Association Between Therapeutic Hypothermia and Survival After In-Hospital Cardiac Arrest

Therapeutic hypothermia is used for patients following both out-of-hospital and in-hospital cardiac arrest. However, randomized trials on its efficacy for the in-hospital setting do not exist, and comparative effectiveness data are limited.

To evaluate the association between therapeutic hypothermia and survival after in-hospital cardiac arrest.

In this cohort study, within the national Get With the Guidelines-Resuscitation registry, 26 183 patients 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 were identified. Follow-up ended February 4, 2015.

Induction of therapeutic hypothermia.

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 (ie, 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.

Overall, 1568 of 26 183 patients with in-hospital cardiac arrest (6.0%) were treated with therapeutic hypothermia; 1524 of these patients (mean [SD] age, 61.6 [16.2] years; 58.5% male) were matched by propensity score to 3714 non-hypothermia-treated patients (mean [SD] 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% CI, 0.80 to 0.97]; risk difference, -3.6% [95% CI, -6.3% to -0.9%]; P = .01), and this association was similar (interaction P = .74) for nonshockable cardiac arrest rhythms (22.2% vs 24.5%; RR, 0.87 [95% CI, 0.76 to 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 to 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 3529 patients]; RR, 0.79 [95% CI, 0.69 to 0.90]; risk difference, -4.4% [95% CI, -6.8% to -2.0%]; P < .001) and for both rhythm types (interaction P = .88).

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. These observational findings warrant a randomized clinical trial to assess efficacy of therapeutic hypothermia for in-hospital cardiac arrest.