Hypothermia

Hypothermia is a condition where the normal body temperature of 37°C (98.6°F) drops below 35° (95°F).

Hypothermia is usually caused by being in a cold environment. It can also be triggered by prolonged exposure (staying outdoors in cold conditions for a long time), rain, wind, sweat or being under cold water.

When your body gets cold, the normal response is to become more active to warm up, put on more layers, or move indoors. However, if exposure to the cold continues, your body's own automatic defence system will try to prevent any further heat loss by:

- shivering to make sure major organs stay at normal temperature,
- restricting blood flow to the skin, and
- releasing hormones to generate heat.

In hypothermia, these responses are not enough to maintain body temperature, and they drain energy reserves at the same time. It is when body energy is exhausted that hypothermia becomes potentially life-threatening. This can happen very quickly, so it is vital that hypothermia is treated as a medical emergency.

Elderly people and those who are ill, and unable to move around easily, are especially vulnerable to hypothermia. They may not notice that their body temperature has fallen, and their rooms may be too cold due to lack of heating. They may also not eat enough, or they may not be active enough to generate energy.

Babies are also more prone to hypothermia because their body's ability to regulate temperature isn't fully developed. They will quickly lose warmth if they stay in a cold room for too long.

Hypothermia is caused by getting too cold. This is most common in cold environments, and the risk is increased if you are not wearing enough layers to keep warm, or do not have your head covered (the largest proportion of body heat is lost through the head).

Hypothermia is also possible in mild weather. For example, if you get soaked in a rain shower and do not dry off properly soon afterwards, particularly if there is also a cool wind. The water evaporating from your skin brings down your body temperature.

Certain groups are at higher risk of hypothermia:

- Babies, who cannot regulate their body temperature as well as older children and adults), can lose heat quickly if left in a cold room. A room thermometer will help to ensure that the temperature is warm enough.
- People who spend a lot of time in extreme weather conditions, for example, climbers, walkers and skiers.
- Older people, particularly if they are not very active, do not eat enough, have other illnesses, or take medication that can interfere with the body's ability to regulate temperature.
- Homeless people who are unable to find shelter.
- Heavy drug and/or alcohol users, as these substances affect your body's ability to retain heat. The blood vessels stay dilated (widened) allowing heat to escape, and you may not be able to tell when you are cold.
- People with mental illnesses such as Alzheimer's disease may not be able to recognise the symptoms of hypothermia or tell when they are cold.
- People who have fallen into cold water, which can cause the body's core temperature to drop very quickly.
- People recovering from accidents.
- People with certain health conditions, for example, heart problems, untreated hypothyroidism, stroke and severe arthritis. These conditions can change the body's ability to respond to temperature changes, for example by affecting the extremities (fingers and toes) where you may first feel cold.
- People taking sedatives, which can interfere with the body's ability to regulate temperature.

The symptoms of hypothermia depend on how cold the environment is and how long you are exposed for. In mild cases, symptoms include:

- shivering,
- feeling cold,
- low energy,
- less able to tolerate the cold than normal
- cold, pale skin.

The symptoms of moderate hypothermia include:

- violent, uncontrollable shivering,
- inability to think or pay attention to events,
- confusion (some people don't realise they are affected),
-loss of judgement and reasoning,
- difficulty moving around or stumbling,
- feeling fearful,
- memory loss,
- fumbling hands,
- drowsiness,
- slurred speech,
- listlessness and indifference,slow,
- shallow breathing and weak pulse.The symptoms of severe hypothermia include:

- loss of control of hands, feet, and limbs,
- shivering stops,
- unconsciousness,
- shallow or no breathing,
- weak, irregular or no pulse,
- stiff muscles, and
- dilated pupils.

Even though it may appear healthy, the skin of a baby with hypothermia will feel cold. S/he may also be limp, unusually quiet and refuse to feed.

Hypothermia is generally diagnosed based on the typical symptoms and environment. For example, if a person has been exposed to cold, is distressed or confused and has slow shallow breathing you should suspect hypothermia and get medical help urgently.

If your child is unusually quiet after playing in the cold for a long time, or appears slightly confused, they may have hypothermia. The skin may look healthy, but feel cold, and babies may be limp, unusually quiet and refuse to feed. Hypothermia is a medical emergency and if you suspect that your child has the condition, you should seek immediate medical assistance.

If possible, the doctor will take a history of exposure. The core body temperature will be measured, usually by putting the thermometer into the person's rectum. For a diagnosis of hypothermia, body temperature will be below 35° (95°F).

Hypothermia is treated by preserving body heat and preventing any more being lost. If treating mild hypothermia at home, or waiting for medical treatment to arrive, you should:

- move the person indoors, or somewhere warm, as soon as possible,
- ensure that they change out of any wet clothing,
- wrap them in blankets, towels, coats whatever you have protecting the head and torso as a priority. Your own body heat can help someone with hypothermia try gently hugging them,
- increase activity if possible, but not to the point where sweating occurs, which cools the skin down again,
- if possible, give the person carbohydrates to eat to provide rapid energy, or fats to provide prolonged fuel to the body,
- give them warm drinks, but not alcohol, and
-once body temperature has increased, be sure to keep the person warm and dry.There are also some things that you should not do when treating someone with hypothermia. You should not:

- re-warm an elderly person using a bath as this may send cold blood from the body's surfaces to the heart or brain too suddenly, and may cause a stroke or heart attack,
- apply direct heat (hot water, a heating pad etc.) to the arms and legs as this forces cold blood back to the major organs, making the condition worse,
-rub or massage the person as, in severe cases of hypothermia, there is a risk of heart attack. It is s therefore important to be gentle, and
- give the person alcohol to drink, as this will decrease the body's ability to retain heat.Severe hypothermia needs urgent medical treatment in hospital. Shivering is a good guide to how severe the hypothermia is. If the person can stop shivering of their own accord, hypothermia is mild, but if they cannot stop shivering, it is moderate to severe.

Medical treatment aims to warm up the body from the inside. Doctors do this by giving warm fluids intravenously (through a vein). In some cases, haemodialysis may be used. This is a treatment to take blood out of the body and warm it up before returning it. The blood is filtered through an artificial kidney, much like dialysis treatment for people with kidney failure.

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There are some things you can do to reduce your risk of hypothermia:

- If the weathers cold, make sure you're dressed appropriately before you go outside. Most body heat is lost through the head, so wear a warm hat.
- Layers of clothing trap air, which helps to keep you warm tightly woven, waterproof clothes are best. A scarf and gloves are a good idea too. Children don't always realise how cold they are when playing outdoors, so make sure they're wrapped up warm.
- If you have a baby, put a room thermometer in the room where they sleep to monitor the temperature. It should be between 16-20 °C (60.8 - 68 °F).
- Drink plenty of fluids and hot drinks (not alcohol) and eat regular, balanced meals to give you energy.
- Keep active when it's cold, but not to the point where you're sweating. If you exercise outdoors in the winter and get sweaty from this, make sure you dry off and put on warm clothes immediately after.
- Keep dry and change out of wet clothes as soon as possible. Wet clothes lose about 90% of their insulating power.
- Cut down on alcohol, caffeine and nicotine as all three aggravate heat loss.
- Keep your house warm during cold weather. If you're concerned about heating costs, you could try just keeping one room in the house warm. Keeping windows and doors closed also helps to trap heat. The government now offers winter fuel payments for people who are vulnerable to hypothermia, (for example older people living alone). You can check out whether you are eligible at the Department of Social Security website (see links).
- See your GP regularly to manage any illnesses effectively, and ask whether medication you may be taking affects the ability to regulate body temperature. NHSOCT08