See also ch. 17
Cold weather-related injuries of the skin are mainly related to frost. They can, however, occur even when temperatures are above freezing, in particular with high winds and/or humidity, e.g. wet clothing. In addition to temperature, the duration of exposure will determine the extent and severity of cold weather-related injuries.
Chilblains and trench foot may occur without the freezing of body tissue. Frostbite develops consequent to freezing of body tissue.
Chilblains (pernio) are a common condition among outdoors workers that may develop in predisposed individuals after exposure to cold and humid conditions. This condition may also be the presenting sign of a connective tissue disorder. Chilblains reflect an abnormal vascular response during re-warming several hours after that the area has been exposed to cold. The skin becomes itchy, painful, reddish or purplish with areas of swelling, blisters or small open sores that may affect the fingers, toes, nose, or ears. Chilblains may last for days, and healing of the affected area several weeks. Besides cold-sensitivity of the affected area, there is usually no permanent damage. Prevention requires keeping the digits and ears warm and dry.
Trench foot develops after prolonged exposure of the feet to a wet, cold environment and is more serious than chilblains. Tight fitting, constricting boots and footwear may exacerbate the condition. The foot is painful, itching and numb. The affected foot may swell and become red, blotchy or even bluish-black with advanced injury. As with chilblains, blisters and open sores can develop. Severe cases may result in tissue necrosis and gangrene.
Frostbite is the most serious of the cold-related injuries. It usually affects the hands, feet, nose, ears, and cheeks. Decreased blood-flow and heat delivery to body tissues leads to damaging ice crystal formation and cell death. Re-warming causes vascular damage, metabolic abnormalities and ultimately leads to necrosis. The tissue damage is most pronounced following prolonged exposure to cold. Frostbite injuries can be classified as either superficial (involving the skin and subcutaneous tissues) or deep (extending beyond the subcutaneous tissues and involving tendons, muscles, nerves, and even bone).
Superficial frostbite may cause pain, burning, tingling, numbness, pale skin, clear blisters, and firm-feeling skin with soft underlying tissue, which can move over bony ridges. Progressing injury that involves deeper tissue structures may result in complete loss of sensation and pale, yellowish, bluish, gray, or mottled skin in which blood-filled skin blisters may develop. The skin as well as the underlying tissue is firm, hard and solid. Advanced frostbite injury is indicated by blackening of the affected area and by development of gangrene.
The seafarer with any cold weather-related injury should be removed from the cold environment to prevent further heat loss. Indoors, wet and constricting clothing should be replaced with dry clothing. Massaging or rubbing of the affected area should be avoided. Concomitant presence of hypothermia should also be dealt with.
Cream, optionally with a content of corticosteroids, may be beneficial with chilblains. Open sores should be kept clean and be monitored for signs of infection. Trench feet should be elevated, cleaned and air-dried. Antibiotics and/or surgical management may be necessary.
Frostbite is a medical emergency, which requires treatment in a health-care facility. To prevent further trauma, the affected area should be wrapped in a dry clean bandage and cotton may be placed between the affected toes or fingers. Rapid re-warming is accomplished by immersing the affected area into 400 to 420C hot water until thawing is complete (20 – 40 minutes). Alternatively, warm wet packs at the same temperature may be used. Re-warming and thawing followed by refreezing leads to more severe tissue damage and must be avoided. The re-warming process may cause intense pain that requires oral or intravenous analgesics. After 1 to 3 months, the extent of tissue damage and the potential need for surgery may be assessed. Long-term sequelae such as sensitivity to the cold with associated pain or burning are common.