Found down, pulseless and cold: Outcomes following unwitnessed hypothermic cardiac arrest

Hypothermic out-of-hospital cardiac arrest (OOHCA) without an apparent abrupt cause for hypothermia presents a dilemma for emergency physicians. This study compared outcomes among hypothermic and normothermic OOHCA arrest patients "found down" following unwitnessed arrest who required ongoing chest compressions in the emergency department (ED).

This secondary analysis of Resuscitation Outcomes Consortium (ROC) Epistry 3 data included OOHCA patients ≥15 years old transported to hospital by EMS who required continued or recurrent chest compressions in the ED. Per current resuscitation guidelines, patients with initial core temperatures <30 °C were considered hypothermic; temperatures between 35 °C and 38 °C were classified as normothermic. We excluded patients with initial temperatures recorded >30 min after arrival. We compared survival to hospital admission, survival to hospital discharge and survival with good neurologic status (i.e., Modified Rankin Scale ≤2) for hypothermic and normothermic patients. Sensitivity analyses explored alternate hypothermia cut-points (< 35 °C; 28 °C).

The primary analysis included 22 hypothermic and 416 normothermic patients. Outcomes for hypothermic and normothermic patients did not significantly differ: survival to hospital admission was 13.6 % vs. 28.6 % (difference -15 %, CI: -30.0 %; +0.01 %); survival to hospital discharge was 4.6 % vs. 3.1 % (difference + 1.4 %, CI: -4.2 %; +13.3 %); survival with good neurologic status was 4.6 % vs. 1.2 % (difference + 3.4 %, CI: -5.4 %; +12.1 %). Using alternative cut-points to define hypothermia did not meaningfully alter the results.

In this analysis, outcomes did not differ for hypothermic and normothermic adult OOHCA patients "found down" following unwitnessed OOHCA who required continued chest compressions in the ED.