Scald Burns

In civilian practice, scalds, usually resulting from hot water, are the most common cause of burns. Water at 60° C (140° F) creates a deep partial-thickness or full-thickness burn in 3 seconds. At 68.9° C (156° F), the same burn occurs in 1 second. Freshly brewed coffee from an automatic percolator is generally about 82° C (179.6° F). Boiling water always causes deep burns, and soups and sauces, which are thicker in consistency, remain in contact longer with the skin and often cause deep burns. In general, exposed areas tend to be burned less deeply than areas covered with thin clothing. Clothing retains the heat and keeps the liquid in contact with the skin for a longer time.

Immersion scalds are deep and severe burns.^18,28,92 Although the water may be cooler than with a spill scald, the duration of contact is longer, and these burns frequently occur in small children or older adult victims with thin skin. Consequently, many states have passed legislation to set home and public hot water heaters to maximum temperatures well below 60° C (140° F).

Scald burns from grease or hot oil are generally deep partial thickness or full thickness. Cooking oil and grease, when hot enough to use for cooking, may be in the range of 204.4° C (400° F). Tar and asphalt burns are a special kind of scald. The “mother pot” at the back of the roofing truck maintains tar at a temperature of 204.4° to 260° C (400° to 500° F). Burns caused by tar directly from the mother pot are invariably full thickness. By the time the tar is spread on the roof, its temperature has decreased enough that most of the burns are deep partial thickness (Figure 13-2). Unfortunately, the initial evaluator cannot usually examine these burns because of the adherent tar. The tar should be removed by application of a petroleum-based ointment (such as Vaseline) under a dressing. In the field, mayonnaise may serve this purpose (Figure 13-3). The dressing may be removed and the ointment reapplied every 2 to 4 hours until the tar has dissolved. Only then can the extent of the injury and the depth of the burn be accurately estimated.^40,91

FIGURE 13-2 Tar burn of hand.

(Courtesy Paul S. Auerbach, MD.)

FIGURE 13-3 Mayonnaise used to dissolve tar off a hand burn.

(Courtesy Paul S. Auerbach, MD.)

Flame Burns

Flame burns are the next most common burn injuries. Although injuries in house fires have decreased with the advent of smoke detectors, a significant number of burn injuries still result from careless smoking, improper use of flammable liquids, automobile accidents, and clothing ignited from stoves or space heaters. Victims whose bedding or clothes have been on fire rarely escape without some full-thickness burns. Outdoor misadventures result from using cooking stoves fueled by white gasoline, taking lanterns into tents, smoking in a sleeping bag, and starting (or improving) charcoal fires with gasoline or kerosene. Most accelerants, whether gasoline, kerosene, propane, or diesel, behave similarly with ignition temperatures of 210° to 280° C (410° to 536° F) and therefore burn at a high temperature with rapid tissue injury and full-thickness burns.

Flash Burns

Flash burns are next in frequency. Explosions of natural gas, propane, gasoline, and other flammable liquids cause intense heat for a very brief time. For the most part, unignited clothing protects the skin in flash burns. Flash burns generally have a distribution over all exposed skin, with the deepest areas facing the source of ignition. Flash burns are partial thickness, with the depth dependent on the amount and kind of fuel that explodes. Although such burns generally heal without requiring extensive skin grafts, they may be very large and associated with significant thermal damage to the upper airway.

Contact Burns

Contact burns result from hot metals, plastic, glass, or hot coals. Such burns are usually limited in extent but are deep. Victims involved in industrial accidents commonly have both severe contact burns and crush injuries, because these accidents often occur from presses or from hot, heavy objects. With the increased use of wood-burning stoves, an increasing number of toddlers are burned each year. The most common injuries are deep burns on the palms because the child falls with hands outstretched against the stove. Contact burns, especially in unconscious persons or those dealing with molten materials, are frequently fourth degree.^16,53,80 In the wilderness setting, the most common contact burn is from hot coals, which are often as hot as 537.8° C (1,000° F). Intoxicated campers dance around and then into the campfire, architects of “river saunas” mishandle hot rocks, children fall into fires, and beach walkers may sustain deep burns when coals are buried in sand overnight. Even though the injured areas may be small, they can be deep and devastating when the hiker must walk a considerable distance on burned feet.²⁴

Electrical Burns

Electrical burns are actually thermal burns from very high-intensity heat. As electricity meets the resistance of body tissues, it is converted to heat in direct proportion to the amperage of the current and the electrical resistance of the body parts through which it passes. The smaller the body part through which the electricity passes, the more intense is the heat and the less it is dissipated. Therefore fingers, hands, forearms, feet, and lower legs are frequently totally destroyed, whereas larger-volume areas, such as the trunk, usually dissipate the current enough to prevent extensive damage to the viscera, unless the contact point is on the abdomen or chest. Although cutaneous manifestations may appear limited, massive underlying tissue destruction may be present because muscle, nerves, blood vessels, and bones can be burned beyond recovery.^15,33,34,66

Arc burns occur when current takes the most direct path rather than the one of least resistance. These deep and destructive wounds, which may be initiated at extremely high temperature, occur at joints that are in close apposition at the time of injury. Most common are burns of the forearm to the arm when the elbow is flexed, and from the arm to the axilla if the shoulder is adducted when current passes from the upper extremity to the trunk.

Electrical burns cause a particular set of other injuries and complications that must be considered during the initial evaluation. As mentioned previously, injuries related to a fall are common. The intense associated muscle contractions may cause fractures of the lumbar vertebrae, humerus, or femur and may dislocate shoulders or hips.

Electrical cardiac damage may have symptoms like those of a myocardial contusion or infarction. Alternatively, the conduction system may be deranged. There can be actual rupture of the heart wall or of a papillary muscle, leading to sudden valvular incompetence and refractory cardiac failure. Household current at 110 volts generally either does no damage or induces ventricular fibrillation. Alternating current is more likely to induce fibrillation than is direct current. If no cardiac abnormalities are present when a victim is first seen after shocks of 110 to 220 volts, the likelihood that they will appear later is small.

The nervous system is particularly sensitive to electricity. The most severe brain damage occurs when current passes through the head, but spinal cord damage is possible any time current passes from one side of the body to the other.^44,48 Myelin-producing cells are susceptible. The devastating effects of transverse myelitis may develop days or weeks after injury. Conduction remains normal through existing myelin, but as the old myelin wears out, it is not replaced and conduction stops. Peripheral nerves are commonly damaged and may demonstrate severe permanent functional impairment.^20,30 Every victim with an electrical injury must have a thorough neurologic examination as part of the initial assessment. Myoglobinuria is a frequent accompaniment of severe electrical burns. Disruption of muscle cells releases cell fragments and myoglobin into the circulation to be filtered by the kidneys. If untreated, this can lead to permanent renal failure.

Lightning strikes are discussed in Chapter 3, and reviews are available.*

Chemical Burns

Chemical burns, usually caused by strong acids or alkalis, are most often the result of industrial accidents, home use of drain cleaners, assaults, and other improper use of harsh solvents.^† In contrast to thermal burns, chemical burns cause progressive damage until the chemicals are inactivated by reaction with the tissue or by dilution by flushing with water. Although individual circumstances vary, acid burns may be more self-limited than are alkali burns. Acid tends to tan the skin (as leather is tanned), creating an impermeable barrier that limits further penetration of the acid. Alkalis combine with cutaneous lipids and saponify the skin until they are neutralized. A full-thickness chemical burn may appear deceptively superficial, appearing as only a mild brownish surface discoloration. The skin may appear intact during the first few days after the burn and then begin to slough spontaneously. Unless the observer can be absolutely certain, chemical burns should be considered deep partial thickness or full thickness until proved otherwise.

Estimation Of Burn Size

Burns are the only quantifiable form of trauma. The single most important feature in predicting mortality, need for specialized care, and the complications expected from the burn is the overall burn size in proportion to the victim’s TBSA. Treatment plans, including initial resuscitation and subsequent nutritional requirements, are derived directly from the size of the burn.

A general idea of burn size is provided by the “rule of nines.” Each upper extremity accounts for 9% TBSA, each lower extremity accounts for 18%, the anterior and posterior trunk each account for 18%, the head and neck account for 9%, and the perineum accounts for 1% (Figure 13-4). Although the rule of nines provides a reasonably accurate estimate of burn size, a number of more precise charts have been developed. A diagram of the burn can be drawn on a chart so that a relatively precise calculation of burned area can be made from the accompanying TBSA estimates given. Children less than 4 years old have much larger heads and smaller thighs in proportion to body size than do adults. In an infant, the head accounts for approximately 18% of the TBSA; body proportions do not fully reach adult percentages until adolescence. To further increase accuracy in burn size estimation, especially when burns are in scattered body areas, the observer might calculate the unburned areas on a separate diagram. If the calculations of the unburned areas and the burned areas do not add up to 100%, the observer should begin again with a new diagram to recalculate the burned areas. For smaller burns, an accurate assessment of burn size can be made by using the victim’s hand. The hand amounts to 2.5% TBSA. The dorsal surface accounts for 1%, the palmar surface for 1%, and the vertical surface for 0.5% (including the fingers).

FIGURE 13-4 Rule of nines used for estimating burned surface area. A, Adult. B, Infant.

Depth Of Burn

An understanding of burn depth requires an understanding of skin anatomy (Figure 13-5). The epidermis, an intensely active layer of epithelial cells under layers of dead keratinized cells, is superficial to the active structural framework of the skin, the dermis. Although metabolically very active, the dermis has no regenerative capacity, and epithelial cells must eventually cover the surface of the dermis before the burn is healed. The skin appendages (hair follicles, sebaceous glands, and sweat glands) all contain an epithelial cell lining, so when the surface epidermis has been killed, epithelial covering must take place from overgrowth of the epithelial cells lining the skin appendages. As these cells reach the surface, they spread laterally to meet their neighbors, creating a new epithelial surface. As the burn extends deeper into the dermis, fewer and fewer appendages remain, and the epithelial remnants must travel farther to produce a new surface covering, sometimes taking many weeks to produce coverage. When the burn extends beyond the deepest layer of the skin appendages, the wound can heal only by epithelial ingrowth from the edges, by wound contraction, or by surgical transplantation of skin from a different site.

FIGURE 13-5 Skin anatomy.

The thickness of skin varies both with the age and sex of the individual and with the part of the body considered. Although the thickness of the living epidermis is relatively constant, keratinized epidermal cells may reach a height of 5 mm (0.2 inch) on palms of hands and soles of feet. The thickness of the dermis, on the other hand, may vary from less than 1 mm (0.04 inch) on eyelids and genitalia to more than 5 mm (0.2 inch) on the posterior trunk. Although the proportional thickness of skin in each body area is similar in children, infant skin thickness in each specific area may be less than one-half that of adult skin; the skin does not reach adult thickness until adolescence. Similarly, in patients older than 50 years, dermal atrophy causes all areas of skin to become quite thin.

Burns are classified by increasing depth as first degree, superficial partial thickness, deep partial thickness, full thickness, and fourth degree. The following descriptions appear to separate burns into clearly defined categories, but many burns have a mixture of characteristics that give the observer an imprecise diagnostic ability. Considerable research is under way to devise instruments that will more precisely measure the depth of injury. Much of current burn treatment depends on knowledge of the depth of the burn.

Superficial Partial-Thickness Burns

Superficial partial-thickness burns (Figure 13-6) include the upper layers of dermis and characteristically form blisters with fluid collection at the interface of the epidermis and dermis. Blistering may not occur for some hours after injury. Burns initially thought to be first degree may therefore be diagnosed as superficial partial thickness by day 2. When blisters are removed, the wound is pink and wet, and it is quite painful when contacted by currents of air. The wound is hypersensitive to touch and blanches with pressure, and blood flow to the dermis is increased over that of normal skin. If infection is prevented, superficial partial-thickness burns heal spontaneously within 3 weeks without functional impairment. They rarely cause hypertrophic scarring, but in pigmented individuals the healed burns may never completely match the color of the surrounding normal skin.

FIGURE 13-6 Superficial partial-thickness burn. Note pink color and moist surface.

Deep Partial-Thickness Burns

Deep partial-thickness burns (Figure 13-7) also blister, but the wound surface is usually a mottled pink and white color immediately after the injury. Alternatively, the burned dermis may be dry, with a cherry red color. The victim complains of discomfort rather than pain. When pressure is applied to the burn, capillary refill returns slowly or may be absent. The wound is often less sensitive to touch than is the surrounding normal skin. By the second day, the wound may be white and is usually fairly dry. If infection is prevented, such burns heal in 3 to 9 weeks but invariably do so with considerable scar formation. Unless active physical therapy is continued throughout the healing process, joint function may be impaired and hypertrophic scarring, particularly in pigmented individuals and children, becomes inevitable.

FIGURE 13-7 Deep partial-thickness burn. Note cherry-red color.

Full-Thickness Burns

Full-thickness burns (Figure 13-8) involve all layers of the dermis and can heal only by wound contracture, epithelialization from the wound margin, or skin grafting. Full-thickness burns are classically described as leathery, firm, depressed when compared with the adjoining normal skin, and insensitive to light touch and pinprick. Unfortunately, the difference in depth between a deep partial-thickness burn and a full-thickness burn may be less than 1 mm (0.04 inch). Full-thickness burns are easily misdiagnosed as deep partial-thickness burns, because the two types have many of the same clinical findings. For example, they may be mottled in appearance. They rarely blanch with pressure and may have a dry, white appearance. The burn may be translucent with clotted vessels visible in the depths. Some full-thickness burns, particularly immersion scalds, have a red appearance and can be confused with superficial partial-thickness burns. However, these red, full-thickness burns do not blanch with pressure. Full-thickness burns develop a classic burn eschar. An eschar represents the structurally intact but dead and denatured dermis that, over days to weeks, separates spontaneously from the underlying viable tissue.

FIGURE 13-8 Full-thickness burn. Note thick, leathery, white eschar.

Care At The Scene

First Aid at the Scene for Smaller Burns

Not all burns need immediate medical attention. Burns less than 5% TBSA (excluding deep burns of the face, hands, feet, perineum, or circumferential extremity) can be treated successfully in a wilderness setting if adequate first-aid supplies are available and wound care is performed diligently. Except for the very shallow burn that heals within a few days, most burns should be seen by a physician within 3 to 5 days after injury.

Burns should be washed thoroughly with plain soap and water and dried with a clean towel. The water used should be suitable for drinking, but it need not be sterile or bottled. Any obviously dead skin should be peeled off (which may be painful) or trimmed with sharp manicure scissors (usually painless). Large (greater than 2.5 cm [1 inch]), thin, fluid-filled blisters should be drained and the dead skin trimmed to prevent a potential closed-space infection. Deep burns, as from a flame, are firm and leathery, usually do not blister, and do not require immediate debridement. A small tube of silver sulfadiazine cream and tubes of bacitracin or Neosporin antibiotic ointment should be available in the first-aid kit. Either may be used and should be spread lightly over the wound. The wound may then be wrapped in dry, clean gauze, which need not be sterile. Simple dressings (one type of topical cream, plain gauze) are sufficient. Some patients prefer nonadherent dressings, such as Telfa or Adaptic (sometimes known as “greasy gauze”), because they are less likely to stick to the wound during dressing changes. The same effect can be achieved by soaking (with water) a plain gauze dressing that appears stuck to the wound, waiting a few minutes, and then removing the dressing with additional water if necessary. Other dressings (hydrogels, silver-coated dressings, silicone gel sheets, calcium alginate) designed to minimize the frequency of dressing changes and promote healing are available but are not necessary. The authors recommend simple antibiotic ointments such as silver sulfadiazine or bacitracin and plain gauze dressings rather than “specialty” dressings for inclusion in first-aid kits because they are simple, cheaper, and effective. Although patients may prefer one dressing over another for various reasons, no dressing has been shown conclusively to accelerate the healing of burn wounds. As such, the first-aid kit should be stocked with general-use supplies, which are less expensive and easier to replenish.

Mobility of the wound area must be actively maintained, and concentrated efforts should be made to avoid dependent positioning, especially when the victim is resting or sleeping. Focal edema in a small burn wound can be painful and alarming and should be prevented with extremity elevation and active range-of-motion exercises several times a day. Wound care should be performed once a day if the outer dressing remains dry. A wet, sticky outer dressing needs more frequent wound care to keep up with drainage from the wound. If only the outer dressing is dirty, whether soiled from food, dirt, or other substance, it may be changed as often as needed to maintain a clean dressing and aid in patient comfort. For the quickest healing of superficial burns, daily wound care should remove all exudates and crust, both of which significantly retard wound healing. Once a wound has epithelialized or is nearly epithelialized, a moisturizing lotion is recommended to aid in hydration and decrease scarring. Vitamin E, aloe, and oat beta glucan are often used for their antiinflammatory and soothing properties. Melaleuca is a topical antibacterial and antifungal tea tree oil that Australian aboriginal people have used for a variety of medicinal purposes. It is the active ingredient in Burnaid, a popular cream used for superficial partial-thickness burn injuries.

When determining the type of dressing to apply to a burn wound, the following considerations are important:

• The dressing should cover the entire burned area (an enclosed dressing), leaving no burned skin exposed to air or air currents.

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