Timing of inducing therapeutic hypothermia in patients successfully resuscitated after out-of-hospital cardiac arrest

Background: Therapeutic hypothermia can improve neurological status in cardiac arrest survivors. Objectives: We investigated the association between the timing of inducing therapeutic hypothermia and neurological outcomes in patients who experienced out-of-hospital cardiac arrest. Methods: We evaluated data from 116 patients who were comatose after return of spontaneous circulation and those who received therapeutic hypothermia between January 2013 and April 2017. The primary endpoint was good neurological outcomes during index hospitalization, defined as a cerebral performance category score of 1 or 2. Therapeutic hypothermia timing was defined as the duration from the return of spontaneous circulation to hypothermia initiation. We analyzed the effect of early hypothermia induction on neurological results. Results: In total, 112 patients were enrolled. The median duration to hypothermia initiation was 284 min (25th–75th percentile, 171–418 min). Eighty-two (69.5%) patients underwent hypothermia within 6 h, and 30 (25.4%) had good neurological outcomes. The rates of good neurological outcomes by hypothermia initiation time quartile (shortest to longest) were 28.3%, 34.5%, 14.8%, and 28.6% (p = 0.401). The good neurologic outcomes did not differ between hypothermia patients within 6 h or after (26.5% vs 26.7%, p = 0.986). Short low-flow time and bystander resuscitation were associated with good neurological outcomes (p = 0.044, confidence interval: 0.027–0.955), but the timing of hypothermia initiation was not (p = 0.602, confidence interval: 0.622–1.317). Conclusion: A shorter low-flow time was associated with good neurological outcomes in out-of-hospital cardiac arrest patients who experienced hypothermia. However, inducing hypothermia sooner, even within 6 h, did not improve the neurological outcomes. Thus, as current guidelines recommend, initiating hypothermia within 6 h of recovery of spontaneous circulation is reasonable.