The occurrence of cold-related injuries depends on the degree of cold exposure, as well as environmental and individual factors. Frostbite is the prototypical freezing injury and is seen when ambient temperatures are well below freezing. Nonfreezing cold injuries occur as a result of exposure to wet conditions when temperatures are above freezing. The most common nonfreezing cold injuries are trench foot and chilblains. Although frostbite may result in permanent tissue damage, nonfreezing cold injuries are characterized by usually mild but uncomfortable inflammatory lesions of the skin. This chapter describes the occurrence, risk factors, treatment, and prevention of the nonfreezing cold injuries—trench foot and immersion foot, chilblains or pernio, panniculitis, and cold urticaria—and the freezing injury—frostbite.

TRENCH FOOT

Trench foot and its more severe variant, immersion foot, are rare conditions in civilians but can be a significant problem in military operations. The pathophysiology of trench foot is multifactorial but involves direct injury to soft tissue sustained from prolonged cooling, accelerated by wet conditions. The peripheral nerves seem to be the most sensitive to this form of injury.

Early symptoms progress from tingling to numbness of the affected tissues. On initial examination, the foot is pale, mottled, anesthetic, pulseless, and immobile, with no immediate change after rewarming. A hyperemic phase begins within hours after rewarming and is associated with severe burning pain and reappearance of proximal sensation. As perfusion returns to the foot over 2 to 3 days, edema and possibly bullae form, and hyperemia may worsen. Anesthesia frequently persists for weeks and may be permanent. In more severe cases, tissue sloughing and gangrene may develop. Hyperhidrosis and cold sensitivity are common late features and may persist for months to years. Severe cases may be associated with prolonged convalescence and permanent disability.¹

Treatment is supportive, but vasodilator drugs may be tried. Oral prostaglandins can increase skin temperatures, which suggests improved circulation.² Feet should be kept clean, warm, dryly bandaged, elevated, and closely monitored for early signs of infection. Prophylaxis for trench foot includes keeping warm, ensuring good boot fit, changing out of wet socks several times a day, never sleeping in wet socks and boots, and, once early symptoms are identified, maximizing efforts to warm, dry, and elevate the feet.

CHILBLAINS OR PERNIO

Chilblains, or pernio, are characterized by mild but uncomfortable inflammatory lesions of the skin caused by long-term intermittent exposure to damp, nonfreezing ambient temperatures. Symptoms are precipitated by acute exposure to cold.³ The most common areas affected are the feet (toes), hands, ears, and lower legs. Chilblains are primarily a disease of women and children, and although rare in the United States, the disease is common in the United Kingdom and other countries with a cold or temperate, damp climate.³ In addition, young females with Raynaud’s phenomenon and other immunologic abnormalities such as lupus erythematosus, as well as those in households with inadequate heating and lack of warm clothing, are at greatest risk. Some studies suggest that a low body mass index may be associated with increased risk.^3,4

Early symptoms progress from tingling to numbness of the affected tissues. The cutaneous manifestations, which appear up to 12 to 24 hours after acute exposure, include localized edema, erythema, cyanosis, plaques, nodules, and, in rare cases, ulcerations, vesicles, and bullae. Patients may complain of pruritus and burning paresthesias. Rewarming may result in the formation of tender blue nodules, which may persist for several days.

Management is supportive. The affected skin should be rewarmed, gently bandaged, and elevated. Some European studies support the use of nifedipine, 20 milligrams PO three times daily; pentoxifylline, 400 milligrams PO three times daily; or an analog of prostaglandin E₁, limaprost, 20 micrograms PO three times daily, as both prophylactic and therapeutic treatment for local cold injury.^2,5 Topical corticosteroids (0.1% triamcinolone cream) are also effective.⁶

PANNICULITIS

Panniculitis is characterized by mild degrees of necrosis of the subcutaneous fat tissue that develops during prolonged exposure to temperatures just above freezing. It is observed in children (e.g., “popsicle panniculitis” of the cheeks) and on the thighs and buttocks of young women involved in equestrian activities.⁷ During resolution of the mild inflammation, adipose fibrosis may result in cosmetic defects, such as unevenness of the skin. There is no effective treatment for the injury.

COLD URTICARIA

Cold urticaria is a distinctive example of hypersensitivity to cold air or water, which in rare cases may lead to fatal anaphylaxis.⁸ Most cases are idiopathic,⁹ but they can also be associated with increased affinity of immunoglobulin E to mast cells and viral infections.⁹ The diagnosis can be confirmed with the cold water test during follow-up. Young adults and children and those with atopy or other forms of inducible urticaria are most commonly affected.^8,10

Cold urticaria is treated similarly to urticarial lesions from other causes. Antihistamines (H1) are recommended for acute cases, although higher than usual dosing may be required.¹¹ Other potential therapies include leukotriene receptor antagonists (zafirlukast, montelukast)^12,13 and topical capsaicin. For persistent cold urticaria, ketotifen or doxantrazole may be tried, but oral preparations of these mast cell stabilizers are not available in the United States. Prescribe epinephrine autoinjectors for patients with a history of cold-induced anaphylaxis.

EPIDEMIOLOGY

Groups at high risk for frostbite include military personnel, winter sports enthusiasts, outdoor workers, the elderly, the homeless, people who abuse drugs or alcohol, and those with psychiatric disorders. Individual attributes, such as anthropometry, physiology, behavior, and general health, affect an individual’s likelihood of developing cold-related injuries^14,15 (Table 208-1).

The areas most commonly affected by frostbite are the head (31% to 39.1% of cases), hands (20% to 27.9%), and feet (15% to 24.9%).^16–18 Studies vary regarding which of these sites is most commonly affected, with military personnel reporting higher incidences of foot and hand involvement than civilians.¹⁸ Although most cases of frostbite are mild (frostnip), 12% of cases are more severe (Table 208-2).

RISK FACTORS FOR FROSTBITE

Age and Gender

Both age and gender influence the incidence of frostbite. Among Finnish teens, twice as many teenage boys as girls report having had frostbite of at least blister grade during the previous year (4.1% of boys and 2.4% of girls).¹⁹ Young men entering the military service report a cumulative lifetime incidence of 44%.¹⁶ Although frostbite injuries occur more frequently in men as they age, the same is not true of women.¹⁹ In general, the occurrence of frostbite is higher in men than in women,^19,20 which is possibly related to different occupational and leisure time activity patterns. The smaller size of women and their larger surface area–to–mass ratio increase the cooling rate, which makes women more susceptible to cooling and cold injuries.^15,21

Temperature and Windchill

The incidence of frostbite among civilians is governed by latitude of residence, the annual number of days on which the ambient temperature is below –15°C (5°F), and the length of daily cold exposure.¹⁹ In the United States, the majority of occupational outdoor cold injuries occur during the few coldest days of winter. Wind strongly increases the injury rate. Rates of injury begin to increase when temperatures fall below –12°C (10.4°F) and wind speeds exceed 4.5 m/s (10 mph).²² Wind markedly increases the cooling rate by increasing convective heat loss and reducing the insulation value of clothing, thus increasing the risk of frostbite. In addition, the colder temperatures at high altitudes, combined with high wind speeds, increase the risk of frostbite. Frostbite risk is clearly increased above 5182 m (17,000 ft).^23,24

The National Weather Service windchill temperature index provides the relative risk for frostbite and predicted time for freezing risk at given air temperatures and wind speeds. The risk of frostbite is <5% when the ambient temperature is above –15°C (5°F), but increased surveillance is warranted when the windchill temperature falls below –27°C (–16.6°F).¹⁵

Frostbite most often occurs at environmental temperatures below –20°C (–4°F). Exposure times for injury vary from hours to several days depending on magnitude of exposure, degree of protective clothing, and physical activity level.

Skin temperature is <0°C (<32°F) when frostbite occurs. Of note, the risk of finger frostbite increases linearly from 5% to 95% when temperature at the skin surface decreases from –4.8°C to –7.8°C (23.4°F to 18.0°F).²⁵

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Emergency Medical Services Bioterrorism Bomb, Blast, and Crush Injuries Chronic Pain Postrepair Wound Care Puncture Wounds and Bites

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