Time to first shock by emergency medical technicians with automated external defibrillators.
The interval from collapse to electrical rescue shock is a critical determinant of successful defibrillation in cardiac arrest. In order to achieve the earliest possible defibrillation, many emergency medical services (EMS) systems equip first-responding units with an automated external defibrillator (AED).


OBJECTIVE
To measure the time from on-scene emergency medical technician (EMT) recognition of cardiac arrest to AED application and shock in ventricular fibrillation (VF) arrest. In addition, the authors sought to understand the reasons for delays.


METHODS
Using the AED recordings and written EMS reports, the authors conducted a retrospective cohort study of all persons who experienced an EMS-attended VF cardiac arrest in which an AED was applied and a shock delivered by an EMT, from January 1999 through December 2000 (n = 177). Based on the bimodal distribution of times, two groups were assembled: no delay (time to shock < or = 90 seconds) and delayed (time to shock > 90 seconds). Patient and event characteristics associated with delay status were determined using Mantel-Haenszel methods.


RESULTS
The median (25th, 75th percentile) time from cardiac arrest recognition to shock was 51 (43, 64) seconds. Ninety-four percent (n = 166) of the cohort received a shock within 90 seconds. Delayed shock was associated with unwitnessed arrest status (odds ratio = 9.3, 95% confidence interval = 2.3, 36.8) and nursing home location (odds ratio = 10.0, 95% confidence interval = 2.1, 47.5).


CONCLUSIONS
The findings suggest that a 1-minute goal and a 90-second minimum standard for time to first shock are appropriate for EMT AED defibrillation in the field.
Brillhart
Aaron M
AM
University of Washington School of Medicine, Seattle, USA.
Rea
Thomas D
TD
Becker
Linda
L
Eisenberg
Mickey S
MS
Murray
John A
JA
D000368:Aged; D000369:Aged, 80 and over; D016887:Cardiopulmonary Resuscitation; D015331:Cohort Studies; D004554:Electric Countershock / Q000592:standards / Q000706:statistics & numerical data*; D004632:Emergency Medical Services / Q000592:standards*; D004634:Emergency Medical Technicians / Q000592:standards* / Q000706:statistics & numerical data; D005260:Female; D006323:Heart Arrest / Q000628:therapy*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D013996:Time and Motion Studies; D014481:United States; D014693:Ventricular Fibrillation / Q000628:therapy