Therapeutic Hypothermia after Cardiac Arrest
The Article: Targeted Temperature Management at 33⁰C versus 36⁰C after Cardiac Arrest. Nielsen et al. (2013) The New England Journal of Medicine. 369(23): 2197-2206.
The Idea: To determine whether hypothermia after cardiac arrest at a targeted temperature of 33⁰C was superior to 36⁰C. Previous trials have determined that therapeutic hypothermia, defined as 32-34⁰C for 12-24 hours, showed significant improvement in neurologic function and survival versus standard treatment. However, it is unknown whether this is due to fever prevention in post-arrest patients or if there is additional benefit with lower temperatures.
The Study: Randomized clinical trial of 939 patients from 36 ICU’s in Europe and Australia. Patients were randomly assigned in a 1:1 ratio to one of the two targeted temperatures. Inclusion criteria consisted of age >18 years, out of hospital arrest with a presumed cardiac cause, unconscious at presentation with a GCS of <8, and 20 consecutive minutes of spontaneous circulation after resuscitation. Exclusion criteria included an initial rhythm of asystole, suspected stroke/intracranial hemorrhage, 240 minutes between ROSC and screening, and a temperature <30⁰C. The primary outcome was all cause mortality and secondary outcomes included poor neurologic function or death at 180 day follow up. The patients were rapidly cooled to their targeted temperature, gradually re-warmed at 28 hours to 37⁰C, and kept below 37.5⁰C for 72 hours. At 72 hours, the patients had a neurologic examination by a blinded physician.
The Findings: There was no significant difference between the two groups in overall mortality at the end of the trial. In addition, there was no significant difference in mortality or neurologic function at 180 days. The study found no harm with a targeted temperature of 33⁰C.
The Takeaway: In unconscious patients suffering from out of hospital cardiac arrest, hypothermia at a targeted temperature of 33⁰C did not confer a benefit in overall mortality or neurologic function at the end of the trial or at 180 days, when compared to 36⁰C.