THURSDAY, Feb. 5, 2004 (HealthDayNews) -- Two pioneering studies, one of which borrows from the U.S. space program, show stroke damage can be reduced by helmets that cool the brain, American and Japanese researchers say.
The studies included only a handful of patients -- 17 in Japan, six in the United States -- who suffered ischemic strokes, in which a clot blocks a brain artery, but the results were promising enough to warrant further investigation, the researchers told those at American Stroke Association's annual meeting in San Diego on Feb. 5.
The human trials build on animal studies finding that cooling the brain can reduce brain damage after a stroke by as much as 70 percent, Dr. Huan Wang, an assistant and resident of neurosurgery at the University of Illinois College of Medicine who reported on the American trial, says in a statement.
That trial used a liquid cooling technology developed at the National Aeronautics and Space Administration (NASA) on six people in the hours after they suffered strokes. The technology was devised by former NASA scientist William Elkins, a pioneer in developing space suits that could withstand extreme temperatures.
Measurements showed the patients' brains cooled an average of 6 degrees Fahrenheit in the first hour, while overall body temperature did not go down significantly.
That selective effect is important because cooling the entire body can increase the risk of infection, abnormal heartbeats and blood abnormalities, Wang says.
His group did not report on patient outcomes. The Japanese researchers say that six of the patients they treated had "good" functional outcomes three to 10 months after they wore the cooling helmets for as long as seven days, starting three to 12 hours after a stroke was diagnosed.
Cooling has been recognized as "a very promising therapy" to limit the damage of both strokes and heart attacks, says Dr. Vinay M. Nadkarni, an associate professor of anesthesia and critical care at the Children's Hospital of Philadelphia and a spokesman for the American Heart Association.
"There are many possible tools with which to accomplish that task," he says. "What is being sought is the best tool, and there are many possibilities."
Cooling limits damage in three ways, Nadkarni says. It reduces the formation of oxygen free radicals, which attack and kill cells. It slows brain metabolism, reducing its need for blood, and it can prevent damaging inflammation, "particularly if you cool rapidly or deeply."
Alternative cooling methods that have been experimented with include simply packing the brain with ice or injecting cold fluid into the bloodstream, Nadkarni says. All have potential problems to match their potential benefits.
The injection technique affects the entire body, he notes. Techniques such as the cooling helmets affect only the brain, "so you get the benefit of cooling but not the risk," Nadkarni says.
"But in a low-flow state, such as after a stroke, those things that require cooling to travel from the surface into the brain tend to be less effective," he says.
The studies reported at the meeting are "very early," as are other trials of cooling methods, Nadkarni says.
"Most studies have been of feasibility, not large-scale studies," he says. "There are no studies showing that a method that can be effective if broadly applied. A method that could be applied by every emergency room technician would be a real breakthrough."
More information
Current methods of treating stroke are described by the American Heart Association and the National Stroke Association.
