Doctors believe drastically reducing the temperature of patients who have suffered serious blows to the skull could spare them severe brain damage.
Victims of car crashes and assaults who are treated in the intensive care unit of Edinburgh's Western General are now being given ice cold intravenous drips and cold blankets to see if it improves their recovery.
Researchers will check how well patients are doing six months after their admission to hospital and compare progress with that of a control group of patients not treated in this way.
Professor Peter Andrews, head of critical care medicine at Edinburgh University, who is working on the trial, said: "This is a fantastic opportunity to try to improve outcomes for what are a very vulnerable group of patients who can suffer severe disability after their injury."
Swelling caused by bleeding or bruising inside the skull is particularly dangerous as it is a confined space. It can result in the flow of blood to the brain being restricted, depriving the brain of oxygen and causing damage or death.
The team believes that, by cooling the body to between 32˚C and 35˚C, they will reduce swelling in the skull. Inducing hypothermia also puts the body into artificial hibernation, in which the brain can survive with a lower blood supply.
Extreme cooling to allow surgeons to stop a patient's heart long enough to carry out surgery and then revive them has already been established.The team hopes the effects together will give patients a better chance of returning to good health.
Mr Andrews it was unlikely patients with the most severe injuries would recover completely, but he added: "What we might do is make the difference between them being totally dependent on other people and being independent, which is huge.
"For the less severely injured patients it may make a difference between some disability and minimal disability."
The trial, known as Eurotherm3235, is taking place in 53 centres around the world but is being led by Edinburgh University. A total of 600 patients will take part, including 300 who will not be given the therapy.
As part of a pilot study more than 30 Scottish patients have already received the treatment, carried out while they are in intensive care and sedated. Relatives are asked beforehand.
The £2 million trial is funded by the National Institute for Health Research.