'Therapeutic Hypothermia' Can Protect the Brain in the Aftermath of Cardiac Arrest
For decades, conventional wisdom in treating patients with cardiac arrest was that if the heart stopped beating for longer than six to 10 minutes, the brain would be dead. Now a new treatment being embraced by a growing number of U.S. hospitals suggests that patients can be brought back to a healthy life even if their heart is stopped for 20 minutes, perhaps longer.
The difference is profound. In recent months around the U.S., doctors and nurses say, cardiac-arrest patients who would previously have been given up for dead have been revived and discharged to return to their families and jobs with all or nearly all of their cognitive abilities intact.
The treatment is called therapeutic hypothermia and at its core is the simplest of technologies: ice. Once a patient's heartbeat is restored, emergency-room doctors, cardiologists and rescue squads are quickly applying ice and other coolants to moderately lower a patient's body temperature by about six degrees. Then the patient is put in a drug-induced coma in intensive care for 24 hours before gradually being warmed back up to normal temperature.
"We've had patients who have been stone-cold out for least 20 minutes—we know that for sure—and they've come back normal or nearly normal," says Michael Mooney, a cardiologist who heads the therapeutic hypothermia program at Minneapolis Heart Institute. An early adopter of the cooling technique, the cardiology practice has treated more than 140 patients since 2006 and says 52% have survived, compared with single digits historically; of those, about 75% have had a "favorable neurologic recovery," including many who report a full return to normal.
Experience with the treatment is injecting optimism in a field long plagued by frustration. Despite faster emergency squads, deployment of automated defibrillators at airports and other public places, and improvements in cardiopulmonary resuscitation techniques, fewer than 10% of the 300,000 Americans who suffer cardiac arrest each year survive long enough to leave the hospital—a rate that hasn't budged much over the years.
The rationale behind the new treatment is that the brain is more resilient than previously believed during the early period after the heart goes down. Of course, the brain can't live long without the oxygen provided by normal blood flow. But an initial rush of blood to the brain, when resuscitation gets the heart beating again, also kills tissue and is "a more important insult," Dr. Mooney says.
At normal temperatures, the restoration of blood flow triggers a cascade of inflammatory and other responses over the following minutes and hours, which can injure tissue in the brain and exact a lethal toll. Scientists say icing the body slows metabolism and protects the brain from at least some of the damage caused by the restored blood flow.
The benefits of cooling in cardiac arrest were demonstrated in two landmark studies, one done in Australia, the other in Europe, and both published in 2002 the New England Journal of Medicine. The findings prompted the American Heart Association to include therapeutic hypothermia in 2005 guidelines for treating cardiac-arrest patients outside of a hospital.
The case of Christine Flicek-Reak illustrates the phenomenon. Her twin daughters found their 43-year-old mother unconscious shortly after she collapsed in her home in Montgomery, Minn., on July 21, 2008. They called 911, summoning an ambulance crew that got her heartbeat restored about 20 minutes after she went down, doctors estimate.
She was taken to 28-bed Queen of Peace Hospital in nearby New Prague, where an emergency team packed her body in blue ice bags before loading her on a helicopter to Abbott Northwestern Hospital in Minneapolis about 40 miles away. There she was wrapped in a cooling blanket that kept her body temperature at about 92 degrees Fahrenheit before it was restored to normal the following day. Five days later, Ms. Flicek-Reak regained consciousness and went home five days after that. She was back at work at the bowling center she owns within a month.
source: online.wsj
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