This is a large pragmatic, randomized controlled trial comparing pre-hospital initiation of therapeutic hypothermia by Emergency Medical Services (EMS) providers to conventional post-resuscitation care. The goal of this trial is to increase the proportion of cardiac arrest patients that are appropriately treated in-hospital with therapeutic hypothermia to reach the target body temperature within 6 hours of hospital arrival. The investigators believe that EMS-initiation of cooling will be a powerful reminder to in-hospital clinicians to continue therapeutic hypothermia, and will lead to care improvements across a health system.