Spetzler can keep patients in cardiac standstill for as long as 72 minutes. The risks are high, with a mortality rate of about 25%, and he does it only when not operating would mean almost certain death. “It’s a very invasive procedure,” he says, with some patients dying weeks or even months later, though it’s difficult to determine whether their deaths are attributable to the procedure or to residual problems with the aneurysms.

In another approach to suspended animation, Sam Tisherman, a University of Pittsburgh surgeon and Safar Center researcher who is a colleague of Kochanek’s, is preparing to lead a clinical trial of trauma victims suffering from exsanguination cardiac arrest, a condition in which the heart stops as a result of blood loss. Patients who lose a pulse because of massive bleeding die more than 90% of the time. “You can’t start the heart because the tank’s on empty,” Kochanek explains. “And if you give blood intravenously, it just leaks out.”

Tisherman hopes to save these patients by cooling their bodies to 50°F prior to surgery. His approach originated in the mid-1980s, when Peter Safar, a Pittsburgh professor and critical care pioneer, persuaded Tisherman, then a fellow in Safar’s lab, to launch a series of studies. Safar, now deceased, knew that there is a brief window during which the brain and other vital organs stay viable after the heart stops, and he wanted Tisherman to create an animal model to investigate how suspended animation could be used to save victims of exsanguination cardiac arrest.

Today, Tisherman and a research team at the Safar Center are perfecting their approach. Dubbed emergency preservation and resuscitation, or EPR, it relies on massive infusions of ice-cold saline. First, an anesthetized dog is bled until its heart stops. Then a device called a roller pump, hooked to the aorta or femoral artery, flushes the dog with an infusion of ice-cold saline (as much as 20 liters may circulate through the dog’s body to cool it to the desired temperature). As the cooling fluid moves through the animal’s body, draining out through a catheter in the jugular vein, researchers monitor brain temperature until it reaches 50°F. (According to several studies, that’s the optimal temperature for decreasing metabolism without causing brain damage.) At that point the dog is packed in ice, and surgeons inflict and repair a wound to the spleen, mimicking human trauma. Finally, a cardiopulmonary bypass machine slowly returns the animal’s preserved, oxygenated blood. Most dogs that have undergone EPR, followed by 36 hours of mild hypothermia that researchers maintain with a cooling blanket and fan, recover without brain damage or other problems, according to research findings described in the April 25, 2006, issue of the journal Circulation.

Hasan Alam, a Safar Center collaborator, trauma surgeon and director of trauma research at the Massachusetts General Hospital, has achieved similar results in multiple studies. Alam uses ice-cold fluid to induce suspended animation in exsanguinated animals, but unlike the Safar Center scientists, he works in the laboratory with human-size Yorkshire pigs. His latest findings, described in the April 2007 issue of the Journal of the American College of Surgeons, confirm that a temperature of 50°F preserves vital organs while surgeons repaired inflicted wounds to the colon, spleen and vascular system. Each surviving animal recovered without brain damage, future learning impairments or evidence of organ dysfunction.

Bolstered by success in animal models, Tisherman is preparing to test EPR in humans, with one of the most daring clinical trials ever attempted in trauma care. The idea is to rush victims of gunshot wounds and other penetrating injuries to participating trauma centers. If a patient’s heart stops after transfer to a trauma center, a medical team will employ the same method developed in animals, using a roller pump to circulate through the patient’s body as much as 30 liters of ice-cold saline saturated with dissolved oxygen and glucose. Time is of the essence, Tisherman emphasizes. His animal studies suggest cooling won’t save brain function if it’s delayed by more than eight minutes after cardiac arrest.

During the procedure, the fluid enters through a large catheter, usually inserted into the femoral artery that runs from groin to knee. But if the patient’s chest has already been opened by an emergency thoracotomy (in the field or after arrival in the ER), the catheter can be threaded into the aorta, which serves as an arterial pipeline from the heart to other vessels. (Thoracotomy is a standard procedure for locating and stopping internal bleeding from chest wounds.) The goal is for the cold saline, pumped at a rate of two to three liters per minute, to saturate the brain, heart and other organs, reducing core temperature to roughly 50°F.