the acute phase and by developmental assessment at 1, 6 months and 2, 5 years. Favorable effect of hypothermia with minimal risks may open the door for the implementation of hypothermia as a standard care in PCICUs.

Inclusion Criteria:

1. Every child entering the PCICU, age < 7 years

2. The child will enter arm 1 or 2 if he underwent the event described in section 3.

3. Hypoxic ischemic event that would render hypothermia treatment is defined as

   • During the hospitalization in the PCICU before or after the surgery:

   Resuscitation comprised of chest compressions for more than 2 minutes, and the first blood tests immediately after the resuscitation show a serum lactate level of more than 90 mg/dl OR Resuscitation comprised of chest compressions for more than 2 minutes, and the first blood tests immediately after the resuscitation shows a serum lactate level of more than 40 mg/dl and a blood pH level of less than 7.1

   • During the surgery Near infra red spectroscopy lower than 40 for more than 5 minutes AND Serum lactate levels of more than 90 mg/dl during the event OR The patient is re-connected to cardio-pulmonary bypass machine as a result of the event

4. Initiation of hypothermia treatment within 6 hours following the hypoxic ischemic event defined in section 3.

Exclusion criteria

• Suspected hypoxic ischemic event as described in the Inclusion Criteria in the 2 weeks prior to the PCICU admission
• Prolonged low cerebral perfusion before the PCICU admission, with 3 repeated tests in 1 hour of lactate level higher than 40 mg/dl and pH lower than 7.1
• Rejection criteria
• A second resuscitation after the hypoxic ischemic event and before a brain MRI is done