Cold Injuries at a Glance
- Skin is important for maintaining core body temperature within a narrow physiologic range.
- Cold weather, wind, humidity, dampness, and altitude combine to inflict skin damage.
- Nonfreezing and freezing conditions can both produce cold injuries.
- Frostbite occurs after exposure to intensely cold air, liquids, or metals. Several degrees of frostbite are recognized.
- Winter xerosis and acrocyanosis are common consequences of prolonged exposure to cold.
- Erythrocyanosis tends to occur over skin areas with thick adipose tissue, whereas chilblain is more frequently seen in lean persons.
- Cold urticaria is rare and occurs at the sites of localized cooling.
- Primary erythromelalgia is a rare neuropathic disorder to which there is a genetic predisposition.
The human capacity for physiologic adaptation to cold is minimal. This deficiency may cause problems, because seasonal changes in the outdoor environment are quite prominent, even in the temperate zones of the world. In this context, skin is important in thermoregulation, and cutaneous blood flow and the resulting skin temperature may vary widely to help preserve the core body temperature.1–3 Physiologic, behavioral, and environmental factors modulate skin responses to cold exposure.
Core body temperature is maintained within a narrow range by thermoregulatory mechanisms that rely largely on control of the cutaneous blood flow. Arteriovenous anastomoses are abundant in acral areas, and they regulate the volume of blood that passes through the skin. When the skin is cooled, there is usually an immediate acute reduction in the amount of blood that flows to the surface. These events alter skin temperature, heat loss, and color. Skin reactivity and the anatomic pattern of blood supply differ in the skin of newborns, adults, and older people. For instance, a reticulate appearance of cooled skin is a common finding in young infants (Fig. 94-1).
Reticulate appearance of cooled skin in the newborn due to the anatomic pattern of the blood supply and factors influencing flow such as arteriolar vasoconstriction and the increased viscosity of cooled blood.
The parallel arrangement of large arteries and veins in the limbs allows countercurrent exchange of heat. Vasoconstriction due to cold results in shunting of blood from the superficial to the deep venous system, and heat is transferred from arteries to veins. Thus, the blood going to the acral part of the limbs is precooled, and less heat is lost to the environment. With such thermoregulation, the body can maintain a constant core temperature of approximately 37°C (98.6°F) over a range of external temperatures between 15°C and 54°C (59°F and 129.2°F).
Normally, the skin is to some extent adapted to a cooler environment than the 37°C (98.6°F) of internal organs. Given the presence of many cold-adapted enzymes, the skin may even function more effectively when slightly cooled. In the case of adipose tissue, mild long-term exposure ...