Study designs of evaluations included in the review
Randomised controlled trials (RCTs) and quasi-RCTs were eligible for inclusion in the review.
Specific interventions included in the review
Studies that compared mild induced hypothermia (32 to 34 degrees C) with normothermia within 24 hours of the patient's presentation were eligible for inclusion. Where reported, the included studies used different methods of cooling, including cooling mattress (plus ice packs if required), ice packs and
cooling helmet. The duration of cooling ranged from no time after mild hypothermia was reached to 3 days.
Participants included in the review
Studies of adults (aged older than 18 years) who had a primary cardiac arrest and were comatose (Glasgow Coma Scale <8) following return of spontaneous circulation (ROSC) were eligible
for inclusion. Where reported, patients in the included studies presented with ventricular fibrillation, pulseless ventricular tachycardia, asystole or pulseless electrical activity. The median time from collapse to ROSC ranged from 21 to 34 minutes.
Outcomes assessed in the review
Studies that assessed neurological outcomes or mortality were eligible for inclusion. In the review, a 'good' neurological outcome was defined as no disability or mild to moderate disability, while a 'poor' neurological outcome was defined as more severe degrees of disability. The review also assessed
adverse effects. The included studies used different scales to assess neurological outcomes: Glasgow-Pittsburgh Cerebral Performance, Glasgow Outcome Scale and classification based on discharge destination.
How were decisions on the relevance of primary studies made?
One reviewer screened titles and abstracts and selected potentially relevant studies. Two reviewers then independently selected the studies from retrieved full reports. Any disagreements on inclusion were resolved through discussion with a third author.