The US Food and Drug Administration (FDA) has given the go ahead for a trial where 10 emergency patients with life threatening injuries will be suspended between life and death by surgeons at the UPMC Presbyterian Hospital in Pittsburg, Pennsylvania. This state of "suspended animation" will hopefully buy surgeons more time to fix the otherwise fatal injuries.

Suspended animation may sound like something out of a science fiction novel, but doctors are hoping that it may actually save the lives of severely injured people, for example those with serious gunshot wounds who have lost a lot of blood. The technique will only be performed on individuals where the heart has already stopped beating, and is not responding to attempts to restart it. It involves draining all of the blood of the individual and pumping a cold saline solution through the heart to brain. After this the cold saline solution is pumped through the entire body, dropping the body temperature from the normal 37 degrees to around 10 degrees. At this point, the patient will be "clinically dead" and the surgeons have around a 2 hour window to operate in an attempt to fix the injuries.

This may sound odd, but there is science behind it. The benefits of this cooling, or induced hypothermia, have been known for a long time. The cells of your body are very energy hungry and require a constant supply of oxygen; this is supplied to your organs by the heart pumping oxygenated blood around your body. When your heart stops beating, your cells start to starve of oxygen and begin to die; the brain is particularly susceptible to this. But if you drop the temperature of the body, reactions begin to slow down in cells and metabolism virtually ceases, which reduces the need for oxygen. The cells will still produce energy, through anaerobic glycolysis, but it will be occurring at such a low rate that the cells can be sustained for hours instead of the normal few minutes that this type of glycolysis provides. During this time the surgeons can operate on the damaged body parts; if successful they will replace the saline with blood and the temperature of the body will slowly rise again. At this time, the heart should start beating of its own accord, but if not doctors can attempt to resuscitate.

"Every day at work I declare people dead," said Peter Rhee from the University of Arizona Tucson, one of the surgeons who helped develop the technique. "They have no signs of life, no heartbeat, no brain activity. I sign a piece of paper knowing in my heart that they are not actually dead. I could, right there and then, suspend them. But I have to put them in a body bag."

This technique has never before been trialed in people, but in 2002 at the University of Michigan Ann Arbor Hospital it was successfully tested in pigs. Although some of the pigs required resuscitation as their hearts did not begin beating on their own, the animals recovered well with no apparent physical or cognitive problems. The trial will involve 10 people who fit the criteria for the procedure to go ahead, who will be compared to another 10 people who did not have this procedure because the appropriate medical team was not available. The trial is allowed to proceed because it is considered to be exempt from informed consent because the injuries are so severe that they would otherwise be fatal, and there is no current alternative. This will continue on groups of 10 patients, tweaking the procedure each time to improve it, in the hope of eventually gathering enough data to be able to confirm or dismiss it as viable treatment option.

This trial may take a considerable amount of time to gather enough data to yield comprehensive results since surgeons must wait for the right patient to arrive. But it is hoped that eventually this technique may be extended to conditions other than gunshot or knife wounds.