For the first time ever, surgeons at UPMC Presbyterian Hospital in Pittsburgh could save patients by putting them between life and death. They're ready to test a technique that would place patients in a state of "suspended animation," giving surgeons enough time to operate on injuries that would otherwise be fatal.

The process involves removing the patient's blood, and fast: all of the blood would be drained from the body and replaced with a saline solution that stops almost all cellular activity. This is similar to inducing hypothermia — cells at lower temperatures need less oxygen to perform chemical reactions, so an entire body cooled could be kept technically alive (and technically not dead) for longer periods of time than a body at a normal temperature of 98.5 degrees Fahrenheit.

To test the suspended animation method, UPMC Presbyterian doctors will first need the right patient: someone suffering from cardiac arrest after an injury like a gunshot wound, who doesn't respond to attempts to restart their heart. Then the saline solution will first be pumped to their heart and brain, and eventually through the entire body. At the time of operation, the patient will be clinically dead, with no blood in the body, no brain activity, and no breathing. At the metabolic level in this state, cells produce energy at a very slow rate through a process called anaerobic glycolysis, allowing the cells to survive for hours. The surgeons have a window of about two hours to fix the patient's injuries and replace the saline solution with blood. If all goes well, the heart should restart slowly, but patients could need a jumpstart.

Suspended animation was tested in pigs back in 2002, and some of the pigs successfully survived the treatment without any deleterious effects. But trying this technique in humans is controversial: since the participants will be coming from the emergency room, neither the patient nor the family can give consent. The US Food and Drug Administration is letting the trial happen because these patients are not likely to survive their injuries. Samuel Tisherman, one of the hospital's surgeons, told New Scientist that suspended animation will first be tested on ten patients and compared to another ten patients who were not treated in the same way. The team will continue in batches of ten until there is enough data to analyze.