Each year thousands of people suffer severe head trauma in car crashes or other accidents. Most such patients require long-term care, and so far, treatments have been disappointing new researchers at several hospital are testing whether they can help more patients recover fully by cooling them with ice water. The idea is to lower body temperature enough to slow a person's metabolism, thereby slowing a cascade of chemical reactions that immediately follow head injury and cause the death of brain cells. During hypothermic - or cooling - therapy, patients are covered with cool blankets attached to pumps that provide a constant infusion of water. The body temperature is lowered in four to six hours to about 33 degrees celsius - low enough to slow metabolism but not so low to cause life-threatening complications, like irregular heartbeat. Patients remain in this state for 24 or 28 hours.