WEDNESDAY, Aug. 31 (HealthDay News) -- More is not necessarily
better when paramedics give cardiac arrest patients CPR before
administering shocks to the heart, a new study finds.
On the contrary, providing CPR (cardiopulmonary resuscitation)
for a longer period of time could actually harm certain
"We found that extra CPR didn't help and, in fact, in some patients it was not a good thing. It would make it worse," said Dr. Ian Stiell, lead author of a paper published in the Sept. 1 issue of the New England Journal of Medicine. "Our study showed that there's no reason to do two minutes of CPR or to delay defibrillation."
But the study didn't address CPR delivered by a bystander so the
message to the public is still the same.
"We absolutely believe that bystanders should start CPR right away," said Stiell, chair of emergency medicine at the University of Ottawa, Canada, and a senior scientist with the Ottawa Hospital Research Institute. "This trial doesn't address that."
Fewer than 10 percent of the 350,000 people each year in the
United States and Canada who have a cardiac arrest out of the
hospital survive the event.
Early CPR -- a combination of manual chest compressions and
rescue breathing -- increases blood flow and is thought to put the
heart in better shape to receive and respond to defibrillation,
which restores a normal heart rhythm.
But how much CPR is optimal remains unclear. "We all knew that
the earlier to defibrillation the better . . . but no one really
knew how long that period of time was," said Dr. Joseph Feldman,
chairman of emergency services at Hackensack University Medical
Center in New Jersey.
In guidelines released in 2010, the American Heart Association
(AHA) cited "inconsistent evidence" either for or against extended
CPR and any delay in heart rhythm analysis.
In the largest study on cardiac arrest ever performed, involving
nearly 10,000 patients, Stiell and his team divided emergency
responders into two groups: those who would provide 30 to 60
seconds of initial CPR and those providing three minutes of
About 6 percent of patients in both groups lived to be
discharged from the hospital.
But in the 10 percent of patients who had also received
bystander CPR and were candidates for defibrillation, longer CPR
from paramedics actually decreased the odds of survival.
"Before, the theory was to do a bunch of CPR to make the heart stronger and more responsive to the shock, but we didn't show that," said Stiell. "We showed that too much is not a good thing."
At this point, Stiell recommends that paramedics and
firefighters deliver just one minute of CPR.
In a second CPR study published in the same journal issue,
researchers report disappointing results for the "impedance
threshold device" (ITD), which was designed to increase the
beneficial effects of CPR.
The device increases blood flow to the heart while someone is
Nearly 9,000 patients in the United States and Canada were split
into two groups, one of which received ITD treatment and another
that got sham ITD treatment. The researchers, noting that about the
same number in each group survived to hospital discharge, said the
ITD did not significantly improve results.
American Heart Association for help finding a CPR class.