Randomised controlled trials (RCTs) of patients 15 years or older who received therapeutic hypothermia after cardiac arrest in the pre-hospital setting were eligible for the review. Therapeutic hypothermia was defined as a body temperature between 32°C and 34°C. Interventions for hypothermia included intravenous infusion of cooled lactated ringers, infusion of cooled intravenous saline or a transnasal-cooling device in addition to the normal standard of care by emergency systems. Control groups received the standard of care used by each emergency system. Participants were required to be comatose after successful return of spontaneous circulation during transportation to the receiving facility. Studies were excluded if they were of people who experienced traumatic arrest, obviously pregnant women (>20 weeks gestation), paediatric patients, patients who were awake and followed commands after resuscitation, patients who had a non resuscitation order and patients with body temperature less than 34°C after return of spontaneous circulation.
One study used an intranasal cooling device, one used infusion of 4°C normal saline with a goal of two litres by arrival to hospital and two studies used infusion of two litres of Ringer's solution.
The authors did not state how many reviewers selected studies for the review.