After brain injury, the brain produces certain chemicals that are harmful to the injured tissues. Moderate hypothermia—also called body cooling—may slow or prevent the production of these chemicals. Hypothermia also decreases the amount of oxygen needed by the brain, which may provide some protection during this critical period. Earlier studies have shown that maintenance of moderate hypothermia may have a helpful effect in head injury patients ages 16 to 45 who arrive at the hospital with a low body temperature suggesting that very early cooling may be beneficial.