The investigators hypothesized that, following cardiac arrest in pediatric patients, hypothermia therapy will improve the proportion of patients with a good functional outcome compared to a normothermic control group.

Cardiac arrest is associated with a high morbidity and mortality in children and hypothermia therapy has the potential to be beneficial in children following cardiac arrest. We have a track record of both clinical and laboratory research of hypothermia therapy following cardiac arrest at the Hospital for Sick Children and have completed a 3-site randomized controlled pilot study of hypothermia therapy following cardiac arrest in children funded by The Hospital for Sick Children Research Institute and the Heart and Stroke Foundation of Ontario. This protocol was used to develop the protocol for the THAPCA trials (see 2 manuscripts published Moler et al NEJM 2015 and 2017 and multiple other manuscripts). Hypothermia therapy, compared to active maintenance of normothermia, had no beneficial effect on functional outcome or mortality in children with out-of-hospital or in-hospital cardiac arrest.

Inclusion Criteria:

• Informed consent by parent or legal guardian
• Age ≥ 38 weeks gestation up to and including 17 years
• Patient admitted with a diagnosis of a cardiac arrest requiring compressions ≥3 minutes
• Remain comatose i.e. have Glasgow Coma Score less than or equal to 10 assessed at the tertiary level pediatric hospital at least 1 hour post- cardiac arrest
• Invasive mechanical ventilation

Exclusion Criteria:

• Cardiac arrest lasting ≥45 minutes, irregardless of commencement of ECMO
• Refractory hemorrhagic shock
• Dysrhythmia leading to cardiac arrest, where cooling would be part of standard therapy
• Suspected diagnosis of brain death as defined as fixed and dilated pupils, Glasgow Coma Score of 3 and no evidence of brain function on neurological examination
• Patients who have had a prolonged cardiac arrest at the scene of a trauma
• Decision to withhold (DNR) or withdraw life sustaining therapies
• Acute Birth asphyxia
• Terminal illness, not expected to survive 12 months
• Cardiac arrest caused by septic shock
• Severe neurodevelopmental disability or persistent vegetative state prior to cardiac arrest
• Near drowning in ice water and temperature <32ºC on admission to study site
• It has been more than 6 hours following cardiac arrest (estimated by first responder)
• Previous enrolment in the HypCAP Pilot Study
• Pregnant
• Parent/Guardian refuse consent
• Responsible physician refuses to enrol patient