Etiology of prehospital cardiac arrest largely determines outcome in patients treated with mild hypothermia

Introduction

Clinical and experimental investigations have demonstrated improved neurological outcome after therapeutic mild hypothermia in patients after successful resuscitation from prehospital cardiac arrest. In these investigations only patients with prehospital cardiac arrest due to ventricular fibrillation were included. After the presentation of controlled studies, therapeutic hypothermia moved into the topical international guidelines.

Methods

We investigated efficacy and outcome of mild therapeutic hypothermia in the treatment of out-of-hospital cardiac arrest due to varied etiologies. We compared retrospectively 168 patients admitted in the years 2001–2006 to our medical ICU with the indication for cooling therapy after cardiac arrest. Eighty-nine patients received cooling therapy (MHT Group), 79 patients were not cooled after cardiac arrest (NO-COOL Group). Cooling was obtained by endovascular cooling device or surface cooling. Survival in the two groups and factors associated with survival were analysed.

Results

In the MHT Group, survival was significantly higher (53% versus 47%, P = 0.0012). Age and duration of resuscitation therapeutic hypothermia were independently associated with survival. In patients with first registered rhythm of asystole (8/25 (32%) vs 2/13 (15%), P = 0.06), prolonged resuscitation, time from return to spontaneous circulation >20 minutes and prolonged time to arrival on scene, cooling therapy was associated with a significant improvement in neurological outcome.

Conclusion

Therapeutic hypothermia improves significantly survival and neurological outcome of out-of-hospital cardiac arrest in patients independent of first registered rhythm. Patients with a prolonged episode of hypoxia and prolonged time to return of spontaneous circulation profit significantly from treatment with therapeutic hypothermia.