At a hospital in Pittsburgh, surgeons are now allowed to place patients into a state of suspended animation. If a patient arrives with a traumatic injury, and attempts to restart their heart have failed -- if they're on the doorstep of death -- they will have their blood replaced with a cold saline solution, which stops almost all cellular activity. At this point, the patient is clinically dead -- but if the doctors can fix the injury within a few hours, they can be returned to life from suspended animation by replacing the saline with blood.