Even when people are rushed to hospital emergency rooms after cardiac arrest, the death rate is high and brain damage is common. Until now, no treatment had been proven to prevent brain damage after cardiac arrest.
However, the two studies that appear in tomorrow's issue of the New England Journal of Medicine prove hypothermia -- body cooling -- can preserve brain function for many patients, the researchers say.
The European research was carried out by the Hypothermia After Cardiac Arrest Study Group, headquartered in Vienna, Austria. It included 273 people who suffered cardiac arrest -- the heart stops -- because of an abnormal heartbeat called ventricular fibrillation. Half were maintained at normal body temperature, while others were exposed to a flow of cold air that lowered their temperature to approximately 92 degrees.
Overall, 75 of the 136 hypothermia patients were alive, with little or no brain damage, six months later. This compared to 54 of the 137 patients whose temperatures were not lowered.
The death rate for those with normal temperature was 55 percent. In that group, 76 of the 137 patients died, compared to a 41 percent death rate, or 56 deaths among 136 patients, for the hypothermia group.
The Australian researchers used a different cooling technique, applying ice packs to the head and body, with similar results in a smaller group of patients. Only nine of the 34 normal-temperature patients survived with little or no brain damage, compared to 21 of the 43 treated with hypothermia.
"The exciting advance here is that a relatively simple intervention may help accomplish a good neurological outcome," says Dr. Gregory D. Curfman, executive editor of the New England Journal of Medicine and author of an accompanying commentary.
Dr. Peter Safar, a distinguished professor of resuscitative medicine at the University of Pittsburgh, a longtime proponent of hypothermia and author of an accompanying editorial, says the results were to be expected.
Safar says the new studies, together with the extensive animal trials he and others have done, clearly show that "cerebral or whole-body hypothermia should be used in patients with cardiac arrest."
However, the method is not widely used in the United States, Safar says, mostly because it is not recommended in the treatment guidelines set by the American Heart Association and the American College of Cardiology. Hypothermia is listed in European guidelines, he explains.
The new studies may lead to reconsideration of the American guidelines, Curfman says.
"Two studies done more or less simultaneously on two different continents, using two methods of cooling, add credibility to the idea," he says. "It also makes clinicians sit up and take notice, and consider applying this methodology."
A change might not come quickly in the United States, Curfman says, because "guidelines always take a little while to catch up." However, while continuing research on hypothermia should be done, "we should consider applying this method now," he says.