Longer CPR may do more harm than good: Study

By Dr. Ananya Mandal, MDAug 31 2011

A new study reveals that providing CPR (cardiopulmonary resuscitation) for a longer period of time could actually harm certain patients.

“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,” he stressed.

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.

“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 CPR. 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.

The scientists in the study, which also involved the University of Ottawa and the Resuscitation Outcomes Consortium (ROC), said the new research settles the question once and for all. “I think it is better to be on the safe side and stick with the traditional shorter initial CPR approach,” Stiell said.

Cardiologist Dr. Peter Guerra, a heart rhythm specialist at the Montreal Heart Institute, said Wednesday the study is important because it challenges the way cardiac arrest is treated. “I think one of the important points is that with out-of-hospital cardiac arrest, survival is abysmally low,” said Guerra, who was not involved in the study. “So whatever we can do to improve that is important.”

Manuel Arango, director of Health Policy for the Heart and Stroke Foundation of Canada, said studies by the Resuscitation Outcomes Consortium are essential for refining the science of resuscitation and will help save more lives. “This knowledge furthers our understanding of optimal resuscitation techniques and will help inform the next Heart and Stroke Foundation Emergency Cardiac Care guidelines,” he said.