Early advanced life support attendance is associated with improved survival and neurologic outcomes after non-traumatic out-of-hospital cardiac arrest in a tiered prehospital response system

Objective: Data demonstrating benefit of advanced life support (ALS) practitioners for out-of-hospital cardiac arrest (OHCA) is conflicting. In our tiered emergency medical services (EMS) system, we sought to determine if the ALS response interval was associated with patient outcomes. Methods: We performed a secondary analysis of consecutive adult OHCAs (2006-2016) in British Columbia. Primary and secondary outcomes were survival and favorable neurological outcomes (mRS < 3) at hospital discharge. Logistic regression estimated the association of ALS response interval (911 call-to-ALS arrival, continuous and categorical analyses) and outcomes, adjusting for first EMS response interval, and other clinical characteristics. We calculated the optimal time threshold to differentiate early vs late ALS response intervals for a binary comparison. Results: Of 12,722 included cases, 12% survived to discharge. Median response interval was 6.4 min (IQR 5.2-8.3) for the first EMS unit and 11.8 min (IQR 8.7-16.5) for ALS. ALS response interval (per minute) was associated with decreased survival (adjusted OR 0.98, 95% CI 0.96-0.99) and favourable neurological outcome (0.98, 95% CI 0.97-0.99). ALS response < 10 min (the optimal threshold) was associated with improved survival (adjusted OR 1.46; 95% CI 1.27-1.68) and favourable neurological outcomes (adjusted OR 1.41; 95% CI 1.18-1.68). Conclusion: In our tiered EMS system, earlier ALS arrival was associated with improved survival and favorable neurological outcomes. ALS attendance within 10 min of the 9-1-1 call in tiered systems of prehospital care may improve patient outcomes and serve as a quality metric.