Background: Out-of-hospital cardiac arrest (OHCA) is a critical issue due to poor neurological outcomes and high mortality rate. Severe ischemia and reperfusion injury often occur after cardiopulmonary resuscitation (CPR) and return of spontaneous circulation (ROSC). Targeted temperature management (TTM) has been shown to reduce neurological complications among OHCA survivors. However, it is unclear how "time-to-cool" influences clinical outcomes. In this study, we investigated the optimal timing to reach target temperature after cardiac arrest and ROSC.

Methods: A total of 568 adults with OHCA and ROSC were admitted for targeted hypothermia assessment. Several events were predicted, including pneumonia, septic shock, gastrointestinal (GI) bleeding, and death.

Results: One hundred and eighteen patients [70 men (59.32%); 48 women (40.68%)] were analyzed for clinical outcomes. The duration of CPR after ROSC was significantly associated with pneumonia, septic shock, GI bleeding, and mortality after TTM (all p < 0.001). The duration of CPR was also positively correlated with poor outcomes on the Elixhauser score (p = 0.001), APACHE II score (p = 0.008), Cerebral Performance Categories (CPC) scale (p < 0.001), and Glasgow Coma Scale (GCS) score (p < 0.001). There was a significant association between the duration of CPR and time-to-cool of TTM after ROSC (Pearson value = 0.447, p = 0.001). Pneumonia, septic shock, GI bleeding, and death were significantly higher in the patients who underwent TTM with a time-to-cool exceeding 360 minutes (all p < 0.001).

Conclusions: For cardiac arrest patients, early cooling has clear benefits in reducing clinical sequelae. Clinical outcomes could be improved by improving the time to reach target temperature and feasibility for critically ill patients.