When 35-year-old Mitsutaka Uchikoshi was found last October lying in an ice-cold field on Japan’s Rokko Mountain, a bucolic hiking spot north of Kobe, he was presumed dead. He had no detectable pulse or respiration, and his body temperature was 71 degrees Fahrenheit, 27 hatch marks shy of normal. While returning alone from a party on the mountain, Uchikoshi had stumbled and hit his head; he spent the next 24 days sprawled unconscious in the frigid air, without food or water. But when he arrived at Kobe City General Hospital, something remarkable occurred: He woke up. To the astonishment of the doctors who treated him for severe hypothermia and blood loss, Uchikoshi made a full recovery without a trace of brain damage. “I was in a field, and I felt very comfortable. That’s my last memory,” he told reporters before walking out of the hospital.

Freak survival stories like Uchikoshi’s pop up every so often in the news. In May 1999, a female Norwegian skier was submerged in icy water for over an hour and deemed clinically dead—no heartbeat, no respiration, and a core temperature of 57ºF—only to snap back to life in the hospital. In February 2001, doctors revived a Canadian toddler whose heart had stopped beating for nearly two hours and whose body had cooled to 61ºF after she wandered outside, unnoticed, on a freezing night. These strange tales hint at what was, until quite recently, an underappreciated facet of our nature. Humans, it seems, can hibernate.

By exposing mice to toxic hydrogen sulfide gas, molecular biologist Mark Roth triggers a latent hibernation response that seems to exist in all mammals. | Photo courtesy of Dean Forbes

These death cheaters survived by entering a state of suspended animation, in which the machinery of life temporarily comes to a grinding halt. Far more than a biological curiosity, suspended animation has the makings of a powerful medical tool. In the past five years, labs around the country have begun artificially inducing this state by cooling animals to ultralow temperatures, pumping them full of fake blood, and plying them with toxic gases in order to reversibly arrest life’s basic processes. Human tests are now just around the corner. If successful, they will pave the way for a revolution in trauma care that could save the lives of thousands of patients­—suffering heart attacks, strokes, or near-fatal injuries—who would survive if only there were a way to shut down the body long enough to reach the operating room.

Two summers ago, anesthesiologist Patrick Kochanek of the Safar Center for Resuscitation Research at the University of Pittsburgh dramatically demonstrated the power of suspended animation. He and his team revived dogs that had been clinically dead for three hours—with no heartbeat, no breathing, and no brain activity. The researchers discovered they could preserve a dog in limbo for several hours by cooling the animal and flushing its veins with a chilled solution of salt, glucose, and dissolved oxygen. The dogs came back to life after they were given a blood transfusion and reheated, although a few of them experienced minor brain damage.

To the horror of the Safar scientists, the tabloid press responded to this work with morbid glee, publishing ghoulish stories about “zombie dogs” alongside images of werewolves. Such slavering was perhaps unsurprising, given that suspended animation has often been associated with sci-fi images of astronauts hibernating in pods en route to distant stars. In the late 1960s and 1970s, NASA even funded research on halting metabolic activity during long-duration space travel but abandoned the effort after it was deemed technologically unfeasible. These days it is the United States military and the National Institutes of Health that finance such research, with the Safar group—which now hides behind a cloak of silence—being one of the grantees.