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NONFREEZING COLD INJURIES

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Trench foot is a direct soft tissue injury that results from prolonged exposure to nonfreezing cold and moisture. The foot is initially pale, mottled, pulseless, and anesthetic and does not improve quickly with rewarming. Several hours after rewarming, the foot becomes hyperemic and painful as perfusion returns after 2 to 3 days. Bullae and edema are late findings. Anesthesia may persist for weeks or even permanently. Hyperhidrosis and sensitivity to cold are late features and may last for months to years. Chilblains (pernio) are painful inflammatory lesions typically affecting the ears, hands, and feet caused by chronic exposure to intermittent damp, nonfreezing conditions. Localized edema, erythema, and cyanosis appear up to 12 hours after the exposure and are accompanied by pruritis and burning paresthesias. Tender blue nodules may form after rewarming and can persist for several days. Treatment of trench foot and chilblains includes drying, elevation, warming, and bandaging of the affected body part. With chilblains, add nifedipine 20 mg PO three times daily, pentoxifyline 400 mg PO three times daily, or limaprost 20 μg PO three times daily, as well as topical corticosteroids, such as 0.025% fluocinolone cream.

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FROSTBITE

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Clinical Features

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Freezing of tissue causes frostbite. Patients initially complain of stinging, burning, and numbness. Frostbite injuries are classified by the depth of injury and amount of tissue damage based on appearance after rewarming. First-degree frostbite (frostnip) is characterized by partial thickness skin freezing, erythema, edema, lack of blistering, and no tissue loss. Second-degree frostbite is characterized by deeper, full-thickness skin freezing and results in the formation of clear bullae. The patient complains of numbness, followed by aching and throbbing. Deep cold injury or third-degree frostbite involves freezing of the skin and subdermal plexus leading to hemorrhagic bullae and skin necrosis. Fourth-degree frostbite extends into muscle, tendon, and bone with mottled skin, nonblanching cyanosis, and eventual dry, black, mummified eschar formation. Early injuries are better classified as superficial or deep because it is difficult to initially evaluate the depth of injury. Laboratory testing and imaging are not needed to diagnose frostbite.

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Treatment

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  1. Provide rapid rewarming in circulating water at 37°C to 39°C (98.6°F to 102.2°F) for 20 to 30 minutes until tissue is pliable and erythematous.

  2. Debridement of clear blisters and aspiration of hemorrhagic blisters are controversial. Consult with a surgeon for local preference.

  3. Apply topical aloe vera every 6 hours.

  4. Provide pain management, local wound care, and dressing. Splint and elevate the affected extremities. Patients may require parenteral opioids initially, followed by oral NSAIDs.

  5. Provide tetanus immunoprophylaxis, if needed.

  6. Patients with superficial, local frostbite may be discharged home with close follow-up arranged.

  7. Patients with deeper injuries require admission for ongoing care.

  8. The use of prophylactic bacitracin ointment, antibiotics, and silver sulfadiazine is controversial.

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HYPOTHERMIA

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Hypothermia, a core body temperature of <35°C (<95°F), results from heat loss through conduction, convection, radiation, or evaporation.

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