Abstract 344: The Association Between ALS Response Interval and Out-of Hospital Cardiac Arrest Outcomes
Objective: There is conflicting data in studies investigating the effectiveness of advanced life support (ALS) for out-of-hospital cardiac arrest (OHCA). Within a tiered BLS-ALS system, we sought to determine if the ALS response interval was associated with patient outcomes. Methods: This secondary analysis examined prospectively identified consecutive non-traumatic adult OHCAs from 2006-2016 in British Columbia. We excluded EMS-witnessed arrests and those not treated by ALS. The primary and secondary outcomes were survival and favorable neurological outcomes (mRS ≤3) at hospital discharge. Using logistic regression we estimated the association of ALS response interval (9-1-1 call to ALS arrival) and outcomes, adjusting for treatment year, response interval of the first EMS unit, and other baseline characteristics. We drew spline curves to illustrate this relationship. Results: Of 12,722 included cases, survival was 12%. The median response interval for the first EMS unit was 6.4 minutes (IQR 5.2 - 8.3) and for ALS was 11.8 minutes (IQR 8.7 - 16.5).The adjusted odds of survival and favourable neurological outcome for each additional minute in ALS response interval were 0.98 (95 % CI 0.96-0.99) and 0.98, (95% CI 0.97-0.99) respectively. The spline curve demonstrated an initial decline in survival probability that moderated at approximately 11 minutes. Conclusion: Among ALS-treated subjects within our tiered EMS system, earlier ALS arrival was associated with improved survival and favorable neurological outcomes. The greatest yield of ALS care may be prior to 11 minutes. This may help inform the optimal deployment configuration of prehospital providers.