Coling therapies are used to lower the temperature of the body and protect the brain in people whose hearts suddenly stop. Now, researchers want to learn if this same therapy, called hypothermia, can protect the brain from the devastating damage strokes cause.
“We have known for a while that cooling can have protective effects,” says Stephan A. Mayer, M.D., associate professor of Clinical Neurology and Neurosurgery at Columbia University and Director of the Neuro-ICU at New York Presbyterian Hospital-Columbia Medical Center. He helped lead one of the first studies evaluating the use of hypothermia for acute stroke in the late 1990s.
These therapies include using cooling blankets and ice packs to reduce body temperature, self-adhesive pads that circulate cooled water over the skin, and inserting catheters in the blood vessels that contain circulating liquid to lower the temperature of the blood.
Two major studies published in the New England Journal of Medicine in 2002 showed for the first time that cooling a patient who was resuscitated after cardiac arrest (sudden heart stoppage) increased the likelihood of survival and protected the brain. The brain needs blood to live and, prior to cooling therapies, there was no effective treatment for patients whose brains were temporarily deprived of it.
Christine Wijman, M.D., an assistant professor of Neurology and Neurological Sciences at Stanford University and director of the Stanford Neurocritical Care Program routinely cools people who remain comatose after cardiac arrest.
She is also involved in a multi-center study, sponsored by the federal National Institutes of Health, which uses cooling catheters for people who have experienced an acute ischemic stroke.
The procedure cools people down quickly to about 91 degrees for 24 hours.
Many studies in animals have shown that cooling quickly after stroke onset diminishes brain tissue injury and increases the chance of a good recovery says Dr. Wijman. But it is not entirely clear exactly how cooling protects the brain.
What researchers do know is that it decreases the brain's need for oxygen and glucose (the simple sugar that is the body's energy source). In addition, it may slow down or block the chain reactions caused by the stroke that lead to cell injury she explains.
Cooling therapy is also being considered as a protective treatment for the brain at stroke onset. Neurologists often use a clot-busting drug called tissue plasminogen activator (tPA) to dissolve the blood clot causing the stroke. This treatment increases the chance of a good recovery from the stroke but may also cause some damage due to blood flowing through brain tissue injured by stroke. Cooling the brain may also help prevent this injury, says Dr. Wijman.
She is involved in a study to determine the ideal time period after a stroke when cooling is most effective. Researchers will also be watching for side effects of cooling therapies, which may include infection, heartbeat irregularities and metabolic problems such as hyperglycemia (too much glucose in the blood). Although these complications can be serious, most are treatable.
Whether or not cooling therapies help people who experience stroke remains to be seen, concludes Dr. Mayer. “It's a work in progress,” he says.