With the body fully cooled, its biochemical processes should pause, bringing metabolism to a virtual standstill and reducing the demand for oxygen by as much as 95%. In the operating room, wounds will be plugged and vessels repaired, and then cardiopulmonary bypass equipment will begin circulating blood through a heat exchanger, slowly raising the body temperature so that a heartbeat can be restored.

“I think this could be the beginning of something huge,” says Thomas Scalea, physician-in-chief at the R. Adams Cowley Shock Trauma Center in Baltimore, considered one of the best in the world. “It’s a fantastic leap in sophistication.”

Tisherman concedes the approach carries substantial risk. Hypothermia reduces clotting, which can be problematic when trying to save a patient who has already lost a great deal of blood. And cold raises the threat of infection because immune cells that protect the body from viruses and bacteria lose their effectiveness when body temperature drops. But the biggest worry is that the patient might suffer permanent brain damage.

The best way to avoid poor outcomes, Kochanek asserts, is to select the right patients—those who have been healthy and strong; haven’t had extensive brain trauma; are already at an appropriate trauma center; and can be prepped for EPR within the critical eight-minute window. It’s that last part that will be especially difficult. “The technical feasibility of doing this fast enough is our biggest stumbling block,” Kochanek says.

Tisherman hopes to launch the trial in five top trauma centers, in which EPR will be compared with the standard treatment for trauma victims who have lost a pulse: blood infusions, emergency thoracotomy and CPR. Surgeons will be trained to perform the new procedure, which involves some skills—using cardiopulmonary bypass equipment, for example—that may not figure in their clinical repertoire.

The trial faces additional challenges, including regulatory hurdles at the FDA and the Department of Defense, which is providing funding. Unlike ordinary clinical trials where patients can give informed consent, the trauma victims in this trial will be unconscious and near death, and there likely won’t be time to ask relatives to agree to the procedure. So researchers will have to secure in advance what’s known as an exception from informed consent, an authorizing statement from each community served by the trauma centers in the trial. Assuming most communities assent and federal agencies give the green light, a launch is expected later this year, Tisherman says.

As Tisherman prepares for his clinical trial, another researcher, biologist Mark Roth of the Fred Hutchinson Cancer Center in Seattle, has developed an altogether different way to reduce metabolic demand for oxygen—using hydrogen sulfide. Because the gas binds readily with vital oxygen receptors in the cell, it slows down metabolism, sending cells into a sort of hibernating trance.

Hydrogen sulfide interferes with a metabolic pathway called oxidative phosphorylation, which converts oxygen and nutrients to energy. When oxygen drops to levels that can’t sustain life, the pathway goes haywire and spits out free radicals that destroy cell membranes. But a priming dose of hydrogen sulfide blocks that process, protecting animals from declines in oxygen that would normally kill them.