Mild hypothermia during advanced life support: a preliminary study in out-of-hospital cardiac arrest

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Abstract
Introduction: Induction of mild hypothermia after cardiac arrest may confer neuroprotection. We assessed the feasibility, safety and effectiveness of therapeutic infusion of 2 l of normal saline at 4°C before return of spontaneous circulation during cardiopulmonary resuscitation after out of hospital cardiac arrest. Methods: This was a prospective, observational, multicenter clinical trial conducted in Emergency Medical Services units and in a medical intensive care unit at Caen University Hospital, Cen, France. Results: In patients who had suffered out of hospital cardiac arrest, hypothermia was induced by infusing 2 l of 4°C NaCl 0.9% over 30 minutes during advanced life support prior to arrival at the hospital. A total of 33 patients were included in the study. Eight patients presented with ventricular fibrillation as the initial cardiac rhythm. Mild hypothermia was achieved after a median of 16 minutes (interquartile range 11.5 to 25.0 minutes) after return of spontaneous circulation. After intravenous cooling, the temperature decreased by 2.1°C (P < 0.0001) to a mean body temperature of 33.3°C (interquartile range 32.3 to 34.3°C). The only observed adverse event was pulmonary oedema, which occurred in one patient. Conclusion: We concluded that prehospital induction of therapeutic hypothermia using infusion of 2 l of 4°C normal saline during advanced life support was feasible, effective and safe. Larger studies are required to assess the impact that this early cooling has on neurological outcomes after cardiac arrest.