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Back To Vidyya Induced Hypothermia Can Help Prevent Stroke Damage

A Few Degrees May Protect Against Permanent Brain Damage

For the first time, researchers have shown that lowering stroke victims' temperatures a few degrees may protect them from permanent brain damage.

Finding ways to cool the body has emerged as one of the most competitive areas of stroke research. Several companies are working on devices that can do this quickly and easily.

Many animal experiments have show that lowering temperature even a degree or two can reduce stroke damage. But accomplishing this in people is extremely difficult, and a small study presented Wednesday was the first to attempt it in a systematic way.

"This is very exciting, but it is also very preliminary," said Dr. Derk Krieger, who presented the results at a meeting in Fort Lauderdale of the American Stroke Association.

Krieger and colleagues from the Cleveland Clinic found that people who were quickly cooled down with alcohol rubs following severe strokes did substantially better than expected.

Half suffered little or no permanent damage and were well enough to return to work. Only 10 percent of people who got standard care did this well. Brain scans suggested that the cooling reduced the size of victims' brain damage by about 30 cubic centimeters.

The study involved 10 patients who underwent cooling and a comparison group of nine equally sick people who did not.

Doctors cannot cool just the brain. Instead, they must cool the entire body. In this experiment they did it the old-fashioned way -- by cooling the skin to lower the body temperature nine degrees for two days.

However, this triggers violent shivering, so doctors must paralyze patients to keep them still. This means they must also be put on breathing machines and knocked unconscious. Cooling the patients this way took an average of almost four hours and required a team of five doctors and nurses.

"It's a very labor-intensive approach," said Dr. Michael DeGeorgia of the Cleveland Clinic. "It's amazing how resistant your body is to even a slight change in temperature. Doing this is a big deal."

Dr. Mary A. Kalafut of the Scripps Clinic called the results promising, but she noted, "It is very uncomfortable for patients, and there can by complications."

To simplify the process, several companies have developed cold-tipped catheters that can be inserted into a vein and cool the body from the inside out. Krieger said doctors can keep patients' skin warm, and they remain awake and alert with no sense of being cold.

The Cleveland Clinic team plans to begin tests soon with one of these catheters in a study that will enroll about 350 stroke patients.

Strokes typically occur when a blood clot lodges in the tree of arteries in the head, choking off the flow. Quickly giving the clot dissolver TPA can forestall much of the damage, but most patients do not get to the hospital soon enough for the medicine to do any good.

Brain cells continue to die off for several more hours, killed by a chemical chain reaction triggered by proteins that ooze from neighboring damaged cells. Doctors believe cooling the head will prevent this by slowing metabolic processes.

The experimental catheters are threaded from the groin up to the inferior vena cava, the big vein that runs down the center of the abdomen. There it cools the blood flowing over it and can precisely lower body temperature several degrees in a half hour.

Brain cells may start to die within a few minutes of a stroke, so doctors are likely to begin hypothermia, as they call it, as quickly as possible.

"If hypothermia is effective, and that's a big if, and it can be used outside the intensive care unit, it may become standard treatment in the ambulance before the patient gets to the hospital," said Dr. Marc Mayberg, also of the Cleveland Clinic.

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Editor: Susan K. Boyer, RN
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