Chill Therapy Is Endorsed for Some Heart Attacks
Hoping to save thousands of heart-attack victims a year, the American Heart Association has endorsed the cooling of comatose patients whose hearts have been restarted so that they can be brought back to life slowly, suffering less brain damage.
Studies in Europe and Australia have shown that comatose patients whose bodies were cooled to 89.6 to 93.2 degrees Fahrenheit and maintained at that temperature for up to 24 hours suffered significantly fewer deaths and less brain damage than patients who were quickly resuscitated, the association said.
Some major teaching hospitals already put comatose cardiac arrest victims on ice, but many smaller ones do not. The association now recommends that all hospitals use the procedure, a spokeswoman, Julie Del Barto, said.
The guideline was based on the findings of an international expert panel, the International Liaison Committee on Resuscitation.
About 680 Americans a day who have heart attacks go into sudden cardiac arrest, in which the heart stops beating and begins to fibrillate — quivering, in a common description, ”like a bag of worms.”
Unless its rhythm is rapidly restored by a defibrillator, the patient’s oxygen-starved brain will begin to die, the fate suffered by about 95 percent of those who suffer total cardiac arrest outside hospitals.
A major public health campaign is under way to save some of those lives by mounting portable defibrillators in airliners, office buildings and other public places.
After a few minutes without circulation, victims slip into comas. Then, even if the heart is restarted, they usually die anyway, or live with severe brain damage.
Doctors believe much of the damage to resuscitated patients is done when oxygenated blood rushes back into the brain, prompting inflammation.
An explosion of free radicals from the wastes built up during oxygen deprivation kills many cells. Cold slows that process. Inflammation is also part of the immune response, and a higher rate of infections is a troublesome side effect.
Many questions remain, including how to chill patients very rapidly but safely, whether to start in the ambulance and how long patients should stay in the hibernationlike state of ”therapeutic hypothermia.”
Cooling must be done carefully, said Mary Fran Hazinski, a resuscitation instructor at Vanderbilt University Medical Center, and may, for example, include injecting muscle relaxants to prevent shivering.
Shivering, a natural reaction to cold, ”is the body trying to increase oxygen consumption, which contradicts what you’re trying to do,” Ms. Hazinski noted.
New cooling techniques now in experimental stages include cooling helmets; injecting cold saline solution into patients’ veins; threading loops of tubing carrying supercold liquids down arteries; pouring ice slurry into stomachs; or even pumping oxygen-carrying perfluorocarbon slurry into the lungs.
In 2000, a small Danish study that cooled stroke victims for six hours with a stream of cold air found that only half as many of the cooled patients died as the uncooled ones.
It took the association’s expert panel years to come to a firm conclusion because it is difficult to run clinical studies of cardiac arrest victims.
More than 90 percent of candidates were dropped from the two studies analyzed, which followed patients in nine hospitals in Europe and four in Melbourne, Australia.
Hypothermia is not used on alert patients because they are not showing brain damage. Doctors often do not try to restart the hearts of people who have clearly been brain-dead for so long that they will be left in a vegetative state.
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