In a historic first, doctors have placed human patients into a state of suspended animation in an effort to buy time to heal the patients’ fatal injuries.

Suspended animation is a state in which all biological functions are stopped with the intent to revive them; in other words, it’s extreme hibernation, or temporary, clinical death. The effort is part of a U.S. trial that aims to reduce brain damage and death, which often results when injuries are so serious the heart stops circulating blood.

“I want to make clear that we’re not trying to send people off to Saturn,” Dr. Samuel Tisherman, a critical care surgeon at the University of Maryland School of Medicine who has devoted his career to researching what is medically known as emergency preservation and resuscitation (EPR), told New Scientist, which broke the news. Tisherman is leading the groundbreaking study. “We’re trying to buy ourselves more time to save lives.”

Results from the trial, which will conclude at the end of 2020 and include 10 fatally injured patients in suspended animation, will be compared to the outcomes of 10 fatally injured patients who received standard emergency care.

The current practice in cases of such severe injury that a patient is likely to die within minutes is to induce therapeutic hypothermia, which lowers the body’s temperature to around 34 degrees Celsius — roughly three degrees lower than typical body temperature.

By contrast, EPR rapidly drops the body’s temperature far beyond that threshold, to 10 to 15 degrees Celsius, by replacing the blood with “ice-cold saline,” according to New Scientist. At this temperature, patients have neither a pulse nor measurable brain activity.

Related on The Swaddle:

Japan Approves Research to Grow, Harvest Human Organs from Animal Embryos

EPR buys doctors about two hours to treat severe wounds, instead of a few extra minutes, before body tissue must be reheated.

“If EPR works, it’ll be a game-changer,” Dr. Kevin Fong, a consultant anesthetist at University College London hospital who is not involved in the trial, told The Guardian.

Unlike hypothermia, EPR carries no risk of tissue frostbite, but it does deprive tissue of oxygen. This deprivation, depending on how long it lasts, could complicate the re-warming phase with reperfusion, in which the risk of tissue death counterintuitively increases as oxygen-rich blood is pumped back into the body.

The trial will allow doctors to study reperfusion more fully and, ideally, find ways to manage against it, Tisherman told New Scientist, perhaps by finding the right cocktail of drugs to minimize fallout injuries.

Despite the risk of reperfusion, and the risk inherent in any experimental procedure, previous research involving pigs suggests EPR can save lives, though not with a 100% success rate.

“We felt it was time to take it to our patients,” Tisherman told New Scientist. “Now we are doing it and we are learning a lot as we move forward with the trial. Once we can prove it works here, we can expand the utility of this technique to help patients survive that otherwise would not.”