Chapter 118. Frostbite and Hypothermia

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 and perfusion returns after 2 to 3 days. Bullae and edema are late findings. 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. Treatment of trench foot and chilblains include elevation, warming, and bandaging of the affected body part. Nifedipine 20 milligrams PO 3 times daily, pentoxifyline 400 milligrams PO 3 times daily, or limaprost 20 micrograms PO 3 times daily, as well as topical corticosteroids, such as 0.025% fluocinolone cream or a brief burst of oral steroids may be added.

Clinical Features

Freezing of the 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 skin freezing and results in the formation of clear bullae. The patient complains of numbness, followed by aching and throbbing. Deep cold injury, third-degree frostbite, involves freezing of the skin and subdermal plexus leading to hemorrhagic bullae and skin necrosis. Fourth-degree frostbite, extends deeper to muscle, tendon, and bone with mottled skin, nonblanching cyanosis, and eventual dry, black, mummified eschar formation. Because it is difficult to initially evaluate the depth of injury, early injuries are better classified as superficial or deep. Laboratory testing or imaging is not needed to diagnosis frostbite.

Treatment

1. Provide rapid rewarming in circulating water at 40°C to 42°C (104.0°F to 107.6°F) 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 affected extremities. Patients may require parenteral opioids initially, followed by oral NSAIDs.

5. Update tetanus immunoprophylaxis.

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, prophylactic antibiotics, and silver sulfadiazine is controversial.

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

Clinical Features

Patients with mild hypothermia (32°C to 35°C [90°F to 95°F]) present with shivering, tachycardia, ...