US doctors have developed a method of inducing hypothermia to shut down the body's functions for up to three hours.

In tests, they reduced the body temperature of injured pigs from 37C to 10C before operating on them and then reviving them.

Now they are applying for permission to test the procedure on casualty patients without a pulse who have lost large amounts of blood, New Scientist magazine reported.

It is thought this method and others could one day be used on car crash and gunshot victims, as well as in the battlefield to treat wounded soldiers.

A surgeon at Massachusetts General Hospital in Boston, Hasan Alam, has tested the technique about 200 times on pigs, with a 90 per cent success rate.

First he anaesthetises the animal, then cuts a major vein and artery in its abdomen to simulate multiple gunshots to a person's chest and abdomen.
As the pig rapidly loses about half its blood and enters a state of shock, Dr Alam drains its blood and stores it before pumping chilled organ preservation fluid into its system.

The animal's body temperature falls to about 10C until it is in a state of "profound hypothermia" and has no pulse and no electrical activity in its brain.

But after the blood stored earlier is warmed and pumped back into the pig's body its heart starts beating again and it comes back to life.

"It is still pretty awe-inspiring," Dr Alam said. "Once the heart starts beating and the blood starts pumping, voila, you've got another animal that's come back from the other side.

"Technically, I think we can do it in humans."

He now wants automatic consent to use the technique on all patients brought to his hospital who have lost blood and would probably die with only standard care.

Other US researchers are working on methods to place organisms in suspended animation by exposing them to a cocktail of gases, including hydrogen sulphide.