HYPOTHERMIA
Layering is a part any system. But there are other tricks.
COLD-

C = clean. Stay as clean as possible and keep your clothing as clean as possible.

O = Overheat. Prevent overheating by dressing in...

Last Memorial Day weekend (2004) I traveled the harmless path into the floor of Tuckerman Ravine on Washington. It was a nice mid-spring day. From the mid point on up there was light snow drifting on the breeze but there was mostly sunshine with thin clouds. I kept plodding along. I always sweat a lot. I also know I didn't have the clothing I have now. I am sure it was a cotton shirt and I know it was jeans. I carried a jacket in my daypack but never felt the need to use it.

I reached the caretaker's house on the floor of the ravine (well actually took time to explore the cabins first), then pushed on to the headwall as the deck on the house was PACKED.

I made it up to the edge of the remaining snow and watched the skiers. After an undetermined amount of time watching, taking pictures, and talking to people, I finally felt cold for the first time all day.

I made my way back to the caretaker's building and went inside. That is where I saw the electronic weather station and saw it was 31 degrees with a 15 degree wind chill. I stared at it in disbelief.

I then went to sign the register and that's when I discovered that while I could hold the pen, I could NOT write my name. All that came out was a line across the page.

I went out into the sun, found a spot with no wind. Ate just about everything I had brought and drank a lot of water. In 30 minutes or so I was able to go back in and write my name.

Scary

PCM

I had the similar experience and have come up with a personal way to test my cognition and fitness for duty. I will periodically do a Mini Mental Status Exam on myself: recall the day and date, my addresses and phone numbers, recalling my 3 "items" of the day, do serial 7's or spell words backwards, identify and name (out loud) flora I pass by, and assess whether I'm a happy or an unhappy camper. I do this about 2-3 times a day if walking alone.

I sing out loud. I try skipping or picking up objects along the path.

Some of this simply provides exercise and calorie burning. Some of this lets me know of early cognitive/brain failure. When I screw up, I stop and eat something and consider early camp and extra clothing.

I prefer to do this with another hiker. It is easier to recognize problems in another, especially when conversation begins to lag.

Doctari, That is exactly what I was talking about. I think that if those that have suffered from hypothermia reverse the process in their mind they will often find that the road to disaster began before the first sign of hypothermia. We have all heard the old adtage that "cotton kills". Well could it be that mal-nutrition, exhaustion and illness are the "modern" stepping stones to hypothermia, at least for those that are experienced hikers. I know that I will often abuse my body while hiking and will fail to notice that when my body gets tired or sick my mind will be the next thing to suffer. Your article and other posts have given me reason to re-evaluate some of my habits.
Doc I understand your passion for the subject, I feel the same when it comes down to developing an understanding of where and how such problems begin. I hope that others will continue to post their experiences with hypothermia so that we all may learn from them.

Orangebug - That is a great approach to self analysing one's state of physical and mental well being. It would be especially handy for someone hiking alone. I could be wrong but I think that would be a good addition to Doc's article. Thanks for the info

heck i kinda like a little hypothermia, last spring I climbed up from fontana to mollies ridge shelter, about half way up it started to snow by the time I got to the shelter there were 5-6 inches around, I only had on hiking shorts and a poly pro shirt. my left arm not just my hand was very slow moving and I was covered in snow and wet. once at the shelter I stripped got into my bag, shivered a bit , got the stove going and made hot tea,,,i kinda like being cold.

edgy stuff...ok orangebug what is the DX?

a couple hikers I meet going up to Mollies offered me ponchos and stuff.that I refused .I had plenty of gear with me, just like the feel of cold....

I do the same up in AK...frostnipped my nose once this past winter out snow-shoeing at -28 F..but i really dig the cold.

1) DEFINITION AND DESCRIPTION
Hypothermia: From “Hypo” meaning: Low, lowered, lowering or below. And “Thermia” meaning temperature, so: Lowered (body ) Temperature.
Hypothermia Is a state of low body temperature, specifically low body core temperature. When the core temperature of the body drops below 97º (36º C) an individual is considered to be in a hypothermic state. Hypothermia can be attributed to either: a decrease in heat production (perhaps due to illness or injury, dehydration, or lack of food); or an increase in heat loss (perhaps due to; lack of adequate clothing for the temperature, wet, windy conditions.); or a combination of both.

2) HYPOTHERMIA vs FROSTBITE
Years ago you heard of people dying of “exposure.” What we used to call exposure is hypothermia. This is different from frostbite, which can only occur below freezing. Frostbite is freezing of an exposed part of the body. With frostbite the cells in the affected area freeze and the cell walls burst actually killing the tissue in that area, like nerves, skin, muscle, and capillaries. This is why you see severe frostbite areas turning black from the dead tissue. Serious frostbite can be extremely painful and require months of recovery with possible loss of fingers, limbs, etc.. Contrary to popular old wife’s tales an area of frostbite should not be rubbed as this will just cause more damage. The treatment of frostbite is similar to that of burns. With hypothermia there is no tissue damage.

Links to further info:
Frostbite treatment Warning! Graphic photos

It is amazing how misunderstood hypothermia is. Basically, the human body functions over a very narrow internal temperature range. The loss of core temperature, or losing heat faster than it can be generated by the body, results in hypothermia. The body’s normal temperature is 98.6°F and a drop of under 2°F will start this process. Note that hypothermia is caused only by loss of core temperature and you could have frostbite on your hands and still not be hypothermic. Hypothermia also doesn’t require near freezing temperatures, in fact, a person with low body fat and a low metabolic rate could easily get hypothermic sitting in a swimming pool or bath at 75°F. Your body’s ability to generate heat depends on health, level of fitness, proper hydration, food, etc. Alcohol consumption will make you FEEL warm, when in reality the alcohol, in addition to clouding your judgment further (see “97°F” above), dilates the blood vessels in your skin thereby increasing heat loss (& causing that flushed feeling/look). Coffee and some other drinks are also diuretics and can cause dilation of blood vessels in the extremities and accelerate heat loss. Most cases of hypothermia associated with hiking occur in the summer months when the temperature is 40°F-50°F and you have wet, windy conditions.

Hypothermia victims can be divided into three main categories According to Core Body temperature range: mild, moderate & severe:
A core temperature between 94º and 97º F (34 – 36 C) is considered mild hypothermia.
A core temperature between 86º and 94º (30 – 34 C) is Moderate Hypothermia.
A core temperature less than 86º F (30 C) is Severe Hypothermia.

So let’s see what happens as you lose core temperature:
98.6°F- your brain functions normally
97°F - judgment starts to go; as temperature decreases so does mental ability
96°F - you begin shivering, there is loss of fine motor skills like tying shoes
94°F - coordination is failing, you start stumbling; shivering increases
92°F - shivering is severe; you will be unable to walk
90°F - shivering is convulsive; you are unable to talk; you assume the fetal position
88°F - shivering stops because the body is giving up on that method of re-warming itself
86°F and below -you are in what is referred to as a “metabolic icebox” where you may appear dead. You are unconscious, ashen gray, no perceivable pulse or breathing.

Links to further info:
Hypothermia, a complete guide
Hypothermia

3) SYMPTIONS -WHAT TO LOOK FOR
Although the “umbles” (grumble, mumble, stumble, tumble) have been mentioned as telltale symptoms of hypothermia, keep in mind that these aren’t necessarily obvious or occur in exact order. Also, these symptoms are generally not obvious to the person who is getting hypothermic because of their depressed brain function. Almost always it will be a fellow hiker that recognizes the symptoms.

Grumble The grumbling occurs when we get irritable, but some people start out that way. What you should be looking for in your fellow hikers is a change from what is normal for them. A lot of people who grumble aren’t hypothermic, that’s just normal for them. However, if it is cold and wet and someone starts to grumble, try to figure out the cause. If it is the onset of hypothermia, take corrective measures.

Fumble As your hands get cold, there is loss of fine motor skills like those required to tie shoes. This may also be caused by localized cooling and not hypothermia.

Mumble Contrary to popular belief, this doesn’t have a lot to do with the brain. There are facial muscles that move the jaw and when they get cold and stiffen up we have trouble forming words. If you start talking nonsense then it probably is the brain that is involved.

Stumble Again, the brain is not the only thing that could cause this problem. If your legs get really cold there are two big nerve bundles in your legs that control things like foot drop, etc. If you’ve ever watched a drunk, you can recognize this staggering, flatfooted foot slapping on the floor type of gait. The inability to send and receive nerve messages from the feet are one thing that causes this problem. This could occur alone or in combination with the brain having problems because of hypothermia.

Tumble This one is pretty obvious and almost always comes after some combination of the previous three “umbles”. This is when you are getting into a really serious stage of hypothermia.

Some of the other symptoms that you may notice are the hypothermic person becoming combative, or even taking off clothing. Even well prepared hikers suffering from hypothermia have died despite having everything they needed to survive right in their pack. Don’t expect rational thought processes from someone who is hypothermic.

links to further info:
Recognizing Hypothermia

4) TREATMENT –HOW DO I TREAT SOMEONE WHO IS HYPOTHERMIC?
The first thing to do is to recognize a person who is hypothermic, remove the cause, and take corrective measures. The only true way is to measure core temperature is with a special low-reading rectal hypothermia thermometer. A friend of mine who trains EMTs and is an expert in cold weather related injuries claims if you are willing to let him take your rectal temperature, you ARE truly hypothermic.

If the hypothermia is mild and the person can still walk, the best course of action is to remove the cause. If the clothes are wet, strip the person and put on dry warm clothes. If they haven’t been eating or drinking, feed them. And, most important, keep them moving. It is easier to keep them producing their own heat than for you to try to warm them by other means. This works only if the hypothermia is mild and the person can still walk. Always ambulate before carry if possible because any backcountry litter carry involves a large group of rescuers and many hours.

If the hypothermia is more moderate, keep this one thought in mind: never strip them and put them in a sleeping bag with a functioning warm person. Almost always you will succeed in creating two hypothermic people. This is a very bad idea. What you need to do is to remove the cause of the hypothermia, like their wet clothes, and put them in a hypothermia wrap or sleeping bag (see link for details). You should try to warm the core and not the extremities. Warming the arms and legs can “fool” the body into thinking it is warmer and flushing the warmer blood from the core to the extremities, further cooling the core. The last reference below shows how to create this “human burrito,” as it is sometimes called, to re-warm a hypothermic person.

If a hypothermic person is conscious and is capable of drinking (after removing the cause of the heat loss and protecting them), be very careful that the drinks you give them aren’t too hot. Because the sensation of touch and warmth is so depressed it is very easy for a hypothermic person to be burned by steaming hot liquids that a normal person could not drink. Any drinks should be tested or measured by thermometer to be no more than 105°F. Never try to give drinks or food to an unconscious person.

One last thing. Never assume that if there are no visible signs of life in a severly hypothermic person that it is too late. The experts in this field of medicine say they aren’t dead until they are warm and dead. Respiration can be near zero and the pulse rate could be 6 per minute. Because the blood supply to the extremities is basically shut down, you will get no distal pulse. The muscles stiffen up with the cold and the heart is a muscle. A severe hypothermic person who appears to be dead may just be in this “metabolic icebox.” The severely hypothermic person's heart is extremely susceptible to ventricular fibrillation, which even the slightest jolt can cause. A severely hypothermic person should never be re-warmed in the field. They must be protected from further heat loss and carefully transported to a hospital as soon as possible.

links to further info:
Mild hypothermia
Severe hypothermia
thermo-wrap (human burrito)

5) PREVENTION –FUEL FOR THE BODY
I know some of you are saying: “Hey, that doesn’t sound like any fun, how to I prevent it?” Well, to prevent it you have to know a little bit about thermodynamics, fortunately, very little. You have to understand how the body generates heat and distributes it through the body as well as how the body loses heat. Metabolism, level of conditioning, illness, drugs, alcohol, and fatigue also can play a big role in hypothermia.

First of all, the body can be thought of as a furnace, burning the fuel (food) that you feed it. The blood forms an important part of this system sending the processed fuel to the cells. Anything that compromises this flow (even restrictive clothing) will cause problems. As you get dehydrated the blood becomes more viscose, or thicker, and its ability to transport oxygen and fuel to the cells decreases. The sensation of thirst isn’t a good indication of when to drink. When you “feel” thirsty, you are already down a quart or so. The sensation of thirst is also depressed by the cold affecting the brain. This is why it is so important pay attention to staying hydrated.

Not all foods are created equal and not all fluids are either. Sugars give you a quick shot of energy but pastas, potatoes, and fats are slower burning and are best to eat before bedtime to help keep your furnace going through the night, but they require more water to digest as well. The problem with fruit juices and some energy drinks is they are too concentrated and are absorbed by the body slowly. Juices diluted about 2 to 1 are absorbed faster. Alcohol, coffee and some other drinks should be avoided. Coffee is a diuretic and can cause dilation of blood vessels allowing the extremities to radiate more heat. The effects of drinking coffee could be thought of like taking off an insulation layer.

links to further info:
Eating and drinking right
Vegetarian Eating and drinking right


6) PREVENTION –CLOTHING AND THERMOREGULATION
There are several ways the body can lose heat. The main ways are:

Conduction One way is by direct contact like lying on the ground. If you and your clothing are wet the loss of heat is up to 25 times greater than if you are dry.

Convection is heat loss due to a breeze and is known as “wind chill.” Again, if you are in damp or wet clothing, the problem is much worse. Although fleece is a good insulation layer, it is very porous and is next to useless in a wind. One way to improve fleece is to add a wind block layer. Another way is to wear a thin wind shirt over the fleece. A tent, or an enclosed hammock, would be warmer than an open-faced shelter by blocking wind and adding some insulation.

Respiration A lot of heat is lost during respiration as a combination of conduction and evaporation. Inhaled cold air is warmed by contact with the upper airway & lungs and the warm exhaled air has moisture from evaporation in the lungs if the inhaled air is dry. The drier the air, the more respiration also contributes to dehydration. Higher altitude, colder and drier air, and rapid breathing all contribute to higher heat loss and dehydration.

Radiation The rate of radiation increases as the difference in temperature between you and the air increases. Like convection, this form of heat loss can be lessened considerably by adding a layer of insulation.

Evaporation Sweating is the body’s natural way of trying to regulate our temperature when we get too hot. The amount of sweat produced by a body at rest could be about 100ml per day. With heavy exercise this could climb to 5000ml or 5 liters per day. If this moisture can’t pass through your clothing to the outside, you will get soaked.

The materials used for your clothing layers are important. Remember cotton absorbs water, loses its insulation ability, gets heavy, and should not be used as a layer. The phrase "cotton kills" says it all. The base layers should be hydrophobic, i.e., not absorb or attract water, the synthetic base layer should freely pass sweat to the outer layers and keep your body as dry as possible. Any of the layers you use should not be constrictive as this will restrict blood flow and make you feel colder. Always think of your layers as part of a “system” that has to fit together properly. When you buy your outer rainproof layer, make sure it is large enough to fit over all the other layers you could be wearing underneath it. Added features like full front zippers and "pit-zips" in jackets and full-length side zippers in rain/wind pants can make them much more versatile and easy to put on or take off. Check the references on layering for a more complete description of material options and layering.

Putting on or taking off layers of clothing allows you to bring your body’s temperature back closer to the normal range under widely varying conditions which could include wind, sun, rain, snow, or your differing levels of exertion. If you do not have the proper clothing for the conditions you are in, you are at risk of hypothermia. A popular belief is that the body tries to “protect” the core organs by shunting blood flow away from the extremities. While this is the effect, the reason is simply to prevent heat loss from the extremities. Not as much heat is radiated from the head as is commonly believed but a hat is an important part of a clothing system. Gloves are also important to prevent your hands from getting wet and cold, which could lead to loss of coordination.

Trying to prevent having to go pee in the middle of a cold night by not drinking (hydrating) properly before bed isn’t wise and can cause you to sleep colder. The old wife’s tale about it taking energy to keep the water in your bladder warm defies logic and science. One practical suggestion to add warmth is to fill a water bottle with hot water and take that to bed with you. This should be done with care because if the water leaks, then you are in trouble. My personal feeling is that you should be carrying enough clothing and a warm enough sleeping bag so this isn’t necessary for warmth.

Also, the air in the sleeping bag doesn’t hold some mystical property that make you sleep warmer when naked. The bottom line is more insulation equals more warmth. If you put on a layer of dry clothing, you will sleep warmer. One footnote should be that an equal sized volume filled with down (or any other type of sleeping bag insulation) is warmer than an equal sized volume filled with air. The reason is convection currents in the larger air areas allows heat flow. The down actually doesn’t have any insulation properties itself, it does, however, break up the possibly convection current heat losses by creating many micro pockets of air, and it is very light and compressible. Keep in mind that if down gets wet, it is useless as an insulator, and is very heavy. Synthetic insulation (like Primaloft) is much better in this regard.

links to further info:
Layering 1
Layering 2
Sleeping bag ratings


7) Summation:

-Hypothermia is sneaky and can kill. The hypothermic victim is generally not the person who notices their problem.
-Hypothermia (lowered core temperature) should not be confused with frostbite (localized freezing of tissue). These are two different things. Both are serious and require immediate attention.
-If you are hypothermic, or find someone who is hypothermic, remove the cause and prevent further heat loss. Take corrective measures as described above depending on the severity and level of consciousness of the person.
-Alcohol and any diuretics are to be avoided; they will cause the blood vessels to dilate, especially in the skin, causing you to feel warm but in fact accelerating the heat loss.
-Cotton clothing is totally inappropriate for hiking: The saying “Cotton Kills” may seem over used, but cotton & cold, wet weather do not mix. Always carry extra appropriate clothing, raingear, and shelter. Be prepared.

On the UMBLES, I'd scratch TUMBLE and insert BUMBLE. This gets to the lack of fine motor eye/hand coordination and difficulty dealing with gear.

BTW, it looks great!

I prefer FUMBLE, whether TUMBLE is left in or not.

Actually STUMBLE and BUMBLE are pretty much the same (dictionary, BUMBLE-to proceed unsteadily : STUMBLE). TUMBLE is definately different than those two because you are actually falling down.

I like coming into a cabin and standing by a wood stove when I have to defrost....

I lieka good chillin

WOW!

So much info. I'm gonna have to sit down & do some actual work now.

Ah well, I did volunteer to do this.

Keep it comming.

I also am getting help from a few of the other EMTs here via E-mail. So this thing should be quite the definitive paper on wilderness Hypothermia. With definitions (Thanks Old Fhart) Examples, treatment & stuff.

We may also have to deviate into frostbite, just to have cold weather totally covered. For now tho I'm trying to save that for another article.

Doctari.

I really like how The Old Fhart laid that out and referenced the piece.

Me too,

no,

wait, , , , ,

(Doctari now enters "whine mode")

Ah man, now I has to do more work! And I was almost done


Actually, That is a wonderful version. I have a few things to add, but "Damn" that was fine work, specially for an OLD GUY

Rock is/was right, my version didn't "Feel right", at least on a hiking forum.

Thanks Old Fhart, I really apreciate this!!!!!! Especially the links & stuff

Doctari.

So do we want to go with Old Fharts or are you going to do some updates using that as a part of the article and give dual credit?

Sorry for the delay. Family chrisis after family chrisis, etc.

I just edited the 2 together, going to send that to OF, & back & forth. He can have credit, did the most work

Doctari.

I made changes to my post #25 on hypothermia after input from Doctari and others. There may be mistales because I did this quickly as I'm leaving for Trail Days in 1 hour. See you there!

Beautiful job. Much better than my version, thanks!!!

Have a good time at trail days!!

Wish I could be there, sigh.


Doctari.

An obervation / inquiry which may or may not be directly on topic.


Q1:

I have read suggestions to wear Zip-Loc bags* over the feet in cold and wet conditions - - this is usually recommended for people wearing hiking shoes with soft-uppers - - to take advantage of the Vapor Barrier Effect (VBE).

The Vapor Barrier Effect depends upon minimizing the evaporation of moisture, and it is specified as useful when you are cold.

I recall cold & wet feet are the ideal environment for Trench Foot. The military suggests wearing clean and dry socks as a precaution - - as if CLEAN and DRY socks are always available.

The point is, the Vapor Barrier Effect seems to maximize conditions which give rise to Trench Foot.

I’m mindful, in a few days, hikers will be in town - - whereas the infantry may be living in field conditions nonstop for months - - therefore, using the Vapor Barrier Effect may not be of sufficient duration to cause Trench Foot among hikers.

I’m ambivalent.


Q2:

Should Zip-Loc bags be used only during “extreme” emergency circumstances? I’m unsure what conditions would qualify as an “emergency,” let alone “extreme.”


Q3:

Some people suggest wearing a liner sock over your foot, then covered by a Zip-Lock bag, wearing a regular hiking sock as the outer layer (not counting the shoe).

I’m under the impression, the Vapor Barrier Effect works best when the moisture-evaporation-restricting layer is in direct contact with the skin. The Effect may in fact be non-existent if the Barrier isn’t touching.

Is the liner sock suggested to enhance comfort? It seems to me, the liner sock would abrade moisture-softened skin and further reduce walking ability.

Any and all ideas are welcome.

Vi


* Re using Zip-Loc bags for the Vapor Barrier Effect. Other relatively non-porous materials may also be used - - large balloons, latex/non-latex gloves, MYLAR plastic (space bag/blanket), plastic wrap, heavyweight-silk bandana, waterproofed nylon, etc.

My understanding of the use of the zip lock or any VBL is to keep your feet dry, therefore warm in cold conditions. And indeed many swear by the Vapor Barrier Liner especially in a sleeping bag. My concern is the lack of breathability, thereby causing your sweat to accumulate, getting your feet (or other body parts) wet, causing you to be chilled. Or: causing the condition you were trying to avoid.

Seems to me the cold would be the bigest concern, but extended time having wet feet can cause trench foot. Probably not really a big problem on the AT, but if it's a concern to you, have a pair of dry socks for in camp, take the time to dry your feet completely (bandanas work well here.) then put on the dry socks. A little foot powder (Gold Bond is popular) goes a long way. Clean feet are happy feet, some use rubbing alcohol, altho I wouldn't use it during cold weather.

Give them a try, just be aware of the hazzards. Frost bite / frozen feet can be a bad thing. Could ruin your hike, will at least ruin your day. And trust me, hypothermia SUCKS!!!! No matter the cause.

Doctari.

Doctari,

My hope, when submitting my post (#277), was that someone intimately familiar with the Vapor Barrier Effect would advise me which of my presumptions are in error and where my concerns aren’t warranted.

I had three general areas of concern: (1) How does the Vapor Barrier work? Hopefullly this would include a discussion of the theory and some specific demonstrable anecdotes. (2) What are the limits of the Vapor Barrier Effect? How long does it work, and what stops it from continuing to work? (3) If, as I understand it, immediate contact with the skin is the most efficacious, how are suggestions to place things between the skin and the barrier explainable? Extending this, is the Vapor Barrier Effect causing some of my feeling of warmth when all I’m doing (or at least all I think I’m doing) is using a wind shell? (I.e., the windshell isn’t in direct contact with my skin, a la VBE, but separated by one or more layers.)

I dislike being wet, especially in winter, Vapor Barrier notwithstanding. I would consider carrying some type of plastic for emergency use if the VBE proves to be effective. But, as I suggested, I equate wetness in winter with inviting hypothermia.

My recollection, which may be imperfect, is the Vapor Barrier stimulates the retention of your perspiration (i.e., inhibits its evaporation) and the skin is "fooled" into "thinking" no more perspiration is needed. Your body registers that it is warm - - or, is it actually warmer?

I read an extensive explanation why the Vapor Barrier Effect works, but I’m unsure how much “science” was involved. I’m not finding that or any other “hard” information, so I’m asking around.

This would be great if it were true, but it's not. Your body and skin cannot be fooled. Even with no activity, like when you are sleeping, your skin gives off water.