Porth's Essentials of Pathophysiology, 4e

1170

Integumentary Function

U N I T 1 3

Respiratory System Dysfunction. Another injury commonly associated with burns is postburn lung injury from smoke inhalation. Victims often are trapped in a burning structure and inhale significant amounts of smoke, carbon monoxide, and other toxic fumes. Water- soluble gases found in smoke from burning plastics and rubber, such as ammonia, sulfur dioxide, and chlorine, react with mucous membranes to form strong acids and alkalis that induce ulceration of the mucous membrane, bronchospasm, and edema. Lipid-soluble gases, such as nitrous oxide and hydrogen chloride, are transported to the lower airways, where they damage lung tissue. There also may be thermal injury to the respiratory passages. Manifestations of inhalation injury include hoarseness, drooling and inability to handle secretions, hacking cough, and labored, shallow breathing. Serial blood gases show a fall in the partial pressure of arte- rial oxygen (PO 2 ). Signs of mucosal injury and airway obstruction often are delayed for 24 to 48 hours after a burn. Other pulmonary conditions, such as pneumonia, pulmonary embolism, or pneumothorax, may occur sec- ondarily to the burn. Hypermetabolic Response. The stress of burn injury increases metabolic and nutritional requirements. Secretion of stress-related hormones such as catechol- amines and cortisol is increased in an effort to main- tain homeostasis. Heat production is increased in an effort to balance heat losses from the burned area. Hypermetabolism, characterized by increased oxy- gen consumption, increased glucose use, and protein and fat wasting, is a characteristic response to burn trauma and infection. The hypermetabolic state peaks at approximately 7 to 17 days after the burn, and tissue breakdown diminishes as the wounds heal. Nutritional support is essential to recovery from burn injury. Enteral and parenteral hyperalimentation may be used during this time to deliver sufficient nutrients to prevent tissue breakdown and postburn weight loss. Sepsis. Immunologically, the skin is the body’s first line of defense. When the skin is no longer intact, the body is open to bacterial infection. Destruction of the skin also prevents the delivery of cellular components of the immune system to the site of injury. There also is loss of normal protective skin flora and a shift to coloniza- tion by more pathogenic flora. Thus, a significant com- plication of the acute phase of burn injury is sepsis. It may arise from the burn wound, pneumonia, urinary tract infection, infection elsewhere in the body, or the use of invasive procedures or monitoring devices. The burn site is an ideal growth area for microorganisms; the serum and debris provide nutrients, and the burn injury compromises blood flow. Emergency and Long-TermTreatment Regardless of the type of burn, the first step in any burn situation is to stop the burning process, cool the burn, provide pain relief, and cover the burn. Active cooling removes the heat and prevents progression of the burn.

Immersion or irrigation with lukewarm water for at least 20 minutes can be extremely helpful. Immediate submer- sion is more important than removal of clothing, which may delay cooling the involved areas. The application of ice or cold water is not recommended because it can further limit blood flow to an area, turning a partial- thickness into a full-thickness burn. Depending on the depth and extent of the burn, medical treatment may be necessary. Emergency care consists of resuscitation and stabilization with intrave- nous fluids while maintaining cardiac and respiratory function. Once hospitalized, the immediate treatment regimen focuses on continued maintenance of cardio- respiratory function, pain alleviation, wound care, and emotional support. After hemodynamic and pulmonary stability have been established, treatment is directed toward initial care of the wound. Treatment of the burn wound focuses on protection from desiccation and fur- ther injury of those burn areas that re-epithelialize in 7 to 10 days (superficial second-degree burns). “Nature’s own blister” is the best protection for these burns. Topical antimicrobial preparations (e.g., silver sulfadia- zine) and dressings are used to cover the wound when the blister has been broken. Wounds that will not heal spontaneously in 7 to 10 days (deep second-degree and third-degree burns) are usually treated by excision and skin grafts. The sloughed tissue, or eschar, produced by the burn is excised as soon as possible. This decreases the chance of infection and allows the skin to regenerate faster. Burns that encircle the entire surface of the body or a body part (e.g., arms, legs, torso) can act as a tourni- quet, causing major tissue damage to the muscles, ten- dons, and vascular under the area of the leathery burn eschar. These burns are called circumferential burns . The eschar is incised longitudinally (escharotomy), and sometimes a fasciotomy (surgical incision through the fascia of the muscle) is performed. Systemic infection remains a leading cause of mor- bidity among persons with extensive burns. Continuous microbiologic surveillance is necessary; protective isola- tion measures are often instituted. There is an increasing trend toward use of prophylactic antibiotic treatment in persons with major burns. Skin grafts are surgically implanted as soon as possi- ble, often at the same time the burn tissue is excised, to promote new skin growth, limit fluid loss, and act as a dressing. 51 Skin grafts can be permanent or temporary, and split thickness or full thickness. Permanent skin grafts are used over newly excised tissue. Temporary skin grafts are used to cover a burned area until the tissue underneath it has healed. Various sources of skin grafts exist: autograft (skin obtained from the person’s own body), homograft (skin obtained from another human being, alive or recently dead), and heterograft (skin obtained from another species, such as pigs). The best choice is autografting when there is enough unin- terrupted skin on the person’s body. The thickness of these grafts depends on the donor site and the needs of the burn patient. A split-thickness skin graft is one that includes the epidermis and part of the dermis.