This time the whole conversation is about prevention and what you can do to stop the incident way in advance of the injury! Humans exhibit peripheral vasoconstriction upon cold exposure. The resulting decrease in peripheral blood flow reduces convective heat transfer between the body’s core and shell (skin, subcutaneous fat and skeletal muscle), effectively increasing insulation by the body’s shell. Because heat is lost from the exposed body surface faster than it is replaced, skin temperature declines.
Frostbite and cold weather-related injuries facts
- Cold weather-related injuries occur with and without freezing of body tissues.
- Cold weather-related injuries include chilblains, trench foot, frostnip, and frostbite.
- Signs and symptoms may include:
- numbness, and
- changes in the color and texture of the skin.
Winter cold and snow provide a number of opportunities to get outside and participate in activities such as skiing, sledding, and snowmobiling. However, without proper protection, cold weather-related injuries can occur even when temperatures are above freezing (32 F, 0 C). This is especially true if there are high winds or if clothing is wet. In general, however, it is both the temperature and the duration of exposure that play a role in determining the extent and severity of cold weather-related injuries.
During whole-body cold exposure, the vasoconstrictor response extends beyond the fingers and occurs throughout the entire body’s peripheral shell. Skin vasoconstriction begins when skin temperature falls below about 95 °F (35 °C) and becomes maximal when skin temperature is about 88 °F (31 °C) or less; however, as cold strain becomes greater, other underlying tissues will vasoconstrict and increase the insulating layer while constricting the body core area. Therefore, underlying muscles can become cold and stiff. Thus, the vasoconstrictor response to cold exposure helps retard heat loss and defend core temperature, but at the expense of a decline in peripheral tissue temperatures. The vasoconstriction-induced blood flow reduction and fall in skin temperature contribute to the etiology of peripheral cold injuries, particularly digits and appendages (such as the ears and nose). Cold-induced vasoconstriction has pronounced effects on the hands, fingers, and feet, making them particularly susceptible to cold injury, pain, and a loss of manual dexterity. Another vasomotor response, cold-induced vasodilation (CIVD), modulates the effects of vasoconstriction in the fingers, toes, nose, and ears.
As a workplace SUPERVISOR you should be trained in this topic plus telling and showing staff how to prevent incidents!
How We Lose Heat to the Environment
Cold injury: An injury caused by exposure to extreme cold that can lead to loss of body parts and even to death. Examples of cold injury are chilblain, trench foot, and frostbite. Cold injury occurs with and without freezing of body tissues.
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
· Contact with metal or supercooled liquids (white gas)
· Exposed skin
· Previous cold injuries
· Constricting garments
· Local pressure
· Cramped position
· Body type
· Women do better in cold than men (greater subcutaneous body fat)
· Caloric intake
· Diabetes, some medications
· 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).
Frostnip is a superficial cooling of tissues without cellular destruction. Chilblains are superficial ulcers of the skin that occur when a predisposed individual is repeatedly exposed to cold. Frostbite involves tissue destruction. The recovery time for a frostbite injury depends on the extent of tissue injury and whether or not there are any subsequent complications, such as infection. It may take 1 to 3 months before it is possible to determine the extent of tissue damage, and to clearly delineate which tissue is still viable.
Learn from the WORLDS leading experts in your workplace incidents!
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
Could you maybe see in the workers EYES
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
· 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. Snow
blindness can even occur during a snow storm if the cloud cover is thin.
· 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, and
· Cold compresses and dark environment
· Do not rub eyes
Cold Weather Clothing
It is important to use cold weather clothing properly, maintain adequate hydration and ensure nutritional requirements to ward off cold weather injuries. When wearing clothing in cold weather, remember the acronym C-O-L-D.
C: Keep it Clean; O: Avoid Overheating; L: Wear clothing Loose and in layers; D: Keep clothing Dry
- 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)
· 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 barrier
Total = Heat Retention
Heat Production – (positive factors)
· Exercise, shivering Limited by:
· Fuel stores (glycogen)
· Fluid status (efficient exercise)
· Food intake (kindling, sticks, logs)
Total = Heat Production
COLD WEATHER INJURIES
Cold weather-related injuries include: injuries due to decreased temperature (hypothermia, frostbite, nonfreezing cold injury), injuries due to heaters, carbon monoxide poisoning, and accidents due to impaired physical and/or mental function resulting from cold stress. Cold weather injuries can also occur in warmer ambient temperatures when an individual is wet due to rain or water immersion.
Hypothermia is defined as a body core temperature below 95°F/35°C. Hypothermia is usually characterized as mild, moderate, or severe, based on body core temperature. In order to properly diagnose hypothermia, core temperature must be measured rectally with a thermometer with an extended low range scale. Oral and tympanic temperatures will not yield accurate results in a cold environment, even when care is taken to use the best technique.
- Hypothermia occurs when heat loss is greater than heat production. This can occur suddenly, such as during partial or total immersion in cold water, or over hours or days, such as during extended operations or survival situations.
- Hypothermia may occur at temperatures above freezing, especially when a person’s skin or clothing is wet.
- Vigorous shivering is typically present. Shivering may decrease or cease as core temperature continues to fall.
- Onset of hypothermia is typically associated with the so-called “umbles”, the grumbles, mumbles, stumbles and fumbles that increase as cold affects muscle and nerve function.
- Symptoms of hypothermia consist of confusion, sleepiness, slurred speech, shallow breathing, weak pulse, low blood pressure, change in behavior and/or poor control over body movements/slow reactions.
- The keys to preventing hypothermia are layering clothing and staying dry. Remember the acronym COLD:
Keep it Clean
Wear it Loose and in Layers
Keep it Dry
- Layers can be removed as ambient temperature or physical activity increases, which can reduce sweating and moisture build-up within clothing.
- The goals for field management of hypothermia are to rescue, examine, insulate, and rapidly transport. If untreated, hypothermia is a true medical emergency and requires evacuation.
- Rewarming techniques include: Soldiers generating their own heat via shivering or exercise, insulating against further heat losses, use of heat on the skin and direct delivery of heat to the core. The latter can only be performed in a hospital setting.
- The use of external heat on the skin (radiant heat, hot water bottles, electric blankets) should only be applied to individuals who have ceased shivering or have a toxicological vasodilation that increases heat loss. Patients must be closely monitored and reassessed frequently to prevent burns.
- For most cases, moving the individual to a warmer location, replacing wet clothing and movement/light exercise are sufficient to restore core temperature.
Frostbite accounts for the largest number of CWI each year and occurs when tissue temperature falls below ~28-30°F. Frostbite can occur suddenly due to contact to cold metal or super-cooled liquids such as alcohol, fuel or antifreeze or can develop over time due to prolonged cold exposure. Frostbite is most common in exposed skin such as the hands, nose, ears, and cheeks but can also occur in the feet or in the hands while wearing gloves due to inadequate insulation and reduced skin blood flow.
- Exposure to below freezing temperatures (<32°F) causing freezing of skin, fingers, toes, ears and facial parts.
- Exposure of skin to metal, super cold fuel and POL (petroleum, oil, lubricants), wind chill, and tight clothing, particularly boots.
- Riding in open vehicles, exposure to propeller/rotor-generated wind, running or skiing, and altitude exposure where there is little tree cover can all contribute to greater windchill.
- Numbness in affected area.
- Tingling, blistered, swollen, or tender areas.
- Pale, yellowish, waxy-looking skin (grayish in dark-skinned soldiers).
- Frozen tissue that feels wooden to the touch.
- Significant pain after rewarming
- Monitoring air temperature and wind speed and using the windchill index is the only way to determine the relative risk of frostbite.
- Use contact gloves to handle all equipment; never use bare hands.
- Use approved gloves to handle all fuel and POL (petroleum, oil, lubricants) products.
- Avoid cotton clothing, which holds perspiration in cold-weather environments.
- Keep face and ears covered and dry.
- Keep socks clean and dry.
- Avoid tight socks and boots.
- Immersion of the affected part in a warm (98-104°F) water is very effective, however most minor cases of frostbite can be re-warmed at room temperature or against a buddy’s skin.
- Once a tissue is thawed, it must not freeze again. If there is the possibility of tissue refreezing, it is better not to thaw it in order to avoid damaging tissue further.
- Avoid exposure to excessive heat (open flame, stove tops, steam, heat packs) or rubbing affected tissue.
- All Soldiers with a peripheral freezing injury must be suspected of being hypothermic and treated appropriately. During field management, it is more important to prevent hypothermia than to rewarm frostbite rapidly
NON-FREEZING COLD INJURY
The most common non-freezing cold injuries are chilblain and trenchfoot. Trench foot occurs when tissues are exposed to temperatures from 32-60°F for prolonged periods of time (>12 hrs), whereas chilblains, which is a more superficial injury, can occur after just a few hours of exposure. A non-freezing cold injury is classified by the symptoms and stages of recovery.
Chilblain is a non-freezing CWI that can occur after 1-5 hours in cold-wet conditions when skin temperature is > 32°F/0°C. The most commonly affected areas are the dorsal surface of the fingers, but the ears, face, and other exposed skin are also areas of occurrence. There are no lasting effects from chilblains.
- Continuous or repeated exposure of skin to cold/wet weather conditions at temperatures below 50 °F for more than 1-5 hours.
- Chilblain lesions are swollen, tender, itchy and painful.
- With re-warming, the skin becomes swollen, red (or darkening of the skin in dark-skinned soldiers) and hot to the touch. An itching or burning sensation may continue for several hours after exposure.
- Early diagnosis of chilblains becomes evident when symptoms do not resolve with re-warming.
- Use contact gloves to handle all equipment; never use bare hands.
- Use approved gloves to handle all fuel and POL (petroleum, oil, lubricants) products.
- In extreme cold environments, do not remove clothing immediately after heavy exertion (PT); wait until you are in a warmer location.
- Avoid cotton clothing, which holds perspiration, in cold-weather environments.
- Re-warm affected area, keep warm and dry.
IMMERSION FOOT (TRENCH FOOT)
- Prolonged (>12 hrs) exposure of tissue, especially the feet, to wet cold and conditions at 32°F to 60°F. Inactivity and damp socks and boots (or tightly laced boots that impair circulation) speed onset and severity.
- Cold, numb feet that may progress to hot with shooting pains.
- Swelling, redness, and bleeding may become pale and blue.
- Accompanied by aches, increased pain sensitivity and infection.
- Keep feet clean and dry; change wet or damp socks as soon as possible.
- Wipe dry the inside of Vapor Barrier boots dry at least once per day, or more often as feet sweat.
- Dry leather boots by stuffing with paper towels.
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.
- Remove wet or constrictive clothing, gentle wash and dry affected extremities.
- Elevate affected limbs and cover with layers of loose, warm, dry clothing.
- Do not pop blisters, apply lotions or creams, massage, expose to extreme heat or permit Soldiers to walk, which can increase tissue damage and worsen the injury.
- Evacuate for medical treatment.