Feeling the chill

Mountaineers face the threat of hypothermia

The damage caused to the body by even a few degrees of chill can be life-threatening - but advances in medical techniques make hypothermia a 'surviveable' condition.

The human body is finely tuned to work at almost exactly 37 degrees centigrade, and normally a combination of staying out of the worst weather, and wrapping up warm can keep it that way.

But people caught out in the open, or drenched in water can cause core temperature to drop rapidly.

Doctors define hypothermia as having a body temperature below 35 degrees, but even then, the person might not feel unwell.

Instead, the signs to look out for are erratic behaviour, and even exaggerated confidence or recklessness.

Dr Jel Coward, a GP from Tywyn in North Wales, and an expert in wilderness medicine, says: "The mental process start to slow down and the person will start to behave quite strangely."

At first, the patient will have the body's natural shivering response, designed to warm the body up, but as hypothermia increases, this will stop.

At this stage, getting a person to warmth and shelter may be enough to reverse the decline.

However, once unconsciousness sets in, and the body temperature drops much lower, attention by doctors in a hospital equipped to re-warm the patient are needed.

No pulse

An extremely cold person will , once unconscious, almost reach a state of suspended animation, with the heart rate slowing down to almost inperceptible levels - it can be hard to find a pulse on a severely hypothermic patient.

Most first aiders' initial response to a patient appearing to lack a heartbeat would be to start 'cardiac massage'.

However, research has shown that the heart rhythms of severely hypothermic patients are extremely fragile, and the sudden shock could push them into 'fibrillation', which would stop pumping and lead to death if resuscitation is stopped for any reason.

Hypothermia can kill avalanche victims

Dr Coward says: "You would have to keep resuscitating the person all the way to hospital - and if you're on a cold hillside hours away from that, it could be difficult or even impossible to do this."

Instead, some experts recommend that the adult patient is wrapped up, and taken straight to hospital without resuscitation being attempted.

The lengths of time that the human body can survive in these circumstances are remarkable.

In one case, the "shutdown" of the body was so complete that a Canadian child lived after spending 40 minutes submerged in a frozen lake.

Most experts recommend that resuscitation is carried out on children found unconscious.

Hospital techniques

Once hospital is reached, the delicate process of re-warming can begin.

One method is to pass warm water through the spaces between the organs in the abdominal cavity - in one side, and out the other.

Another, more commonly-used technique is to hook up the victim to a bypass machine, which takes blood from the body, warms it up, then puts it back in.

Dr Coward says: "It's important that anyone with severe hypothermia is taken to hospital. While mild hypothermics may respond to a warm log cabin, more serious cases will not."

He said that attempts to warm up severe cases could be counterproductive.

When the body shuts down, the blood virtually stagnates in the extremities, and cells release potassium into it.

If this blood is warmed and returned to the core, the potassium can harm the heart.