Hypothermia occurs when the body's temperature falls below 35 °C. Severe hypothermia can be fatal without prompt medical treatment. Symptoms of hypothermia include feeling cold, pale skin, shivering, loss of concentration, drowsiness, confusion, dizziness, slurred speech, dilated pupils and slowed breathing. First aid for hypothermia includes keeping the person still and not massaging or rubbing the affected person.
Hypothermia occurs when the body’s temperature falls below 35 °C. The human body has a number of systems that maintain a constant core temperature of around 37 °C. A person doesn’t have to be in subzero temperatures to risk hypothermia – it often happens in temperatures ranging from 0 to 10 °C.
A person can also become hypothermic as a result of some medical conditions. People who lie immobile following a stroke or after taking drugs, for example, can become cold in a surprisingly short time.
Some situations can cause the body to lose more heat than it can generate. These situations can include:
- Prolonged exposure to cold conditions
- Being in cold water for a long time
- Spending excessive time in wet clothes
- Lying immobile in cool air or on a cold surface
Signs and symptoms of hypothermia
The first warning sign of hypothermia is uncontrollable shivering. The person stops shivering as they progress into severe hypothermia. The person may fall into a coma as the body temperature falls below 32 °C.
Once the brain cools to around 30 °C, the structure that regulates body temperature (hypothalamus) stops working. The person’s breathing and heart beat slows severely until it becomes undetectable. The heart no longer pumps blood effectively and the body is starved of oxygen. This is eventually fatal without prompt treatment. However, people with severe hypothermia can demonstrate an amazing capacity to recover if managed correctly.
Stages of hypothermia symptoms
The symptoms of hypothermia can progress slowly and people are often not aware they need medical help. The stages can include:
- Feeling cold
- Cool, pale skin
- Loss of concentration, poor judgement
- Loss of control over fine motor coordination – for example, the muscles of the fingers
- Confusion, irritability
- Difficulty breathing
- Loss of physical coordination, unsteady on feet
- Stops shivering eventually
- Slurred speech, speech difficulty
- Slowed breathing
- Dilated pupils
Risk factors for hypothermia
Factors that may increase a person’s susceptibility to hypothermia include:
- Infancy – children lose heat more quickly than adults, mostly through their head. This is particularly so for babies, who must be protected from the cold
- Old age – people taking medications or suffering other health problems may be less able to regulate their own body heat or detect that they are being affected by temperature. They may also be less able to move about or make necessary changes to help
- Heart problems
- Circulatory system disorders
- A thin body or low body fat
- Cigarette smoking
- Physical exertion.
Severe hypothermia is life-threatening
Mild hypothermia (32–35 °C body temperature) is usually easy to treat. However, the risk of death increases as the core body temperature drops below 32 °C. If core body temperature is lower than 28 °C, the condition is life-threatening without immediate medical attention. Under this temperature, a person will be very cold to touch, unresponsive, rigid, not breathing, have no pulse, and their pupils will be fixed (they will not respond to light changes). They will appear to be dead but they may not be.
First aid for severe hypothermia
First aid steps for severe hypothermia include:
- In an emergency, call triple zero (000).
- While waiting for help to arrive, monitor the person’s breathing. If they have severe hypothermia, their breathing may become dangerously slow or shallow or they may cease breathing.
- Begin cardiopulmonary resuscitation (CPR) immediately if the person shows no signs of life; that is, if they are not breathing normally, are unconscious or unresponsive, or not moving.
First aid for all cases of hypothermia
These first aid tips apply to all stages of hypothermia:
- Don’t massage or rub the person – and do not allow them to help you. Keep them still or they risk a heart attack. If they move, the muscular activity will pump cold blood from their arms and legs into the central circulation and cause their core temperature to drop even more.
- Move the person out of the cold – if this is not possible, protect them from wind, cover their head and insulate their body from the cold ground.
- Remove wet clothing – replace with a dry covering, preferably warm. Cover the person’s head.
- Try to warm the person – but do not apply direct heat. Apply warm compresses to the neck, chest wall and groin. Do not use hot water, a heating pad or a heating lamp to warm the person. Do not attempt to warm the arms and legs – this will send cold blood back to the heart, causing body temperature to drop further.
- Share body heat – to warm the person’s body, remove your clothing and lie next to the person, making skin-to-skin contact. Then cover both bodies with a blanket or get into a sleeping bag if possible.
- Don’t give alcohol – it lowers the body’s ability to retain heat. If the person is alert and is able to swallow, have them drink warm, non-alcoholic beverages. Do not offer liquids if vomiting.
- Do not leave the person alone – stay with them at all times.
- Continually monitor breathing – if the person’s breathing stops, start cardiopulmonary resuscitation (CPR) immediately if you are trained. If unsure, dial triple zero (000) – operators will advise you what to do. Continue CPR until the person starts breathing on their own or until medical assistance arrives.
- Don’t assume the person is dead – CPR can be lifesaving for a person with severe hypothermia who may appear to be dead. They may not be breathing, have no pulse, be cold to touch, have fixed pupils and be rigid – but they may still be alive.
Preventing hypothermia when outdoors
Exposure to cold weather, even for a short time, can be dangerous if you are not prepared. Shivering and feeling cold or numb are warning signs that the body is losing too much heat.
Simple ways to prevent hypothermia include:
- Avoid prolonged exposure to cold weather.
- Be alert to weather conditions that may increase the risk of hypothermia and act accordingly; for example, seek shelter during a snowstorm.
- Wear several layers of clothing to trap body heat, rather than just one bulky layer. Natural fibres like wool are better at holding heat.
- Use a weatherproof outer layer to stay dry.
- Use gloves, scarves and socks, with spares to replace when wet.
- Wear insulated boots.
- Wear warm headgear – a lot of body heat is lost through the scalp.
- Make sure your clothes and boots aren’t too tight. If your blood circulation is restricted, you are more prone to hypothermia.
- Drink plenty of fluids.
- Eat regularly.
- Take regular breaks to reduce the risk of physical fatigue.
- Keep your eye on exact body temperature by taking a clinical thermometer in your first aid kit.
- Change out of wet clothes straight away.
- Avoid alcohol, cigarettes and caffeine.
- Make sure your kit includes a good supply of waterproof matches.
Use a buddy system
When participating in any outdoor activity that has the potential risk of hypothermia, such as bushwalking or mountaineering, use the ‘buddy system’ and check each other for warning signs. You may not be able to recognise your own symptoms of hypothermia due to mental confusion. First aid training is strongly advised.
Hypothermia at home
Hypothermia can occur in the home. The elderly and some people with medical conditions are more susceptible to hypothermia. The risk can be reduced by:
- Ensuring there is adequate heat in the home
- Seeking assistance from government agencies for help with heating, food and clothing if necessary
- Having regular medical check-ups.
Where to get help
- In an emergency, call triple zero (000)
- Your doctor
- The emergency department of your nearest hospital
Things to remember
- Hypothermia occurs when the body’s temperature falls below 35 °C.
- Hypothermia can easily happen in temperatures ranging from 0 to 10 °C.
- Severe hypothermia is life-threatening without prompt medical attention.
You might also be interested in:
- Canoeing and kayaking - preventing injury.
- Emergencies - calling triple zero 000.
- Emergencies - when to call an ambulance.
- Fishing - preventing injury.
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Last reviewed: October 2011
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