The Link Between Migraine and Fever

Body Temperature Isn't A Set Number - Here's What's Considered Normal And What's A Fever

Normal body temperature for a typical adult is widely considered 98.6°F, but the reality is a "normal" body temperature can range between 97°F and 99°F.

A range is more accurate because body temperature is affected by many factors, including time of day and person's gender, age, and activity levels.

A fever is considered any temperature over 100.4°F, which is your body's way of fighting off an illness or infection.

For over a century, normal human body temperature has been considered 98.6°F (37°C). This number was established in 1871 by German physician Carl Wunderlich, who determined the average by testing millions of patients with what was a new instrument at the time: the thermometer.

Since then, however, researchers have observed that normal body temperature varies from person to person and depends on gender, age, and time of day, among other factors.

Here's what you need to know about your body temperature, when it's considered a higher than normal, and how to take it properly.

A normal body temperature can range from 97°F to 99°F

The truth is, there is no one exact "normal" body temperature, and depending on your age, the time of day, and how active you are, it's more accurate to describe a normal body temperature as a range.

"Temperature can vary between individuals, where some members of a family are consistently warmer than others," says Charles Brantly, MD at Central Health. "This is not necessarily a bad thing. The normal range for the vast majority of people is between 97°F (36.1°C) and 99°F (37.2°C)."

While normal body temperatures for adults range between 97°F and 99°F, the spectrum is slightly different for children and older adults.

"On average, children tend to be slightly warmer than adults, and those over [the age of] 65 are cooler," says Brantly. "This is generally a reflection of a faster metabolism in those of a younger age … Exercise, hydration status, and clothing will all affect your day time temperature as well."

Other factors that may affect your body temperature

While core body temperature for men and women is roughly the same, women generally have a lower skin temperature because of their higher percentage of body fat. Brantly says that women can also have varying temperatures during their monthly menstrual cycle.

Chawapon Kidhirunkul, MD at BDMS Wellness Clinic, also says that time of day can impact your temperature. "Our temperature drops at night during sleep and increases over the day," Kidhirunkul says. "The lowest temperature is at around 4 a.M., and the highest peak at 5 p.M."

This rise in temperature is due to increased cortisol - the stress hormone - in the body as we move through the day. Kidhirunkul adds that another factor can be food, which usually increases body temperature slightly after a meal.

So the next time you reach for a thermometer, keep in mind that it is natural for your temperature to fluctuate between 97°F and 99°F, depending on your particular circumstances.

What temperature indicates a fever

High body temperature is one of the first symptoms of illness, and a fever is an indication that your body is fighting off an infection, like the flu virus. According to Cleveland Clinic, temperatures above 100.4°F are considered a fever for adults.

But for children, Cleveland Clinic says fever indications can vary depending on how you take the reading:

99.5°F or higher for oral temperature

100.4°F or higher for rectal temperature

99°F or higher for underarm temperature

Fevers are often associated with other symptoms like chills, headaches, tiredness, body aches, and sweating.

If you're feeling feverish, Brantly advises measuring your temperature and recording it several times a day, as thermometers aren't always accurate and your temperature may rise and fall throughout the day.

While most fevers usually resolve themselves within a week, there are certain steps you can take to relieve discomfort, such as staying hydrated, dressing in lightweight clothing, and getting plenty of rest.

Fever is also a common symptom of the coronavirus. If you think you may have a fever associated with other symptoms of coronavirus, follow the CDC guidelines for taking care of yourself and preventing the spread of the virus.

How to take your temperature

There are several options when taking your temperature, such as armpit, forehead, mouth, ear, and rectal methods, according to Kidhirunkul.

For the most inexpensive and easiest ways to get a temperature reading, a digital thermometer can take a temperature three ways:

Oral: The thermometer is placed under the tongue - a method best for adults and young children.

Rectum: For babies or adults who cannot hold the thermometer under their tongue, this method involves gently inserting the thermometer into the rectum.

Armpit: The axillary method is another option for anyone who cannot tolerate oral temperature. The thermometer is placed under the armpit.

The most common and easiest method of taking your temperature is in the mouth, however, Kidhirunkul says rectal temperatures are the most accurate. When it comes to a professional setting, Brantly notes that most hospitals and clinics rely on ear thermometers, though these are more expensive.

Outdoor Action Guide To

Friday August 30, 2024 by Rick Curtis Traveling in cold weather conditions can be life threatening. The information provided here is designed for educational use only and is not a substitute for specific training or experience. Princeton University and the author assume no liability for any individual's use of or reliance upon any material contained or referenced herein. Medical research on hypothermia and cold injuries is always changing knowledge and treatment. When going into cold conditions it is your responsibility to learn the latest information. The material contained in this workshop may not be the most current. How We Lose Heat to the Environment

Radiation - loss of heat to the environment due to the temperature gradient (this occurs only as long as the ambient temperature is below 98.6). Factors important in radiant heat loss are the surface area and the temperature gradient.

Conduction - through direct contact between objects, molecular transference of heat energy

Water conducts heat away from the body 25 times faster than air because it has a greater density (therefore a greater heat capacity). Stay dry = stay alive!

Steel conducts heat away faster than water

Example: Generally conductive heat loss accounts for only about 2% of overall loss. However, with wet clothes the loss is increased 5x.

Convection - is a process of conduction where one of the objects is in motion. Molecules against the surface are heated, move away, and are replaced by new molecules which are also heated. The rate of convective heat loss depends on the density of the moving substance (water convection occurs more quickly than air convection) and the velocity of the moving substance.

Wind Chill - is an example of the effects of air convection, the wind chill table gives a reading of the amount of heat lost to the environment relative to a still air temperature.

Evaporation - heat loss from converting water from a liquid to a gas

Perspiration - evaporation of water to remove excess heat

Sweating - body response to remove excess heat

Respiration - air is heated as it enters the lungs and is exhaled with an extremely high moisture content

It is important to recognize the strong connection between fluid levels, fluid loss, and heat loss. As body moisture is lost through the various evaporative processes the overall circulating volume is reduced which can lead to dehydration. This decrease in fluid level makes the body more susceptible to hypothermia and other cold injuries.

Response to Cold

Cold Challenge - (negative factors)

Temperature

Wet (rain, sweat, water)

Wind (blowing, moving, e.G. Biking)Total = Cold Challenge

Heat Retention - (positive factors)

Size/shape (Eskimo vs. Masai)

Insulation (layering/type)

Fat (as insulation)

Shell/core (shunt blood to core) shell acts as a thermal barrierTotal = Heat Retention

Heat Production - (positive factors)

Exercise, shivering Limited by:

Fitness

Fuel stores (glycogen)

Fluid status (efficient exercise)

Food intake (kindling, sticks, logs)

Total = Heat Production

Heat Retention + Heat Production less than Cold Challenge = Hypothermia InsulationBody FatSurface to Volume ratioShell to Core shunting   ExerciseShivering   TemperatureWetnessWind     Your Body Core Temperature

1. Heat is both required and produced at the cellular level. The environment acts as either a heating or a cooling force on the body. The body must be able to generate heat, retain heat, and discharge heat depending on the body activity and ambient external temperature.

2. Body temperature is a measure of the metabolism - the general level of chemical activity within the body.

3. The hypothalamus is the major center of the brain for regulating body temperature. It is sensitive to blood temperature changes of as little as 0.5 degrees Celsius and also reacts to nerve impulses received from nerve endings in the skin.

4. The optimum temperature for chemical reactions to take place in the body is 98.6 degrees F. Above 105 F many body enzymes become denatured and chemical reactions cannot take place leading to death. Below 98.6 F chemical reactions slow down with various complications which can lead to death.

5. Core = the internal body organs, particularly the heart, lungs, and brain.Periphery = the appendages, skin, and muscle tissue.

6. Core temperature is the temperature that is essential to the overall metabolic rate of the body. The temperature of the periphery is not critical.

How Your Body Regulates Core Temperature

1. Vasodilation - increases surface blood flow, increases heat loss (when ambient temperature is less that body temperature). Maximal vasodilation can increase cutaneous blood flow to 3000 ml/minute (average flow is 300-500 ml/minute).

2. Vasoconstriction - decreases blood flow to periphery, decreases heat loss. Maximal vasoconstriction can decrease cutaneous blood flow to 30 ml/minute.

3. Sweating - cools body through evaporative cooling

4. Shivering - generates heat through increase in chemical reactions required for muscle activity. Visible shivering can maximally increase surface heat production by 500%. However, this is limited to a few hours because of depletion of muscle glucose and the onset of fatigue.

5. Increasing/Decreasing Activity will cause corresponding increases in heat production and decreases in heat production.

6. Behavioral Responses - putting on or taking off layers of clothing will result in heat regulation

Hypothermia

1. Hypothermia - "a decrease in the core body temperature to a level at which normal muscular and cerebral functions are impaired." - Medicine for Mountaineering

2. Conditions Leading to Hypothermia

Cold temperatures

Improper clothing and equipment

Wetness

Fatigue, exhaustion

Dehydration

Poor food intake

No knowledge of hypothermia

Alcohol intake - causes vasodilation leading to increased heat loss

3. What are "hypothermia" temperatures

Below freezing

40 degrees - Ex. Shenandoahs, wind and rain

60 degrees - Ex. Rayanna and hurricane

Any temperature less than 98.6 degrees can be linked to hypothermia (ex. Hypothermia in the elderly in cold houses) or peripheral circulation problems such as trench foot and frostbite.

4. Signs and Symptoms of Hypothermia

a. Watch for the "-Umbles" - stumbles, mumbles, fumbles, and grumbles which show changes in motor coordination and levels of consciousness

b. Mild Hypothermia - core temperature 98.6 - 96 degrees F

Shivering - not under voluntary control

Can't do complex motor functions (ice climbing or skiing) can still walk & talk

Vasoconstriction to periphery

c. Moderate Hypothermia - core temperature 95 - 93 degrees F

Dazed consciousness

Loss of fine motor coordination - particularly in hands - can't zip up parka, due to restricted peripheral blood flow

Slurred speech

Violent shivering

Irrational behavior - Paradoxical Undressing - person starts to take off clothing, unaware s/he is cold

"I don't care attitude" - flattened affect

d. Severe Hypothermia - core temperature 92 - 86 degrees and below (immediately life threatening)

Shivering occurs in waves, violent then pause, pauses get longer until shivering finally ceases - because the heat output from burning glycogen in the muscles is not sufficientto counteract the continually dropping core temperature, the body shuts down on shivering to conserve glucose

Person falls to the ground, can't walk, curls up into a fetal position to conserve heat

Muscle rigidity develops - because peripheral blood flow is reduced and due to lactic acid and CO2 buildup in the muscles

Skin is pale

Pupils dilate

Pulse rate decreases

at 90 degrees the body tries to move into hibernation, shutting down all peripheral blood flow and reducing breathing rate and heart rate.

at 86 degrees the body is in a state of "metabolic icebox." The person looks dead but is still alive.

e. Death from Hypothermia

Breathing becomes erratic and very shallow

Semi-conscious

Cardiac arrythmias develop, any sudden shock may set off Ventricular Fibrillation

Heart stops, death

5. How to Assess if someone is Hypothermic

If shivering can be stopped voluntarily = mild hypothermia

Ask the person a question that requires higher reasoning in the brain (count backwards from 100 by 9's). If the person is hypothermic, they won't be able to do it. [Note: there are also other conditions such as altitude sickness that can also cause the same condition.]

If shivering cannot be stopped voluntarily = moderate - severe hypothermia

If you can't get a radial pulse at the wrist it indicates a core temp below 90 - 86 degrees

The person may be curled up in a fetal position. Try to open their arm up from the fetal position, if it curls back up, the person is alive. Dead muscles won't contract only live muscles.

Stage Core Temperature Signs & Symptoms Mild Hypothermia 99º - 97ºF Normal, shivering can begin 97º - 95ºF Cold sensation, goose bumps, unable to perform complex tasks with hands, shiver can be mild to severe, hands numb Moderate Hypothermia 95º - 93ºF Shivering, intense, muscle incoordination becomes apparent, movements slow and labored, stumbling pace, mild confusion, may appear alert. Use sobriety test, if unable to walk a 30 foot straight line, the person is hypothermic. 93º - 90ºF Violent shivering persists, difficulty speaking, sluggish thinking, amnesia starts to appear, gross muscle movements sluggish, unable to use hands, stumbles frequently, difficulty speaking, signs of depression, withdrawn. Severe Hypothermia 90º - 86ºF Shivering stops, exposed skin blue of puffy, muscle coordination very poor, inability to walk, confusion, incoherent/irrational behavior, but may be able to maintain posture and appearance of awareness 86º - 82ºF Muscle rigidity, semiconscious, stupor, loss of awareness of others, pulse and respiration rate decrease, possible heart fibrillation 82º - 78ºF Unconscious, heart beat and respiration erractic, pulse may not be palpable 78º - 75ºF Pulmonary edema, cardiac and respiratory failure,death. Death may occur before this temperature is reached. Treating Hypothermia

The basic principles of rewarming a hypothermic victim are to conserve the heat they have and replace the body fuel they are burning up to generate that heat. If a person is shivering, they have the ability to rewarm themselves at a rate of 2 degrees C per hour.

Mild - Moderate Hypothermia

1. Reduce Heat Loss

Additional layers of clothing

Dry clothing

Increased physical activity

Shelter

2. Add Fuel & Fluids

It is essential to keep a hypothermic person adequately hydrated and fueled.

a. Food types

Carbohydrates - 5 calories/gram - quickly released into blood stream for sudden brief heat surge - these are the best to use for quick energy intake especially for mild cases of hypothermia

Proteins - 5 calories/gram - slowly released - heat given off over a longer period

Fats - 9 calories/gram - slowly released but are good because they release heat over a long period, however, it takes more energy to break fats down into glucose - also takes more water to break down fats leading to increased fluid loss

b. Food intake

Hot liquids - calories plus heat source

Sugars (kindling)

GORP - has both carbohydrates (sticks) and protiens/fats (logs)

c. Things to avoid

Alcohol - a vasodilator - increases peripheral heat loss

Caffeine - a diuretic - causes water loss increasing dehydration

Tobacco/nicotine - a vasoconstrictor, increases risk of frostbite

3. Add Heat

Fire or other external heat source

Body to body contact. Get into a sleeping back, in dry clothing with a normothermic person in lightweight dry clothing

Severe Hypothermia

1. Reduce Heat Loss

Hypothermia Wrap: The idea is to provide a shell of total insulation for the patient. No matter how cold, patients can still internally rewarm themselves much more efficiently than any external rewarming. Make sure the patient is dry, and has a polypropylene layer to minimize sweating on the skin. The person must be protected from any moisture in the environment. Use multiple sleeping bags, wool blankets, wool clothing, Ensolite pads to create a minimum of 4" of insulation all the way around the patient, especially between the patient and the ground. Include an aluminum "space" blanket to help prevent radiant heat loss, and wrap the entire ensemble in plastic to protect from wind and water. If someone is truly hypothermic, don't put him/her naked in a sleeping bag with another person.

2. Add Fuel & Fluids

Warm Sugar Water - for people in severe hypothermia, the stomach has shut down and will not digest solid food but can absorb water and sugars. Give a dilute mixture of warm water with sugar every 15 minutes. Dilute Jello™ works best since it is part sugar and part protein. This will be absorbed directly into the blood stream providing the necessary calories to allow the person to rewarm themselves. One box of Jello = 500 Kilocalories of heat energy. Do not give full strength Jello even in liquid form, it is too concentrated and will not be absorbed.

Urination - people will have to urinate from cold diuresis. Vasoconstriction creates greater volume pressure in the blood stream. The kidneys pull off excess fluid to reduce the pressure so the person will urinate. In order to reduce the potential heat lost from wet clothing fashion a 'diaper" for the person inside the hypothermia wrap and wrap that with a garbage bag. That will serve to allow them to urinate and prevent the wetness from leading to evaporative heat loss. You will need to keep them hydrated with the dilute Jello solution described above.

3. Add Heat

Heat can be applied to transfer heat to major arteries - at the neck for the carotid, at the armpits for the brachial, at the groin for the femoral, at the palms of the hands for the arterial arch.

Chemical heat packs such as the Heat Wave™ provides 110 degrees F for 6-10 hours.

Hot water bottles, warm rocks, towels, compresses

For a severely hypothermic person, rescue breathing can increase oxygen and provide internal heat.

Afterdrop

Is a situation in which the core temperature actually decreases during rewarming. This is caused by peripheral vessels in the arms and legs dilating if they are rewarmed. This dilation sends this very cold, stagnate blood from the periphery to the core further decreasing core temperature which can lead to death. In addition, this blood also is very acetic which may lead to cardiac arrythmias and death. Afterdrop can best be avoided by not rewarming the periphery. Rewarm the core only! Do not expose a severely hypothermic victim to extremes of heat.

CPR & Hypothermia

When a person is in severe hypothermia they may demonstrate all the accepted clinical signs of death:

Cold

Blue skin

Fixed and dilated pupils

No discernable pulse

No discernable breathing

Comatose & unresponsive to any stimuli

Rigid muscles

But they still may be alive in a "metabolic icebox" and can be revived. You job as a rescuer is to rewarm the person and do CPR if indicated. A hypothermia victim is never cold and dead only warm and dead. During severe hypothermia the heart is hyperexcitable and mechanical stimulation (such as CPR, moving them or Afterdrop) may result in fibrillation leading to death. As a result CPR may be contraindicated for some hypothermia situations:

1. Make sure you do a complete assessment of heart rate before beginning CPR. Remember, the heart rate may be 2-3/minute and the breathing rate 1/30 seconds. Instituting cardiac compressions at this point may lead to life-threatening arrythmias. Check the carotid pulse for a longer time period (up to a minute) to ascertain if there is some slow heartbeat. Also, even though the heart is beating very slowly, it is filling completely and distributing blood fairly effectively. External cardiac compressions only are 20-30% effective. Thus, with its severely decreased demands, the body may be able to satisfy its circulatory needs with only 2-3 beats per minute. Be sure the pulse is absent before beginning CPR. You will need to continue to do CPR as you rewarm the person.

2. Ventilation may have stopped but respiration may continue - the oxygen demands for the body have been so diminished with hypothermia that the body may be able to survive for some time using only the oxygen that is already in the body. If ventilation has stopped, artificial ventilation may be started to increase available oxygen. In addition, blowing warm air into the persons lungs may assist in internal rewarming.

3. CPR Procedures

Check radial pulse, between 91.4 and 86 degrees F this pulse disappears

Check for carotid pulse - wait at least a full minute to check for very slow heartbeat

If pulse but not breathing or slow breathing, give rescue breathing (also adds heat).

If no discernible heartbeat begin CPR and be prepared to continue - persons with hypothermia have been given CPR for up to 3.5 hours and have recovered with no neurological damage

Begin active rewarming

Cold Injuries

Tissue temperature in cold weather is regulated by two factors, the external temperature and the internal heat flow. All cold injuries described below are intimately connected with the degree of peripheral circulation. As peripheral circulation is reduced to prevent heat loss to the core these conditions are more likely to occur.

1. Factors influencing cold injuries

Low ambient temperature

Wind chill - increases rate of freezing dramatically

Moisture - wet skin freezes at a higher temp than dry

Insulation

Contact with metal or supercooled liquids (white gas)

Exposed skin

Vasodilation

Vasoconstriction

Previous cold injuries

Constricting garments

Local pressure

Cramped position

Body type

Dehydration

Women do better in cold than men (greater subcutaneous body fat)

Caloric intake

Diabetes, some medications

Alcohol

Caffeine, nicotine

2. Cold-induced Vasodilation - When a hand or foot is cooled to 59 degrees F, maximal vasoconstriction and minimal blood flow occur. If cooling continues to 50 degrees, vasoconstriction is interrupted by periods of vasodilation with an increase in blood and heat flow. This "hunting" response recurs in 5-10 minute cycles to provide some protection from cold. Prolonged, repeated exposure increases this response and offers some degree of acclimatization. Ex. Eskimos have a strong response with short intervals in between.

3. Pathophysiology of Tissue Freezing - As tissue begins to freeze, ice crystals are formed within the cells. As intracellular fluids freeze, extracellular fluid enters the cell and there is an increase in the levels of extracellular salts due to the water transfer. Cells may rupture due to the increased water and/or from tearing by the ice crystals. Do not rub tissue; it causes cell tearing from the ice crystals. As the ice melts there is an influx of salts into the tissue further damaging the cell membranes. Cell destruction results in tissue death and loss of tissue. Tissue can't freeze if the temperature is above 32 degrees F. It has to be below 28 degrees F because of the salt content in body fluids. Distal areas of the body and areas with a high surface to volume ratio are the most susceptible (e.G ears, nose, fingers and toes - this little rhyme should help remind you what to watch out for in yourself and others).

Surface frostbite generally involves destruction of skin layers resulting in blistering and minor tissue loss. Blisters are formed from the cellular fluid released when cells rupture.

Deep frostbite can involve muscle and bone

  Cold Response Mild Frostnip Superficial Frostbite Deep Frostbite Sensation Painful May have sensation Numb Numb Feels Normal Normal Soft Hard Color Red White White White

4. Cold Response

Circulation is reduce to the are to prevent heat loss.

The area may be pale, cold.

It may have sensation or be numb.

5. Frostnip

Freezing of top layers of skin tissue

It is generally reversible

White, waxy skin, top layer feels hard, rubbery but deeper tissue is still soft

Numbness

Most typically seen on cheeks, earlobes, fingers, and toes

Treatment

Rewarm the area gently, generally by blowing warm air on it or placing the area against a warm body part (partner's stomach or armpit)

Do not rub the area - this can damage the effected tissue by having ice crystals tear the cell

6. Frostbite

Skin is white and "wooden" feel all the way through

Superficial frostbite includes all layers of skin

Numbness, possible anesthesia

Deep frostbite can include freezing of muscle and/or bone, it is very difficult to rewarm the appendage without some damage occurring

Treatment

Superficial frostbite may be rewarmed as frostnip if only a small area is involved

If deep frostbite, see below for rewarming technique

7. Rewarming of Frostbite

Rewarming is accomplished by immersion of the effected part into a water bath of 105 - 110 degrees F. No hotter or additional damage will result. This is the temperature which is warm to your skin. Monitor the temperature carefully with a thermometer. Remove constricting clothing. Place the appendage in the water and continue to monitor the water temperature. This temperature will drop so that additional warm water will need to be added to maintain the 105 - 110 degrees. Do not add this warm water directly to the injury. The water will need to be circulated fairly constantly to maintain even temperature. The effected appendage should be immersed for 25 - 40 minutes. Thawing is complete when the part is pliable and color and sensation has returned. Once the area is rewarmed, there can be significant pain. Discontinue the warm water bath when thawing is complete.

Do not use dry heat to rewarm. It cannot be effectively maintained at 105 - 110 degrees and can cause burns further damaging the tissues.

Once rewarming is complete the injured area should be wrapped in sterile gauze and protected from movement and further cold.

Once a body part has been rewarmed it cannot be used for anything. Also it is essential that the part can be kept from refreezing. Refreezing after rewarming causes extensive tissue damage and may result in loss of tissue. If you cannot guarantee that the tissue will stay warm, do not rewarm it. Mountaineers have walked out on frozen feet to have them rewarmed after getting out with no tissue loss. Once the tissue is frozen the major harm has been done. Keeping it frozen will not cause significant additional damage.

8. Special Considerations for Frostbite

If the person is hypothermic and frostbitten, the first concern is core rewarming. Do not rewarm the frostbitten areas until the core temp approaches 96 degrees.

No alcohol - vasodilation may increase fluid buildup

No smoking - nicotine as a vasoconstrictor may increase chances for developing frostbite

Liquids such as white gas can "supercool" in the winter (drop below their freezing point but not freeze). White gas also evaporates quickly into the air. Spilling supercooled white gas on exposed skin leads to instant frostbite from evaporative cooling. Always were gloves when handling fuel.

Touching metal with bare skin can cause the moisture on your skin to freeze to the metal. (In really cold conditions, metal glasses frames can be a problem). When you pull away, you may leave a layer of skin behind. Don't touch metal with bare skin.

9. Trench Foot - Immersion Foot

Trench foot is a process similar to chillblains. It is caused by prolonged exposure of the feet to cool, wet conditions. This can occur at temperatures as high as 60 degrees F if the feet are constantly wet. This can happen with wet feet in winter conditions or wet feet in much warmed conditions (ex. Sea kayaking). The mechanism of injury is as follows: wet feet lose heat 25x faster than dry, therefore the body uses vasoconstriction to shut down peripheral circulation in the foot to prevent heat loss. Skin tissue begins to die because of lack of oxygen and nutrients and due to buildup of toxic products. The skin is initially reddened with numbness, tingling pain, and itching then becomes pale and mottled and finally dark purple, grey or blue. The effected tissue generally dies and sluffs off. In severe cases trench foot can involve the toes, heels, or the entire foot. If circulation is impaired for > 6 hours there will be permanent damage to tissue. If circulation is impaired for > 24 hours the victim may lose the entire foot. Trench Foot cuases permanent damage to the circulatory system making the person more prone to cold related injuries in that area. A similar phenomenon can occur when hands are kept wet for long periods of time such as kayaking with wet gloves or pogies. The damage to the circulatory system is known as Reynaud's Phenomenon.

Treatment and Prevention of Trench foot

Includes careful washing and drying of the feet, gentle rewarming and slight elevation. Since the tissue is not frozen as in severe frostbite it is more susceptible to damage by walking on it. Cases of trench foot should not walk out; they should be evacuated by litter. Pain and itching are common complaints. Give Ibuprofen or other pain medication.

Prevention is the best approach to dealing with trench foot. Keep feet dry by wearing appropriate footwear. Check your feet regularly to see if they are wet. If your feet get wet (through sweating or immersion), stop and dry your feet and put on dry socks. Periodic air drying, elevation, and massage will also help. Change socks at least once a day and do not sleep with wet socks. Be careful of tight socks which can further impair peripheral circulation. Foot powder with aluminum hydroxide can help. High altitude mountaineers will put antiperspirant on their feet for a week before the trip. The active ingredient, aluminum hydroxide will keep your feet from sweating for up to a month and their are no confirmed contraindications for wearing antiperspirant. [Some studies have shown links between alumnium in the body and Alzheimers.] Vapor barrier socks may increase the possibility of trenchfoot. When you are active and you are wearing a vapor barrier sock, you must carefully monitor how you sweat. If you are someone who sweats a lot with activity, your foot and polypropylene liner sock may be totally soaked before the body shuts down sweating. Having this liquid water next to the skin is going to lead to increased heat loss. If you don't sweat much, your body may shut down perspiration at the foot before it gets actually wet. This is when the vapor barrier system is working. You must experiment to determine if vapor barrier systems will work for you.

10. Chillblains

Caused by repeated exposure of bare skin to temperatures below 60 degrees

Redness and itching of the effected area

Particularly found on cheeks and ears, fingers and toes

Women and young children are the most susceptible

The cold exposure causes damage to the peripheral capillary beds, this damage is permanent and the redness and itching will return with exposure

11. Avoiding Frostbite and Cold related Injuries

"Buddy system" - keep a regular watch on each other's faces, cheeks, ears for signs of frostnip/frostbite

Keep a regular "self check" for cold areas, wet feet, numbness or anesthesia

If at any time you discover a cold injury, stop and rewarm the area (unless doing so places you at greater risk).

12. Eye Injuries

a. Freezing of Cornea

Caused by forcing the eyes open during strong winds without goggles

Treatment is very controlled, rapid rewarming e.G. Placing a warm hand or compress over the closed eye. After rewarming the eyes must be completely covered with patches for 24 - 48 hours.

b. Eyelashes freezing together

Put hand over eye until ice melts, then can open the eye

c. Snowblindness

Sunburn of the eyes

Prevention by wearing good sunglasses with side shields or goggles. Eye protection from sun is just as necessary on cloudy or overcast days as it is in full sunlight when you are on snow. Snowblindness can even occur during a snow storm if the cloud cover is thin.

Symptoms

Occur 8-12 hours after exposure

Eyes feel dry and irritated, then feel as if they are full of sand, moving or blinking becomes extremely painful, exposure to light hurts the eyes, eyelids may swell, eye redness, andexcessive tearing

Treatment

Cold compresses and dark environment

Do not rub eyes

BIBLIOGRAPHY

The Backpacker's Field Manual, Rick Curtis, Random House, New York, 2005.

Hypothermia: Causes, Effects, and Prevention, Robert Pozos, David Born, New Century, 1982.

Management of Wilderness and Environmental Emergencies, Paul Auerbach, Edward Geehr, Macmillan, 1983.

Medicine for Mountaineering, James Wilkerson, The Mountaineers, 1992.

Hypothermia - Death by Exposure, William Forgey, ICS, 1985.

Hypothermia, Frostbite, and other Cold Injuries, James Wilkerson, Cameron Bangs, John Hayward, The Mountaineers, 1986

Medicine for the Backcountry, Buck Tilton and Frank Hubbell, ICS Books, 1994.

Animal Survival In Extreme Temperatures

Animals have some amazing adaptations that help them live in even the most hostile environments. Consider camels, for instance. They can thrive in some of the hottest and driest places on Earth. Their legs don't get burned when they kneel on hot sand due to thick leathery patches on their knees. They can survive for an entire week without water but, at the same time, they can drink 32 gallons of water at once. Their body temperature ranges from 93 °F to 107 °F, so they don't need to sweat very often and can conserve water this way. The spongy bones in their noses absorb any excess moisture to keep every drop of water in, so the air they breathe out is dry air. In addition to camels, other animals' adaptations are equally remarkable. How do they do it? Chemistry helps!

Warm-Blooded or Cold-Blooded?

The most important adaptation is how animals regulate their body temperature. Animals can be either warm-blooded or cold-blooded.

Warm-blooded animals, which are mostly birds and mammals, need to maintain a relatively constant body temperature or they would suffer dire consequences. It doesn't matter what the outside temperature is—they must maintain the same internal temperature. For us, the commonly accepted average body temperature is 98.6 °F (even though it may vary among individuals). Most other mammals range from 97 °F to 103 °F; birds have an average body temperature of 105 °F.

Cold-blooded animals do not maintain a constant body temperature. They get their heat from the outside environment, so their body temperature fluctuates, based on external temperatures. If it is 50 °F outside, their body temperature will eventually drop to 50 °F, as well. If it rises to 100 °F, their body temperature will reach 100 °F. Most of the rest of the animal kingdom—except birds and mammals—are cold-blooded.

In most instances, the size and shape of an organism dictate whether it will be warm-blooded or cold-blooded. Think about some large animals—elephants, whales, and walruses. Their volume is so large that relying on the outside environment to heat them up would be inefficient and would slow their response times, putting their survival at risk. For that reason, nearly all large animals are warm-blooded.

Figure 1. Body temperature vs. Ambient temperature for warm-blooded animals (endotherms) and cold-blooded animals (ectotherms).

http://www.Nature.Com/scitable/knowledge/library/homeostatic-processes-for-thermoregulation-23592046

What about all the birds and mammals that are not large, such as mice and sparrows?  The other factor—body shape—comes into play here. Small warm-blooded animals tend to have a rounded shape, which ensures that the interior of an organism stays warm the longest time possible. Most cold-blooded organisms have either an elongated or a flat shape. If you look at a typical fish, their bodies tend to be flat when viewed head-on from the front. Snakes, lizards, and worms tend to be long and slender. These shapes ensure they can heat up and cool down rapidly.

Within a given species, animals tend to be larger in colder climates and smaller in warmer climates, an observation known as Bergmann's rule. For example, whitetail deer in the southern part of the United States tend to have a smaller body size and less overall mass than whitetail deer in the far northern states.

There are exceptions but, overall, this rule holds true, for the following reason: As the volume of an object decreases, the ratio of its surface area to its volume increases. In other words, the smaller an animal is, the higher the surface area-to-volume ratio. These animals lose heat relatively quickly and cool down faster, so they are more likely to be found in warmer climates. Larger animals, on the other hand, have lower surface area-to-volume ratios and lose heat more slowly, so and they are more likely to be found in colder climates.

Generating Energy

Warm-blooded animals require a lot of energy to maintain a constant body temperature. Mammals and birds require much more food and energy than do cold-blooded animals of the same weight. This is because in warm-blooded animals, the heat they lose is proportional to the surface area of their bodies, while the heat they produce is proportional to their mass. This means that larger warm-blooded animals can generate more heat than they lose and they can keep their body temperatures stable more easily. Smaller warm-blooded animals lose heat more quickly. So, it is easier to stay warm by being larger. Warm-blooded animals cannot be too small; otherwise, they will lose heat faster than they can produce it.

This energy produced by warm-blooded animals mostly comes from food. Food represents stored chemical energy (potential energy), which is converted into other forms of energy within the body when the food is metabolized. Metabolism refers to the all of a body's chemical reactions.

The metabolism of food within the body is often referred to as internal combustion, since the same byproducts are generated as during a typical combustion reaction—carbon dioxide and water. And like combustion reactions, metabolic reactions tend to be exothermic, producing heat.

For a warm-blooded animal, food is not just a luxury—it is a matter of life and death. If food is not available for energy, the body's fat is burned. Once fat reserves are used up, death is imminent if a food source is not found. The smaller the warm-blooded animal, the more it must eat—relative to its body size—to keep its internal furnace stoked. That's why most songbirds fly south for the winter.

These turtles just walked out of a pool of cool water.

NASA/JPL-CALTECH

On the other hand, cold-blooded animals require less energy to survive than warm-blooded animals do, because much of the energy that drives their metabolism comes from their surroundings. It is common to see turtles basking in the sun on rocks and logs. They are not trying to get a suntan, but rather are revving up their metabolism. The sun gives them an energy boost. Muscle activity in cold-blooded animals depends on chemical reactions, which run quickly when it is hot and slowly when it is cold (because the reacting molecules move faster when temperature increases).

Some reptiles, such as the python, can go a year without eating, because they do not use food to produce body heat. And if they lie still, they use little energy, so they can afford to eat little. 

Cold-blooded animals have a disadvantage compared to warm-blooded animals: There is a certain temperature below which their metabolism just won't work. The reason is that all chemical reactions slow down as the temperature is lowered, so at low temperatures, all the chemical reactions in an organism slow down.

You may notice that few cold-blooded animals are active in the winter, and the farther north you go, the rarer they become. By contrast, warm-blooded animals are present in a wider variety of environments and for a longer part of the year than cold-blooded animals.

Hibernation

For warm-blooded animals that don't migrate, one way to survive the winter is to sleep through it. Hibernation is a great strategy that enables animals to conserve energy when food is scarce. During hibernation, body temperature drops, breathing and heart rate slows, and most of the body's metabolic functions are put on hold in a state of quasi-suspended animation.

It is almost as if the warm-blooded animal becomes cold-blooded, as its body temperature drops considerably. But they are still alive, and they live off their fat reserves. Hibernation for extended periods of time is only accomplished by those animals that can store a great deal of body fat, such as bears, groundhogs, and chipmunks. A black bear loses 15%–30% of its weight while hibernating.  

Cold-blooded animals hibernate, too. But they need to store less fat than warm-blooded animals because they require less energy. Turtles and frogs bury themselves in mud under lakes and ponds for up to six months at a time, and for all practical purposes, they appear dead. There are no external signs of life.

When many cold-blooded animals hibernate, something interesting happens at the cellular level. The fluid around the cells, but not in the cells, is frozen solid. As water freezes outside the cell, water from within the cell is drawn out through osmosis. Osmosis is a process in which water moves across a semipermeable membrane—in this case, the cell membrane—from an area of low solute concentration to an area of high solute concentration.

As water freezes outside of the cell, the solute concentration increases, because the quantity of liquid water decreases while the amount of solute stays the same. As a result, water flows out of the cell to equalize the concentrated solution outside of the cell (Fig. 2).

Figure 2. Some cold-blooded animals have found ways to counteract the formation of ice, which can damage their tissues and potentially kill them. For example, antifreeze proteins (1) bind to the surface of ice crystals outside the cells to prevent these ice crystals from growing (2). As these ice crystals form, water flows out of the cells to compensate for the increasing concentration of solute in liquid water outside the cells (3). Inside the cells, compounds called cryoprotectants (4) increase the concentration of solutes, preventing further water loss and cell damage. Proteins on the cell membranes, called aquaporins (5), allow water and some cryoprotectants to flow inside the cells.

Joelle Bolt; Reprinted with permission from The Scientist; www.The-scientist.Com/?Articles.View/article No/34223/title/Freezing-Cells/

At the same time water is leaving the cells, glucose migrates into the cells in copious amounts. By removing water and adding glucose, the concentration of dissolved solute within the cell increases—a lot. The glucose acts as a natural antifreeze, as any solute will lower the freezing point of a given solvent—in this case, water. The presence of high concentrations of solutes in the cells allows animals such as frogs to hibernate at temperatures below freezing and still survive. While the water around the cells is frozen, the water in the cells is not. If water within a cell were to freeze, the cell membrane would be ruptured, killing the cell.   

Keeping Warm

When it is cold outside, you put on more clothes. Your winter coat does not keep out the cold, but rather keeps in the heat. (Cold itself doesn't exist—it is simply the absence of heat; see the article titled "Why Cold Doesn't Exist," on p. 10.) Birds and mammals also rely on insulation to prevent heat loss. The most effective insulation traps air, since air is one of the best insulators. Wool tends to be warm because its fibers are curled, effectively trapping air and keeping you (and sheep) warm. Birds fluff up their feathers when they want to stay warm, since fluffing introduces air.

For mammals without hair, insulation is accomplished by blubber, a thick layer of fat tissue which helps to insulate an animal's body because fat does not transfer heat as well as muscle and skin. This blubber may be two feet thick in some whales! Whales, tuna, dolphins, and other warm-blooded marine animals also rely on another ingenious method to conserve heat. To prevent excessive heat loss from extremities such as fins and flippers—which are not well insulated—aquatic animals rely on a "countercurrent heat-exchange method," in which the arteries that carry warm blood away from the heart are positioned directly against the veins that carry cool blood to the heart. So, the warmer blood leaving the heart through the arteries warms the cooler blood entering the heart through the veins.

In contrast to birds and mammals, lizards, frogs, snakes, and other cold-blooded animals do not need insulation—it would only slow down heat transfer into their bodies.

Keeping Cool

When you get hot, what's the first thing that happens? You s