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Background: Despite evidence that therapeutic hypothermia improves patient outcomes for out-of-hospital cardiac arrest, use of this therapy remains low. It is unknown if the use of therapeutic hypothermia and patient outcomes have changed following publication of a trial that supported more lenient temperature management.Methods: In the Cardiac Arrest Registry to Enhance Survival (CARES), we identified 45,935 U.S. patients who experienced out-of-hospital cardiac arrest and survived to admission at 649 hospitals between 2013 and 2016. Using segmented hierarchical logistic regression, we determined risk-adjusted trends in the use of therapeutic hypothermia overall and stratified by presenting rhythm of ventricular tachycardia or ventricular fibrillation (VT/VF) vs pulseless electrical activity or asystole (PEA/asystole). We used mediation analysis to assess the impact of temporal trends in the use of therapeutic hypothermia on risk-adjusted survival trends at a patient- and hospital-level.Results: Overall use of therapeutic hypothermia was 46.4%. In unadjusted analyses, the use of therapeutic hypothermia dropped from 52.5% in the last quarter of 2013 to 46.0% in the first quarter of 2014 after publication of a trial that supported more lenient temperature management. Use of therapeutic hypothermia remained at or below 46.5% through 2016. After risk-adjustment, these trends in use persisted (see Figure). Compared with the last quarter of 2013, the risk-adjusted odds of therapeutic hypothermia was 18% lower in the first quarter of 2014 (OR 0.82, 95% CI 0.71, 0.94, P=0.006). Similar findings were observed in analyses stratified by presenting rhythm (see Figure). Overall risk-adjusted patient survival was 36.9% in 2013, 37.5% in 2014, 34.8% in 2015, and 34.3% in 2016 (P for trend<0.001). Trends in hypothermia use did not explain trends in survival.Conclusions: In a U.S. registry of out-of-hospital cardiac arrest, the use of therapeutic hypothermia decreased after publication of a study supporting more lenient temperature thresholds. Concurrent to this change, overall risk-adjusted survival of cardiac arrest decreased, but was not attributed to lower use of therapeutic hypothermia.