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News

Rapid cooling is endorsed for heart attack patients

University Of Chicago : 08 July, 2001  (Technical Article)
Hoping to save thousands of heart-attack victims a year, the American Heart Association has endorsed the technique of rapidly cooling 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 comatose patients whose bodies were cooled to between 89.6 and 93.2 degrees and maintained at that temperature for up to 24 hours suffered significantly fewer deaths and less brain damage than patients who were resuscitated quickly, the association said.

'This is very exciting, there are potentially a lot of people who can benefit,' said Dr. Terry Vanden Hoek, a professor of emergency medicine at the University of Chicago and a co-author of the heart association's endorsement, which was published Monday in Circulation, the journal of the association.

Some major teaching hospitals already put comatose cardiac arrest victims on ice. The association now recommends that all hospitals use it, a spokeswoman 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, or quiver. 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 of 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.

But 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 occurs when oxygenated blood rushes back into the brain, triggering inflammation. 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 to be answered, including how to chill patients rapidly but safely, whether to start in the ambulance and how long patients should stay in the hibernation-like state of 'therapeutic hypothermia.'

The European study used a cold mattress with a cover that blows cold air; the Australian one used ice packs. Either way, it could take up to eight hours to cool a patient, Vanden Hoek said.

Cooling needs to be done carefully, explained Mary Fran Hazinski, a resuscitation instructor at Vanderbilt University Medical Center, and may, for example, include injecting muscle relaxants to prevent shivering.

New cooling techniques now in experimental stages include cooling helmets; injecting cold saline solution into patients' veins; threading loops of tubing carrying super-cold liquids down arteries; pouring ice slurry into stomachs; or even pumping oxygen-carrying perfluorocarbon slurry into the lungs.

The notion that cooling could help some heart-attack and stroke victims has been around since the 1950s. But according to the heart association committee making Monday's endorsement, hypothermia was abandoned in the United States because it was difficult and, even as late as 2000, when the association updated its cardiac care guidelines, the evidence of benefits was considered shaky.

Since then, studies on dogs and pigs supported the idea, and newer human studies showed clear advantages.

In the European study of 273 patients, 55 percent of those in the hypothermia group were living independently six months later, compared with 39 percent of the unchilled group. Only 41 percent of the hypothermia group was dead, while 55 percent of the unchilled group was.

The Australian study had only 67 patients, but was even more favorable for those who had been cooled. About 51 percent of its hypothermia group had died while 68 percent of the unchilled had.
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