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Hypothermia Can Sometimes Save Lives

As the body temperature decreases, so does the rate at which chemical reactions occur. Physicians can use this to a patient's advantage.

This article was first published in The Montreal Gazette.

It was a dreadful accident. Orthopedic surgery resident Anna Bagenholm had skied down the same mountain in Norway many times before, but that day in 1999 she lost control of her skis and tumbled down head first, crashing through the ice of a frozen stream. Trapped under the thick layer of ice, she managed to avoid drowning thanks to an air pocket between the water and the ice. Two colleagues with whom she had been skiing tried frantically to pull her out, with no success. By the time a rescue team arrived and managed to cut a hole through the ice, some 80 minutes had passed. Bagenholm was not breathing, had no pulse, and her pupils were fully dilated. She appeared to be dead. Nevertheless, CPR was started and she was transported to a hospital by helicopter.

Luckily, the emergency physicians at the Norwegian hospital were experienced in dealing with hypothermia and immediately connected her to a cardiopulmonary bypass machine that took over the work of her heart and lungs as her blood was warmed up. An hour later, her heart began to beat, but her lungs did not regain function, requiring that she be placed on a ventilator. Although she would need the assistance of this device for a month, just 10 days after the accident she emerged from her coma. Bagenholm spent two months in intensive care and eventually made an almost total recovery, going back to working as a physician, albeit not as a surgeon, but a radiologist.

To what did Bagenholm owe her miraculous recovery? Hypothermia! And of course, the dedication and expertise of the close to 100 doctors and nurses involved in her care.

The chemical reactions that constitute brain function require a constant supply of oxygen. Brain death occurs if the oxygen supply is interrupted for more than a few minutes, but there is an exception to this. As the body temperature decreases, so does the rate at which chemical reactions occur. At around 14 degrees C, the reactions are so slow that they require virtually no oxygen. That was exactly the scenario in this case. Mads Gilbert, the physician who led the team in the emergency room of the hospital where Bagenholm was taken, ended up coining the phrase, “Nobody is dead until warm and dead.” In 2014, 15 years after the miraculous recovery, Gilbert and colleagues published a comprehensive paper on resuscitation after hypothermic cardiac arrest.

While hypothermia is of course generally to be avoided, there are situations in which it can actually be useful. After trauma inflicted by an accident or shooting, there is major blood loss that leads to brain damage before surgeons have a chance to repair the wounds. If the patient can be quickly cooled, the brain’s oxygen requirement is reduced, allowing more time for surgery. Experiments on animals have already shown that it is possible to place a body in “suspended animation” for hours by cooling, followed by reanimation.

Hasan Alam, a surgeon at the University of Michigan, has carried out some fascinating experiments along these lines. He stimulated gunshot wounds in pigs by severing a major artery and vein in the anesthetized animals, causing major blood loss. The pigs’ remaining blood was then drained and stored, replaced with a special salt solution cooled to about 2 degrees C. This is the same sort of solution that is used to preserve organs for transplantation and contains a variety of nutrients and antioxidants to prevent tissue damage.

As the salt solution cruises through the pig’s circulatory system, its body temperature drops to about 10 degrees, at which point there is no longer any heart or lung function. Surgery to repair the wounds can then be performed, followed by reintroduction of the stored blood warmed to the right temperature. Alam has carried out such experiments numerous times with a 90-per-cent success rate of reanimation. By training the pigs to perform specific tasks before the experiment, and then demonstrating that they remembered the skills after reanimation, he has also shown that brain function is not lost. Furthermore, the animals’ ability to learn new skills is not impaired.

There certainly are ethical considerations here that go even beyond the question of experimenting on pigs in this fashion. Trauma victims are generally unable to give consent for such a hypothermic procedure, and because of the need to act extremely quickly, there isn’t time to contact the person’s family. So far, hospitals have not approved procedures that involve draining the blood in this fashion, but based on animal experiments there is the potential that they could be life-saving.

This form of cooling the body to achieve suspended animation should not be confused with “cryonic resurrection,” the far-fetched idea of preserving dead people in liquid nitrogen cooled cylinders with hopes of bringing them back to life once science has found a cure for the disease that caused their death. Strangely enough, the companies that provide such cryopreservation are not willing to wait for payment until their customers are reanimated.