This trial is currently a single-center, randomized, double-blind investigator initiated prospective clinical trial initiated at the University of Ottawa Heart Institute (UOHI). The plan is to expand the trial shortly as a multi-center project. The patients for this study will be recruited amongst comatose survivors of out-of-hospital cardiac arrest (OHCA). The aim of this study is to determine whether neurologic outcomes at six months are improved with moderate (31 degrees Celsius) versus mild (34 degrees Celsius) therapeutic hypothermia (TH) following return of spontaneous circulation (ROSC) in patients suffering OHCA, with ROSC defined as the resumption of sustained perfusing cardiac activity.