Health

Keeping Cool During A Heart Attack

By CBSNews.com staff CBSNews.com staff

February 21, 2002 / 4:13 PM EST / CBS

Cooling the body just a few degrees appears to prevent brain damage in people who survive cardiac arrest but are left unconscious.

If treated quickly enough, cardiac arrest can be reversed and the heart restarted with electric shock. But doctors have not figured out how to stop the brain damage that begins minutes after blood flow stops.

In separate studies, researchers from Europe and Australia found that reducing the temperature to 91 degrees Fahrenheit for at least 12 hours increased the chances of survival in patients whose hearts had stopped for at least 5 minutes, and often far longer. Brain cells usually start to die after four or five minutes without oxygen. Normal body temperature is 98.6 degrees Fahrenheit.

The findings suggest the technique could save thousands of heart attack patients around the world from death or brain damage each year, researchers said.

Although further research is needed, Dr. Peter J. Safar of the University of Pittsburgh Medical Center said there is enough evidence now to make the treatment routine in the United States.

"It's pretty clear-cut now. This should immediately go into guidelines for regular use," said Safar, whose lab did some of the animal tests that renewed interest in the approach.

"The fact that the two studies yielded similar results makes the important conclusions even more compelling."

Dr. Stephen Bernard, deputy director of intensive care at Dandenong Hospital and chief author of the Australian study, told Reuters the results were so convincing, all cardiac arrest patients brought to the hospital are being cooled.

"We thought it would no longer be ethical to not use hypothermia" in all patients in a follow-up study, he said, adding that the hospital was examining techniques for cooling.

About 225,000 people in the United States suffer cardiac arrest each year and those cases account for half of all deaths from heart disease. Although rescue workers are sometimes able to restore a heartbeat, brain cells can continue to be damaged.

The new studies were an attempt to see if cooling the body -- using ice packs or a special mattress cover that delivers cold air over the body -- could slow or prevent the damage, giving the brain time to recover.

In the larger test, led by Dr. Michael Holzer of the University Clinic for Emergency Medicine in Vienna, Austria, 275 patients at nine medical centers in five countries were either cooled for 24 hours or kept at normal temperature. In each case, at least five minutes -- but no more than 15 minutes -- had passed before resuscitation efforts were begun, and a normal heartbeat was restored within 60 minutes.

After six months, 41 percent in the hypothermia group had died compared to 55 percent of the patients whose bodies were kept at normal levels.

In addition, the likelihood of having a good recovery or only moderate disability was 55 percent among the people whose bodies were cooled, versus 39 percent for those who did ot receive the hypothermia treatment.

Holzer's team calculated that seven patients would need to be treated by hypothermia to prevent one death. To prevent serious brain damage in one patient, six people with cardiac arrest would need to receive the hypothermia treatment.

The researchers excluded 92 percent of cardiac arrest patients for various reasons. They recommended more study to see if the findings work for a broader spectrum of patients.

Even under their strict criteria, their findings suggest that 2,571 deaths and 3,000 cases of disability could be prevented in the United States each year. The researchers said hypothermia therapy could help 1,200 to 7,500 Europeans survive and recover from cardiac arrest annually.

Bernard's smaller Australian study used 12 hours of hypothermia. But instead of beginning the treatment in the hospital, rescue workers who restarted the hearts removed clothing and began applying ice packs at the scene.

While just 26 percent of the 34 patients given standard care survived, the success rate was 49 percent for the 43 patients treated with hypothermia.

Bernard, interviewed by telephone, said his study is probably a better reflection of how the treatment would work in the real world because it included more types of patients.

Researchers in both studies said quicker, more efficient ways to cool patients are needed. Several devices are being developed, and Bernard said he is testing ice-cold liquids given intravenously.

The technique is also being tested for stroke and brain injuries, and Safar said other uses warrant study, such as spinal cord injury.