Prior randomized trials have established hypothermia as a promising therapy to improve outcomes of cardiac arrest.  It has been suggested that the benefit of hypothermia may be increased through early initiation of cooling in the field prior to hospital arrival.  In this trial, 1,364 patients with out-of-hospital cardiac arrest were randomized to usual care or pre-hospital cooling with infusion of cold normal saline immediately after return of spontaneous circulation. The intervention was associated with a reduction in core temperature, but no change in clinical outcomes. Among patients with arrest in the setting of ventricular fibrillation, there were no differences between patients treated with cold saline vs control in survival to discharge (62.7% vs. 64.3%, P.69) or neurologic recovery (57.5% vs. 61.9%, P=.69). Similarly, among patients without ventricular fibrillation, the proportion of patients surviving to discharge (19.2% vs 16.3%, P=.30) or with neurological recovery (14.4% vs. 13.4%, P=.30) did not differ between the intervention and control groups.

Conclusions

In this randomized trial of pre-hospital cooling of patients with out-of-hospital cardiac arrest, this therapy resulted in no improvements in clinical outcomes despite more rapid reduction of core temperature.  As the method of achieving reductions in core temperature may influence the benefit of this therapy, alternate approaches to cooling that do not result in expansion of patient intravascular volume should be considered.

 Summarized by Steven M. Bradley and Supriya Shore

• Kim F, Nichol G, Maynard C, et al. Effect of prehospital induction of mild hypothermia on survival and neurological status among adults with cardiac arrest: a randomized clinical trial. JAMA. 2014 Jan 1;311(1):45-52.