Influence of cardiopulmonary resuscitation prior to defibrillation in patients with out-of-hospital ventricular fibrillation.
BACKGROUND
Use of automated external defibrillators (AEDs) by first arriving emergency medical technicians (EMTs) is advocated to improve the outcome for out-of-hospital ventricular fibrillation (VF). However, adding AEDs to the emergency medical system in Seattle, Wash, did not improve survival. Studies in animals have shown improved outcomes when cardiopulmonary resuscitation (CPR) was administered prior to an initial shock for VF of several minutes' duration.


OBJECTIVE
To evaluate the effects of providing 90 seconds of CPR to persons with out-of-hospital VF prior to delivery of a shock by first-arriving EMTs.


METHODS
Observational, prospectively defined, population-based study with 42 months of preintervention analysis (July 1, 1990-December 31, 1993) and 36 months of post-intervention analysis (January 1, 1994-December 31, 1996).


METHODS
Seattle fire department-based, 2-tiered emergency medical system.


METHODS
A total of 639 patients treated for out-of-hospital VF before the intervention and 478 after the intervention.


METHODS
Modification of the protocol for use of AEDs, emphasizing approximately 90 seconds of CPR prior to delivery of a shock.


METHODS
Survival and neurologic status at hospital discharge determined by retrospective chart review as a function of early (<4 minutes) and later (> or =4 minutes) response intervals.


RESULTS
Survival improved from 24% (155/639) to 30% (142/478) (P=.04). That benefit was predominantly in patients for whom the initial response interval was 4 minutes or longer (survival, 17% [56/321] before vs 27% [60/220] after; P = .01). In a multivariate logistic model, adjusting for differences in patient and resuscitation factors between the periods, the protocol intervention was estimated to improve survival significantly (odds ratio, 1.42; 95% confidence interval, 1.07-1.90; P = .02). Overall, the proportion of victims who survived with favorable neurologic recovery increased from 17% (106/634) to 23% (109/474) (P = .01). Among survivors, the proportion having favorable neurologic function at hospital discharge increased from 71% (106/150) to 79% (109/138) (P<.11).


CONCLUSIONS
The routine provision of approximately 90 seconds of CPR prior to use of AED was associated with increased survival when response intervals were 4 minutes or longer.
Cobb
L A
LA
Department of Medicine, University of Washington, Harborview Medical Center, Seattle 98104, USA. lcobb@u.washington.edu
Fahrenbruch
C E
CE
Walsh
T R
TR
Copass
M K
MK
Olsufka
M
M
Breskin
M
M
Hallstrom
A P
AP
D000368:Aged; D016887:Cardiopulmonary Resuscitation; D004554:Electric Countershock; D004632:Emergency Medical Services; D004634:Emergency Medical Technicians; D005069:Evaluation Studies as Topic; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018709:Statistics, Nonparametric; D016019:Survival Analysis; D016896:Treatment Outcome; D014693:Ventricular Fibrillation / Q000401:mortality / Q000628:therapy*