Porth's Essentials of Pathophysiology, 4e

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Integumentary Function

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Thermal Injury About 450,000 people in the United States require med- ical care for burns each year, with 40,000 requiring hos- pitalization. 48 Flame burns occur because of exposure to direct fire. Scald burns result from hot liquids spilled or poured on the skin surface. The effects and complications of burns fully illustrate the essential function that the skin performs in protect- ing the body from the many damaging elements in the environment while serving to maintain the constancy of the body’s internal environment. The massive loss of skin tissue not only predisposes to attack by microor- ganisms that are present in the environment, but also allows for the massive loss of body fluids, interferes with temperature regulation, challenges the immune sys- tem, and imposes excessive demands on the metabolic and reparative processes that are needed to restore the body’s interface with the environment. Classification of Burns Burns are typically classified according to the depth of involvement as first-degree, second-degree, and third- degree burns. 49,50 The depth of a burn is largely influ- enced by the duration of exposure to the heat source and the temperature of the heating agent. First-degree burns (superficial partial-thickness burns) involve only the outer layers of the epidermis. They are red or pink, dry, and painful. There usually is no blister formation, as with a mild sunburn. The skin maintains its ability to function as a water vapor and bacterial barrier and heals in 3 to 10 days. First-degree burns usually require only palliative treatment, such as pain-relief measures and adequate fluid intake. Extensive first-degree burns on infants, the elderly, and persons who receive radia- tion therapy for cancer may require more care. Second-degree burns involve both the epidermis and dermis. Second-degree partial-thickness burns involve the epidermis and various degrees of the dermis. They are painful, moist, red, and blistered. Underneath the blisters is weeping, bright pink or red skin that is sensi- tive to temperature changes, air exposure, and touch. The blisters prevent the loss of body water and superfi- cial dermal cells. Excluding excision of large burn areas, it is important to maintain intact blisters after injury because they serve as a good bandage and may promote wound healing. These burns heal in approximately 1 to 2 weeks. Second-degree full-thickness burns involve the entire epidermis and dermis. Structures that originate in the subcutaneous layer, such as hair follicles and sweat glands, remain intact. These burns can be very painful because the pain sensors remain intact. Tactile sensation may be absent or greatly diminished in the areas of deep- est destruction. These burns appear as mottled pink, red, or waxy white areas with blisters and edema. The blis- ters resemble flat, dry tissue paper, rather than the bul- lous blisters seen with superficial partial-thickness injury. After healing in approximately 1 month, these burns maintain their softness and elasticity, but there may be the loss of some sensation. Scar formation is common.

booths continues to rise, while adherence of tanning booths to national guidelines is often violated. 46 Clinical Features. Sunburn is caused by excessive expo- sure of the epidermal and dermal layers of the skin to UV radiation, resulting in an erythematous inflamma- tory reaction. 47 Sunburn ranges from mild to severe. Mild sunburn consists of various degrees of skin redness. The burn continues to develop for 24 to 72 hours, occa- sionally followed by peeling skin in 3 to 8 days. Some peeling and itching may continue for several weeks. Inflammation, blistering, weakness, chills, fever, mal- aise, and pain often accompany severe forms of sunburn. Scaling and peeling follow any overexposure to sunlight. Dark skin also burns and may appear grayish or gray- black. Severe sunburns are those that cover large por- tions of the body with blisters or are accompanied by a high fever or intense pain. The UV rays of sunlight or other sources can be com- pletely or partially blocked from the skin surface by sunscreens. There are two primary types of sunscreens available on the market—chemical (soluble) agents and physical (insoluble) agents. 45 Chemical agents (e.g., para-aminobenzoic acid [PABA] derivatives) protect the skin from absorbing sunlight, and physical agents (e.g., micronized titanium dioxide and microfine zinc) work by reflecting sunlight. The sun protection fac- tor (SPF) rating of the various sunscreen products is based on their ability to obstruct UV radiation (UVR) absorption. The ratings usually are on a scale of 1 to 30+, with the higher ratings indicating greater blocking of UVR. 45 Products with a higher SPF screen out more UVB rays, which are primarily responsible for acute sun damage. Shielding the skin with protective cloth- ing and hats or head coverings helps decrease UVR exposure. Mild to moderate sunburns are treated with anti- inflammatory medications, such as aspirin or ibuprofen, until redness and pain subside. Cold compresses, cool baths, and applying a moisturizing cream, such as aloe, to affected skin help treat the symptoms. Steroid and nonsteroidal agents are used depending on the severity of the burn. Blisters should not be broken to preserve the protective layer of the skin, hasten the healing process, and decrease the risk of infection. Extensive second- and third-degree sunburns may require hospitalization and specialized burn care techniques, as described in the sec- tion on thermal injury. Drug-Induced Photosensitivity Some drugs are classified as photosensitive drugs because they produce an exaggerated response to UVR when the drug is taken in combinationwith sun exposure. Examples include some of the anti-infective agents (sulfonamides, tetracyclines, nalidixic acid), antihistamines (cyprohepta- dine, diphenhydramine), antipsychotic agents (phenothi- azines, haloperidol), diuretics (thiazides, acetazolamide, amiloride), hypoglycemic agents (sulfonylureas), and nonsteroidal anti-inflammatory drugs (phenylbutazone, ketoprofen, naproxen).