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Hypothermia

Posted Nov 13 2012 1:20pm

Breaks must be kept very short in the winter.

The following information was provided by ORT’s Certified.  The following are his credentials, guess why we call him Certified?  He will be one of our instructors Saturday December 15th for the Class V training. Folks can sign up for this day only, there is no fitness test requirement for attending Saturday.

American Medical Response

Reach & Treat Team WEMT-P, FTO

BS, NREMT-Paramedic

Charles. Svela@emsc.net

Association of Professional Patrollers

Board Member

NSP/APP Certified Patroller

AAI/AMGA Avalanche Forecaster

NSP Avalanche Instructor

 

HYPOTHERMIA/ HEAT LOSS

The human body is somewhat like that perfect bowl of porridge in “Goldilocks and the Three Bears.” It’s not too hot, not too cold, but just right.

Our bodies maintain internal body temperatures that allow our insides to keep on cooking without burning up or slowing down — usually around 98.6 degrees Fahrenheit (37 degrees Celsius). There’s even a part of our brain called the Hypothalamus that regulates this internal heat to keep everything running smoothly.

 

But when that core temperature of major organs drops down to 95 degrees or lower, it is called Hypothermia. Just like when you have a high fever, hypothermia can slow your body and possibly lead to death.

When it comes to our bodies, a lot depends on heat. Heat is the byproduct of biochemical reactions within our bodies. The food and beverages we consume are just like the wood and kindling that make a fire. Our bodies gain energy from food, and that energy pumps our hearts, grows our hair and helps our digestive track break that food down into usable units. This process is called metabolism

 

Think about all of the internal processes that take place when you run. It requires energy to move so many parts of your body at the same time. When all those parts crank up, we burn up energy, producing heat.

In the cold, our bodies strive to retain as much heat, or energy, as possible. In many parts of the body, blood vessels in our skin tissue constrict, or tighten up. This tightening helps keeps blood away from the cold outer layer of the body and helps circulate warmer blood to our core areas. This tightening is also why you may feel stiff after being in the cold for a long time.

 

However, areas with large blood vessels, particularly around the head, neck, chest and groin, are more susceptible to heat loss because those blood vessels don’t constrict as effectively as the smaller ones near the skin. ­With all of these internal actions and reactions taking place within the body, what can we do to protect our core temperature and defend ourselves from hypothermia?

 

While it is important to keep our bodies properly warm, it is equally important for us to be able to cool down. But in certain environmental conditions our bodies cool down too much. Our temperatures drop too far when they dip into hypothermic internal temperatures of 95 degrees and lower.

 

HEAT LOSS- 5 METHODS
In life there are 5 main methods of heat loss. This becomes very important to understand when we place it in the context of wilderness living or wilderness survival.

  1. Radiation
  2. Respiration
  3. Convection
  4. Conduction
  5. Perspiration and Moisture

Radiation- This method is simply the loss of heat, outwardly and upward into space. Our bodies create heat from energy and so we are always venting this heat through the process of Radiation. Approximately 60%-85% of our internal heat vents out our heads, faces and neck regions. That is a lot of Radiation! This is especially so when we are in extreme conditions. When it is very cold outside, if we don’t make sure our heads and necks are covered our bodies are going to have to work extra hard to stay warm within. This extra work will wear us down and make us susceptible to coldness. This goes opposite if we are in extreme heat. The neck and head should be allowed to vent this excess heat from within our bodies. Look to the fire for the properties of Radiation. Light a fire and stand by it. Observe where the heat goes and you will have a good idea of what happens with our body heat. 30-35% of our body heat is lost through Radiation! We constantly release heat in the form of radiation. In the same way the sun emits heat down on us as we bask on a beach our bodies exude heat as a natural by-product of our metabolism

Respiration- When we breathe we exhale heat from our lungs. This is not much of a heat loss but in extreme conditions it can make a huge difference. When it is very hot birds will sit around with their beaks hanging open. This is the same as dogs panting. It is a way to vent heat from the body. The same thing happens in extreme cold. This is why when you go outdoors in subzero temps for a good while or plan on spending the night outside, it is wise to cover your mouth with a face mask of some sort. A good 10% of our heat is lost through Respiration, breathing!

Convection- How does a convection oven work? Air flow. Convection outdoors is the process of heat being affected by the movement of air. This can also be termed “wind chill”. If it is cold and you allow wind to access your body you are losing lots of heat through Convection. It is essential to protect the body from the wind during times of coldness. Houses lose heat through Convection all the time. In winter you may notice it is much harder to keep your house warm when it is windy outside verses calm. This is due to the process of Convection. The moving air blows away our heat that exists between the layers of our clothes. About 50% of our heat is lost through Convection!
If we give away heat to something in motion, however, convection takes place. When wind puts air particles in motion, they take away heat as they hit our bodies and move away. That’s why a wind chill can make it feel colder outside than the true temperature.

Conduction- This method of heat loss is when a warm object comes in contact with a cold object. The fact is Cold draws and shrinks while heat pushes and expands. Our inner heat is in a constant state of expansion- out and up. If we sit on a cold surface our body will lose heat through that cold surface because the heat naturally vents out and cold naturally draws. So the cold surface draws the heat right out of our body and drains us through Conduction. This is why you should never sit on the cold ground when you are cool or trying to conserve your body heat. Never sleep on the cold ground without an insulating cover between you and the earth. A solid 5-10% of the body’s heat is lost through Conduction. When you hold a chocolate chip in your hand for a few minutes, it will likely begin to melt. This process is called conduction. It occurs when our bodies come into contact with something that has a lower temperature. The body gives away heat to that other object.

Perspiration/Moisture- This is a 2 part process. Heat carries moisture which is how evaporation works. Heat draws moisture and carries it into space as a vapor. When we breathe it is not only heat loss through Respiration but also through the act of “Mouth Perspiration” and thus evaporation. It is a fact that humid air feels warmer than dry air of the same temperature. This is also why the earth stays warmer under cloud cover then under clear sky. When we sweat we lose heat through this process. It is a way the body cools itself down. This is a negative thing when it is very cold out. If it is freezing out and you do hard work snowshoeing up a mountain you will sweat. This is heat loss through Perspiration. This holds true anytime we get wet outdoors in the cold. This could happen from Rain, snow, mist, immersion, etc. Stay dry at ALL costs if you are outdoors in cold weather and plan on staying outdoors. If you get wet in the cold and remain so you will fall to hypothermia. It is more than just “evaporation” Our bodies lose vast amounts more heat when we are wet than if we are dry. Remember that water can take heat away from the body up to 27-30 times faster than the normal air! When wet the water is what it stealing the heat from the body, not the act of evaporation. Finally, when we work up a sweat, we experience evaporation when water on our skin transforms into a gas. Evaporation can fall into two categories- Perspiration and also Convection.

Those are the 5 main methods of heat loss that we must be aware of when exiting outdoors in cold weather. I have come across far too many outdoor travelers who had succumbed to hypothermia because they did not observe the 5 methods of heat loss and take precautions. The fact is if you fail to heed the warnings of heat loss in cold weather you will eventually fall to hypothermia and if not treated, will die from it. True that you cannot get hypothermia as long as you are moving, but eventually we all must stop and rest.

Our blood vessels also play an integral role in heating and cooling. They expand or constrict to free or restrict blood circulation to our skin tissue. When our metabolism heats up our insides, it warms our blood as well. To control that building heat, blood vessels at our skin dilate — like our pupils in low light — to circulate more of that warmed blood toward the skin’s surface and allow the body to release heat. This opening of the blood vessels is called vasodilation. Alcohol and tobacco both cause vasodilatation, which is why both substances can give you the sensation of warmth, even though your core temperature is colder.

 

Since our bodies naturally give away heat to colder, active particles, air particles in wind and water particles can accelerate that effect. Water is denser than air, so it absorbs more heat. That’s why water can steal up to 32 times more heat from our bodies than air can. Even when we get caught in a rain shower, it can lead to hypothermia because of how quickly water cools us.

To combat this rapid cooling, we shiver. Think about being outside on a winter day and how, as the cold hits, you instinctively bring in your arms and legs and tighten those muscles. Shivering is our bodies’ way of generating heat by exciting our muscles. Our blood vessels also constrict to limit the amount of blood traveling toward our skin.

 

When someone’s re-warming reactions, like shivering, aren’t enough to overcome the cooling process, hypothermia can set in. Look for several important signs indicating the different stages of hypothermia.

  • Mild Hypothermia: shivering, goose bumps, difficulty with complex motor skills
  • 95F-35C- Maximum shivering
  • 93.2F-34C- Amnesia and poor judgment
  • 91F-32.7C- Ataxia sets in
  • Moderate Hypothermia: violent shivering, sluggish, speech problems, difficulty with fine motor skills
  • 89F-31.6C- Stupor, lethargy
  • 87.7F-30.9C- Shivering stops
  • 86F-30C- A-fib and bradycardia may be present
  • Severe Hypothermia: rigid muscles, dazed, shivering has stopped, blue skin, erratic heartbeat, an unconscious state, may have disorganized rhythm which is incompatible with life i.e.; V-Fib, asystole.
  • 82.4F-28C- V-Fib threshold, pt subject to disorganized rhythm.
  • 80.6F-27C- Loss of reflexes
  • 56.8F-13.7C- Lowest survival

If severe hypothermia sets in, complications can include coma and even death. Other cold weather injuries are also associated with hypothermia, such as frostbite, chilblains (ulcers on the toes) and trench foot (a foot infection). For more information on protecting yourself from the cold, read. “How to survive the freezing cold”

 

Although many cases of hypothermia arise from being outdoors in cold weather or water, it can happen at home as well. During the winter, stay aware of how cold your house is. People have become hypothermic in houses that were around 60 degrees Fahrenheit (15.5 degrees Celsius). Power outages in the winter can also send temperatures plunging, making it essential to wrap up and keep warm.

 

People are most susceptible to hypothermia outdoors. Whether you get stranded in a snowy field or fall into a chilly lake, you can become hypothermic quickly. So you should be prepared.

 

First, properly fuel yourself. Remember that the body requires food and nutrients to make heat, so going out without eating enough or being dehydrated can put you at risk. Carbohydrates, proteins and fats are the prime food groups to munch on since they provide both short- and long-term energy supplies. Sweet, non-caffeinated beverages are also appropriate, since the sugar will boost energy quickly. Caffeinated drinks hinder your body from absorbing water, promoting dehydration. Alcohol and smoking should also be completely avoided. Both of these make your blood vessels expand, and cause vasodilation, and your body lets off heat faster.

 

In wintery weather, it is also essential that you dress for the C.O.L.D.:

  • Cover: Since we lose so much heat from our head, we should wear scarves and hats over head, neck and face. Mittens are also better protectors than gloves because they trap more heat.
  • Overexertion: Be careful to not overwork yourself in the cold. If you deplete your body’s energy reserves, you will have a harder time warming back up when you get cold.
  • Layer: Wear loose clothing in multiple layers. To prevent yourself from sweating and cooling down too much, remove a layer if you get hot. Looser clothing retains heat well, but your sleeves should fit snugly at the wrists. Thermal underwear can also be an effective base layer to keep heat close to your body.
  • Dry: Choose insulating fabrics such as wool, silk and polypropylene, rather than absorbent cotton. If your clothes get wet, remove them as soon as possible since water cools the body much faster than cold air.

Even in warmer weather, water-related accidents can lead to hypothermia. For that reason, wear a lifejacket while on boats and do not drink alcohol while on boats or around water.

 

If you fall into cold water, it can cool your body up to 32 times faster than air. Freezing cold water can also render someone unconscious in less than 15 minutes. It’s critical to preserve body heat. People who have fallen in cold water should resist the automatic urge to tread water, and unless the shore is less than 200 yards away, you shouldn’t try to swim to land. Doing so only drains precious energy stores. Instead, if alone in the water, you should pull your knees into your chest with your hands at your sides. If a group of people are in the water, they should huddle together to share body heat.

 

Nearly 700 people in the United States die each year from hypothermia. Hypothermia is a silent killer because once your body temperature drops below 95 degrees, you lose awareness of the cold and become disoriented because less oxygen reaches the brain. For that reason, take special precautions if you’re alone in the cold. You may not be aware that your body is in peril.

 

Groups of people should look after each other for the signs of hypothermia discussed in the previous section. If someone does appear hypothermic, there are a number of things that you can do to prevent that person from dying. In mild to moderate cases, the body can re-warm at a rate of 3.6 degrees per hour.

 

To start that warming process, first move into shelter. If there is nowhere to go indoors, at least move the person out of the wind, since wind can speed up hypothermia. Remove any wet clothing and replace them with dry blankets or fresh clothing.

 

For people with mild or moderate hypothermia, some food/ oral glucose and beverages may be helpful. Warm, sweet liquids, such as diluted gelatin mix or hot chocolate will give the body quick energy boosts to help it produce heat. Proteins, fats and carbohydrates in the form of trail mix and granola can also stimulate the metabolism.

 

In more severe cases, getting a person out of any wet clothes and into a hypothermic wrap is essential. There should be several layers of insulation between the wrap and the cold ground. A hypothermic wrap covers every part of the body with as few open spaces as possible. A sleeping bag or multiple blankets can serve as hypothermic wraps, as long as the person is completely protected from the cold.

 

Additionally, extra clothing or blankets should be applied to the neck, groin, armpits and chest to protect major arteries. Sharing body heat by removing your clothes and getting into the wrap with the person may also prove beneficial, except in very severe cases. Also, do not apply heat directly to the skin or give the person a massage because it can circulate the colder blood near the skin to the core, shocking the body.

Hypothermic wraps cover people’s bodies entirely while being insulated from cold ground.

 

Hypothermic Risk Groups

Infants and the elderly are the most at risk for developing hypothermia. Babies do not preserve body heat as well as adults, and the elderly may not have a high enough metabolism to stay warm. For both, it is important that their bedrooms not be too cold and that they are regularly monitored during the winter.

 

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