Burns
Burns are injuries to tissue that result from heat, electricity, radiation, or chemicals.
Burns are usually caused by heat (thermal burns), such as fire, steam, tar, or hot liquids. Burns caused by chemicals are similar to thermal burns, whereas burns caused by radiation (see Section 24, Chapter 292), sunlight (see Section 18, Chapter 214), and electricity (see Section 24, Chapter 293) tend to differ significantly.
Thermal and chemical burns usually occur because heat or chemicals contact part of the body's surface, most often the skin. Thus, the skin usually sustains most of the damage. However, severe surface burns may penetrate to deeper body structures, such as fat, muscle, or bone.
When tissues are burned, fluid leaks into them from the blood vessels, causing swelling and pain. In addition, damaged skin and other body surfaces are easily infected because they can no longer act as a barrier against invading organisms.
More than 2 million people in the United States require treatment for burns each year, and between 3,000 and 4,000 die of severe burns. Older people and young children are particularly vulnerable.
 See the sidebar When Chemicals Burn the Skin.
Classification
Doctors classify burns according to strict, widely accepted definitions. These definitions may not correspond to a person's understanding of those terms. For example, a doctor may classify a burn as serious even though the person regards it as minor. The definitions classify the burn's depth and the extent of tissue damage.
The depth of injury from a burn is described as first, second, or third degree. First-degree burns are the most shallow (superficial). They affect only the top layer of skin (epidermis). Second-degree burns extend into the middle layer of skin (dermis). Third-degree burns involve all three layers of skin (epidermis, dermis, and fat layer), usually destroying the sweat glands, hair follicles, and nerve endings as well.
 See the figure Estimating the Extent of a Burn.
Burns are classified as minor, moderate, or severe. The severity determines how they are predicted to heal and whether complications are likely. Doctors determine the severity of the burn by estimating the percentage of the body surface that has been burned. Special charts are used to show what percentage of the body surface various body parts comprise. For example, in an adult, the arm constitutes about 9% of the body. Separate charts are used for children, because their body proportions are different. All first-degree burns as well as second-degree burns that involve less than about 15% of the body surface usually are classified as minor, although they may seem severe to the person. A third-degree burn may be classified as minor if it involves less than 5% of the body surface, unless it involves the face, hands, feet, or genitals. Burns involving these areas or involving deeper layers of skin over larger areas of the body are classified as moderate or, more often, as severe.
See the sidebar Smoke Inhalation.
Symptoms and Diagnosis
First-degree burns are red, moist, swollen, and painful. The burned area whitens (blanches) when lightly touched but does not develop blisters. Second-degree burns are red, swollen, and painful, and they develop blisters that may ooze a clear fluid. The burned area may blanch when touched. Third-degree burns usually are not painful because the nerves have been destroyed. The skin becomes leathery and may be white, black, or bright red. The burned area does not blanch when touched, and hairs can easily be pulled from their roots without pain. No blisters develop. The appearance and symptoms of deep burns can worsen during the first hours or even days after the burn.
Complications
Most minor burns are superficial and do not cause complications. However, deep second-degree and third-degree burns swell and take more time to heal. In addition, deeper burns can cause scar tissue to form. This scar tissue shrinks (contracts) as it heals. If the scarring occurs at a joint, the resulting contracture may restrict movement.
Severe burns can cause serious complications due to extensive fluid loss and tissue damage. Complications from severe burns may take hours to develop. The longer the complication is present, the more severe are the problems it tends to cause. Young children and older adults tend to be more seriously affected by complications than other age groups.
Dehydration eventually develops in people with widespread burns, because fluid seeps from the blood to the burned tissues. Shock develops if dehydration is severe (see Section 3, Chapter 24). Destruction of muscle tissue (rhabdomyolysis) occurs in deep third-degree burns. The muscle tissue releases myoglobin, one of the muscle's proteins, into the blood. If present in high concentrations, myoglobin harms the kidneys. Rhabdomyolysis can be diagnosed from tests of the blood and urine.
Thick, crusty surfaces (eschars) are produced by deep third-degree burns. Eschars can become too tight, cutting off blood supply to healthy tissues or impairing breathing.
Treatment
Before burns are treated, the burning agent must be stopped from inflicting further damage. For example, fires are extinguished. Clothing--especially any that is smoldering (such as melted synthetic shirts), covered with hot tar, or soaked with chemicals--is immediately removed.
Hospitalization is sometimes necessary for optimal care of burn injuries. For example, elevating a severely burned arm or leg above the level of the heart to prevent swelling is more easily accommodated in a hospital. In addition, burns that prevent a person from performing essential daily functions, such as walking or eating, make hospitalization necessary. Severe burns, deep second- and third-degree burns, burns occurring in the very young or the very old, and burns involving the hands, feet, face, or genitals are usually best treated at burn centers. Burn centers are hospitals that are specially equipped and staffed to care for burn victims.
Superficial Minor Burns: Superficial minor burns are immersed immediately in cool water if possible. The burn is carefully cleaned to prevent infection. If dirt is deeply embedded, a doctor can give analgesics or numb the area by injecting a local anesthetic and then scrub the burn with a brush.
Often, the only treatment required is application of an antibiotic cream, such as silver sulfadiazine. The cream prevents infection and forms a seal to prevent further bacteria from entering the wound. A sterile bandage is then applied to protect the burned area from dirt and further injury. A tetanus vaccination is given if needed (see Section 17, Chapter 189).
Care at home includes keeping the burn clean to prevent infection. In addition, many people are given analgesics, often opioid analgesics, for at least a few days. The burn can be covered with a nonstick bandage or with sterile gauze. The gauze can be removed without sticking by first being soaked in water.
See the sidebar Small, Shallow Burns.
Deep Minor Burns: As with more superficial burns, deep minor burns are treated with antibiotic cream. However, any dead skin and broken blisters must be removed before the antibiotic cream is applied. In addition, keeping a deeply burned arm or leg elevated above the heart for the first few days reduces swelling and pain. The burn may require frequent re-examination at a hospital or doctor's office, possibly as often as daily for the first few days.
A skin graft may be needed. Most skin grafts replace the burned skin. Other skin grafts help by temporarily covering and protecting the skin as it heals on its own. In a skin grafting procedure, a piece of healthy skin is taken from an unburned area of the person's body (autograft), from another living or dead person (allograft), or from another species (xenograft)--usually pigs because their skin is most similar to human skin. The skin graft is surgically sewn over the burned area after removing any dead tissue and ensuring that the wound is clean. Autografts are permanent. Allografts and xenografts, however, are rejected after 10 to 14 days by the person's immune system. Artificial skin has been developed recently and can also be used to replace the burned skin. Burned skin can be replaced anytime within several days of the burn.
Physical and occupational therapy usually are needed to prevent immobility caused by scarring around the joints. Stretching exercises are started within the first few days after the burn. Splints are applied to ensure that joints that are likely to be immobile rest in positions that are least likely to lead to contractures. The splints are left in place except when the joints are moved. If a skin graft has been used, however, therapy is not started for the first 5 to 10 days after the grafts are attached so that the healing graft is not disturbed. Bulky dressings that put pressure on the burn can prevent large scars from developing.
Severe Burns: Severe, life-threatening burns require immediate care. Dehydration is treated with large amounts of fluids given intravenously. A person who has gone into shock as a result of dehydration is also given oxygen through a face mask.
Destruction of muscle tissue is also treated with large amounts of fluids given intravenously. The fluids dilute the myoglobin in the blood, preventing extensive damage to the kidneys. Sometimes a chemical, sodium bicarbonate, is given intravenously to help dissolve myoglobin and thus also prevent further damage to the kidneys.
Eschars that cut off blood supply to an extremity or that impair breathing are cut open in a surgical procedure called escharotomy. Escharotomy usually causes some bleeding, but because the burn causing the eschar has destroyed the nerve endings in the skin, there is little pain.
Keeping the burned area clean is important, because the damaged skin is easily infected. Cleaning may be accomplished by gently running water over the burns periodically. Wounds are cleaned and bandages changed 1 to 3 times per day.
A proper diet that includes adequate amounts of calories, protein, and nutrients is important for healing. People who cannot consume enough calories may drink nutritional supplements or receive them by way of a tube inserted through the nose into the stomach (a nasogastric tube), or nutrition may be given intravenously. Additional vitamins and minerals are usually given.
Because severe burns take a long time to heal, sometimes years, and can cause disfigurement, the person can become depressed. Depression often can be relieved with drugs or psychotherapy or both.
Prognosis
First- and second-degree burns heal in days to weeks without scarring. Deep second-degree and small (less than 1 inch) third-degree burns take weeks to heal and usually cause scarring. Larger third-degree burns require skin grafting. Burns that involve more than 90% of the body surface, or more than 60% in an older person, usually are fatal.
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