It’s really important to know about this and to be able to recognise the symptoms – it could save a life. Of course hypothermia doesn’t only happen in extremely cold weather. In fact it’s more common in countries like the UK that have regular wet and cool weather.
Hypothermia occurs when the body temperature drops below that required for normal metabolism and bodily functions. In warm-blooded animals, core body temperature is always maintained at a near constant level but when the body is exposed to cold its internal mechanisms may be unable to replenish the heat that is being lost to the surroundings. Normal body temperature in humans is 36.6°C. Some people run a tiny bit hotter, some a tiny bit colder.
Hypothermia can be divided into three progressive stages of severity:
- Body temperature drops by 1-2°C (between 34.6 – 35.6°C)
- Mild to strong shivering occurs.
- The casualty is unable to perform complex tasks with the hands; the hands become numb.
- Breathing becomes quicker and shallow.
- Goose bumps form.
- Body temperature drops by 2-4°C (between 32.6 – 34.6°C).
- Shivering becomes more violent.
- Lack of muscle coordination becomes apparent.
- Movements are slow and laboured, accompanied by a stumbling pace and mild confusion, although the casualty may appear alert.
- The casualty becomes pale. Lips, ears, fingers and toes may become blue.
- Body temperature drops below approximately 32 °C.
- Shivering usually stops.
- Difficulty speaking. Sluggish thinking and amnesia start to appear.
- Inability to use hands and stumbling is also usually present.
- When body temperature drops below 30 °C exposed skin becomes blue and puffy. Muscle coordination becomes very poor. Walking becomes almost impossible. The casualty may exhibit incoherent or irrational behaviour.
- Pulse and respiration rates decrease significantly but fast heart rates can occur.
- Cellular metabolic processes shut down.
- Major organs fail.
- Clinical death occurs.
In cold weather, especially cold, wet weather, always be alert to the possibility of hypothermia. If in a group all members of the group should be on the lookout for symptoms in other members of the group. Prompt action at this stage will allow the casualty to be kept mobile and allow a speedy retreat to safety.
The immediate necessity is to seek shelter from the weather. Out on the trail a group shelter is ideal for this purpose. Once out of the wind, if practical, every effort should be made to get the casualty into dry clothing. The casualty should then be put into a sleeping bag, survival bag or bivvy bag with as much insulation between them and the ground as possible. If it wasn’t possible to change out of wet clothes use a plastic survival bag between the casualty and any insulation such as sleeping bags to prevent them becoming wet and reducing their efficiency.
A hot drink and something to eat complete the early treatment. The rest of the group should huddle round to provide moral support, more shelter and warmth.
Recovery can be rapid but is unlikely to take less than half an hour. Insist on a proper rest period and do not proceed until you are absolutely certain that recovery is complete. Redistribute the casualty’s load between the group and find the quickest and easiest route back to civilisation or base camp.
Summon help – at this point it’s a job for a medical professional. If you’re likely to be in this situation outside the reach of emergency services you need to get yourself some proper medical training. The essential and immediate priority is to prevent further heat loss by providing good insulation all round the casualty. Further treatment is a very specialised and risk-laden business and way outside the scope of my experience.
The ability of humans, not only to survive, but to live comfortably in extremely cold environments is almost entirely due to fitness, appropriate clothing, preparation and experience in avoidance.
- Ensure that the equipment and clothing worn is sufficient for the conditions expected and takes account of sudden and unexpected changes. Waterproof clothing is a must and is effective when worn over wet clothes as it reduces cooling due to evaporation.
- Adequate food and water should be available.
- Emergency food and equipment should be carried.
- When on a walking expedition, progressive training is important. Pace should be regulated carefully to take account of the fitness of all members of the group.
- Take care when carrying loads. Progressive training should include training for carrying this weight.
- Good planning and good morale leads to increased safety.
- It is worth noting that hypothermia doesn’t just happen in extreme cold. In fact it’s more common in temperate regions.
In a situation where hypothermia is imminent there’s a great temptation to push on in order to keep generating heat from activity and to reach safety. This may not be the best option since the activity increases the rate of heat loss and aggravates exhaustion. In bad weather trying to press on regardless has resulted in many deaths, whereas those who take shelter until the weather improve usually survive.