Hypothermia

Hypothermia is a fall in the body's inner temperature below 35 °C, against a normal reading of around 37 °C. It is not "being very cold" but a state in which the body no longer keeps up with the heat it is losing: muscles, heart and brain work worse and worse, and without help a person does not get out of it. The help needed is medical rather than domestic. Dangerous cooling does not require frost: wind, wet clothing and a few hours at eight degrees will do it, and in cold water the margin is measured in minutes.

What cold does to the body

At first the body defends itself: the vessels in the skin narrow so that blood does not chill at the surface, and shivering starts, the quickest way of making heat with muscle. At this stage a person is alert but clumsy, the hands stop obeying and the fingers go white.

If heat keeps draining away, the fuel in the muscles runs out, the shivering weakens and then stops altogether. That is not a sign of improvement: shivering that has stopped means the defence is spent and the temperature is still falling. The heart slows, breathing becomes sparse, the brain runs short of warmth and oxygen. Confusion and indifference set in, and the person stops grasping what is happening: they may refuse help, wander further from shelter and, in the deeper stages, even begin taking clothes off, because the vessels briefly widen and they feel hot. This is why someone who is freezing almost never saves themselves — the decisions have to be made by whoever is beside them.

The signs it is recognised by

• violent shivering that cannot be stopped by willpower;
• pale, cold, dry skin; lips, ears and fingertips turning blue or grey, easier to spot on darker skin on the palms, the soles and the inside of the lips;
• slow, slurred speech, with words hard to find;
• clumsiness: fingers defeated by a zip, laces or keys, and an unsteady walk;
• drowsiness, listlessness, indifference to everything, confusion;
• slow shallow breathing and a slow, weak pulse.

An ordinary household thermometer is no use for checking: it is built for fever and simply will not display a low reading. Go by how the person looks and speaks, not by a number.

How it looks in a baby and in an older person

In a child in the first months of life there may be no shivering at all: babies are barely able to shiver. The body feels cold to the touch, particularly the back, tummy and neck. The baby is unusually quiet, floppy, feeds poorly or refuses the breast, and the cry is weak. The skin, meanwhile, can look deceptively healthy, a bright pink. A quiet, "easy" baby who is hard to rouse in a cold room is a cause for alarm, not for relief.

In older people hypothermia happens more often in their own cold flat than out of doors, and it builds over several days. There may be no shivering, and no complaint about the cold. What the family notices is different: muddled talk, a slower pace, a whole day spent in the armchair, meals forgotten, more falls than before. It is easy to put this down to memory or tiredness when the real trouble is a home that never warms up. If an elderly relative lives alone and sounds odd on the phone during a cold spell, it is worth going round and feeling their hands and neck.

When to call an ambulance

An ambulance is called as soon as hypothermia is suspected. Waiting to see whether someone "warms up" is not an option: without measuring the inner temperature there is no way of telling how far the cooling has gone.

• the person is shivering and at the same time slurring, muddled or drifting off to sleep;
• the shivering has stopped and the state has not improved;
• the skin is cold and the lips blue or grey;
• somebody has been pulled out of cold water, even if they are still on their feet;
• a child feels cold to the touch, is limp and does not wake to a voice;
• breathing is slow and shallow, or the person is unconscious.

The single emergency number in Spain, Italy, Portugal, Poland and Ukraine is 112. Do not drive the person in yourself: they may deteriorate on the way with nobody free to help. If a car journey cannot be avoided, let someone else drive. Gather up any medicines they take and hand them to the crew.

What to do while help is on its way

• get the person indoors, or at least out of the wind;
• take off every wet garment, since damp fabric strips heat away far faster than dry; if undressing is difficult, cut the clothing off;
• wrap them in a blanket, a sleeping bag, dry towels or coats, and cover the head without fail, as a good share of the heat leaves through it;
• put something underneath them: lying on the ground or on tiles loses heat faster than lying in air;
• use your own body heat if there is nothing else: lie beside them under a shared blanket;
• offer a warm sweet drink and something sweet to eat, but only if they are fully conscious and swallowing confidently;
• keep talking to them and do not leave them alone until the crew arrives.

Handle them gently. A deeply chilled heart becomes extremely irritable: sudden movement, shaking, trying to stand someone up or rubbing them can throw the heart rhythm off. Move the person smoothly and flat, and do not make them walk unaided.

If there is no response, check the breathing carefully and unhurriedly, for up to a minute: in deep hypothermia it can be very slow and barely detectable. If you find no signs of life, start resuscitation and keep going until the crew arrives. In cold injury resuscitation is worth continuing for longer than usual, and there are known cases of full recovery after a prolonged arrest in the cold.

What not to do

• do not put the person in a hot bath or pour hot water over them;
• do not apply a hot water bottle or heat them with a lamp or heater held close: chilled skin barely registers pain and a burn happens unnoticed;
• do not rub the hands, feet or ears, whether with your palms, with snow or with spirit;
• do not give alcohol to drink: it widens the skin vessels, speeds heat loss and wipes out any ability to judge one's own condition;
• do not make them move about or send them off to "walk it out and warm up";
• do not leave someone who appears to have recovered unsupervised, and do not let them go back out into the cold.

All these prohibitions point the same way: warming has to come from the inside and gradually. Warming the surface abruptly widens the vessels of the arms and legs, and the cold blood standing in them returns to the heart all at once, so the inner temperature drops further still and blood pressure collapses.

What happens in hospital

The first steps are measuring the inner temperature with a suitable thermometer and putting the person on heart rhythm monitoring, because in the early hours the rhythm is the main threat. Warmed humidified oxygen is given, a drip with warmed fluids is set up, and a blanket that blows warm air is placed over them. Blood sugar is checked: with exhaustion or alcohol it is often low, and rewarming goes badly until it is corrected.

At the same time the team looks for what led to the cooling: a fracture after a fall, an infection, a stroke, poisoning, an underactive thyroid. In older people a low temperature often turns out to be the first sign of a serious infection rather than only the result of a cold home.

In severe cases treatment continues in intensive care, and in the most extreme the blood is warmed outside the body by passing it through a machine. Hands, feet, nose and ears are examined separately for frostbite, which is treated once the overall condition has been steadied.

Why it happens and how to avoid it

Hypothermia is almost always assembled from several circumstances at once: cold plus damp, wind, tiredness, hunger or alcohol.

• thin or soaked clothing, wet shoes, no hat; wind carries heat away far faster than still frost;
• falling into water, or simply a long swim: in water the body cools many times faster than in air at the same temperature;
• alcohol and substances that dull awareness, the usual companions of severe cases, since the person stops feeling cold and falls asleep outdoors;
• a cold home, especially for older people living alone and for anyone economising on heating;
• age: babies lose heat quickly because of their large surface area, older people because shivering is weak and the sense of cold is blunted;
• exhaustion, undernutrition, an underactive thyroid, advanced diabetes, dementia, stroke;
• sedative medicines and some drugs used for psychiatric conditions, which dampen the response to cold;
• an injury or illness that leaves somebody lying motionless for a long time on a cold floor or on the ground.

Protection rests on simple things. Dress in layers rather than one thick garment: the air trapped between layers holds heat better than the fabric does. The outer layer should keep out wind and water. Wear a hat, keep feet and hands dry, and carry spare socks and gloves. No alcohol in the cold or before going out into it. On a walk or a fishing trip, take a hot drink, food and a way of calling for help, and do not take a route alone in cold weather. At home, keep living rooms genuinely warm instead of sitting in a jumper in a chilled flat; in a baby's room, make sure the child is not cold without overheating them either.

And the most effective measure of all: during a cold spell, ring elderly relatives and neighbours who live alone, and call in on them. That is precisely where hypothermia develops quietly and with no witnesses.

Online consultation

An online appointment does not stand in for an ambulance once somebody has already become chilled: in that situation the first move is to dial 112. It is useful afterwards, though, and in advance. A doctor can go through what happened and why, assess how things stand after discharge, explain how to look after patches of skin damaged by cold and what to watch for over the following days. There is also room to discuss how to protect an older relative or a child from the cold, which of the medicines already being taken raise the risk, and what is worth keeping in the car and in a rucksack during the cold months.

This material is for information only and does not replace medical advice.