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Nearly 2 decades ago, the concept of “therapeutic hypothermia” was introduced into the care of patients with coma after cardiac arrest (NEJM JW Gen Med Mar 15 2002 and N Engl J Med 2002; 346:549). Initial studies suggested benefit in neurological outcome with cooling to 32°C for 24 hours. Subsequent studies in which 32°C and 36°C and varied durations of cooling were compared have yielded equivocal results and have raised more questions than answers (e.g., NEJM JW Emerg Med Jan 2014 and N Engl J Med 2013; 369:2197).
Investigators in Sweden randomized 1850 patients with coma after out-of-hospital arrest to either targeted temperature management to 33°C for 28 hours with gradual rewarming (hypothermia) or maintenance of temperature at 37.5°C or lower (normothermia). Three quarters of patients had shockable rhythms, and almost all received bystander cardiopulmonary resuscitation. Prognostication was done by a blinded independent clinician.
Skin-surface cooling devices were used more commonly than intravascular devices (70% vs. 30%), and almost half of the normothermia group also received some cooling. More arrhythmias occurred in the hypothermia group. Mortality and percentage of patients with poor neurological outcomes (54%) did not differ by group. The two groups had similar degrees and duration of sedation.
Dankiewicz J et al. Hypothermia versus normothermia after out-of-hospital cardiac arrest. N Engl J Med 2021 Jun 17; 384:2283. (https://doi.org/10.1056/NEJMoa2100591)
Comment
Protocols that focus on achieving hypothermia (32°C–33°C) confer risk without any clear benefit. Active temperature management with a target of normothermia makes sense and will be my practice moving forward.