Abstract 7: Advanced Cardiac Life Support in Out-of-Hospital Cardiac Arrest - A Propensity Score Matching Analysis
Introduction: Emergency-medical-services (EMS) have invested substantial resources to establish advanced life support (ALS) programs. Prehospital research has found little evidence in support of ALS for OHCA. However, those were unmatched patients because of non-experimental design, and the frequency of negative outcome in OHCA suggests that it is difficult to establish sufficient numbers to detect an effect.
Objective: We aimed to assess whether ALS care has better survival for OHCA than basic life support with rapid defibrillation (BLS-D).
Method: We did a 4-year prospective observational study on a city using a two-tiered model and enrolled 6,783 OHCA patients. Of those patients, 2,995 received ALS care and 3,788 received BLS-D. ALS protocol includes intubation and cardioactive drug administration. A matching process based on propensity-score was done to equalize potential prognostic factors in both groups, and to formulate a balanced 1:1 matched cohort study. Potential prognostic factors included age, sex, arrest witnessed, bystander CPR, initial cardiac rhythms, EMS time intervals, receiving hospitals, and chronological orders. The primary endpoint was survival to hospital discharge.
Results: EMS response time from call receipt to ambulance arrival is 6.5(SD: 3.8) minutes. Unmatched patients who received ALS care had a higher chance for prehospital ROSC (OR 3.6, 95% CI 2.6–5.1, p<0.0001), and for survival to hospital discharge (OR 1.4, 95% CI 1.0–1.9, p=0.04). Between the propensity-score matched groups (each group 1,270 patients), there was significant difference in prehospital ROSC (OR 3.4, 95% CI 2.3–5.1, p<0.0001), but no significant difference in survival to hospital discharge.
Conclusions: ALS interventions provide benefit of prehospital ROSC, but may not improve the rate of survival compared with BLS-D in a rapid response EMS system. A matching process should be done to compare the survival for OHCA study of non-experimental design.
- © 2010 by American Heart Association, Inc.