Inclusion Criteria:  Patients with out of hospital cardiac arrest with sustained ROSC (defined as >20 minutes or sufficient stability to consider conveyance)  Exclusion Criteria:  Any clear non-cardiac cause of arrest (trauma, drowning Overdose, asphyxia, asthma, anaphylaxis). Suspected or confirmed intra-cerebral bleeding Known CPC score 3 or 4 pre-cardiac arrest Known disease limiting survival to 6 months Suspected or known pregnancy