The association between long duration of resuscitation efforts in out-of-hospital cardiac arrest (OHCA) and neurologic outcome is unclear and understudied with advancements in post-cardiac arrest care and high-quality cardiopulmonary resuscitation. We investigated how downtime, defined as the interval from collapse-to-return of spontaneous circulation (ROSC), impacts on neurologic outcome in OHCA patients treated with targeted temperature management (TTM).

A multicenter, registry-based, retrospective cohort study was conducted using cases from 24 hospitals across South Korea. Of the 930 adults (≥18 years) non-traumatic OHCA patients treated with TTM between January 2007 and December 2012 at these hospitals, we included 858 patients who had sufficient data for calculating downtime. Good neurologic outcome was defined as a cerebral performance category score of 1 or 2.

Median downtime was 30.0 (22.0–41.0 min) and 242 patients (28.2%) had good neurologic outcome. When downtime was divided by 10-min intervals (≤10 min, 11–20 min, 21–30 min, 31–40 min, 41–50 min, 51–60 min, and >60 min), their neurologically intact survival rate were 48.2%, 51.6%, 29.2%, 22.1%, 16.1%, 14.8%, and 7.1%, respectively (p = 0.01). Although downtime was associated with poor neurologic outcome [odds ratio 1.06 (1.05–1.08), p < 0.01], the area under the receiver operating characteristic curve of downtime for outcome was only 0.67, 95% CI (0.63–0.71). Furthermore, even with downtime >20 min, 22.2% (150/526) patients still had a good neurologic outcome, and this percentage increased to 50.3% (93/185) in patients with an initial shockable rhythm, and 31.1% (134/431) with age <65 years.

We found that neurologically intact survival can occur at prolonged downtimes and were unable to identify a downtime for which survivability was clearly futile. These data suggest that downtime should not be considered as a factor in determining whether to provide aggressive post-arrest care, especially in patients with young patients or those with an initially shockable rhythm.