Hypothermia is the name given to the condition when the core temperature of the human body falls bellow the required normal operating temperature. It is opposed by Heat Stroke which is the when the core temperature gets too warm.
If left to progress it is fatal.
Our normal core temperature is about 37 degrees centigrade (98°F) with a fluctuation of +/- 1.5 °C for men and 1.2°C for women.
As the core temperature falls, there are 3 distinct stages of hypothermia, each increasingly difficulty to recover from by re-warming.
When the core temperature falls by just a few degrees (as little as 5 °C), We enter the first stage of hypothermia.
At 35 °C to 32 °C we begin to show mild behavioral symptoms known as the “Umbles”
We must look out for these signs on others and ourselves. People may show abnormal self concern or become irritable with no obvious cause. If somebody is acting like this and it is out of character for them, it is time to stop and rewarm them.
Likewise if somebody goes quiet, it is time to take action.
At 34 °C, uncontrollable shivering sets in. This is the body’s response in which it tried to generate some movement and therefore heat to rewarm it’s self. This should never be ignored. If you or somebody else is shivering uncontrollably, it is time to stop and take action to rewarm. It should be remembered that alcohol and some drugs can inhibit this response.
At about 32°C the shivering stops, it has not worked so the body moves on to it’s next defensive measure. At this stage, the casualty begins to become overcome by the symptoms and their ability to rewarm themselves is diminished. This makes it very important to spot hypothermia early and take action straight away.
At 32°C and below, casualties begin to display the following symptoms
they may slur their speech, display reduced dexterity and have difficulty co-coordinating their arms and legs
- Slurred speech
- Staggering around like a drunk person
- Cold and pale skin (more than usual)
- Fast, shallow breathing
These symptoms do not lend themselves to a well ordered, organised person and they may loose vital items such as their gloves or hat.
The next stage is accompanied by unconsciousness as the body continues to cool to around 30°C. At this stage, if alone, the casualty becomes totally helpless and will likely die as they are unable to take any action to rewarm themselves let alone prevent further heat loss.
Vital signs weaken and and it may be very difficult or impossible to detect a pulse or breathing although they may actually still be alive as cooling of the body, as is used in some therapeutic treatments, leads to a general slowdown and a kind of preservation. A doctor is required to pronounce a hypothermia casualty dead although in a remote wilderness scenario, with no means to rewarm the casualty and hope of evacuation, the writing is on the wall.
People often equate hypothermia to cold climates such as the Arctic or Antarctic. This is not really accurate. Hypothermia can get us almost anywhere. Hypothermia comes into play when the air temperature gets to about 12 °C and lower or when people are just not wearing enough dry clothing.
It is actually very rare for people to succumb in these regions of extreme cold as just by being there, they are very likely to be aware, prepared and dressed accordingly.
The cure for hypothermia is to rewarm the body as restore the core temperature.
What to Do
- Prevent further heat loss
- Adjust clothing (tucking everything in helps a lot)
- Remove anything that is wet – water conducts heat away form the body about 25 time faster than air, no clothing is often better than saturated clothing
- Add additional layers and put a warm hat on
- Seek shelter from the wind
- If a cabin is available, go inside
- Start a fire or stove
- Get into a dry sleeping bag if available
- If the situation demands it, a second, healthy person can get into the sleeping bag with the casualty, using their body heat to warm the sleeping bag and casualty. Skin to skin contact is very helpful. Men: It is not gay, just do it.
- Ensure that they are well insulated from the ground with a foam mat or thermarest type sleeping mat. Spruce boughs or other “springy”, dry vegetation will also work.
- Use a second sleeping bag to wrap them in and then wrap a tarp around that to seal the warmth in and prevent the wind from stealing any heat from them.
- Eat something, high sugar foods are best. Digestion generates heat, it is extremely helpful.
- Have a nice cup of sweet, sugar tea or just warm water if that is all you have.
- Gently and progressively rewarm, do not introduce sudden high temperatures
What not to Do
- Do not put the casualty into a hot bath – this can lead to cardiac arrest
- Do not massage limbs
- Do not use heating lamps or introduce other sudden temperature increases
- Do not give them Alcohol to perk them up, this is dangerous
- Rewarm them too quickly
As with most things, Prevention is better than the cure
Wearing layered clothing and adapting the layers to the conditions helps a lot. For example, if you are walking or working hard, you will be generating heat. It is important to take steps to ensure that you do not sweat and that excess heat can be released. At this time, you want minimum layers on.
When you stop working, you will not be generating heat and will begin to cool, at this point you want to be putting layers on.
When you sweat in cold climates, that moisture will collect on your clothing and then freeze. We don”t want this obviously, see this picture of me.
Cold weather clothing is a bit topic and will be covered in another post but for now I will suggest to you that hypothermia often occurs as a result of unpreparedness or as a result of a small mistake made early on that has cascaded into a larger, more serious problem now.
For example; Putting your gloves down on the cold snow or ice or dropping your hat onto the floor when doing something, that will just make your gloves and hat cold which will lead to cold hands and cold head which will lead to a lower core temperature.
Another example could be; Somebody has gone outside utterly unprepared and wearing inadequate clothing, perhaps out for a run so has only worn the minimum so that they do not overheat. They twist an ankle and become unable to walk and have to spend more time outside than they anticipated. In their immobile, weakened state, they are now vulnerable.
Certain demographics are more vulnerable than others however nobody is invulnerable. Generally speaking, the very young and the very old are particularly vulnerable as is anyone who has become weakened by injury or fatigue.
Further reading can be found here in this PDF from the Department of Health and Social Services Division of Public Health Section of Community Health and EMS
For some reason that is link is hosted by the university of Manitoba so just in case that link does not work you can download it from me AlaskaColdGuidelines05