Historically, critical care physicians had a nihilistic approach towards patients who remained unconscious after a cardiac arrest outside hospital. This changed with the publication of two randomised clinical trials of mild induced hypothermia (32-34°C) that showed neuroprotection.1 2 Subsequently this treatment has been embraced by the International Liaison Committee on Resuscitation, European Resuscitation Council, American Heart Association, and, most recently, the National Institute for Health and Clinical Excellence (NICE).

Animal models of cardiac arrest showed that mild hypothermia improved neurological outcome,3 and these data were supported by small observational studies in patients. Clinical trials to determine whether this treatment benefited unconscious patients after cardiac arrest were therefore fitting. However, neither the above randomised trials1 2 nor subsequent studies4 provide sufficiently robust data to justify the conclusion that cooling to 32-34°C should be used after cardiac arrest outside hospital.