Association of the Emergency Medical Services–Related Time Interval with Survival Outcomes of Out-of-Hospital Cardiac Arrest Cases in Four Asian Metropolitan Cities Using the Scoop-and-Run Emergency Medical Services Model

Abstract Background Response time interval (RTI) and scene time interval (STI) are key time variables in the out-of-hospital cardiac arrest (OHCA) cases treated and transported via emergency medical services (EMS). Objective We evaluated distribution and interactive association of RTI and STI with survival outcomes of OHCA in four Asian metropolitan cities. Methods An OHCA cohort from Pan-Asian Resuscitation Outcome Study (PAROS) conducted between January 2009 and December 2011 was analyzed. Adult EMS-treated cardiac arrests with presumed cardiac origin were included. A multivariable logistic regression model with an interaction term was used to evaluate the effect of STI according to different RTI categories on survival outcomes. Risk-adjusted predicted rates of survival outcomes were calculated and compared with observed rate. Results A total of 16,974 OHCA cases were analyzed after serial exclusion. Median RTI was 6.0 min (interquartile range [IQR] 5.0–8.0 min) and median STI was 12.0 min (IQR 8.0-16.1). The prolonged STI in the longest RTI group was associated with a lower rate of survival to discharge or of survival 30 days after arrest (adjusted odds ratio [aOR] 0.59; 95% confidence interval [CI] 0.42–0.81), as well as a poorer neurologic outcome (aOR 0.63; 95% CI 0.41–0.97) without an increasing chance of prehospital return of spontaneous circulation (aOR 1.12; 95% CI 0.88–1.45). Conclusions Prolonged STI in OHCA with a delayed response time had a negative association with survival outcomes in four Asian metropolitan cities using the scoop-and-run EMS model. Establishing an optimal STI based on the response time could be considered.