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Therapeutic Hypothermia and Survival After Cardiac Arrest
Study Questions:
What is the association between therapeutic hypothermia and survival after in-hospital cardiac arrest?
Methods:
In this cohort study, within the national Get With the Guidelines–Resuscitation registry, 26,183 patients were successfully resuscitated from an in-hospital cardiac arrest between March 1, 2002, and December 31, 2014, and either treated or not treated with hypothermia at 355 US hospitals. Follow-up ended February 4, 2015. The primary outcome was survival to hospital discharge. The secondary outcome was favorable neurological survival, defined as a Cerebral Performance Category score of 1 or 2 (i.e., without severe neurological disability). Comparisons were performed using a matched propensity score analysis and examined for all cardiac arrests and separately for nonshockable (asystole and pulseless electrical activity) and shockable (ventricular fibrillation and pulseless ventricular tachycardia) cardiac arrests.
Results:
Overall, 1,568 of 26,183 patients with in-hospital cardiac arrest (6.0%) were treated with therapeutic hypothermia; 1,524 of these patients (mean [standard deviation] age, 61.6 [16.2] years; 58.5% male) were matched by propensity score to 3,714 non–hypothermia-treated patients (mean age, 62.2 [17.5] years; 57.1% male). After adjustment, therapeutic hypothermia was associated with lower in-hospital survival (27.4% vs. 29.2%; relative risk [RR], 0.88; 95% confidence interval [CI], 0.80-0.97; risk difference, −3.6%; 95% CI, −6.3% to −0.9%; p = 0.01), and this association was similar (interaction p = 0.74) for nonshockable cardiac arrest rhythms (22.2% vs. 24.5%; RR, 0.87; 95% CI, 0.76-0.99; risk difference, −3.2%; 95% CI, −6.2% to −0.3%) and shockable cardiac arrest rhythms (41.3% vs. 44.1%; RR, 0.90; 95% CI, 0.77-1.05; risk difference, −4.6%; 95% CI, −10.9% to 1.7%). Therapeutic hypothermia was also associated with lower rates of favorable neurological survival for the overall cohort (hypothermia-treated group, 17.0% [246 of 1443 patients]; non–hypothermia-treated group, 20.5% [725 of 3,529 patients]; RR, 0.79; 95% CI, 0.69-0.90; risk difference, −4.4%; 95% CI, −6.8% to −2.0%; p < 0.001) and for both rhythm types (interaction p = 0.88).
Conclusions:
The authors concluded that among patients with in-hospital cardiac arrest, use of therapeutic hypothermia compared with usual care was associated with a lower likelihood of survival to hospital discharge and a lower likelihood of favorable neurological survival.
Perspective:
In a large national registry, treatment with therapeutic hypothermia was not associated with higher rates of survival to discharge or favorable neurological survival in patients with in-hospital cardiac arrest and was associated with potential harm. Furthermore, these associations were similar for both shockable and nonshockable cardiac arrest rhythms. Overall, these findings do not support current use of therapeutic hypothermia for patients with in-hospital cardiac arrest and warrant reconsideration. A randomized clinical trial is indicated to assess efficacy of therapeutic hypothermia for in-hospital cardiac arrest.
Keywords: Arrhythmias, Cardiac, Heart Arrest, Hypothermia, Hypothermia, Induced, Primary Prevention, Resuscitation, Survival, Ventricular Fibrillation, Tachycardia, Ventricular
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