superficial frostbite after rewarming
Winter this year has been harsh in many areas, and there’s more to come before Spring arrives. Exposure to cold can lead to injuries with lasting, sometimes disfiguring effects. In this article, we’ll discuss two such injuries known as “frostbite” and “immersion foot.” These differ from general cold-related emergencies, known as “hypothermia.”
(Note: To learn about general hypothermia, click here.)
WHAT CAUSES FROSTBITE?
Frostbite is the freezing of body tissues, and it usually occurs in the extremities, especially fingers and toes. Sometimes, the ears, nose, chin, and even the lips may be affected. The body responds to cold temperatures by narrowing the blood vessels, something called “vasoconstriction.” Blood flow to the extremities decreases to preserve flow to the vital internal organs in the body core. As the blood is redirected away from hands and feet, these parts of the body get colder, and ice crystals can form and destroy tissue.
STAGES OF FROSTBITE
Frostbite is often categorized in stages:
First stage: Frostnip- The earliest symptoms of frostbite are known as “frostnip.” In frostnip, the skin turns red and cold and the victim experiences sensations of cold, pain, numbness, and “pins and needles.”
Second stage: Superficial Frostbite- At this level, skin loses color, going from red to white to blue. Tissues are freezing and swelling may be noted. The texture of the skin changes too, becoming stiff and waxy. Although frozen, the victim may feel the sensation of “heat” in the area affected. Upon rewarming (discussed below), clear blisters often form.
Deep frostbite: Deep frostbite is characterized by complete numbness. Deep tissues become hard, almost wooden. The skin is blue or black and develops dark blood blisters. Irreversible damage (called “gangrene”) occurs in severe cases.
Gangrene is the death of tissue resulting from loss of circulation. This usually results in the loss of the frozen body part. Infection may also set in, possibly affecting the entire body. Known as “sepsis,” this infection is life-threatening.
TREATMENT OF FROSTBITE
The earlier that cold-related injuries are recognized and treated, the more likely the victim will recover without permanent damage. Move to warmth immediately and remove wet clothing. If general hypothermia is suspected, warm the body core (torso) before focusing on extremities. Applying warm dry compresses in areas that most effectively transport heat to the body core, such as the armpits, neck, and groin.
When treating frostbite, avoid rubbing affected areas. Exposure to heating pads, heat lamps, hot water bottles, or open fires is also thought to worsen damage to traumatized tissues. Leave blisters unopened. The tradition of massaging the frostbitten area with snow or ice is not beneficial (at all). Also, rewarming should only be attempted in situations where there is no threat of refreezing. Refreezing causes significantly more damage.
In settings where professional help is not an option, treat with a warm water soak (no more than 104-108 degrees F)/40-42 degrees C) of the affected areas. Add warm water as needed to maintain this temperature range. After 30-60 minutes, the skin should recover some pliability and color (redness) if not too far gone. Repeating soaks is not generally recommended.
Once rewarmed, keep the area elevated, dry, and loosely bandaged. Place dry non-stick gauze between affected fingers and toes. Discourage walking on affected areas and work to protect against further trauma.
Expect the victim to experience pain, swelling, and redness during and after rewarming. In superficial frostbite, it’s not uncommon for clear blisters to form as a part of recovery. In deep frostbite, the blisters will likely be filled with blood; skin may appear bruised, blue, or otherwise discolored. They will likely turn into dark, thick scabs. Some of this tissue may be unsalvageable and have to be removed by either amputation or a procedure called “debridement” (discussed elsewhere on this site).
debridement procedure
PREVENTION OF FROSTBITE
Prevention of frostbite involves the use of appropriate clothing for the weather conditions, preferably in layers. Stay as dry as possible. Avoid tight footwear and wear mittens instead of regular gloves. Gear should be wind- and waterproof. Inspect group members frequently in extreme cold and make sure to rewarm periodically.
IMMERSION FOOT
Immersion foot is a condition that causes damage to nerves and small blood vessels due to prolonged, well, immersion in cold (but not freezing) water below 60 degrees Fahrenheit/15-16 degrees Celsius. Historically, it was known as “trench foot,” and seen commonly in soldiers who spent long periods of time in the trenches of WWI. When seen in areas other than the feet, this condition is referred to as “childblains.”
PHASES OF IMMERSION FOOT
Unlike frostbite, which can freeze tissues within a half-hour in extreme cold, immersion foot takes at least 12 hours or even several days to cause injury. It often progresses in phases:
“Prehyperemic phase”: As immersion foot develops, the feet will feel cold, numb, and heavy. Skin will turn pale or blotchy, and somewhat swollen. It may often appear “wet.”
“Hyperemic phase” (seen upon rewarming): As the patient is treated (see below), the patient will experience pain, redness, swelling, tingling, itching, and “pins and needles” sensations.
In severe cases, you can expect to see peeling skin, blisters, and open sores. Prolonged numbness or chronic pain may be seen. Although less frequently noted than in frostbite, the worst untreated cases may lead to gangrene and require amputation.
TREATING IMMERSION FOOT
Immersion foot treatment is somewhat different than frostbite. Do not rush to rewarm. Instead use gradual during and warm (room-temperature) exposure. The feet should be kept elevated, dry, and clean. Like frostbite, walking should be avoided if at all possible. Remove wet or dirty socks. Protect blisters if they form, and check frequently for signs of infection. Pain relief and antibiotics may be required.
PREVENTION OF IMMERSION FOOT
To prevent immersion foot from developing, wear properly-fitting footwear and keep feet dry, clean, and warm. Have spare sets of moisture-wicking socks and change often. Inspect feet daily and avoid cold situations where feet are constantly wet.
Joe Alton MD
Dr. Alton
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