Quicker
transition from cardiopulmonary resuscitation to automated external
defibrillation may improve survival after cardiac arrest
A quicker "hands-off" transition from chest compressions
to automated external defibrillation may result in improved survival
after cardiac arrest, according to a report in the April 23rd rapid
access issue of Circulation. The hands-off interval is the time necessary
for an automated external defibrillator to analyze a cardiac arrest
victim's electrocardiogram, charge, and deliver a shock--- so called
because cardiopulmonary resuscitation chest compressions must stop
during this period and hands are off the patient.
Researchers found indications
that the shorter the interval between discontinuation of chest compressions
and delivery of electrical shock, the better the chance of surviving
ventricular fibrillation.
According to the American Heart
Association, about 250,000 Americans annually die of coronary heart
disease without being hospitalized. That accounts for roughly half
of all deaths from coronary heart disease -- more than 680 Americans
each day. Most of these are sudden deaths caused by cardiac arrest.
"Our study suggests that
not only do you need to act quickly to get an automated external
defibrillator on the scene of a cardiac arrest, but you also should
move as quickly as possible from cardiopulmonary resuscitation to
defibrillation," says study author Dr. Trygve Eftestol of Norway.
To determine the link between
the hands-off interval and survival, researchers studied 634 hands-off
intervals in 156 patients with ventricular fibrillation in which
external defibrillators were used. The durations of hands-off intervals
varied by a median of 20 seconds.
Researchers grouped cardiac
arrest victims according to their initial probability (high, medium
or low) of return of spontaneous circulation, which was estimated
from the starting point of electrocardiographic readings of their
hands-off intervals.
The probability of successful
defibrillation with return to spontaneous circulation was also estimated
at 5, 10, 15, and 20 seconds into each of the hands-off intervals.
Researchers compared the calculated
probabilities with the actual rates of return of spontaneous circulation
for the medium-level and high-level groups. From this comparison
they found that the shorter the hands-off interval, the greater
the chance of regaining spontaneous circulation.
People with the highest initial
likelihood of circulation return would have received the most benefit
from a shorter hands-off interval -- if they had received a shock
immediately, they might have had a rate of return of spontaneous
circulation as high as 50 percent, says Eftestol. Within 5 seconds,
their estimated ROSC rate dropped to 25 percent; after 15 seconds
to15 percent; and after 20 seconds, 8 percent.
For those with a medium initial
probability of return of spontaneous circulation, shock delivery
after a 5-second hands-off period resulted in return of circulation
in 24 percent; after 15 seconds, 17 percent; and at 20 seconds,
11 percent. The group with the lowest probability of return of spontaneous
circulation had only about a 5 percent estimated chance of return
of spontaneous circulation throughout the intervals.
"This study is extremely
important for several reasons," says Mary-Fran Hazinski, R.N.,
M.S.N., former chair of the American Heart Association's emergency
cardiovascular care committee. "First, it reaffirms the importance
of cardiopulmonary resuscitation training and the important role
of cardiopulmonary resuscitation with the use of automated external
defibrillators. Second, it provides very solid data that supports
the need to shorten the time required for defibrillator rhythm analysis
and charging."
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