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Después de lesión seria del cerebro, Tiempo a refrescarse abajo

por Brendon Nafziger, DOTmed News Associate Editor | November 23, 2009
A fresh take on hypothermia
as an intervention
A jury-rigged renal dialysis machine could help patients recover from head trauma or stroke by selectively cooling parts of the brain, scientists say.

"We've known that cooling decreases metabolic rate of cells and tissue for a long time," Mark Preul, M.D., director of the Barrow Neurological Institute at St. Joseph's Hospital and Medical Center in Phoenix, Ariz., tells DOTmed News.

"That's why people we think have drowned in water, if we find out they had been in very cold water, we often hear those people have been resuscitated...and can make a recovery," he says. The reason: hypothermia, by slowing the metabolic rate, slows the production of carbon dioxide and other metabolites that Dr. Preul says could harm the brain and other tissue.

Though some doctors hope that slightly reducing the temperature of the brain could help preserve function following a traumatic brain injury or stroke, cooling methods are in the early stages, and there are questions whether whole-head cooling treatments, such as with helmets or cooling pads, are effective, as some studies suggest the cooling action can't penetrate far into the brain.

That's where Nikkiso Co. Ltd comes in. Nikkiso, a Japanese company that manufactures renal dialysis machines, developed a dialysis unit that also has the ability to inject a cool crystalloid solution, made of Ringer's acetate, into the carotid artery. By doing this, it can selectively chill affected regions of the brain, at least, that's the idea.

Early animal studies using the device, published in the journal Neurological Research this year, and conducted in part by researchers at the Osaka Medical Center in Japan, argue that the project is feasible. In the studies, to balance the fluid in the body, blood was drawn after the solution was injected, and the dogs' right hemispheres were selectively cooled over about 30 minutes.

Although Dr. Preul says he and his colleagues are the first to show that the brain can be selectively cooled through solutions delivered through a catheter directed through the arterial system into a selected brain artery, much work still needs to be done. The doctors have to figure out a safe threshold for cooling, so they don't damage the brain through blood clotting, a risk when temperatures go too low. And any part of the brain that's cooled has to be re-warmed. If they cool too low, or for too long, re-warming rapidly could cause metabolic problems, Dr. Preul says.

To find the perfect temperature, probably in the low to mid 30 degrees Celsius, Dr. Preul says they're working up the logistics for a second round of tests.

But in some ways, though new, the treatment has a long pedigree. In fact, Dr. Preul says, in spinal surgeries in the 1940s, doctors would often pack patients' backs with ice to prevent nerve damage. "This is what the old-time surgeons used to do," he explains.