Frostbite is a cold injury that results from exposure to below-freezing temperatures for several hours and usually affects the extremities, nose, cheeks, and ears; male genitalia may be affected as well. Frostbite can occur with above-freezing temperatures if there is a strong wind, high altitude, or extreme wetness. Superficial frostbite is characterized by injury to the skin and subcutaneous tissues that resolves within 3 to 4 weeks. Deep frostbite involves muscle, nerves, and blood vessels and may result in tissue necrosis and gangrene. Historically, frostbite has been a problem among military personnel and high-altitude climbers, but anyone exposed to extreme cold for a long period of time (e.g., homeless individuals or those sitting in a broken-down car) may develop frostbite.

The physiologic response to cold is to preserve the core (internal) temperature. One way in which this is accomplished is through peripheral vasoconstriction and shunting, thereby preventing hypothermia (a generalized lowering of body temperature below 93 degrees Fahrenheit (34 degrees Celsius). This, in turn, prevents adequate blood flow and heat to the extremities. Extremity heat is initially preserved by alternating cycles of cold-induced vasoconstriction and vasodilatation (hunting response); this response fails under extremely cold conditions as the preservation of internal body temperature takes precedence over the extremities.

• Intoxication with alcohol or other substances 
• Extremes of age 
• Cardiovascular disease 
• Peripheral vascular disease 
• Diabetes mellitus 
• Psychiatric illness 
• Exhaustion, hunger, malnutrition, or dehydration 
• Winter sports, especially at high altitudes 
• Outdoor occupations 
• Homelessness 
• Trauma 
• Smoking 

• Pain progressing to numbness 
• White color and waxy appearance of the skin of effected body part (the result of vasoconstriction) 
• Hyperemia (blood engorgement) of the body part after rewarming
• Burning sensation and edema that may last for weeks 
• Vesicles and bullae may develop 
• Black eschar may develop several weeks into the course of frostbite 

Exposure history and physical examination generally lead to rapid, unequivocal diagnosis.

A history detailing the temperature and duration of exposure is essential as the extent of cellular damage depends on the length of time the tissue is frozen. Frostbitten areas are initially cold, hard, white, and numb. Warming produces blotchy red areas, edema, and pain. A superficial injury is suggested by soft, pliable subcutaneous tissue. A deep injury is suggested by a violet discoloration after rewarming, hemorrhagic blisters, and lack of edema.

When tissue temperatures drop below 50 degrees Fahrenheit (10 degrees Celsius), numbness occurs, accompanied by vasoconstriction and leakage of plasma into the interstitium. At 32 degrees Fahrenheit (0 degrees Celsius) or less, ice crystals form, usually in the extracellular space but also intracellularly. This results in water exiting from cells; cell death occurs via dehydration when one-third of its volume is lost. Thawing or rewarming may lead to red cell sludging, microthrombi, and hypoxemic vasospasm, affecting the microcirculation and leading to tissue ischemia and necrosis.

Four levels of frostbite injury include: (1) first-degree: redness and edema for several days; (2) second-degree: blisters and bullae formation within 48 hours that heal over several weeks, leaving an eschar; (3) third-degree: severe edema, hemorrhagic vesicles, and ischemic necrosis; and (4) fourth-degree: dry gangrene.

• Serum electrolytes and arterial blood gases—to monitor acid base status and electrolyte shifts, especially during rewarming and rehydration 
• Blood and wound Gram's stains and cultures—to monitor secondary infection and sepsis 

• Traditional and magnetic resonance angiography—to assess peripheral circulation and demarcation of ischemic tissue 
• Roentgenograms—to identify osteoarthritic changes months after injury 
• Technetium (Tc)-99 bone scans—to determine tissue perfusion and viability 

• Microwave thermography
• Doppler ultrasound and digital plethysmography—to assess vascular patency and determine suitability for medical sympathectomy

Mild frostbite is treated with rapid rewarming, daily whirlpool baths, and bed rest. The injured area should be washed with an antiseptic agent and a sterile dressing applied. Deep frostbite is treated by rapid thawing (only if there is no danger of refreezing) in a water bath of 104 to 108 degrees Fahrenheit (40 to 42 degrees Celsius) for 15 to 30 minutes; the patient should be hospitalized and the frostbitten extremity elevated. Narcotics are often necessary for pain. Prevention and early treatment of infection are critical. Cotton wool should be used to separate affected toes or fingers to prevent tissue maceration. Twice daily water (whirlpool) baths with an aseptic solution at 95 to 98.6 degrees Fahrenheit (35 to 37 degrees Celsius) are continued until healing has occurred (weeks to months). Deep frostbite is often accompanied by hypothermia. This is a medical emergency requiring rewarming in a hospital setting because hypoxemia and acid-base and electrolyte disturbances, which accompany rewarming, may lead to fatal ventricular arrhythmias.

Never rub or massage frozen body parts and avoid walking on a frostbitten foot if possible. Use warm, not hot, compresses as patient may be unable to detect temperatures high enough to cause burns. Remove any rings, watches, or bracelets to prepare for the swelling that occurs during rewarming.

• Opioid analgesics—to treat pain during rewarming 
• Ibuprofen (and other NSAIDs)—to treat pain and inflammation during healing 
• Tetanus toxoid—to update immunization and prevent tetanus 
• Topical antibacterials (providone-iodine)—to prevent infection 
• Broad-spectrum antibiotics—to prevent or treat bacterial infections 
• Reserpine and guanethidine—to institute a medical sympathectomy; the efficacy of these meds for this purpose, though, is not established

Initially frostbite looks worse than it is because the skin may be more seriously affected than the subcutaneous tissues; thus, the decision to amputate should be delayed until necrotic demarcation occurs; this process may take several months. However, surgery should not be delayed in patients with refractory pain; sepsis; or wet, infected gangrene.

• Amputation—to treat gangrene or sepsis 
• Sympathectomy—to decrease severe edema, increase tissue salvage, and alleviate sequelae; long-term benefits have not been proven 

As described earlier, frostbite warrants immediate medical attention with conventional therapies to help salvage and protect viable tissue in affected areas. Nutritional support may enhance conventional medical therapy (Purkayastha et al. 1993). General advice for the prevention of hypothermia (which may lead to frostbite, see section entitled Etiology) includes maintenance of adequate hydration and caloric intake prior to and during cold exposure to preserve core temperature.

Vitamin C:

A controlled animal study of 150 albino rats evaluated the therapeutic role of vitamin C and Indian black tea following frostbite. Rats were randomly assigned to one of six groups. Oral vitamin C plus rapid rewarming in a warm water bath, and rapid rewarming in the tea decoction alone, showed greater preservation of tissue compared to controls (P<0.05). Rapid rewarming in a tea decoction plus oral vitamin C showed the greatest preservation of tissue (P<0.01). Comparatively, this group also experienced the smallest number of severe injuries (Purkayastha et al. 1993).

Research is necessary to assess the efficacy of both vitamin C and black tea for treatment of frostbite in humans. The association of reduced tissue necrosis with rapid rewarming in Indian black tea decoction demonstrated in the rats may be partly related to the constituents of tea, but the exact mechanism is not known. The contents of the tea that may have been responsible for the positive clinical results include:

• Quercetin – may reduce capillary fragility; free radical scavenger
• Caffeine – may relax smooth muscle and act as a nerve stimulant
• Theophylline – may enhance thermogenesis

Improved outcomes for the groups administered vitamin C may be due to the following:

• Favorable alterations in metabolic and circulatory function
• Enhancement of wound healing
• Potentiation of cellular immunity, thereby reducing infection
• Free radical scavanging (Purkayastha et al. 1993).

Vitamin E:

A review of free radical generation during rewarming and reperfusion of frozen tissues suggests that antioxidant therapy, especially with lipid-soluble antioxidants (e.g., vitamin E), may be protective against cold-induced injuries (Bhaumik et al. 1995).

• Poplar buds (Populus spp. including P. nigra, P. Canadensis, and P. tachamahaca), also known as balm of Gilead and balm of Mecca, are approved by the Commission E for external use in the case of frostbite. Poplar buds, which contain essential oils, flavonoids (including quercetin), and phenol glycosides (including caffeic acid and fatty acids), have antimicrobial and analgesic properties. Semi-solid ointment or other topical preparation containing 20% to 30% of bud exudate is applied to affected frostbitten area (Blumenthal et al. 2000).

• Cayenne Pepper (Capsicuum spp.) in topical form has been used traditionally in China and Japan to treat frostbite (Blumenthal et al. 2000).

Formal scientific studies evaluating homeopathic remedies have not been documented to date for prevention or treatment of frostbite. However, experienced homeopaths, after considering a patient's constitution, have used the following remedies in the clinical circumstances described:

• Arsenicum album—For coldness of the extremities with black discoloration of the nails. Patients for whom this is appropriate are typically restless and very anxious. 
• Hepar—For intolerance of cold and intense sensitivity to pain, particularly when the head and ears are exquisitely sensitive to wind and cold. The patients for whom this is appropriate tend to complain of splinter-like pain or of abscesses that are slow to heal. 
• Veratrum album—For weakness and collapse with a sensation of internal coldness that is described as ice water in the veins; also used for the patient suffering from cold hands, feet, and face accompanied by headache. 

Massage is contraindicated in the case of frostbite.

Because the extent of frostbite is not usually evident on clinical presentation, monitoring over weeks to months is essential to determine the depth of injury.

• Several layers of warm clothing, especially protection from wind and water, that do not constrict movement 
• Dry, warm gloves, socks, and insulated boots 
• Head covering, preferably with ear flaps in extreme conditions, as 30% of heat loss occurs from the head 
• Consuming fluids and food before and during lengthy outdoor excursions 
• Attention to white areas on face and ears of companions who might be unaware of impending frostbite 

• Increased cold sensitivity in the affected area following recovery 
• Changed skin color 
• Faulty nail growth 
• Hyperhidrosis 
• Pain with use of affected extremity post-recovery 
• Loss or alteration of sensation 
• Frostbite arthritis 
• Squamous and epidermoid cell carcinomas 

Prognosis is entirely dependent on the extent of tissue injury, ranging from complete recovery with no sequelae to amputation.

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