Doctors at UPMC Presbyterian Hospital in Pittsburgh are beginning the first-ever human trials of “suspended animation” among gunshot victims with potentially fatal injuries. In order to buy more time to fix their wounds, doctors will replace all of the patients’ blood with a saline solution, which will cool down the body and practically stop cellular activity.

As they’re coursing with saline, the patients will be technically dead: They won’t breathe, and there will be no brain activity. But the cells will stay alive, working at a much slower pace at the lower temperature. After about two hours, the doctors will re-infuse the patients with blood, and they should come back to life as though they had just taken a brief, frosty nap. The scientists who study this phenomenon have a common refrain: “You’re not dead until you’re warm and dead.”

Scientists have previously performed the procedure on pigs with a 90 percent success rate. In most cases, the animals’ hearts began beating again on their own after their blood was replaced. Their physical and mental functioning was unharmed. In 2006, scientists in Boston induced hypothermia and a slowed heart rate in mice by using hydrogen sulphide gas. The mice returned to normal two hours after they began breathing normal air again.