Objective: To determine whether the interval between the arrival of basic life support (BLS) providers and the arrival of advanced life support (ALS) providers is associated with patient outcome after cardiac arrest.
Methods: We conducted a retrospective cohort study of all witnessed, out-of-hospital ventricular fibrillation (VF) cardiac arrests between January 1, 1991, and December 31, 2007. Eligible patients (n = 1,781) received full resuscitation efforts from both BLS and ALS providers.
Results: The BLS-to-ALS arrival interval was a significant predictor of survival to hospital discharge (odds ratio [OR] 0.96, 95% confidence interval [CI] 0.93-0.99); the likelihood of survival decreased by 4% for every minute that ALS arrival was delayed following BLS arrival. Other significant predictors of survival were whether the arrest occurred in public (OR 1.48, 95% CI 1.19-1.85), whether a bystander administered cardiopulmonary resuscitation (CPR) (OR 1.34, 95% CI 1.07-1.68), and the interval between the 9-1-1 call and BLS arrival (OR 0.78, 95% CI 0.73-0.83).
Conclusions: We found that a shorter BLS-to-ALS arrival interval increased the likelihood of survival to hospital discharge after a witnessed, out-of-hospital VF cardiac arrest. We conclude that ALS interventions may provide additional benefits over BLS interventions alone when utilized in a well-established, two-tiered emergency medical services (EMS) system already optimized for rapid defibrillation. The highest priorities in any EMS system should still be early CPR and early defibrillation, but timely ALS services can supplement these crucial interventions.