Brain trauma
Lowering a child’s body temperature to limit damage from a head injury doesn’t seem to help — but the jury is still out
By Nathan Seppa
Emergency room doctors treating a child who has a severe head injury sometimes drastically bring down the patient’s body temperature in hopes of limiting brain swelling. But a new study finds that kids who get chilled don’t fare any better than those treated at a normal temperature.
In the cooling, called induced hypothermia, doctors apply liquid-filled packs to the chest and legs — as researchers did in this study — or use infusions of cold fluids. Both lower the body temperature several degrees. Cooling can improve recovery in people who have been resuscitated after a heart attack. Surgeons also cool patients to prevent brain damage during delicate heart or stroke surgery when blood flow must be shut off temporarily.
But for people with brain trauma, the procedure has shown mixed results. In the new study, doctors at trauma centers across Canada, Britain and France identified 205 children admitted to hospitals from 1999 to 2004 with a brain injury. With parental consent, researchers randomly assigned roughly half to receive cooling treatments for 24 hours. During these treatments, a child’s body temperature was brought down to 32.5° Celsius (90.5° Fahrenheit).
Kids who were cooled were just as likely to have died after six months or to have serious medical problems (including vegetative state or severe disability) as children who weren’t cooled, the researchers report in the June 5 New England Journal of Medicine.
Also, those getting hypothermia treatments struggled with crashing blood pressure more often than the others, mainly during re-warming.
The findings don’t close the book on hypothermia, however, says study coauthor James Hutchison, an intensive care physician at the Hospital for Sick Children in Toronto. Rather, they raise questions about the optimal approach for cooling a child, or any individual, with brain trauma.
“It’s still not clear it works,” Hutchison says. “It’s all about protecting the brain.” Cooling slows the brain’s metabolism, easing its demand for oxygen and glucose and lowering the risk that it will experience a shortage of these substances and start losing brain cells.
Brain trauma poses difficulties because every patient is different, says pediatric neurosurgeon David Adelson of the University of Pittsburgh. The head is “a closed box,” he says, and unleashed spinal fluid, blood or incoming inflammatory cells can contribute to swelling. Hypothermia does seem to decrease blood flow in the brain, he says, and quiets brain function.
But the fine points of how to make hypothermia’s effects work in the patient’s favor remain elusive. For example, patients in the new study faced delays in cooling that might have reduced their chances of benefiting from it, Hutchison says. Some waited up to 19 hours to get cooled.
Adelson is leading another study examining children who are being treated within six hours of brain injury. “We’re trying to interrupt the cascade of events leading to swelling and damage,” he says.
Meanwhile, it also remains unknown how long a patient should stay chilled. “Peak brain swelling can last from 48 to 96 hours,” Adelson says. Japanese doctors have cooled trauma patients for a week.
The Pittsburgh trial and another in New Zealand will cool children longer than the 24 hours used in the Canadian trial.
Doctors first noticed a protective effect from hypothermia when people revived after a heart stoppage showed better recovery in the rare cases where they had fallen through ice and been resuscitated. The science of controlled hypothermia got under way in earnest in the 1950s, was shelved for a while, then revived when surgeons found it helped limit brain damage during open-heart surgery.
