Dying to Live
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But in 1986, Robert Spetzler, now director of the Barrow Neurological Institute at St. Joseph’s Hospital and Medical Center in Phoenix, attempted a procedure in which he cooled a patient’s body to a very low temperature, using a variation on a technique first tried in the 1960s. In those days, surgeons opened the heart to attach a catheter, then cooled the blood by running it through a bypass machine to prepare for surgery; about half the patients died.
In his variation, which now has been performed more than 100 times, Spetzler inserts the catheter into the femoral artery and uses barbiturates to reduce metabolic activity. Working with a team of neurosurgeons, cardiologists and anesthesiologists, he uses a bypass machine to cool the blood until the patient’s body temperature reaches about 60°F. At that temperature, the heart stops beating—an induced condition called cardiac standstill—and the team can drain the body of blood. Spetzler then snakes a catheter into the brain to treat hard-to-reach aneurysms. Without blood flowing through it, an aneurysm deflates, allowing Spetzler to attach a clip that prevents the aneurysm from reinflating when blood is returned to the body and the heart is restarted.
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.
