Effect of first-responder automated defibrillation on time to therapeutic interventions during out-of-hospital cardiac arrest

Study objectives: The effect of automated defibrillation provided by basic emergency medical technician (EMT) first-responder units on the time intervals to other critical interventions in the management of out-of-hospital cardiac arrests is unknown. The purpose of this study was to define and compare elapsed time intervals to basic CPR, paramedic arrival, initial countershock, endotracheal intubation, IV access, and initial adrenergic drug therapy in first-responder automated defibrillation/paramedic versus basic EMT/paramedic emergency medical services systems. Design: Prospectively collected data from a 15-month multicenter study of out-of-hospital, nontraumatic cardiac arrests were analzyed. The mean time intervals to critical therapeutic interventions between first-responder automated defibrillation/paramedic and basic EMT/paramedic groups were compared using the Student's t-test with Bonferroni correction. Setting: Three first-responder automated defibrillation/paramedic and three basic EMT/paramedic urban emergency medical services systems. Participants: 1,578 patients with out-of-hospital cardiac arrest. Interventions: The first-responder automated defibrillation/paramedic group received initial ECG analysis and/or automated countershock by first-responder/EMTs; the basic EMT/paramedic group received initial ECG analysis and/or manual countershock by paramedics. Results: Elapsed time intervals in minutes ± SD for first-responder automated defibrillation/paramedic versus basic EMT/paramedic groups, respectively, were as follows: Collapse to CPR, 4.3 ± 3.9 versus 5.4 ± 5.2 (P = .017); collapse to countershock, 10.7 ± 5.9 versus 13.0 ± 6.0 (P = .017); collapse to paramedic arrival, 13.0 ± 5.4 versus 10.3 ± 6.1 (P = .0001); paramedic arrival to IV access, 5.1 ± 3.9 versus 7.0 ± 5.0 (P = .0001); paramedic arrival to endotracheal intubation, 4.8 ± 4.0 versus 6.8 ± 5.8 (P = .0001); paramedic arrival to initial adrenergic drug therapy, 7.4 ± 4.5 versus 8.2 ± 4.7 (P = .015); collapse to IV access, 17.7 ± 6.1 versus 16.6 ± 7.4 (P = .10); collapse to endotracheal intubation, 17.3 ± 6.4 versus 16.6 ± 7.8 (P = .32); collapse to initial adrenergic drug therapy, 20.4 ± 6.7 versus 18.1 ± 7.2 (P = .010). The time intervals from paramedic arrival to IV access, endotracheal intubation, and initial adrenergic drug therapy remained shorter in the first-responder automated defibrillation/paramedic systems despite stratification by presenting cardiac rhythm. Conclusion: First-responder automated defibrillation/paramedic systems provide not only shorter times to initial countershock, as compared with basic EMT/paramedic systems, but by having delegated initial countershock to first-responders, they also allow for significantly shorter times from paramedic arrival to IV access, endotracheal intubation, and initial adrenergic drug therapy interventions.