Fly Fishing Safety
Hypothermia vs. Hyperthermia
The below information was written for 'all' possible weather conditions.
Hypothermia is a condition in which an organism's temperature drops below that required for normal metabolism and bodily functions. In warm-blooded animals, core body temperature is maintained near a constant level through biologic homeostasis. But, when the body is exposed to cold, its internal mechanisms may be unable to replenish the heat that is being lost to the organism's surroundings. Hyperthermia, in its advanced state referred to as heat stroke or sunstroke, is an acute condition which occurs when the body produces or absorbs more heat than it can dissipate. It is usually caused by prolonged exposure to high temperatures. The heat-regulating mechanisms of the body eventually become overwhelmed and unable to effectively deal with the heat, causing the body temperature to climb uncontrollably. Normal or Core Body Temperature is 36.8°C (98.2°F). Hypothermia can be divided in three stages of severity.
Three Stages of Hypothermia
Body temperature drops by 1-2°C (1.8-3.6°F) below normal temperature (35-37°C or 95-98.6°F). Mild to strong shivering occurs. The victim is unable to perform complex tasks with the hands; the hands become numb. Blood vessels in the outer extremities constrict, lessening heat loss to the outside air. Breathing becomes quick and shallow. Goose bumps form, raising body hair on end in an attempt to create an insulating layer of air around the body (which is of limited use in humans due to lack of sufficient hair, but useful in other species). Often, a person will experience a warm sensation, as if they have recovered, but they are in fact heading into Stage 2. Another test to see if the person is entering stage 2 is if they are unable to touch their thumb with their little finger; this is the first stage of muscles not working.
Body temperature drops by 2-4°C (3.8-7.6°F). Shivering becomes more violent. Muscle miss-coordination becomes apparent. Movements are slow and labored, accompanied by a stumbling pace and mild confusion, although the victim may appear alert. Surface blood vessels contract further as the body focuses its remaining resources on keeping the vital organs warm. The victim becomes pale. Lips, ears, fingers and toes may become blue. •
Body temperature drops below approximately 32 °C (89.6 °F). Shivering usually stops. Difficulty speaking, sluggish thinking, and amnesia start to appear; inability to use hands and stumbling is also usually present. Cellular metabolic processes shut down. Below 30 °C (86.0 °F), the exposed skin becomes blue and puffy, muscle coordination becomes very poor, walking becomes almost impossible, and the victim exhibits incoherent/irrational behavior including terminal burrowing or even a stupor. Pulse and respiration rates decrease significantly, but fast heart rates can occur. Major organs fail. Clinical death occurs.
Treatment for hypothermia consists of drying, sheltering, and gradually warming (making sure to not rub the patient's body, to warm with blankets and, if possible, to transfer your own body heat). While blankets help a person retain body heat, they are not sufficient to treat hypothermia. It is vital that the core of the body is warmed first or else the cold blood will be forced towards the heart and may cause death. In the field, a mildly hypothermic person can be effectively re-warmed through close body contact from a companion and by drinking warm, sweet liquids. Moderate and severe cases of hypothermia require immediate evacuation and treatment in a hospital. In hospital, warming is accomplished by external techniques such as heated blankets for mild hypothermia and by more invasive techniques such as warm fluids injected in the veins or even washing of the bladder, stomach, chest and abdominal cavities with warmed fluids for severely hypothermic patients. These patients are at high risk for arrhythmias (irregular heartbeats), and care must be taken to minimize jostling and other disturbances until they have been sufficiently warmed, as these arrhythmias are very difficult to treat while the victim is still cold.
Wind Chill & Frost Bite:
Wind chill is the apparent temperature felt on exposed skin, which is a function of the air temperature and wind speed. The wind chill temperature is always lower than the air temperature, except at higher temperatures where wind chill is considered less important. In cases where the apparent temperature is higher than the air temperature, the heat index is used instead.
Frostbite is the medical condition whereby damage is caused to skin and other tissues due to extreme cold. At or below 0º C (32°F), blood vessels close to the skin start to narrow (constrict). This helps to preserve core body temperature. In extreme cold, or when the body is exposed to cold for long periods, this protective strategy can reduce blood flow in some areas of the body to dangerously low levels. The combination of cold temperature and poor blood flow can cause severe tissue injury by freezing the tissue. Frostbite is most likely to happen in body parts farthest from the heart and those with a lot of surface area exposed to cold. The initial stages of frostbite are sometimes called "frostnip". If frostbite is not treated immediately then the damage and the frostbite become permanent. Nerve damage will occur due to oxygen deprivation. Frostbitten areas will turn discolored, purplish at first, and soon turn black. After a while nerve damage becomes so great that feeling is lost in the frostbitten areas. Blisters will also occur. If feeling is lost in the damaged area, checking it for cuts and breaks in the skin is vital. Infected open skin can lead to gangrene and amputation may be needed.
To treat frostbite move the victim to a warm location and seek medical help. Soak frostbitten areas in warm (not hot) water or, if in wilderness, warm by contact with the skin of a non-frostbitten person. Continue until the victim has regained sensation and movement in the afflicted region; this often follows great pain as the nerves thaw. Never rub, slap, or shake the stricken region as ice crystals in the frostbitten skin will damage surrounding tissue. For frostbite in the feet, keeping feet in warm saline water will provide relief. Follow the treatment with a period of constant warmth: refreezing following thawing worsens the damage.
How to Prevent Heat Loss & Reduce Exposure to Cold/Wind:
1) Insulation: Cotton vs. Synthetic/Wool Fabrics
Wearing cotton in cool/cold weather is a particular hypothermia risk as it retains water, and water rapidly conducts heat away from the body. Even in dry weather, cotton clothing can become damp from perspiration and chilly after the wearer stops exercising. Synthetic and wool fabrics provide far better insulation when wet and are quicker to dry. Some synthetic fabrics are designed to wick perspiration away from the body. Last, poor circulation can cause heat loss. So, tight clothing or boots, cramped positions, fatigue, certain medications, smoking, alcohol use, or diseases that affect the blood vessels, such as diabetes can cause poor blood circulation.
When dry, down feather insulation is among the best in the world. However, when wet, down feathers will lose almost all insulation properties and take more time to dry than wool or poly- insulates such as sleeping bag material and poly-synthetics such as Polar Fleece.
3) Wind and Weather Proofing
Whether we are exposed to cold or warm weather, our number one priority is to protect our skin and insulate our bodies. You have many modern “high tech” options such as Poly/Nylon weave with a Gore-Tex type material. This type of outer shell material offers the following: strength, light weight, windproof, waterproof and breathable performance. Traditional protective clothing such as rain coats, down jackets, or heavy wool jackets work well but they all come with pro’s and con’s.
4) Layering System
For insulation and barrier protection, all outdoor enthusiast and experts agree that layering is the best method. By layering your clothes, you are able to add or subtract clothing when necessary. Ultimately, the key to a good layering system is dependent on each person’s knowledge of their own body performance in different climates, education of materials available for purchase and real world experience. For instance, Polar Fleece is available in 100, 200, 300 weight (typically, the higher the number the more insulation offered). But, a heavier weight layering system may not provide you the best insulation system available. Why? While active, a heavier weight layering system may lead to excessive perspiration may which will lead to wet clothing, which may lead to body heat loss.
- Feet: Water proof/insulated boots or rubber insulated boots. Gators. Poly/Nylon and wool sock combination. Extreme cold: down bootie inserts or fur products.
- Body: (1-2) Layers of poly/synthetic underwear followed by light weight (100) polar fleece and wool.
- Internal Shell: light weight poly shell, down or fleece.
- External Shell: Synthetic “high tech.” 5. Hands: Waterproof outer shell. Inner fibers wool and down mittens or gloves.
- Head & Neck: Windproof fleece, regular fleece and wool hats, wool scarf. Why wool scarf’s? Great back-up system to warm hands.
- Eyes: Polarized glasses or ski goggles.
- Face & Lips: SPF skin lotion.
- Note: Under normal cold conditions, and while physically active, I find the combination of fleece/poly and wool products work best. However, in extreme cold conditions, when I am not physically moving, I find fur products (hat, gloves) and more down products, keep me warmer.