Introduction:
Out-of-hospital cardiac arrest (OHCA) has less than 10% hospital survival. While therapeutic hypothermia resulted in a 16%-24% improvement in neurologic outcome in patients with ventricular fibrillation (VF) in prior trials, recent trials have not shown benefit of pre-hospital initiation hypothermia or of hospital cooling to 33 vs 36 degrees.
Methods:
We studied patients who suffered OHCA in North Carolina from 2012-2013 captured in the CARES database as part of the Heart Rescue Project. To limit selection bias, we excluded patients without return of spontaneous circulation after arrest and without intubation in the field as they may have regained consciousness.
Results:
847 patients were included in the analysis of pre-hospital hypothermia. The patients that received pre-hospital hypothermia had more bystander initiated CPR (p-value < 0.45). Pre-hospital hypothermia was associated with a significant increase in survival to hospital discharge (OR 1.55, 95% CI 1.03-2.32) and neurologic outcome at discharge (OR 1.56 95% CI 1.01-2.40). When looking at arrest types, the significant association was seen after VF arrest (figure). 537 patients survived to hospital admission and included in the analysis of in-hospital hypothermia. Patients who received hospital hypothermia were younger, had more VF, more witnessed arrest and more pre-hospital hypothermia. Hypothermia showed a non-significant trend toward better survival to discharge.
Conclusions:
The association between pre-hospital hypothermia after VF arrest and improved survival, in light of randomized data showing no effect, may be due to confounding or to a greater likelihood of in-hospital hypothermia in this group. The trend in better outcome using in-hospital hypothermia is consistent with a benefit from temperature management. These findings suggest the need for ongoing efforts to understand the value of hypothermia in context of other efforts to improve survival from cardiac arrest.
Time to intra-arrest therapeutic hypothermia in out-of-hospital cardiac arrest patients and its association with neurologic outcome: a propensity matched sub-analysis of the PRINCESS trial
