Section 17. Skin Changes Due to Other Physical and Chemical Factors

Human beings are homeotherms: we maintain our internal, or core temperature of the body within a narrow range despite thermal stresses. Thermal stress can arise from variations in environmental temperature or from the human body itself, as with heat generation by skeletal muscle during dynamic exercise. When thermal stresses arise from the environment, changes in skin temperature occur prior to any change in internal temperature. When thermal stresses arise from the body itself as with exercise, changes in core temperature occur prior to any change in skin temperature. In either case, thermal gradients are established between the skin and the body core. If skin temperature is lower than core temperature, heat will be lost from the body unless skin blood vessels constrict. If skin temperature is greater than core temperature, the body will gain heat, unless skin vessels dilate and sweat glands produce perspiration. The skin is thus a crucial component of human thermoregulation.

Human thermoregulation is achieved through an integration of several physiological processes. These integrated processes make up thermoregulatory reflexes that maintain a stable internal temperature at a “set point” of 37°C (98.6°F) despite thermal stresses. The set point is not invariant and may fluctuate as much as 0.5°C–1.0°C (0.9°F–1.8°F) according to circadian rhythms and during the menstrual cycle in females. The thermoregulatory reflexes designed to preserve internal temperature at the set point are coordinated by thermally sensitive neurons in the anterior hypothalamic–preoptic area and spinal cord, which respond to the changes in internal and skin temperatures. For example, cold-sensitive neurons in the anterior hypothalamic–preoptic area and spinal cord integrate afferent sensory inputs and activate heat-conserving mechanisms that include cutaneous vasoconstriction and increased metabolic heat production (shivering). Conversely, the stimulation of heat-sensitive neurons in the anterior hypothalamic–preoptic area and spinal cord integrate afferent sensory inputs and activate heat-dissipating mechanisms that include cutaneous vasodilation and sweat production.

To maintain thermal balance, heat gained or lost by the body must equal heat dissipated from, or produced by the body. This concept can be mathematically expressed as:

where

• ΔS = change in heat storage by the body
• M = metabolic heat production and is defined as the rate of transformation of chemical energy into heat and mechanical work
• E = evaporative heat loss and is defined as the rate of heat loss by evaporation of water from skin and surfaces of the respiratory tract. E is dependant on (1) rate of sweat secretion, (2) water vapor pressure of the environment, and (3) the area of evaporative surface.
• R = radiant heat gain or loss and is defined as heat exchange by emission and absorption of electromagnetic (infrared) radiation. This component accounts for 50%–60% of the heat loss in a thermally comfortable (thermoneutral) individual, but can easily become a net heat gain as when one is in direct sunlight.
• C = convective heat gain or loss and is defined as heat exchange due to forced movement of a fluid, either liquid or gas. This component is responsible for the transfer of heat to the skin through skin blood flow and transfer from the skin to the environment by air or water movement. Within the body, the cardiovascular system is the major mediator of convective heat transfer. C is dependent on (1) body surface area, (2) temperature differences, and (3) fluid (or air) movement.
• K = conductive heat gain or loss and is defined as heat transfer by flow down a temperature gradient, as between tissues and blood, between blood and skin, and between skin and the environment. This is usually combined with convective heat transfer.
• W = useful mechanical work

The sum of R, C, and K is determined by the temperature gradient between the skin and the environment. If ΔS is zero, the body is in heat balance. This “thermoneutral” condition is characterized as having low skin blood flow of approximately 5% of cardiac output. Sweating does not occur during thermoneutrality.

If ΔS < 0, the body is losing heat, core temperature is falling, and thermoregulatory reflexes are evoked to conserve heat. Thermal stability is maintained through reduction of skin blood flow that can approach zero during maximal vasoconstriction. Reduction in skin blood flow increases the thermal insulation between the body and the environment by minimizing losses through conductive (K), convective (C), and radiant (R) mechanisms. If heat loss continues despite low skin blood flow, metabolic generation of heat (M) through the shivering of skeletal muscle is initiated to restore and maintain core temperature. Brown adipose tissue can also be a source of metabolic heat generation through nonshivering thermogenesis.1 Although originally thought to be important only in human neonates where brown adipose tissue is 2%–5% of body weight, some brown adipocytes persist into adulthood.2 These adipocytes can directly generate heat (M) to maintain core temperature.3 If, despite all these mechanisms, ΔS remains negative, core temperature will fall and life-threatening hypothermia may result.

If ΔS > 0, the body is gaining heat and core temperature is rising. Under this circumstance of heat stress, thermal stability is maintained by increases in skin blood flow to facilitate heat loss through K, C, and even R losses. If heat gain continues despite these mechanisms, sweating is evoked to increase heat loss through evaporation (E) of perspiration. If ΔS remains positive, blood flow is diverted from skeletal muscle and gastrointestinal beds, providing for dramatic increases in skin blood flow. Sweat rate will also increase until maximal levels are achieved. If, despite maximal skin blood flow and maximal stimulation of sweating, ΔS remains positive, core temperature will rise and life-threatening hyperthermia, i.e., heat stroke, will occur.

Anatomic Considerations

The critical role of the skin in human thermoregulation is well understood: thermoregulation is achieved through variations in blood flow and sweat production so as to maintain thermal stability.4 Without these variations, thermal stability cannot be maintained resulting in risk of hypothermia or hyperthermia (see Chapters 94 and 95). Under normothermic conditions, skin blood flow ranges from 30–40 mL/min/100 g of skin in resting humans. However, the cutaneous vasculature is exceedingly compliant so that skin blood flow can vary from nearly zero during cold stress periods with maximal vasoconstriction to 8 L/min over the body's surface during maximal vasodilation in heat stress.5

Blood vessels in the skin are arranged in several plexuses in superficial and deep layers parallel to the skin surface. Most vessels are in the superficial layer and consist of high-resistance terminal arterioles, papillary loops, and postcapillary venules. Papillary loops are true capillaries. Blood flow through the loops is controlled by highly innervated arterioles. The loops are located near the dermal–epidermal junction, a region characterized by a maximal thermal gradient because of its proximity to the skin surface. Since the papillary loops also have a large surface area, blood flow through these vessels is a major determinant of heat exchange through vasodilation during heat stress and vasoconstriction during cold stress.

While papillary loops are found in both glabrous (palms, plantar aspect of feet, and lips) and nonglabrous skin (most of the body's surface, including the limbs, head, and trunk), arteriovenous anastomoses (AVAs) are found mainly in glabrous skin. They represent direct connections between arterioles and venules that bypass the high-resistance arterioles and capillaries of the papillary loops. AVAs have thick muscular walls with rich noradrenergic innervation and lie deep to papillary loops.6 Because of their deeper location in the dermis and smaller surface area, AVAs are less efficient in heat transfer than papillary loops. While AVAs dilate in response to heat stress and constrict during mild-to-moderate cold stress, their major role is to mediate local vasodilation during prolonged cold exposure. AVA vasodilation delivers warm blood to maintain tissue temperature and thus tissue viability through “cold-induced vasodilation.”7

Sweat glands also play a major role in human thermoregulation (see Chapter 83). The critical thermoregulatory role of the eccrine sweat glands that are found over most of the body surface is well known. Clearly, the main function of eccrine sweat glands is to increase heat loss through the evaporation of sweat. The density of these glands varies from 700 glands per cm2 in planar and plantar skin to 64 glands per cm2 on the back8; these glands may hypertrophy with repeated heat exposure.9 Each gland is made up of a secretory coil found in the dermis with a duct that extends through the dermis and epidermis to the surface of the skin. Sweat is secreted as an isotonic fluid by the coils. NaCl is reabsorbed within the ducts so sweat that is finally delivered to the surface is hypotonic.10 Each liter of sweat evaporated is capable of removing 580 kcal from the body. Although apocrine sweat glands have been dismissed as “atavistic scent glands,” this has recently been questioned.11 Apocrine glands are usually associated with hair follicles and are most developed on the scalp, face, upper back, and chest. It has been proposed that sebum from apocrine glands acts as a surfactant at high temperatures and, thus, facilitates dispersion of eccrine sweat over the skin's surface. At low temperatures, sebum may function to repel water from the skin and, thus, reduce heat loss.

Cutaneous Thermoregulatory Mechanisms

Cutaneous circulation is a major effector of human thermoregulation.4 During heat stress, elevated internal temperature and skin temperature lead to cutaneous vasodilation through neural mechanisms and the local effect of higher temperatures on the skin vessels themselves. During the periods of cold stress, reduced temperatures mediate a cutaneous vasoconstriction through neural as well as local vascular effects. Under normothermic conditions, skin blood flow averages approximately 5% of cardiac output; however, the absolute amount of blood in the skin can vary from nearly zero during periods of maximal vasoconstriction in severe cold stress to as much as 60% of cardiac output in severe heat stress.5

Sweating

Heat dissipation through the secretion and evaporation of eccrine sweat is critical to maintaining thermal stability in hot environments or during heat stress induced by strenuous dynamic exercise. Indeed, when environmental temperature exceeds blood temperature, the evaporation of sweat is the sole mechanism for heat dispersal. Sweat secretion is controlled primarily by sympathetic cholinergic nerves that release acetylcholine (Ach) to activate muscarinic receptors on the glands. Sweat secretion can be augmented by local production of nitric oxide near sweat glands.12 Stimulated glands produce an isotonic fluid that becomes progressively hypotonic as the Na+ is reabsorbed in the sweat gland duct by active ion transfer (see Chapter 84).

Neural Control Mechanisms of the Cutaneous Vasculature

In glabrous skin, cutaneous arterioles are innervated by sympathetic vasoconstrictor nerves that release norepinephrine and other cotransmitters.7,13–16 All thermoregulatory reflex changes in blood flow in these areas are caused by changes in noradrenergic vasoconstrictor activity and the effects of local temperature on the skin blood vessels themselves (Fig. 93-1).4,7,17

In nonglabrous skin, changes in skin blood flow are mediated by two branches of the sympathetic nervous system: (1) noradrenergic vasoconstrictor nerves as found in glabrous skin and (2) a cholinergic active vasodilator system.4,7,17 These dual sympathetic neural control mechanisms are the major effectors of thermoregulatory responses. Vessels in nonglabrous skin also respond to the effects of local temperature changes (Fig. 93-2).4,7,17

In normothermia, cutaneous arterioles are under little neural tone. During cold stress, reduction of skin temperature and/or internal temperature cause a thermoregulatory reflex-mediated reduction in skin blood flow to conserve body heat. Enhanced noradrenergic vasoconstrictor tone mediates an arteriolar vasoconstriction and, thus, decreases skin blood flow.

Conversely, during heat stress, thermoregulatory reflexes that facilitate body cooling are affected. As internal temperature continues to rise over a threshold value of approximately 37°C (98.6°F), a cutaneous vasodilation begins. At this threshold, active vasodilator tone to the cutaneous arterioles is enhanced. At rest, sweating also begins at the same internal temperature threshold. Vasodilator tone increases as internal temperature increases. Enhanced vasodilator activity decreases smooth muscle tone, leading to an arteriolar vasodilation, and, thus, an increase in skin blood flow, especially through the papillary loops. High skin blood flow delivers heat to the body surface where it is dissipated to the environment in conjunction with the evaporation of sweat. Overall, the active vasodilator system is responsible for 80%–95% of the elevation in skin blood flow that accompanies heat stress. A small, but significant portion of the vasodilation is mediated by the direct vasodilator effects of local heat on the cutaneous vessels.18

Dual vasoconstrictor nerves and vasodilator nerves in skin were first suggested in 1931 by Lewis and Pickering19 and confirmed by Grant and Holling.20 They measured skin temperature as an index of blood flow in the human forearm and found that large increases in response to heat stress could be abolished by sympathectomy or nerve blockade. They noted that while sympathectomy or nerve blockade caused only a slight cutaneous vasodilation during normothermia, heat stress elicited a much greater increase in skin blood flow. In addition, nerve blockade during established heat stress abolished any cutaneous vasodilation. These results suggested that cutaneous vessels in nonglabrous skin are innervated by sympathetic active vasodilator as well as sympathetic vasoconstrictor nerves. In the 1950s, their findings were confirmed by Edholm et al21 and by Roddie et al.22 In addition, it has been shown that bretylium tosylate (a prejunctional noradrenergic neuronal blocking agent) abolishes the cutaneous vasoconstriction induced by cold stress, but does not alter the vasodilator responses induced by heat stress.23 This confirmed that dual efferent neural systems control the cutaneous arterioles: a noradrenergic vasoconstrictor system and a nonadrenergic active vasodilator system.

Cutaneous Active Vasodilator Mechanisms

Sudomotor Activity and Active Vasodilation

Cotransmission and Cutaneous Active Vasodilation

Nitric Oxide and Active Vasodilation

Local Warming of the Skin and Vasodilation

Cutaneous Active Vasoconstrictor Mechanisms

Local Cooling of the Skin and Vasoconstriction

Thermoregulatory responses undergo physiological acclimatization after repeated thermal challenges over a prolonged (2-week) time period. After repeated exposure to a hot environment, sweat glands hypertrophy to produce more sweat and cutaneous active vasodilation begins at lower internal and skin temperatures to facilitate long-term thermal stability by favoring earlier and greater heat dissipation.87 Humans also acclimate to cold environments after repeated exposure by increasing metabolic heat generation (in part through increased amounts of brown adipose tissue) and habituating to cold. These adaptations are less effective in promoting thermal stability than adaptations to heat.88

Acute and chronic dermatological disorders can impair thermoregulation. For example, sunburn compromises sweat production, thus impairing evaporative cooling and reducing heat tolerance. At the same time, the inflammatory vasodilation that accompanies sunburn can compete against thermoregulatory reflex vasoconstriction during cold exposure. This will compromise the ability to reduce skin blood flow to conserve body heat, thus reducing cold tolerance.87 Other inflammatory skin conditions, of which erythroderma is the most extreme, have the same effect.

Medications can alter thermal tolerance, especially during heat exposure. Numerous medications have anticholinergic effects. Since the cutaneous active vasodilator system and sweat glands are both controlled by cholinergic sympathetic nerves, it is not surprising that such agents have deleterious thermoregulatory consequences. Examples of commonly used medications that can compromise heat stress responses include first generation antihistamines, H2-receptor antagonists, and tricyclic antidepressants. These systemic agents (and many others) can reduce sweat secretion, attenuate cutaneous active vasodilation, and increase the risk of thermoregulatory failure.17

Aging also modifies thermoregulatory reflexes. Relative to younger subjects, in healthy older persons, noradrenergic mechanisms are more important than cotransmitter mechanisms in vasoconstricting skin during cold stress.89 During heat stress, older subjects show a delay in the onset and reduced magnitude of cutaneous vasodilation.90 These alterations in cutaneous responses to thermoregulatory challenges contribute to increased morbidity and mortality during thermal stresses in older persons.

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).

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 to cooling may lead to progressively better insulation. Habitually cold-exposed skin also develops a more efficient system for shunting blood away from the surface. These adaptive mechanisms are most flexible during the first years of life. Tissues in the aged are less able to develop new shunts.

The effect of swimming in cold water after extreme heating—for example, after using a sauna4—is somewhat comparable to accidental cold water immersion. Well-being depends substantially on the degree of subcutaneous insulation, so that overweight persons, as well as those who are well clothed, can survive prolonged accidental cold-water exposure.5

Viscosity of fluids generally increases as temperature decreases. However, blood is a non-Newtonian fluid that exhibits thixotropy, i.e., it becomes less viscous with increasing flow velocity, independent of temperature. This effect is strongly influenced by hematocrit and by packing of erythrocytes. Macrophages also can block capillaries when they develop pseudopods as a result of reduced flow. The combination of slow flow and leukocyte conformational changes is, in part, a physiologic process that enables these cells to migrate through the endothelial lining.6 Other factors affecting blood viscosity include increased platelet adhesiveness, changes in concentrations of proteins, and the presence of abnormal proteins. Fibrinogen level is particularly important.

Local and systemic thermoregulation is complex. A group of neurons in the hypothalamus responds directly to temperature. When the temperature decreases, the rate of discharges decreases. From this temperature-sensitive area, signals radiate to various other portions of the hypothalamus to control either heat production or heat loss. Stimuli that influence the autonomic nervous system, such as painful stimuli, mental stress, arousal stimuli, and deep breaths, can all produce cutaneous vasoconstriction in warm subjects but vasodilation in cold subjects.7,8

Cold exposure produces an initial massive cutaneous vasoconstriction, which results in a fall in skin temperature. This change serves to maintain core temperature, but at the expense of the skin. Conversely, cold-induced vasodilation represents a protective mechanism to prevent skin necrosis. This physiologic reflex, known as the hunting reaction of Lewis, involves transient cyclic vasodilation caused by the opening of arteriovenous anastomoses.9,10

A chilling effect is produced by applications of dedicated hydrogel pads or cushions previously stored in a refrigerator.11,12 This biothermal procedure is commonly used during laser therapy. It also serves to achieve a sustained removal of heat from the skin and its underlying tissues. It produces discrete skin hemodynamic changes and may relieve pain.

Outdoor work and winter sports are common risk situations for cold damages. A cold environment can be a threat to the skin, leading to a subsequent fall in core body temperature. Many physiologic, behavioral, and environmental factors predispose to the global effects of cold injuries. Marked increases in convective, conductive, or radiant heat loss are responsible for the immediate effects of cold exposure. For instance, touching cold metal objects considerably increases conductive cooling (Fig. 94-2). Other predisposing factors increasing heat loss and/or decreasing heat production and insulation from clothing make people especially susceptible to cold.13

There is ample evidence that the effect of low temperature on skin biology is, in part, a function of environmental humidity, wind speed, and altitude. In this respect, the wind chill index is indicative of the convective heat loss. Wind chill affects the gradients of temperature and water content across the stratum corneum, which result in an imbalance in condition between outer and deeper epidermal layers.14 High altitude, which reduces the oxygen supply to tissues, also contributes to increase the skin damage induced by cold.15

Transepidermal water loss (TEWL) plays a prominent role in evaporative thermal loss. The skin temperature and the relative and absolute environmental humidity are key factors affecting cold injuries. The ambient humidity indicates the mass of water vapor present in a unit volume of the atmosphere. An accurate representation of the amount of moisture in the air as a function of temperature is given by the calculation of the dew point,11,16 which is defined as the temperature of the air at which the gaseous moisture begins to condense, that is, the temperature at which relative humidity reaches 100%.

Poor clothing insulation is a common reason for cold injuries. The insulation is insufficient when clothing is too light, wet, tight, permeable to wind, or inadequate to cover the cold sensitive body parts. Individual factors predisposing to cold injuries are physical injuries, leanness, low physical fitness level, fatigue, dehydration, previous cold injuries, sickness, trauma, poor peripheral circulation, the wearing of tight constrictive clothing, and old age.13 Newborns, the elderly, and individuals with impaired mental faculties remain the most vulnerable. Injury is often increased by alcohol, smoking, and psychotropic drug use.

Severe cold injuries have historically influenced the outcome of battles and wars.17,18 Peacetime military operations also impose risks.19–22 However, cold injuries are becoming more prevalent among the general population.21 Many cases are associated with alcohol consumption, homelessness in urban centers, and car breakdown. Frostbite also prevails among winter sport enthusiasts such as cross-country skiers and backpackers who get lost or trapped in a snowstorm.2,22–26 Accidental exposure to liquefied gas is another cause of severe cold injuries.27

Adaptation to cold protects one from responding inappropriately, and a moderate degree of exposure to cooling might be health promoting by stimulating a responsive and protective vasculature. In contrast, individuals who have experienced severe cold injury may have a profoundly delayed or abolished hunting reaction in the affected limbs.28 They are rendered more susceptible to recurrent cold injury with pain, hyperesthesia, or paresthesia.29 Some of these individuals also have coldness of the skin, which is very persistent and probably related to a functional imbalance in the sympathetic nervous system that results from increased α-adrenergic receptor density or affinity for norepinephrine.30 In addition, altered vascular structure may reduce vasocompliance after cold exposure. There may also be impairment of normal vascular reflexes to various stimuli, including deep inspiration, venous occlusion, neck cooling, and ipsilateral skin cooling.30

Freezing and nonfreezing injuries can be distinguished according to the severity and duration of chilling. However, the damage caused depends on many variables other than the actual temperature. Recognition is generally easy at a clinical level, but awareness of potential uncommon underlying disorders is important. Treatment, both physical and pharmacologic, is aimed at keeping the body warm and maintaining vasodilation.

Frostbite is the consequence of extreme and prolonged freezing conditions. In addition, the whole body may cool down so much that life-threatening hypothermia may ensue. This is an important concern for people who enjoy cold weather sports, particularly in mountains and circumpolar regions. Prompt recognition and treatment are of paramount importance, because many hypothermia victims can recover from very low body temperatures. Treatment in an adequate medical facility can make the difference between full recovery and lifelong problems. Even if the victim appears to be dead from exposure to cold, resuscitative efforts should be started and continued until the proper core body temperature is reached.31

Extreme and often conductive heat loss at a given body site freezes the tissues and results in localized blistering and necrosis (Fig. 94-3). Several cutaneous disorders also occur when the tissue temperature is maintained just above freezing for long periods. These conditions include chilblains, cold urticaria, cold panniculitis, erythrocyanosis, and acrocyanosis, among others. These disorders may be a consequence of impaired blood flow, reduced sensory perception, or a change in the physical properties of the tissues, such as in adipose tissue.

Minor but long-term cold exposure combined with environmental desiccation may have profound effects on the biology of the epidermis, leading, for example, to winter xerosis.32,33 Persistent erythema of the face and the hands is not a rare finding (Fig. 94-4).

Frostbite occurs when tissue freezes after exposure to extremely cold air, liquids, or metals. The clinical effects of accidental injury that leads to the death of tissues are similar to those caused by cryosurgery.34 The components of tissue that may lead to damage when frozen are water, with formation of ice crystals at 0°C (32°F), and lipids such as fat globules or cell membrane constituents.

Contrasting with damaging cryoinjuries, cryopreservation is used to preserve or “to freeze” in vitro most of the biomolecules present in tissues.35 Any metabolic activity is blocked in these circumstances. Cryoscopy is a diagnostic procedure applicable in vivo.36 It relies on an acute but short icing of the stratum corneum in order to disclose some structures exhibiting different capacities of thermal conductivity.

The rate of freezing determines the site of injury at the cellular level.37 Extracellular formation of ice occurs most commonly with slow freezing, whereas fast freezing tends to produce intracellular ice. The formation of ice crystals in the extracellular space alters the osmotic properties of the tissues and disturbs the flow of water and electrolytes across the cell membranes. Thawing may be as damaging as the freezing itself, and repeated freeze and thaw cycles, as may occur in accidental injury, compound the damage, making more water available, which rapidly leads to intracellular flooding. The rewarming rate is also important. In slow rewarming, ice crystals become larger and more destructive. Cells are also exposed to a high concentration of electrolytes for a longer period than with rapid rewarming.

As the body cools, there is a reflex constriction of the arteries and veins in the extremities.31 This results in increased venous pressure, decreased capillary perfusion, and sludging. Cooling also creates a leftward shift in the oxygen dissociation curve, and hemoglobin gives up its oxygen less readily. These two conditions result in hypoxia and damage to the capillaries and surrounding tissue. Oxygen tension is further decreased by thrombus formation in the microvasculature, which results in arteriovenous shunting. Arterial and arteriolar constriction, mediated by sympathetic outflow, initiates and probably maintains circulatory impairment. In addition, segmental vascular necrosis occurs in areas of erythrostasis, which suggests that ultimate damage may depend more on insufficient clearance of toxic substances than on initial vasoconstriction.

Cell types vary in their susceptibility to cold injury. Melanocytes are very sensitive to cold, and irreversible damage may occur at −4°C to −7°C (24.8°F–19.4°F). This sensitivity explains the hypopigmentation that often follows cryotherapy. In addition, it appears that black persons are more susceptible to frostbite than whites. Nerve axons are also easily damaged by cold, and nerve injury may occur with axonal degeneration of large myelinated fibers. Autonomic fibers are also affected, and this may account for the abnormal sweating and cold sensitivity that follow nonfreezing cold injury.38,39 Nerve sheaths are quite resistant to cold, as are bone and cartilage.28 Desolidification of lipids in adipose tissue and disruption of endothelial cells lining blood vessels and lymphatics, with secondary disturbances of permeability and blood flow, are other consequences of severe cold. In the overall assessment, there are marked similarities in the pathologic processes to those seen in thermal burns and in ischemia-perfusion injuries.

Three stages of cooling are recognized. The first is massive vasoconstriction, which causes a rapid fall in skin temperature. In a second step, the hunting reaction follows with a cyclic rise and fall in skin temperature. If cold exposure continues, the third stage of freezing occurs as the skin temperature falls to approach ambient temperature. The events that ensue in freezing and nonfreezing cold injuries are similar.17,40 Consequences of cold injuries and their classification are presented in Tables 94-1 and 94-2, respectively.

Frostbite commonly affects fingers, toes, ears, nose, and cheek.41,42 The clinical presentation of frostbite falls into three categories corresponding to mild frostbite or frostnip, superficial frostbite, and deep frostbite with tissue loss.

Frostnip involves only the skin and causes no irreversible damage. There is a sensation of severe cold progressing to numbness followed by pain. Erythema is usually present on the cheeks, ears, nose, fingers, and toes (Fig. 94-5). There is no edema or bleb formation. Frostnip is the only form of frostbite that can be treated safely in the field with first aid measures.

Superficial frostbite involves the skin and immediately subcutaneous tissues. It includes the previously described signs but with the pain subsiding to feelings of warmth. This is a sign of severe involvement. The skin has a waxy appearance, but deeper tissues remain soft and resilient. Clear blebs form, accompanied by edema and erythema within 24–36 hours after thawing. Lesions may become eroded (Fig. 94-6).

Deep frostbite extends to the deep subcutaneous tissue. The injured skin becomes white or bluish white with a variable degree of anesthesia. Most often the affected skin becomes deceptively pain free, and the discomfort of feeling cold vanishes. The tissue is totally numb, indurated with immobility of joints and extremities. Muscles may be paralyzed. Nerves, large blood vessels, and even bone may be damaged. Large blisters form 1 to 2 days after rewarming, and they can be classified according to depth, as in heat-induced burns (Fig. 94-7). Frostbite blister fluid contains high amounts of prostaglandins, including prostaglandin F2α and thromboxane A2. These mediators may contribute to increased vasoconstriction, platelet aggregation, leukocyte adhesiveness, and ultimately progressive tissue injury. The blister fluid begins to be resorbed within 5 to 10 days, which leads to the formation of hard, black gangrene. Weeks later, a line of demarcation occurs, and the tissues distal to the line undergo autoamputation (Fig. 94-8).

Prevention

Prevention is key to protecting individuals from the effects of cold weather; and frostbite, frostnip, and hypothermia always should be taken seriously. Prognostic factors25,43–46 are listed in Table 94-3. Wearing protective clothing, warm hat, earflaps and scarf together with preventive behavior such as turning bare areas away from the wind are the most important procedures for preventing frostbite. Nonmedicated waterless ointments are traditionally used for protection against facial frostbite, but their benefit is undocumented. The thermal insulation they provide is indeed minimal.41,42 The use of protective emollients seems to cause a false sensation of safety, which leads to an increased risk of frostbite, probably through neglect of other, more efficient protective measures.47,48 In less extreme conditions, however, some specific topical formulations bring beneficial effects.49 The most effective products are those reducing TEWL and perspiration because these biological functions cause emission of body thermal energy and thus cool the skin.

Management

The first consideration in frostbite treatment is to be aware that the victim may be suffering from hypothermia.25,31,50,51 Because of the difficulty in assessing the depth of frostbite injury, conservative waiting after the frostbite episode is often encouraged in an attempt to delineate the extent of tissue loss. Beyond this, the main principles are to avoid trauma, friction, pressure, massaging with snow, and refreezing. Slow rewarming increases tissue damage, and therefore rapid rewarming is the keystone of treatment.20 It should be performed in a water bath no warmer than 40°C–42°C (104°F to 107.6°F) until the most distal parts of the body are flushed. Large amounts of analgesics may be required. The damaged part should be elevated, and blisters should be left intact. Surgical debridement is often best delayed until 1 to 3 months after demarcation. However, triple-phase bone scans, magnetic resonance imaging, and magnetic resonance angiography can be used to predict ultimate tissue loss and to assess the possibility of earlier surgical intervention.40,52,53

There is no uniformly accepted protocol for other measures allegedly beneficial in the treatment of frostbite injury.51 Intra-arterial reserpine and sympathectomy have been used to reverse vasospasm, which may contribute to tissue loss. Their role is controversial, although some patients have benefited from this therapy. To counteract vasoconstriction caused by local release of inflammatory mediators, the use of topical aloe vera, which inhibits thromboxane synthetase, and systemic ibuprofen, which inhibits cyclooxygenase, have been advocated. Oxpentifylline has been presented as an advanced therapy.54 In addition, several adjunctive therapies, including vasodilators, thrombolysis, and hyperbaric oxygen, are sometimes useful.55 Tetanus toxoid should be given in the case of open wounds. Surgery and amputation remain the ultimate strategies to help the victims.56

Sequelae

Sequelae of frostbite include permanent hypersensitivity to cold and, less often, hyperhidrosis.38 Squamous cell carcinoma is a rare outcome, usually occurring on the heel 20–30 years later.57 Epiphyseal plate damage or premature fusion may occur in children. Premature fusion can result in shortened digits, joint deviation, and dystrophic nails. In addition, frostbite arthritis, resembling osteoarthritis, may occur weeks to years later.

Nonfreezing cold injury occurs when tissues are cooled to temperatures between approximately 15°C (59°F) and their freezing point for prolonged periods. This type of injury, which is exacerbated by dampness, has claimed numerous casualties in warfare. Nonfreezing cold injury may be followed by cold sensitivity and hyperhidrosis, which may persist for years.

During World War I, trench foot was identified as a separate entity. Wet conditions at temperatures above freezing and limb dependency due to immobility and constrictive footwear were important pathogenic factors. Three stages were described. Stage I consisted of initial erythema, edema, and tenderness. Stage II followed within 24 hours with paresthesia, marked edema, numbness, and sometimes blisters. Stage III corresponded with progression to a usually superficial gangrene. Immersion foot, similar to trench foot, was described in shipwreck survivors during World War II.

Tropical immersion foot was described during the Pacific campaign in World War II. Occurring after exposure to the warm, wet conditions of jungle warfare, this condition differed from classic trench foot and immersion foot in that it caused less tissue destruction, numbness, and anesthesia and was followed by more rapid complete recovery. The role of temperature in tropical immersion foot is unclear and may not be important.58 As with trench foot and immersion foot, prevention is most important.

Another specific condition known as pulling-boat hands was described, characterized by the presence of erythematous macules and plaques on the dorsum of the hands and fingers of sailors aboard rowboats.59 Small vesicles developed later, accompanied by itching, burning, and tenderness. These individuals were exposed to long periods of high humidity, cool air, and wind, an ideal setting for the development of nonfreezing cold injury. In addition, hours of vigorous rowing daily produced repetitive hand trauma.

Many individuals present with dryness of the skin, particularly on the lower extremities, during wintertime. The hands, forearms, cheeks, lips, and trunk also may be affected. Itching, a dry appearance, chapping, and cracking of the stratum corneum are more or less prominent. The condition is markedly influenced by cold environments, especially in combination with low humidity.38,39 Predisposing factors include atopic dermatitis, ichthyosis, and increasing age. Excessive washing exacerbates winter xerosis. Indeed, irritant dermatitis of the hands worsens in a cold and dry environment.60 Emollients and improvement in the environmental temperature and humidity are helpful in controlling this condition.

Acrocyanosis is a bilateral dusky mottled discoloration of the hands, feet, and sometimes the face. It is persistent and accentuated by cold exposure. When the temperature is very low, the skin may be bright red. Trophic changes and pain do not occur, and pulses are present. This condition must be distinguished from Raynaud phenomenon (see Chapter 170), which is clearly episodic, often segmental, and painful, as well as from obstructive arterial disease (see Chapter 173).

Acrocyanosis is genetically determined and usually starts in adolescence. Chronic vasospasm of small cutaneous arterioles or venules with a secondary dilatation of the capillaries and subpapillary venous plexus has been postulated. Stasis in the papillary loops with aneurysmal dilatation at the tips redistributes blood flow to the subpapillary venous plexus. The blood flow may be compromised by altered erythrocyte flexibility, increased platelet adhesiveness, and other plasma viscosity factors. Cold agglutinins may exacerbate the acrocyanosis manifestations.61,62 The “puffy hand syndrome” is defined by the presence of hand edema superposed on acrocyanosis.63

Tissues are less sclerotic in acrocyanosis than in Raynaud phenomenon. They contain twisted collagen fibrils and large pericytes. In cases developing for the first time late in life, an underlying myeloproliferative disorder should be excluded. Remittent necrotizing acrocyanosis is associated with enhanced susceptibility to cooling and pain, as well as ulceration and gangrene of the fingers. Arteriolar occlusion by thrombi or intimal proliferation may occur. Cold pain should be distinguished from cold allodynia and cold hyperalgesia.

There is no effective treatment for acrocyanosis. Supportive measures to keep the skin warm are helpful.

Erythrocyanosis is a dusky cyanotic discoloration, worse in winter, which occurs over areas with a thick layer of subcutaneous fat (Fig. 94-9). The condition is seen most often on the lower legs and thighs of adolescent girls and middle-aged women. Nodular lesions similar to chilblains may occur and have been described in women with severe erythrocyanosis and paraplegia. Keratosis pilaris, angiokeratomas, and telangiectasia are commonly associated. Spontaneous improvement often occurs after a few years. However, the disease may persist with long-standing edema and fibrosis.

The wearing of warm clothes and weight reduction are important to decrease the insulating effect of the subcutaneous fat, which is responsible for a chronically low skin temperature. The outcome remains unpredictable.

Chilblains, also called pernio or perniosis (Fig. 94-10), are localized inflammatory lesions caused by continued exposure to cold above the freezing point.64,65 Dampness and wind that increase thermal conductivity and convection play a part. Absolute temperature is less important than the cooling of nonadapted tissue. The condition shows a genetic predisposition. It has been described most often in temperate regions, where winters are occasionally cold and damp. Chilblains are seen less often in very cold climates, where well-heated houses and warm clothing are available. Both acrocyanosis and chilblains appear to be more common in children, women, and persons with low body mass index. Spontaneous remission is common when spring arrives, and relapse is frequent during the following winters. However, chilblains do not always occur at the time of maximum cold.

Chilblains develop acutely as single or multiple, burning, erythematous, or purplish swellings (see Fig. 94–10A and C). Patients may complain of itching, burning, or pain. In severe cases, blisters (see Fig. 94-10B), pustules, and ulceration may occur. Characteristic locations include the proximal fingers and toes, plantar surfaces of the toes, heels, nose, and ears, but other sites like the calves and thighs can be affected66,67 (see Fig. 94-10C). Lesions usually resolve in 1 to 3 weeks but may become chronic in elderly people with venous stasis. Tight garments such as gloves, stockings, and shoes are especially to be avoided in cases in which there is also peripheral vascular disease. A papular form of chilblains resembles erythema multiforme and occurs at all times of the year, usually in crops on the sides of the fingers,68 often superimposed on a background of acrocyanosis.

A peculiar clinical presentation may occur in young women riding horses for several hours daily during winter.69,70 Indurated red-to-violet tender plaques develop on the lateral calves and thighs (see Fig. 94-10C). The condition is quite similar to the nodular perniotic lesions described in adolescent girls with erythrocyanosis. For prophylaxis, experienced riders usually wear baggy breeches that provide insulation and are not tight enough to compromise the circulation.

Perniotic lesions have been described in association with myeloproliferative disorders,71 probably as a consequence of blood flow changes, presence of cold agglutinins, and altered inflammatory response on cooling.

Idiopathic perniosis is characterized histologically by edema of the papillary dermis and by the presence of superficial and deep perivascular lymphocytic infiltrates. Necrotic keratinocytes and lymphocytic vasculitis also have been reported. Thickening of blood vessel walls with intimal proliferation may lead to obliteration of the vascular lumen.72–74

Chilblain lupus is a distinct disease and is similar to discoid lupus erythematosus.75,76 Lupus pernio is a variant of sarcoidosis (see Chapter 152) and is unrelated to cold injuries.

The unfamiliarity of physicians with chilblains sometimes gives rise to unnecessary hospital admissions with expensive laboratory and radiologic evaluations and, at times, hazardous therapy. The most important point in management is prophylaxis through the use of adequate, loose, insulating clothing and appropriate warm housing and workplace. Maintaining the blood circulation by avoiding immobility is also helpful. A short course of ultraviolet light therapy at the beginning of winter was a recommendation but has been challenged.77 Once chilblains occur, treatment is symptomatic with rest, warmth, and topical antipruritics. Calcium channel-inhibiting drugs may be effective in the treatment of severe recurrent perniosis,78 although they may cause headache and flushing that are troubling to some patients. In cases of crippling severity, thyrocalcitonin and hemodilution may be helpful.

Acquired cold urticaria is a form of physical urticaria (Fig. 94-11). Lesions occur at sites of localized cooling, usually when the area is rewarmed. The disease is recognized by wheal and flare-type reactions and/or angioedema. The condition may be idiopathic or associated with some serologic abnormality.79–83 It accounts for approximately 2% of cases of urticaria (see Chapter 38).

Most cases fall into the group of essential cold urticaria. They can be subdivided into a rare familial type and an acquired form. Immunoglobulin E and, more rarely, immunoglobulin M have been implicated in the pathogenesis. The antigen is likely a normal metabolite produced on exposure to cold. Histamine is one of the most important mediators, but leukotrienes, platelet-activating factor, and others have been incriminated. In this disease, exposure to cold causes prolonged edematous papules and plaques, often with headache, fever, arthralgia, and leukocytosis. Swelling of the oral mucosa and esophagus may occur on ingestion of cold liquids. A rather distinctive combination of cold urticaria and dermographism or cholinergic urticaria is not uncommon. Alarming signs resembling those of histamine shock may lead to loss of consciousness. Death while swimming in cold water has been reported.

Familial cold urticaria is a rare autosomal dominant condition with onset at an early age.84,85 A mutation in the gene responsible for the cold-induced autoinflammatory syndrome-1 (CIAS1) has been identified.85 Urticaria develops when the patient is exposed to generalized cooling, particularly chilling wind, rather than local cold application. The delayed type of familial cold urticaria is characterized by localized angioedema developing 9 to 18 hours after cold exposure.

Cold urticaria may occur in 3%–4% of patients with cryoglobulinemia, and it also may be associated with cold agglutinins, cryofibrinogens, and cold hemolysins. Cold urticaria has been reported in cases of infectious mononucleosis in association with either cryoglobulins or cold agglutinins, but such occurrences are rare. Cold urticaria may also be a sign of the Muckle–Wells syndrome that associates urticaria, deafness and amyloidosis.86 In this rare genetic disorder recurrent bouts of urticaria, fever, chills and malaise may occur from birth and persist throughout life. Helicobacter pylori has been suggested as a causative agent in some cases of acquired cold urticaria.87

Diagnosis of cold urticaria is confirmed by a cold challenge induced by an ice cube wrapped in a plastic bag placed on the skin of the forearm for periods varying from 30 seconds to 10 minutes (see Fig. 94-11). Wheals form on rewarming. Sometimes water at 7°C (44.6°F) is more effective, presumably because it causes less severe vasoconstriction. Peltier effect-based temperature challenge appears to be an improved method for diagnosis.88 The Peltier effect relies on using two different heat-transferring metals to generate a precise skin surface temperature, sufficiently cold, to induce lesions. The temperature is regulated by a microprocessor control unit monitoring the actual temperature at the test site.

Cold erythema seems to be a related disorder with erythema and pain but without urticaria. Familial polymorphous cold eruption is a rare autosomal dominant disease characterized by childhood onset of nonpruritic, erythematous patches often accompanied by influenza-like symptoms and leukocytosis after generalized exposure to cold. Results of the ice cube test are negative. The pathogenesis remains unknown. The disease frequently has been referred to as familial cold urticaria, although the skin lesions are not urticarial.89

Avoiding cold wind exposure and swimming in cold water are important preventive measures. Antihistamines reduce clinical signs and symptoms. Desensitization to cold is possible by immersing one arm into water at 15°C (59°F) for 5 minutes daily.

Cold injuries may affect the subcutaneous tissue in different ways. The freezing injury in deep frostbite results in tissue gangrene. Nonfreezing injuries also can alter the hypodermis. Among them, cold panniculitis is more common in children than in adults. It affects the cheeks and legs most commonly. Tender erythematous subcutaneous nodules appear 1 to 3 days after exposure and subside spontaneously within 2 to 3 weeks. Ice cube challenge to the child's skin for 10 minutes results in the development of an erythematous plaque 12 to 18 hours later.

A perivascular mixed infiltrate with neutrophils, lymphocytes, and histiocytes is present at the dermal–subcutaneous junction after 24 hours, followed by a well-developed panniculitis at 48 to 72 hours. Some adipocytes are necrotic and rupture to form cystic spaces. The reaction subsides completely in 2 weeks. Infants have a higher content of saturated fatty acids in adipose tissue than do adults, and this may result in solidification at higher (less cold) temperatures.90,91 Cold panniculitis should be distinguished from other related disorders, including erythrocyanosis with nodules, sclerema neonatorum, and subcutaneous fat necrosis of the newborn.

(See Chapters 70 and 107)

Sclerema neonatorum and subcutaneous fat necrosis of the newborn are distinct disorders involving the subcutaneous fat of the newborn. As noted in the prior paragraph, infant fat differs from adult fat in that it has a higher saturated–unsaturated fatty acid ratio, which results in solidification at a higher temperature. Prematurity and immaturity of enzyme systems may result in a relative inability to desaturate fatty acids, which alters the ratio further. Sepsis, dehydration, chilling, infection, and other stresses also may inhibit the enzyme system. Thus, infants in general, and premature or otherwise compromised newborns in particular, are susceptible to such disorders.

Sclerema neonatorum is a rare disorder characterized by diffuse, rapidly spreading hardening of the skin and subcutaneous tissue in infants.92 It starts on the buttocks and trunk, usually in the first week of life. Palms, soles, and scrotum are spared. Fifty percent of affected infants are premature. They have difficulty feeding and are lethargic, and many are otherwise debilitated. Septicemia is frequent, and the prognosis is poor. Cold exposure does not seem to be important in the etiology of sclerema neonatorum; however, similar clinical findings have been seen in cases of primary cold injury.93 Histologically, the subcutaneous layer is greatly thickened by enlarged fat cells and wide, fibrous bands. There is no fat necrosis, and many of the fat cells contain fine needle-like clefts.94

Treatment of sclerema neonatorum involves correcting dehydration and electrolyte imbalance and treating septicemia if present. The value of systemic glucocorticoids is controversial. Successful treatment with exchange transfusions has been reported.95

Subcutaneous fat necrosis of the newborn is characterized by discrete red to violaceous mobile plaques and nodules that usually appear within a few days of birth. The back, thighs, and cheeks are most commonly affected. Fat necrosis and crystallization are the hallmarks of the disease. There may be a granulomatous inflammatory response with foci of calcification. In most cases, the condition is benign and self-limited, although it has been associated with hypercalcemia and death.96

As in sclerema neonatorum, there is no clear etiologic relationship to cold, and the cause is likely multifactorial. It has been postulated that an underlying defect in fat composition, poor nutrition, and various physical stresses such as hypothermia may be important.

Erythromelalgia or erythermalgia is a rare chronic cutaneous disorder characterized by erythema, burning discomfort, and warmth of the extremities.97,98 Primary erythromelalgia is an autosomal dominant neuropathic disorder involving a mutation in a voltage-gated sodium channel subunit.99–106 Vasoconstriction apparently precedes reactive hyperemia, similar to that seen in Raynaud phenomenon. An early-onset type and an adult-onset type have been recognized. When the extremity is lowered or heat is applied, the pain is intensified. The application of cold or elevation of the extremity has the opposite effect of decreasing the pain. Idiopathic erythromelalgia may involve increased thermoregulatory arteriovenous shunt flow. Secondary erythromelalgia is associated commonly with myeloproliferative syndrome-related thrombocythemia and is mostly evident in the adult-onset type.

Treatment for adults with erythromelalgia includes a single daily dose of acetylsalicylic acid (aspirin), but children who have no associated underlying disorder obtain little to no relief from the drug. Other drugs including mexiletine107 and venlafaxine108 may also help. Pain may be decreased by topical amitriptyline combined with ketamine.109 Lidocaine in patches110 or administered intravenously in combination with oral mexiletine111 may also alleviate pain. Sympathectomy in the upper extremities is another option for treating refractory primary erythromelalgia.112

(See Chapter 170)

(See Chapter 169)

(See Chapter 173)

The very young and very old are at increased risk of domestic burns.1,2 Active young adults in industrial jobs are at modest increased risk. In developed countries, about 70% of pediatric burns are caused by hot liquid. Flame injuries are more common in older children and young working adults. Scalding and flame injuries each account for approximately half of burn injuries in the elderly, with kitchen and bathing accidents being predominant. Approximately 20% of burns in younger children involve abuse or neglect.

The development of an envelope of cornified skin was a crucial component of the adaptation of aquatic sea animals to the land environment. The vapor and fluid barrier created by the epidermal layer facilitates the maintenance of fluid and electrolyte homeostasis within very narrow limits. The dermis provides strength and flexibility, and the reactive dermal vasculature facilitates control of internal body temperature within very narrow limits. The appendages provide lubrication and prevent desiccation. All of these critical functions are lost when substantial areas of the skin are burned.

There is both a local and a systemic response to the burn wound.3,4 The local response consists of coagulation of tissue with progressive thrombosis of surrounding vessels in the zone of stasis over the first 12–48 postinjury hours. An ability to truncate this secondary microvascular injury and its associated tissue loss is a major area of ongoing investigation. In larger burns, a systemic response develops that is driven initially by release of mediators from the injured tissue, with a secondary diffuse loss of capillary integrity and accelerated transeschar fluid losses. This systemic response is subsequently fueled by by-products of bacterial overgrowth within the devitalized eschar.

Burn wounds are initially clean but are rapidly colonized by endogenous and exogenous bacteria.5 As bacteria multiply within the eschar over the days following injury, proteases result in eschar liquefaction and separation. This leaves a bed of granulation tissue or healing burn, depending on the depth of the original injury. In patients with large wounds involving 40% or more of the body surface, the infectious challenge generally cannot be localized by the immune system, leading to systemic infection. This explains the rare survival of patients managed in an expectant fashion with burns of this size.

The systemic response to injury is characterized clinically by fever, a hyperdynamic circulatory state, increased metabolic rate, and muscle catabolism.6 This stereotypical response to injury has been retained by all mammalian species. It is effected by a complex cascade of mediators, including changes in hypothalamic function resulting in increases in glucagon, cortisol, and catecholamine secretions; deficient gastrointestinal barrier function with translocation of bacteria and their by-products into the systemic circulation; bacterial contamination of the burn wound with systemic release of bacteria and bacterial by-products; and some element of enhanced heat loss via transeschar evaporation. It is likely that this response has significant survival value, but control of some of the adverse aspects of this response, particularly muscle catabolism, is an active area of ongoing investigation.7,8

(See Box 95-1)

Burns are classified by depth:

• First degree: Red, dry, and painful and are often deeper than they appear, sloughing the next day (Fig. 95-1A).
• Second degree: Red, wet, and very painful with enormous variability in their depth, ability to heal, and propensity to hypertrophic scar formation (see Fig. 95-1B).
• Third degree: Leathery, dry, insensate, and waxy (see Fig. 95-1C).
• Fourth degree: Involve underlying subcutaneous tissue, tendon, or bone (see Fig. 95-1D).

Circumferential burns require special monitoring and possible surgical decompression. If across the torso, they will interfere with ventilation. If they involve an extremity, limb-threatening ischemia may occur during resuscitation.

Although lightning strikes carry large amounts of energy, measured in millions of volts, human injuries are rare, with only about 50 people so injured annually in the United States and a fatality rate of only about 10%. Injury can rarely occur from direct strike, and is usually fatal. More commonly, people are injured by current flow around the skin envelope, or side flash, when a nearby object is struck. Destructive burns are unusual. Serious injury is more often the result of associated blunt trauma or occasional cardiac arrest. In most survivors, lingering symptoms are nonfocal, neurologic in nature, often preceded by an immediate but transient loss of consciousness.9 The most common physical finding in those injured by side flash is an evanescent serpiginous cutaneous erythema, as noted in Figure 95-2.

In the outpatient setting, patient selection should ensure that major complications are few (Table 95-1). The most common issues that arise are wound sepsis, excessive pain and anxiety, and underestimation of burn depth.10 The most common wound infection in this setting is streptococcal cellulitis, which presents initially with surrounding erythema that progresses to lymphangitis and systemic toxicity (Fig. 95-3). These patients often need admission for antibiotics, observation, and sometimes surgery. In some situations, adequate pain and anxiety management is very difficult in the outpatient setting, especially around dressing changes. This can be addressed with judicious medication and sometimes carefully monitored membrane dressings. Some patients will require admission. It is common for burn depth to be underestimated initially, with areas of full-thickness injury not appreciated for several days. These patients may require admission for surgery.

As burns increase in size and depth, the local injury is accompanied by an increasing degree of systemic derangement. Classically, this response has two phases. An initial “ebb” phase of reduced perfusion and metabolic rate, which lasts 24–48 hours, is followed by a “flow” phase of protein catabolism and a hyperdynamic circulation.11 This later phase lasts until well after wound closure. Management of this physiology is an essential part of inpatient burn care. Those with large burns are susceptible to a host of other complications related to sepsis and organ failure. Careful monitoring and early intervention are essential to successful outcomes (Table 95-1).

Patient Evaluation and Treatment Planning

In both outpatient and inpatient settings, a careful evaluation of the patient is essential for treatment planning. Patient evaluation is organized into a primary and a secondary survey, following the guidelines of the American College of Surgeons Committee on Trauma and the Advanced Burn Life Support Course of the American Burn Association. As in trauma, the primary survey begins with an assessment, and control if necessary, of the airway. Deeper burns of the face and neck can result in progressive airway edema. Occasionally, a child will aspirate hot liquids resulting in very severe upper airway edema mandating urgent intubation.

A burn-specific survey evaluates the issues uniquely associated with burn injury (^ch95etb1.1). This may take just a few seconds if the burn is small, but will be much more time consuming in the more seriously injured.12 In those with small injuries, essentials include a detailed determination of the mechanism of injury, a screen for associated trauma, consideration of the possibility of abuse (Fig. 95-4), and a detailed assessment of the burn wound. Delayed presentation for care, confusing stories, sharply demarcated margins, immersion patterns, and contact injuries are physical findings suggesting for abuse or neglect.13 All such children should be admitted for evaluation.

After the patient has been evaluated, the burn wound should be examined for size, extent, depth, and circumferential components.14 Burn extent is best estimated using a chart based on the Lund–Browder diagram that compensates for the changes in body proportions with age (^ch95efg4.1). An alternative is a modified “rule-of-nines,” in which the head and neck is given 18% (instead of the adult 9%), each lower extremity is given 15% (instead of the adult 18%), each upper extremity is given 10% (instead of the adult 9%), and the anterior and posterior torso are each given 16% (instead of the adult 18%). For scattered or irregular burns, the entire palmar surface of the patient's hand represents approximately 1% of the body surface over all ages.

Burn depth is classified as first, second, third, or fourth degree (Fig. 95-1A–D). First-degree burns are red, dry and painful and are often deeper than they appear, sloughing the next day. Second-degree burns are red, wet and very painful. There is an enormous variability in their depth, ability to heal, and propensity to hypertrophic scar formation. Third-degree burns are leathery, dry, insensate, and waxy. Fourth-degree burns involve underlying subcutaneous tissue, tendon, or bone.

Near or completely circumferential burns should be identified for special monitoring, as they may need to be decompressed in the hours following injury to avoid ischemia (extremities) or failure of ventilation (torso).

The majority of burns can be successfully managed in the outpatient setting. However, poorly provided outpatient burn care can be frustrating and painful for patients and providers. The key is careful patient selection (^ch95etb1.2) and a detailed care plan, especially an inpatient care plan (^ch95etb1.3).

Patient Outcomes

Burn wounds and grafts typically develop some degree of hypertrophic scarring.15 This involves a gradual increase in vascularity and collagen deposition in the months following healing. Some wounds will demonstrate significant contracture formation, with important functional and esthetic consequences (Fig. 95-5). Many patients will have bothersome pruritus and sometimes temporary neuropathic pain if burns are deep. A long-term follow-up plan, consisting of scar management strategies, rehabilitation, reconstructive surgery, and emotional support will facilitate optimal outcomes. This care is best provided in a multidisciplinary burn clinic, ideally part of a comprehensive burn program. With such supports in place, the long-term outcome for most patients is surprisingly good. When managed in a comprehensive follow-up program, even those who have suffered devastating burns tend to become happy and productive again.16,17

Outpatient Burns

Practice patterns vary widely, but certain characteristics are universal.18 The wound should be kept generally clean and regularly inspected for infection. Desiccated exudates and topical medications should be periodically cleansed. Burns selected for outpatient management tend to be small and superficial with a corresponding low risk of infection, so clean rather than sterile technique is reasonable. If topical agents rather than membrane dressings are used, wounds may be cleansed with lukewarm tap water and a bland soap. Soaking adherent dressings prior to removal will decrease the pain associated with daily wound care. The wound is gently cleansed with a gauze or clean washcloth, inspected for any sign of infection, patted dry with a clean towel and redressed. It is important to instruct each patient to return promptly if they notice erythema, swelling, increased tenderness, lymphangitis, odor, or drainage so that infectious complications can be addressed early. Most small burns are adequately managed with a daily cleansing and dressing change. In some cases, a membrane dressing is applied once it is clear that early surgery is not needed, early infection is unlikely, and wounds are superficial. Pain and anxiety can be an issue for many. Some will benefit from an oral narcotic given 30–60 minutes prior to a planned dressing change. If dressings are occlusive, pain between dressing changes tends to be modest.

Increasing pain and anxiety associated with dressing changes; inability to keep scheduled follow-up appointments; delayed healing; signs of infection or a wound, which appears deeper than appreciated at the time of the initial examination, should prompt early return and specialty evaluation. Wounds selected for outpatient management are usually fairly superficial and heal within two weeks, but patients with mid and deep dermal injuries may have a deeper component with resulting scarring that may benefit from specialty evaluation. Finally, wounds of the face, ears, hands, genitals, and feet have functional and cosmetic importance out of proportion to their wound size. In some cases, early specialty evaluation may be prudent, as initial care can have an impact on long-term outcome.19

Inpatient Burns

A system of burn center verification has evolved to ensure that the patients requiring care of more serious injuries receive coordinated efforts by experienced providers. Burn center referral criteria can be found at www.ameriburn.org (^ch95etb1.4). Care of severe burns can be divided into phases, each with important objectives (^ch95etb1.3).20 Critical care is an important component, especially in the first three phases. Verified burn programs are required to have embedded burn intensive care units.

Topical Medications and Membranes

There is an increasingly confusing array of wound medications and membranes available for burn wounds. Wound medications and membranes provide three benefits: (1) pain control, (2) prevention of wound desiccation, and (3) reduction of wound colonization.

Topical wound medications range from aqueous solutions through antibiotic-containing ointments and debriding enzymes. Most topical agents in outpatient use have a viscous carrier that prevents wound desiccation and a more or less broad antibacterial spectrum that reduces wound colonization. A gauze wrap minimizes soiling of clothing and protects the wound from trauma. Silver sulfadiazine is in common use because it is painless on application and has a broad spectrum of antibacterial activity. Superficial burns are commonly treated with a clear, viscous antibacterial ointment containing low concentrations of various antibiotics. Wounds around the eyes can be treated with topical ophthalmic antibiotic ointments. Significant ear burns should be treated with mafenide acetate, as it is the only agent that will penetrate the relatively avascular cartilage.

Wound membranes provide transient physiologic wound closure while the underlying wound heals.21 Physiologic closure implies a degree of protection from mechanical trauma, vapor transmission characteristics similar to skin, and a physical barrier to bacteria. The major benefit of wound membranes is that, when successful, they minimize wound manipulations. These membranes help create a moist wound environment with a low bacterial density and are generally intended for use on selected clean superficial wounds and donor sites. Occlusive synthetic membranes must be used with caution if wounds are not clearly clean and superficial, as submembrane infection can occur, deepening underlying wounds and causing systemic infection and toxicity.

There have been a plethora of burn prevention efforts, which have met with mixed success. They can be based on (1) public education, (2) legislation, or (3) engineering.22 Public education campaigns depend for their success on an educated literate community. The “stop, drop, and roll” campaign in elementary schools is an excellent example. Legislation is often more effective. Examples include safe factory set points for home water-heaters and flammability standards for children's bedclothes. Engineering solutions are perhaps the most effective. Examples are common in industry, and include physical isolation of high-power lines and “child-proof” cigarette lighters. Often all the three are combined, a current example being the fire-safe cigarette. A self-extinguishing cigarette has been engineered and, in some places, its sale is mandated after public education influenced the legislative process.

In most centers, artificial limbs are constructed in a modular fashion.1 The stump is placed in a thermoplastic socket that is then fitted into the main body of the limb. The bulk of the prosthesis comprises a metal frame with articulations and an outer casing of acrylic resin or carbon composite material. Before fitting the limb, many patients place their stump in a liner designed to reduce friction on the skin. This may be an expanded plastic cup, a silicon/mineral oil sleeve, or a cotton or nylon sock. The prosthetic limb, once fitted, is held in position by one of a range of suspension elements. In above-knee (Fig. 96-1) or proximal arm amputations, this is usually a fabric belt arrangement worn around the waist or shoulders, respectively. Below-knee amputees require a different system using either a butyl rubber sleeve or corset to hold the appliance firmly onto the thigh (Fig. 96-2). Many patients with above-knee amputations now use a suction socket device that provides sufficient suspension by holding the prosthesis in place through negative pressure without the need for additional belts (see Fig. 96-1).

Limb prostheses are the subject of continual technological development particularly in the field of bionics. Myoelectric devices, for example, rely on skin contact with electrodes to detect neuromuscular signals that can be converted to artificial limb movement. Neuroprosthetic devices involve implantation of electrodes into neural tissue usually through the skin, for example, cochlear implants. Such devices are under development for prosthetic limbs. These devices thus have the potential for causing skin problems.

The skin of an amputation stump is not designed to withstand the physical insults it encounters within a prosthetic limb. For example, although some adaptation to friction or pressure occurs, some skin problems are inevitable. If these dermatoses cannot be prevented or rapidly resolved by prosthesis adjustment or medical intervention, they can incapacitate the patient, particularly those who have lower limb, weight-bearing prostheses. As a result, patients may suffer social isolation, emotional distress, or even financial deprivation if they are unable to work.

Skin problems may occur because of allergy or chemical irritation to materials in contact with the skin, as well as from trauma and occlusion. Examples of physical stresses on the skin include shearing and friction from elements in the socket and pressure on load-bearing areas, especially on the tibial tuberosity in below-knee amputations and the ischial tuberosity, adductor region, or groin in above-knee amputations. In all cases, the occlusion results in increased humidity from trapped perspiration, increasing the likelihood of irritation, allergy, and infection.

The common skin disorders in amputation stumps can be classified into diseases related to the reasons for the amputation, physical effects of a prosthesis, infection, contact dermatitis, and other cutaneous disorders.

Epidemiology

The great majority of artificial limb wearers are amputees, although a small proportion are people with congenital limb malformations. Lower limb amputees are the most numerous and are also the group at greatest risk of skin problems. Traumatic amputations are possibly more likely to be associated with a dermatosis2 although the commonest problems encountered are the same as for all amputees.3 Modern limb prostheses allow many of today's amputees to lead an active life with good mobility. Nevertheless, as many as 73% of one cohort of lower limb amputees reported at least one skin disorder.2 In a further group of 745 lower leg amputees, 40.7% had at least one skin problem. Further analysis identified four factors independently associated with dermatologic disorders, namely transtibial amputation, employment status, type of walking aid used, and peripheral vascular disease.4 A more recent questionnaire-based study of 805 lower limb amputees5 suggests that the factors more likely to be associated with skin problems are, smoking, younger age, female sex, washing the stump frequently and the use of antibacterial soaps. Overall one-third of amputees, either upper or lower limb, experiences a skin problem that significantly interferes with the normal use of the artificial limb.6

Dermatoses Related to the Reasons for Amputation

Several disorders resulting in the need for amputation can have a significant impact on skin integrity. In general, younger patients require artificial limbs because of traumatic amputations, congenital abnormalities, or malignancy, whereas in the older age group, arterial disease and vascular complications of diabetes mellitus predominate. Amputations after trauma or severe vasculitis may be associated with scarring that makes for a suboptimal prosthesis fit (Fig. 96-3). Stump dermatoses appear to be more likely in patients following traumatic amputations. Koc et al2 found a skin problem in nearly three quarters of amputees most of whom had lost a limb as a consequence of mine explosions. The nature of current conflicts means that, presently, such amputations are unfortunately common amongst both service personnel and civilians. Vasculitis resulting in amputation may be ongoing and cause problems in the skin of amputation stumps (Fig. 96-4). However, it is diabetes mellitus that is particularly associated with protracted skin problems (Chapter 151) as a result of impaired wound healing, susceptibility to infection, abnormal sensory nerve function, and disruption of normal tissue fluid balance.7 Diabetic amputees as a group require more frequent clinical review to prevent complications. Treatment of the diabetic amputee not only requires good control of the blood glucose level but possibly a change of the stump environment through adjustment or redesign of the artificial limb. The diabetic amputee highlights the need for close links with a prosthetics department, which allow rapid referral of patients for assessment.

Physical Dermatoses

The physical effects of wearing a prosthesis are the most common causes of skin problems.6,8 These can be divided into those resulting from repeated direct trauma and those secondary to disturbance of tissue fluid dynamics.

Direct Physical Trauma

Ulceration

Ulceration and callus formation are seen where there is chronic pressure or repeated frictional forces on stump skin. Ulceration may also be caused by infection or poor cutaneous nutrition, particularly secondary to diabetes mellitus (Figs. 96-5 and 96-6). Stump ulcers should be treated early as malignancy may develop in long-standing ulceration.9 With repeated infection and ulceration, an amputation scar on the distal stump skin can erode further. In some cases, the skin may become completely adherent to bone and develop thick, callus-like hyperkeratosis (Fig. 96-7), which may necessitate revision of the distal bony surface. Ulceration or other injuries incurred while putting on artificial limb components may be particularly associated with poor manual dexterity consequent on neurological disorders or arthritic changes.10,11 Incorrect use of some appliance components can also result in injury.12 Patient selection and access to follow-up advice is therefore important in reducing such injuries. Apparently spontaneous ulceration at unexpected sites is occasionally seen (Fig. 96-8). In every instance, the cause of the ulceration must be determined to resolve a chronic process that can become totally disabling. However, a recent study examining 102 patients over 4 years suggests that the majority of patients with delayed wound healing or secondary ulcers will experience healing despite continuing to use their prosthesis, provided they are carefully monitored.13

Physical Dermatitis

In some patients, eczema may be caused by a poorly fitted or misaligned prosthesis or by edema and congestion of the terminal portion of the stump; only with alleviation of these problems does the condition clear.

Epidermoid Cysts and Follicular Keratoses

Epidermoid cysts and follicular keratoses are two ends of a spectrum of the same disorder. Repeated pressure and friction from the prosthesis appears to cause invagination of keratin around hair follicles, which then results in a foreign-body reaction. Follicular keratoses are therefore the earliest changes.14 These are very common, often multiple, and distributed at sites of weight bearing such as the anterior tibial area, popliteal fossa, and the adductor or inguinal areas of the thigh (Fig. 96-9A). Fortunately, they cause little trouble in many cases, but they can become inflamed and painful particularly if the patient picks at them to extract the keratin plug or if they become infected. Inflamed follicular keratoses can have an acneiform appearance, leading some to suggest that they represent a form of acne mechanica. When the continued pressure and friction causes the keratin to extend deeper into the dermis, larger cystic lesions, 1–3 cm in diameter, form; these are commonly termed posttraumatic epidermoid cysts. Meulenbelt et al15 described a case of follicular keratoses of a transfemoral amputation stump in a patient who did wear an appliance at all. These lesions recurred after resection and were associated with retention of vellus hairs. This raises the possibility that, in some individuals, mechanisms other than just friction may be involved. Deeper cysts can be very tender when compressed by the prosthesis. Some cysts have an obvious punctum and patients may express keratinous material from them. Large cysts can be so painful that the patient can no longer wear a weight-bearing prosthesis each day (see Fig. 96-9B and 96-9C). Distention of the overlying epidermis can occur, followed by spontaneous rupture. A serous, purulent, or hemorrhagic fluid is then discharged. The resulting sinus is difficult to occlude and the discharge continues as long as the prosthesis is worn. Intercommunicating sinuses can appear and spontaneous ruptures may occur. In advanced cases, a granulomatous reaction occurs around the cyst with considerable capillary dilation, vascularization, and a heavy inflammatory infiltrate progressing to abscess formation (see Fig. 96-9B).

Management of this condition can be difficult. Clearly, prevention is the ideal but is not always possible despite regular prosthetic assessments. The fit of the prosthesis is the single most important method of preventing cyst formation. The problem can sometimes be improved or successfully eliminated by proper fitting and aligning of the prosthesis and continued adjustment by the prosthetist. Rough surfaces in areas of increased contact pressure in the socket, particularly the suction socket, tend to catch the skin, increasing the shearing forces. For this reason, the lining of the socket should be kept smooth. With the idea of inserting a buffer between the skin and the socket, protective devices such as liners and stump socks are used. Various synthetic films and adhesives, such as Teflon, have been found satisfactory as liners. They allow for a smooth, gliding action of the prosthetic socket wall or brim against the skin. Applying a vapor-permeable adhesive membrane to the skin before fitting the appliance can also help reduce frictional trauma. Topical glucocorticoids can be used at night to reduce inflammation and provide symptomatic relief. Intralesional injection of glucocorticoids into the cysts and their channels also results in temporary improvement.

Surgical intervention is useful in cases with a few lesions that are not infected. Lesions can be surgically incised and drained. In other instances, removal of the prosthesis is sufficient to cause the lesion to involute, provided that the cyst has not become too large. However, spontaneous rupture, incision, and drainage, and even spontaneous resorption of the lesion are of only temporary benefit. When the prosthesis is worn again, these cysts can recur so that surgical excision is not always the treatment of choice, especially in continually rubbed areas.

In selected cases, systemic retinoid therapy may be appropriate to minimize hyperkeratosis. One author found oral isotretinoin to be effective in a patient described as having acne mechanica.16

Disturbances of Tissue Fluid Dynamics

Edema

Amputation of a lower extremity greatly disturbs the normal pattern of blood and lymph channels, as well as the relationship of pressure both inside the vessels and in the surrounding tissues of the stump. An important feature of care during convalescence after amputation is the reduction of edema and stabilization of new circulatory patterns in the stump. Swelling can be partially prevented by gradual compression of the stump tissues with an elastic bandage or “shrinker” sock before fitting the prosthesis and socket.

When an amputee begins to wear a suction-socket prosthesis, the skin must adapt to an entirely new environment. The patient can expect edema, reactive hyperemia for days or weeks, a reddish-brown pigmentation resulting from capillary hemorrhage, and, occasionally, serous exudation and crusting of the skin of the distal portion of the stump. These changes are relatively innocuous, usually short lived, and do not usually require therapy.

The extent to which edema may persist or recur in the healed stump depends on many factors.17 Edematous portions of the skin of the distal part of the stump may become pinched and strangulated within the socket (Fig. 96-10). Such areas may ulcerate if they catch in the spring-valve opening and become gangrenous as a result of the impaired blood supply. Therapy includes eliminating all mechanical factors contributing to the edema, such as choking by the socket, poor fitting, and misalignment. Excessive negative pressure in a suction-socket prosthesis also contributes to circulatory congestion and edema. Treatment should be directed toward better support of the distal soft tissues. Occasional use of an oral diuretic sometimes allows the edema to resolve.

Verrucous Hyperplasia

Verrucous hyperplasia refers to a reactive hyperplastic condition, characterized morphologically by numerous, coalescent warty papules (Fig. 96-11). It occurs when the chronic pressure effects of a poor prosthetic fit disrupt vascular and lymphatic channels, resulting in chronic tissue edema. The same appearance is seen around longstanding leg ulcers where there is an element of lymphedema (see Chapter 174). Histologic examination can show evidence of pseudoepitheliomatous hyperplasia, although the condition itself is benign and potentially reversible. However, in neglected cases, malignant change can occasionally occur (see Fig. 96-11C). Bacterial infection may play a role in the development of pseudoverrucous hyperplasia, as secondary mixed flora infections are common because of the poor superficial blood flow and the convoluted surface (Fig. 96-12). External compression is the best method of treatment, in combination with topical control of bacterial infection. In below-knee amputees, the distal part of the stump is edematous; the stump dangles freely in the socket or has no distal support or partial end-bearing. When the stump end is supported in the socket by a temporary cushion or platform, compression gradually reduces and slowly clears the verrucous condition. The greater the compression on the distal stump, the more immediate and lasting is the improvement. The use of compression bandaging, shrinker socks and other pads, and partial end-bearing all have a definite place in therapy and can be skillfully applied by the prosthetist. Short courses of oral diuretics may be indicated to reduce edema of the stump. The medication can be gradually decreased when the stump and its skin return to normal.

Acroangiodermatitis

Acroangiodermatitis occurs when the chronic pressure changes result in vessel proliferation in the upper- and middermis. There is also extravasation of red blood cells and these features combine to give a purplish hue to the papules and plaques that appear on a background of edematous skin. The appearance may mimic Kaposi sarcoma.18 Some authors suggest that acroangiodermatitis occurs in above-knee amputees who use a suction socket prosthesis that exerts negative pressure.19 However, there are reports of acroangiodermatitis in below-knee amputees,20 and the same condition is seen in chronic venous insufficiency and in the patients with arteriovenous shunts (acroangiodermatitis of Mali). Management of this condition is the same as for stump edema and verrucous hyperplasia.

Bacterial and Fungal Infections

The bacterial flora of amputation stumps have been examined in small groups of patients,21,22 and the most common species encountered are Staphylococcus epidermidis, S. aureus, and Streptococcus sp. (see Chapter 176). The moist, occluded environment under a prosthesis is ideal for fungal and bacterial growth so that minor skin infections occur fairly frequently. In one study, S. aureus folliculitis or Trichophyton rubrum infection was identified in 3% of the study population.6 Infections are more common during hot weather and in those amputees who pay insufficient attention to stump hygiene, partly because in these situations the skin becomes macerated more readily and follicular infections become more likely. Although folliculitis (Fig. 96-13) and furuncles are more common, superficial infections of the skin itself may also occur (see Chapter 176). Superficial dermatophyte and candidal infection (see Chapters 188 and 189) are also common and may be difficult to eradicate because of the ideal environment for fungal growth within a prosthesis.

The diagnosis of infection is usually obvious when the rash extends onto skin not covered by the prosthesis. Underneath the prosthesis, any superficial infection may present as a nonspecific scaling erythema indistinguishable from that caused, for example, by chronic irritation. All stump rashes should be swabbed and scraped for bacterial and fungal culture.

In the management of bacterial infections, oral antibacterial therapy should be directed by bacterial culture and sensitivity. Topical antiseptics or antibacterials can be used but some antiseptic preparations can cause irritation and there is also the potential for sensitization.

Superficial fungal infections respond to appropriate topical therapy (see Chapters 188 and 189) but can be hard to completely eradicate because of the favorable conditions for fungal growth. In this situation, systemic antifungal therapy is useful.

Contact Dermatitis

(See Chapters 13 and 48)

The clinical presentations of irritant and allergic contact dermatitis affecting amputation stumps are indistinguishable (Fig. 96-14), ranging from dry, scaling erythema to weeping dermatitis.6 Indeed, the morphologic features may be the same as nonspecific eczematization where no irritant, allergic, or infectious cause is found, and where there is no history of eczema or atopy. Consequently, a careful history and examination is essential if one is to identify irritant or allergic causes (Table 96-1). This includes accurate timing of the onset of dermatitis in relation to changes in the patient's appliance routine or the composition of the prosthesis. The distribution of rash typically matches the site of the contactant. To identify a primary irritant or allergen, it is particularly important for the dermatologist to observe the patient removing and refitting their limb, making note of its construction and any medicaments or other agents such as cleansers, talcs, and creams that the patient uses. These products may contain allergens such as fragrances or preservatives. Colored stump socks may contain potentially allergenic nylon dyes.

Knowledge of the materials used in prosthesis manufacture is also necessary when considering potential sensitizers and irritants. This is best achieved by liaison with the local prosthetist, as different construction techniques may be used in different areas. In general, modern modular prostheses are fabricated with sockets, liners, and casings that may contain acrylic resins, carbon composites, and thermoplastics. Epoxy and, occasionally, polyester resins are still used by some manufacturers. Acrylate-based thread sealants are commonly used in socket bolts and metalwork. Butyl or black rubber material may be used to conceal access points to the metal frame. Rubber materials can also be found in some suction socket valves (Fig. 96-15). Accelerators used in the manufacture of natural or synthetic rubbers are potential allergens, for example, dialkyl thiourea used in chloroprene rubber.23 Suspension elements often include chrome-tanned leather and sometimes have metal fastenings, rivets, or screws containing nickel. Glues containing para-tertiary butylphenol formaldehyde resins are often used.

Repairs or adjustments to prostheses can introduce new irritants and allergens. For example, sockets sometimes have additional leather linings cemented to points of friction or pressure.

Irritant dermatitis (see eFig. 96-15.1) can be due to occluded contact with volatile solvents in glues or resins and from fragrances and detergents in topical medicaments or lubricants. Soaps and other washing materials used to clean appliances can cause irritation if they are not removed by proper washing (see Table 96-1). Burns from a malfunctioning electrode used in a myoelectric prosthesis have been reported.24

Contact allergy should always be considered as a cause of inflammatory and dermatitic disorders affecting the stump, especially if there is secondary spread (see Table 96-1). In addition to standard series patch testing, the authors recommend an extra series of allergens to include components of plastic, including acrylic, epoxy, and polyester resin systems, as well as an azo dye series. It is important to test with pieces of the prostheses and all materials applied to the stump skin including emollients, cleansers, powders, medicaments, and cosmetics. In our experience, the most common relevant allergens are nickel, acrylates, rubber, chromate (in leather), para-tertiary butylphenol formaldehyde resin, and components of topical applications.6

Other Cutaneous Disorders

Common skin diseases, for example, eczema (see eFig. 96-15.2) and psoriasis (see eFig. 96-15.3), may affect amputation stumps. Those diseases that exhibit the Koebner phenomenon, especially psoriasis or lichen planus, have been reported on amputation stumps with little involvement of other areas of skin. Treatment should always take into account the implications of an occluded environment.

Hyperhidrosis can be a problem in some patients resulting in maceration of the skin increasing the risk of erosions and even ulceration. Standard topical antiperspirants can be irritating under occlusion and one novel approach is to use intradermal botulinum toxin A.25

Benign keratoses, warts, nevi, and a variety of cutaneous papillomas may occur on stump skin and occasionally cause discomfort when a prosthesis is worn. Malignancies have also been described and squamous cell carcinoma (Marjolin's ulcer)9 may develop in nonhealing chronic stump ulcers or verrucous hyperplasia (see Fig. 96-11). The patients who have amputations for lymphangiomas may develop the Stewart–Treves syndrome and metastatic lymphangiosarcoma (see Chapter 128). There is a risk that such malignancies may not be recognized as an ulcer might be wrongly blamed entirely on trauma from a poorly fitting prosthesis. A biopsy of persistently ulcerated areas should be undertaken.

Treatment of these benign and malignant tumors is the same as when they occur elsewhere on the skin. Healing after tumor excision may take weeks, during which time the artificial limb may not be worn.

General Management Considerations

Many of the more common skin problems can be prevented or controlled by adherence to an appropriate hygiene and skin-care regimen in conjunction with regular prosthetics reviews, which ensure that the prosthesis remains appropriate and correctly adjusted. To this end, it is important that good communication exists between the dermatologist and prosthetist, which permits rapid referral of patients before skin disorders become established.

As a general routine, the stump skin should be washed at night rather than in the morning because newly washed skin is hydrated and swollen, thereby increasing the likelihood of friction and shearing trauma. Nonperfumed soap should be used to minimize contact with potential sensitizers and fully removed with tepid water and gentle rubbing with a nonabrasive towel.

Antibacterial soaps and washes can reduce the possibility of infection in addition to their cleansing action. However, these antiseptic preparations can cause irritation or allergy in a small number of cases and patients should be warned about this. If a stump sock is worn, it should be changed daily and washed and rinsed fully as soon as it is taken off, before perspiration is allowed to dry within it. Silicone liners should be washed every day.

A stoma is a surgically created opening onto the skin of part of the gastrointestinal or urinary tract in order to drain the effluent from that viscus. The most frequently performed stomas are ileostomies, colostomies, and ileal conduits (urostomies or urinary diversion). The commonest indications for stoma surgery are inflammatory bowel disease, malignancy and neurological problems. A patient with a stoma is usually termed an “ostomist” or “ostomate.”

Epidemiology

There are estimated to be more than 1.4 million ostomates in the United States and 100,000 in the United Kingdom and Ireland. Some stomas are temporary, with surgical anastomosis delayed, pending resolution of the acute disorder. Temporary stomas are often “loop stomas” where a loop of bowel is brought to the skin surface and part of the wall removed to allow preferential drainage into a stoma pouch in order to relieve a distal problem, for example, perianal ulceration. Such stomas are more frequently associated with skin problems secondary to leaks.1 Many stomas formed for malignant indications can be seen as palliative procedures.

A stoma appliance is essentially a device for collecting stoma effluent with a high degree of comfort and security until it can be disposed of. There continues to be promising advances in the design of stoma bags. Essentially, the device is a pouch or bag held in place over the stoma by an adhesive skin barrier made solely or partly from hydrocolloid. Many ileostomists and urostomists use two-piece appliances where the barrier remains on the skin for 2–4 days and is detachable; disposable bags are changed as necessary. Appliances with convexity on the surface next to the skin are available for patients with short or buried stomas (Fig. 97-1). Useful recent innovations include softer convex appliance that apply less pressure on the skin and collars or sleeves that fit snugly around the stoma before applying the bag thereby reducing the chance of leaks of effluent or intestinal mucus under the barrier.

As many as two-thirds of ostomates experience skin problems that interfere with the normal use of their stoma appliance,2,3 and such dermatoses are the commonest reasons for a visit to outpatient stoma services.4,5 The majority of these problems are irritant reactions, usually dermatitis secondary to leaks from the stoma; however, there are also a number of other well-defined irritant reactions. Common coincidental dermatoses, particularly psoriasis and constitutional eczema, account for around 15% of the diseases seen.2,6 An approach to diagnosing peristomal dermatoses is given in eFigure 97-1.1.

Irritant Reactions

Dermatitis

Dermatitis most frequently results from the chronic leakage of effluent onto the skin because the patient is using an inappropriately shaped appliance or one with too large a hole for their stoma. The most common cause is the remodeling of the stoma and abdominal wall that occurs in the months after surgery, whereby a stoma usually becomes a little shorter and thinner, resulting in leaks unless a correctly fitting appliance is selected (Figs. 97-2, 97-3, 97-4, 97-5, and 97-6). Leaks will also occur when patients gain a lot of weight after surgery and the effective length of their stoma diminishes because it becomes buried by subcutaneous fat.7 Irregular scarring after surgery or retraction of the stoma, may also be associated with chronic leakage. Such irregularities can be corrected with topically applied pastes. One effective alternative is to use collagen fillers (Porcine collagen Permacol™)8 to recontour the skin surface. Short stomas (<2 cm long), loop ileostomies and stomas formed as emergency procedures are more likely to be associated with skin problems.1,9 Chronically irritated skin can become markedly hyperkeratotic and acanthotic (Fig. 97-7). These problems can be prevented and resolved by careful postsurgical follow-up by the enterostomal therapist (ET; stoma nurse specialist) to ensure that the correct appliance is being used. Severe, acute irritant dermatitis can be effectively treated with a short course of topical corticosteroid while longer term appliance modifications are being undertaken (Table 97-1).

Anxieties about possible leaks and odors can lead to excessively frequent bag changing, which may cause an irritant dermatitis by stripping the skin. Patients may, for the same reasons, wear waist belts too tightly thereby causing pressure damage even ulcers (eFig. 97-7.1) and occasionally necrosis. Whatever the cause of skin inflammation, a vicious cycle can develop when the damaged skin prevents proper bag adhesion necessitating more frequent bag changes.12 Careful counseling is usually necessary in order to reassure the patient regarding leaks.

Approximately 15% of ostomates with skin problems suffer from a chronic or recurrent dermatitis for which no irritant, allergic, or infective cause can be found, and where primary skin disease is ruled out.2 In the absence of a primary treatable cause, the use of topical corticosteroid lotions is appropriate. Most patients require only occasional short courses for a maximum of 4 weeks’ duration (Table 97-1). A small number of patients require intermittent applications longer term. Provided that the frequency of application is no more than once every 10 days, steroid atrophy of the skin appears to be unusual.

In ileostomy patients with short bowel, the output may be very high and corrosive due to the enzyme and bile salt content. In this situation, some leaks are inevitable, despite the use of proprietary barrier preparations or soothing lotions. Where the irritation has resulted in an eroded dermatitis, sucralfate powder applied at every stoma bag change can be very effective. In addition to forming a sticky barrier, the preparation is thought to promote healing.13 Surgical scars and even large striae (eFig. 97-7.2) can lead to ulcerations and bag failures, which may respond to topical carmellose sodium or sucralfate powders. Wound dehiscence can cause severe difficulties for bag adhesion (eFig. 97-7.3) and presents particular challenges for nursing management where the dermatologist may be called upon for advice as part of the multidisciplinary team.14

Chronic Papillomatous Dermatitis

This term refers to clinical appearance of warty excrescences around urostomies resulting from leaks and pooling of urine on the peristomal skin (eFig. 97-7.4). Recurrent urinary tract infections appear to increase the likelihood of chronic papillomatous dermatitis (CPD) probably due to the presence of ammonia from urea-splitting bacteria. Histologically, there is massive hyperkeratosis and acanthosis. Pseudoepitheliomatous hyperplasia may also be a feature but is not universal. The histology is therefore not specific and comparable to that of other irritant reactions. Verrucous lesions with similar appearances are occasionally seen affecting ileostomies15 (Fig. 97-5). In severe cases, the lesions can encroach on the stoma and cause stenosis (Fig. 97-8). When the leaking of urine is caused by a receding stoma, CPD will resolve rapidly if a convex-backed appliance is used to increase the effective length of the urostomy and thereby stop leaks. Acetic acid soaks (10% domestic vinegar in water)16 at each bag change are effective in some cases (eFig. 97-8.1). Larger excrescences may be shaved off under local anesthetic to allow a bag with a smaller aperture to be used. In severe cases, surgical revision of the stoma may be required.