In cold blood - how therapeutic hypothermia can save lives

In cold blood: how therapeutic hypothermia can save lives

We all know that hypothermia can kill – but increasingly, it’s also being used to save lives.

Early on the morning of 30 December 2007, a drunk 41-year-old man left a party in the city of Stokmarknes, in northern Norway. Soon after, he slipped and fell into a steep-sided ditch. Plunged neck-deep in the freezing water, he was unable to get out and spent nearly an hour in the ditch before passers-by spotted him and hauled him out.

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Despite their best efforts to warm him up, the man remained severely chilled, largely thanks to the air temperature being a biting -2°C. Shortly after the paramedics arrived, he fell unconscious, stopped breathing and went into cardiac arrest. It would be seven hours before his heart started beating properly again, and for five of those he was technically dead. Somehow the extreme cold – the very thing that had caused the man’s heart attack in the first place – had saved his life.

In healthy humans, the body maintains a core temperature of between 36.5 and 37.5°C – anything below this is a dangerous condition known as hypothermia. When someone’s body enters a hypothermic state, their metabolism slows down, their heart rate slows, organs start to shut down and eventually, their heart stops beating. Within a few minutes of the heart stopping, the body’s oxygen reserves are depleted and cells start to produce toxic chemicals. This quickly starts to cause irreversible damage to the delicate tissues of the brain. Even if resuscitation is successful, the danger is not over: most cardiac arrest patients whose hearts are restarted end up dying in hospital from the damage caused by the return of oxygenated blood throughout the body; up to 30 per cent suffer permanent brain damage.

However, there’s an old saying in the medical profession: “No one’s dead until they’re warm and dead”. In cases of cardiac arrest caused by extreme cold, an extraordinary thing can happen: the reduction in body temperature reduces the brain’s need for oxygen. If cooling is rapid enough, it can help prevent toxic chemicals accumulating while the heart has stopped, and continues to protect the brain when oxygenated blood returns.

The Norwegian man arrived at a nearby hospital at 5am, with a temperature of just 25.5°C – easily in the most severe category of hypothermia. After attempts to warm him failed, medics called for a helicopter from the University Hospital of North Norway (UNN), a better-equipped medical centre over 250km away. Doctors continued to do CPR on the man, but by the time the helicopter reached UNN with the patient onboard it was nearly 9am. He had been technically dead for nearly five hours.

At 11.37am, after hours of work by teams of UNN staff, the man plucked from the icy ditch was finally revived, and weaned off machines that had been artificially pumping blood around his body. It had been nearly seven hours since he had entered cardiac arrest – one of the longest resuscitation periods ever recorded. Miraculously, he went on to make a full recovery, with no signs of brain damage at all.

“His metabolism had decreased by…

This is an extract from issue 322 of BBC Focus magazine.

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