The association between intra-arrest therapeutic hypothermia and return of spontaneous circulation among individuals experiencing out of hospital cardiac arrest

Introduction

Therapeutic hypothermia has been shown to improve both mortality and neurologic outcomes following pulseless ventricular tachycardia and fibrillation. Animal data suggest intra-arrest induction of therapeutic hypothermia (IATH) improves frequency of return of spontaneous circulation (ROSC). Our objective was to evaluate the association between IATH and ROSC.

Methods

This was a retrospective analysis of individuals experiencing non-traumatic cardiac arrest in a large metropolitan area during a 12-month period. Six months into the study a prehospital IATH protocol was instituted whereby patients received 2000 ml of 4 °C normal saline directly after obtaining IV/IO access. The main outcome variables were prehospital ROSC, survival to admission, and to discharge. A secondary analysis was conducted to assess the relationship between the quantity of cold saline infused and the likelihood of prehospital ROSC.

Results

551 patients met inclusion criteria with all the elements available for data analysis. Rates of prehospital ROSC were 36.5% versus 26.9% (OR 1.83; 95% CI 1.19-2.81) in patients who received IATH versus normothermic resuscitation respectively. While the frequency of survival to hospital admission and discharge were increased among those receiving IATH, the differences did not reach statistical significance. The secondary analysis found a linear association between the amount of cold saline infused and the likelihood of prehospital ROSC.

Conclusion

The infusion of 4 °C normal saline during the intra-arrest period may improve rate of ROSC even at low fluid volumes. Further study is required to determine if intra-arrest cooling has a beneficial effect on rates of ROSC, mortality, and neurologic function.