Xenon for Neuroprotection During Post-Cardiac Arrest Syndrome in Comatose Survivors of an Out of Hospital Cardiac Arrest

Inclusion Criteria: 1. Age at least 18 years but less than or equal to 80 years 2. Presumed cardiac cause of arrest 3. Sustained (\>20 minutes) spontaneous circulation upon arrival in the emergency department 4. No response to verbal commands on arrival to emergency department and prior to randomization (Glasgow Coma Scale score of \<8) 5. Attending decision that patient is eligible for TTM Exclusion Criteria: 1. Written do not attempt resuscitation reported to providers before randomization 2. Traumatic etiology of arrest, defined as concomitant blunt, penetrating, or burn-related injury, or uncontrolled bleeding or exsanguination 3. Suspected or known stroke or intracranial hemorrhage 4. Unwitnessed cardiac arrest 5. No-flow (cardiac arrest to initiation of cardiopulmonary resuscitation/defibrillation) time of \>10 minutes 6. Sustained restoration of spontaneous circulation (ROSC) greater than 30- minutes post-arrest 7. Interval from arrival at the emergency department to randomization for intervention of \>4 hours. 8. Hypothermia (\<30°C core temperature) 9. Bed-bound prior to cardiac arrest 10. Unconsciousness before cardiac arrest (cerebral trauma, spontaneous cerebral hemorrhage, intoxication etc.) 11. Coagulopathy 12. Systolic arterial pressure \<80 mmHg or mean arterial pressure \<60 mmHg lasting more than 30 minutes after ROSC 13. Known pregnancy 14. Have received an investigational drug, device, or biologic product within 30-days 15. Known terminal phase of chronic illness 16. Hypoxemia (SaO2 \<85%) for \>15 minutes after ROSC 17. Inability to maintain SaO2 \>90% on an FiO2 of 50% 18. Having any other clinically significant laboratory abnormality, medical condition (such as intrinsic liver disease or severe chronic obstructive pulmonary disease), or social circumstance that, in the investigator's opinion, makes it inappropriate for the patient to participate in this clinical trial 19. Logistically impossible to provide intervention 20. Have any condition that would impact the evaluation of modified Rankin Scale (mRS)