There are several ways to prevent hypothermia, the first is quite simple; start with a general knowledge of what it is, so let’s define it:
Hypothermia is an abnormal body temperature below 95°F (35°C).
The next is to understand what causes it.
Hypothermia can result from insufficient heat production, an increase in heat loss, or a combination of both.
There are several signs and symptoms of hypothermia, but they are generally broken down into 3 categories of mild, moderate and severe:
- Mild: 96.8°F (36°C) maximum shivering (how the body generates heat to compensate), increased heart rate and breathing.
- Mild/moderate: 93.2°F (34°C) slurred speech, impaired judgement.
- Moderate: 86°F (30°C) slowed breathing and hear rate, atrial fibrillation (A-fib; upper chambers of heart pump erratically)
- Severe: <86°F (30°C) fixed and dilated pupils, loss of deep tendon reflexes, heart rate/breathing at half of normal rate, ventricular fibrillation (V-fib; cardiac dysrhythmia)
But knowing what it is, and what causes it is only half the battle of survival. One needs to know steps to take to prevent it. This is actually fairly easy. Let’s start with your decisions in the pre-planning phase. Where are you going, and how are you getting around? Understanding your environment is the next piece of the knowledge puzzle to fit into place. Are you going somewhere hot, or cold? Dry or humid? Is it windy? Is there shelter? Are you isolated?
A common misconception is that hypothermia only happens in extreme cold environments. This simply isn’t true. Does it mostly happen in cold environments? Yes, sure. But can it ONLY happen in cold environments? Absolutely not. Let’s go back to the definition: “an abnormal CBT (core body temp) of less than 95°F”. This means that ANY time conditions are met to facilitate this, hypothermia can set in. Let’s say it’s sunny, but very windy, and you are sweating a lot due to great physical exertion, or you fall into a creek or stream, and you are wearing cotton clothing. A decent sustained wind can lead to rapid heat loss through convection and evaporation, and hypothermia can set in.
Perhaps you find yourself submerged in water with no foreseeable exit in the near future. Anytime you are submerged in water that is colder than your body temp for sustained periods of time, you also run the risk of hypothermia.
So, what can you actually DO now to prevent it and increase your odds of survival? To begin with, buy the appropriate gear. Here are some options and general principles to live by (in my opinion):
- Wool is your friend. (if you are not allergic to it). Wool socks/shirts/long-johns will go a long way in the prevention of hypothermia, as will wool knit caps, and wool outer-wear. Wool insulates extremely well, dries fast, and has flame-resistance properties. It’s relatively lightweight, and fairly strong.
- Live by the old adage that “cotton kills”. Without going into the scientific specifics too much, cotton releases heat much faster than wool, and stays wet longer. Since hypothermia is the result of heat loss quicker than heat creation, losing heat is something you don’t want to encourage. The longer you stay wet, via water or sweat, the better your chances of getting hypothermia. A cotton T-shirt may be fine for a day hike in Hollywood hills, CA, but try to steer clear of it otherwise.
- If you can’t swing wool for allergy reasons, synthetics are a good second choice. Me telling you what synthetics are best is like me telling you an ESEE is better than a Ontario knife. It usually sparks a fight. But generally speaking synthetics are cheaper than down, and some like North Face’s Thermoball have a reputation for being a GREAT substitute for it. There poly-blends, and nylon blends, but again, back to the knife analogy, YOU need to try a few and find out what your body responds best to. (pro-tip: if something does NOT work for you, you can sell it on trading post pages on facebook, or other forums. People WILL buy used gear if the price is right).
- Down is great, and lightweight, but… you must keep it dry, it doesn’t do well in humid conditions, and it’s very expensive. It also loses it’s insulating ability as it gets dirty, and loses “fluff”. It’s the fluff, the trapping of air between the feathers that gives down it’s legendary insulation properties, so when it gets wet or matted down, it’s not as useful.
- Fleece. Gotta love fleece. It’s great if you’re going to be very active, as it’s a relatively rugged material compared to say, cotton or down. It’s also lightweight, and dries quickly. It’s not as lightweight as down, nor does is pack away as small as down, but it’s a good option when your budget doesn’t call for down, and you know getting wet may be unavoidable.
So now that we’ve gone over gear, let’s get to some other tips:
Sweating in high winds can cause hypothermia. So, pack a couple extra inner liners, and when you get sweat-soaked, find cover, find shelter from the wind, and change out the sweaty/wet liner for a dry one. Avoid getting wet in similar conditions for the same reasons.
Stay off ridge-lines and windward sides of terrain if you can. The wind on a ridge-line is stronger than say, in a draw, or on the leeward side of a hill or mountain. Remember, windward is the side of a mountain or hill that faces the direction the wind is coming FROM, while leeward is simply the side of the hill/mountain that doesn’t take a direct hit from the wind. This is something you want to commit to memory.
Stay near possible sources of shelter. Hiking through wide open planes is nice, if the weather is guaranteed, which it never is. Staying near a treeline or forest edge will provide field expedient shelter and cover should the elements take a turn for the worse.
Pay attention the sign/symptoms of hypothermia, stop and begin management at the first sign. Do not attempt to “press on” or go much further for shelter and fire. Doing so could lead to loss of fine motor skills and prevent you from creating shelter or fire.
Management of hypothermia:
If the patient is ALERT, shivering and responds appropriately (body temp between 90°-95°F), begin active rewarming (heat packs, hot water bottles to the groin, axillary and cervical regions). Warm fluids by mouth if they can swallow. If the patient is NOT alert, or not shivering, never attempt active rewarming. Doing so could cause a fatal cardiac arrhythmia that requires defibrillation. In this case, use passive rewarming (light a fire nearby, but not too close, after the removal of any wet clothing, and provide a dry blanket or jacket).
Again, in a total submersion scenario, the above may not be an option for quite some time, so utilization of the H.E.L.P. and “Huddle” methods may be your only options there.
All this said, knowledge is your best weapon to battle hypothermia, as it leads to informed action. Prepare well, and understand management, and hypothermia does not have to happen to you.
*sources: Mosby’s Paramedic by Mick J. Sanders EMT-P, MSA (4th ed. ©2012 Mosby Inc.)
Ne te quaesiveris extra.