New Method Boosts Cardiac Arrest Survival
TUESDAY March 11, 2008 -- Cardiac arrest outside of the hospital can quickly turn deadly, but a new method of restarting stalled hearts might boost people's chances of survival, researchers say.
The overall survival rate for people given the technique -- called minimally interrupted cardiac resuscitation (MIRC) -- was 9.1 percent, compared to 3.8 percent of those who got standard emergency measures, according to the report in the March 12 issue of the Journal of the American Medical Association.
And in a subgroup of people who experienced both cardiac arrest and the chaotic heartbeat called ventricular fibrillation, survival rose from about 12 percent before MIRC to 28.4 percent after, the researchers said
Current guidelines call for people who have cardiac arrest to receive an electric shock and periodic chest compressions to get their heart beating again. MIRC's innovation is that it emphasizes near-constant chest compression.
"The technique minimizes all interruption of chest compression, and maximizes the time when chest compressions are being given," said study author Dr. Bentley J. Bobrow, an assistant professor of emergency medicine at the Mayo Clinic in Scottsdale, Ariz. "Patients get pre-shock and post-shock chest depression, and also [the drug] epinephrine," he said.
The blood flow produced by standard chest compression is simply not enough to provide sufficient blood to the heart and the brain, Bobrow explained. In fact, national guidelines issued last year emphasized chest compression over rescue breathing, recommending two breaths for every 30 chest compressions, effectively doubling the number of recommended compressions.
The new study, done in two Arizona cities, included 2,460 people who experienced cardiac arrest outside of the hospital -- 1,799 of whom got treatment before emergency personnel were trained in MIRC.
Only 69 of those pre-MIRC patients survived, the researchers noted. In contrast, 60 of the 661 people given MIRC for cardiac arrest survived.
"One of the really novel things was that this didn't cost anything," Bobrow said. "Usually with a new treatment, cost is an issue. Here, we were really prioritizing how emergency medicine people push on the chest. There is very little cost outside of training."
But the effort needed to train people in the new technique should not be underestimated, said Dr. Mary Ann Peberdy, an associate professor of internal medicine and emergency medicine at Virginia Commonwealth University, in Richmond.
"What the group in Arizona was able to do in orchestrating these complex changes, which are significantly different from the rules drilled into people, was impressive," said Peberdy, who co-authored a related editorial in the journal.
The new study is only the second large trial of MIRC to be reported in the medical literature, she said. Another trial, also conducted in Arizona, found similar results two years ago, Peberdy said.
This latest study "is just a first step," Bobrow stressed. "We are constantly reassessing how we are doing with this protocol. We have to keep on modifying our techniques."
The study shows that "changes in the complicated EMS system are possible," Peberdy added. "People are going to have to look at the science themselves, and decide whether to change the protocol for patients who suffer cardiac arrest inside the hospital as well as outside the hospital."
Virginia Commonwealth has been using a version of MIRC for several years, she said, emphasizing "less interruptions of chest compression and better chest compression. It has improved our neurologically sound clinical survival," meaning that more people live with less brain damage.
Posted: March 2008
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