Hypothermia is subnormal body temperature that occurs when the body loses heat faster than it can produce it. It is most often caused by exposure to cold weather. Other factors that may contribute to the onset of hypothermia include over-exertion, inadequate food and fluid intake, immobility and lack of shelter. While usually associated with below freezing temps, it is worth noting that hypothermia can occur any time that cool (not necessarily cold), wet and windy conditions are prevalent.
Cold-related maladies such as hypothermia and frostbite are far easier to prevent than they are to cure. Here are eight proactive measures that hikers can take in order to avoid hypothermia:
1. Forecast: Always check the forecast before setting out. Adapting is a lot easier if you know what’s coming.
2. Awareness: Watch the weather (forecasts can sometimes by wrong) and know your limitations. If conditions are deteriorating and you’re feeling exhausted, don’t hesitate to set up your shelter and call it a day.
3. Layering: By dressing in multiple lighter layers, as opposed to a single thick or bulky layer, the hiker is able to better adapt to a wider range of conditions. Layers can be removed or added according to the weather and/or exertion level at any given time.
Ideally your clothing selections should compliment one another, so that each layer works together as part of a flexible overall system, designed to maximize efficiency and minimize duplicity. For more information, see Hiking Clothing.
4. Monitor the Extremities: Pay particular attention to the extremities. Your head, hands and feet constitute the body’s initial warning system when hiking in cold, wet and windy conditions.
5. Minimize sweating: Over-dressing and over-exerting can lead to excessive perspiration, which in turn can result in a lowering of body temperature. Make sweating as little as possible a priority in cold conditions (see Layering above). Think tortoise rather than hare, and do your best to maintain a steady pace throughout the hiking day. If the environment in which you are venturing isn’t too exposed or prone to high winds, consider bringing along an umbrella. They can’t be beat when it comes to ventilation.
6. Short breaks: The longer you stop the colder you become. When the weather turns nasty, keep breaks short and to a minimum. If you are taking a longer break, put on an extra layer or two.
7. Food: During the day eat high-energy snacks at regular intervals. Before going to bed, your evening meal should emphasize fats and proteins, which are processed slower by your digestive system, thereby keeping you warmer during the night.
8. Hydration: When conditions are cold and the sun is no where to be seen, hikers often forget to drink enough water. This is a mistake. If you are dehydrated you are more susceptible to hypothermia (see Hydration for details).
Symptoms and Treatment
The onset of hypothermia is typically gradual and the victim is often unaware that they require emergency medical treatment. Physical and mental capabilities are progressively diminished, therefore the key to successfully treating hypothermia is early recognition.
If you are hiking in a group, be alert to any changes in the demeanour of your trekking mates. If you are hiking solo, you need to be even more vigilant in regards to monitoring your own physical and mental state. If you notice changes, take preventative measures sooner rather than later.
Symptoms of mild to moderate hypothermia include:
- Slurred speech
- Loss of balance and coordination
- Loss of dexterity in the fingers
- Slowing in the response mechanism
Severe cases of hypothermia (i.e. when body temperature drops below 28C / 82F) exhibit the following additional symptoms:
- Shallow or no breathing.
- Weak or irregular pulse.
- Dilated pupils
- Muscle rigidity
- Increasingly pale skin colour.
- Progressive loss of consciousness
In treating hypothermia the objective is to prevent further heat loss and slowly rewarm the patient. Note that severe hypothermia is a potentially fatal medical condition. In such cases, every possible effort should be made to contact an emergency response team. To treat someone with hypothermia take the following steps:
- Find or set up shelter.
- Remove wet clothing.
- Put on something warm and dry.
- Get into sleeping bag. Be sure to lay out a sleeping mat first in order to insure sufficient insulation from the ground.
- Eat high-energy snacks such as chocolate.
- Drink warm fluids. Avoid coffee and alcohol which dehydrate and accelerate heat loss.
- If you are shivering and happen to be hiking in a group, share your sleeping bag with someone who is warm and dry.
- Focus on rewarming the centre of the body – groin, stomach, chest, neck and head. Warm (not hot) compresses are ideal. DO NOT attempt to rewarm the limbs as this will push cold blood back towards the lungs, heart and brain.
- It is common for people suffering from severe hypothermia to also have frostbite. DO NOT rub frostbitten areas, as this can severely damage the affected tissues.
- If the victim’s breathing has either stopped or appears threateningly slow or weak, begin CPR immediately.
For an excellent online overview of hypothermia and other cold weather maladies, see Princeton University’s Outdoor Action Website.