Hypothermia - Freezing to Death
A report from a Conference on Hypothermia held at Glenmore Lodge in 1997 and supported by the Scottish Mountain Safety Forum, Boots Across Scotland and SMT.
Recent tragedies in the Scottish hills have again highlighted the dangers of low body temperature, or "hypothermia" (from the Greek hypo, under; themre, heat). Humans work best at a body temperature of around 37 degrees Celsius (96F), which allows the chemical reactions that keep us alive to run smoothly. Left alone, our body temperature will approach the temperature of the surroundings. In Scotland, this usually means we will cool down! We can modify this process in different ways such as exercising to produce heat or wearing clothing and using shelter to reduce heat loss. Digesting food also produces some heat and food is essential as fuel for muscular exercise.
The two most common causes of hypothermia on the hill are exhaustion and injury. Walkers with inadequate food, clothing and shelter will not be able to sustain the level of physical work to replace the heat they are losing. Injury leads to immobility and a similar inability to generate heat – just think how you cool, off when you stop for your 'piece'.
As the body cools, various signs and symptoms will arise. Shivering is a form of muscular exercise and is the body's attempt to generate heat. As muscles cool down they become stiffer and coordination is affected so that slipping and stumbling become more common (incidentally allowing more cooling through contact with wet ground or snow and increasing the chance of injury). Coupled with this is a slowing of mental processes so that intellectual tasks (such as navigation!) become more difficult and judgement is affected. Increased urine production leads to relative dehydration.
If further cooling takes place, shivering stops. The situation is now very serious as the body is no longer generating heat and cooling will be even quicker. As the body temperature drops unconsciousness occurs and all the vital processes such as heartbeat and breathing become slower and less intense. A person who is profoundly hypothermic may appear to be dead (indeed, at the lowest levels of hypothermia, brain and heart activity may be undetectable even with sophisticated equipment). If you are on the hill you may come across just such a person. How do you decide what to do? The conference at Glenmore Lodge developed guidelines for mountain rescuers and these have been circulated amongst Mountain Rescue Teams. They may be useful to all mountaineers and walkers and are reproduced here:
Recommendations for the Evacuation of Cold Uninjured Casualties
|Definitely Alive||Conscious||Insulate from heat loss Monitor regularly Evacuate|
|Definitely Alive||Unconscious Respiration and/or pulse||Insulate from heat loss Maintain airway Evacuate in recovery position|
|May Be Alive||No Respiration No circulation (1 minute) and Airway clear and No obvious fatal injury and Temperature below 32C (if available)||Radio / Phone for medical advice with evacuation plan|
|Definitely Dead||No Respiration No circulation (1 minute) and Airway blocked by snow / ice or Obvious fatal injury or Temperature above 32C (if available)||Evacuate as Dead|
These guidelines may help you decide how urgently you need to get help and how to undertake initial management, if you feel you have the necessary skills (an "obvious fatal injury" might be the head being in a different place from the body!). If you aren't sure about pulse and breathing or the recovery position, maybe you should be thinking about a basic first aid course.
I would add to the above that it would be good to give a conscious casualty food and drink. If the drink is hot, so much the better, but it's the fluid that counts (not alcohol – which increases heat loss).
Remember that hypothermia should be preventable.
- Perhaps the most important factor is adequate clothing. Just remember you don't have to wear all of it all the time! Excessive sweating will wet clothing and reduce its insulating properties. Be prepared to "adjust your layers" and make sure you have spare clothing with you.
- A polythene survival bag will act as a wind and waterproof layer if you are injured. Seeking shelter will decrease the effect of wind-chill.
- Adequate food and drink gives your body fuel to sustain exercise.
- Keep an eye on other members of your party to watch for the early signs of hypothermia and be prepared to change your route, or go back, if necessary and remember to get other members of your party to keep an eye on you!
Further Reading: Langmuir "Mountaincraft and Leadership" has an excellent chapter on mountain hypothermia.
Website: The Workers Compensation Board of British Columbia has a comprehensive summary (pdf file)
by David Syme