Porth's Essentials of Pathophysiology, 4e

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Disorders of Skin Integrity and Function

C h a p t e r 4 6

These burns heal with supportive medical care aimed at preventing further tissue damage, providing adequate hydration, and ensuring that the granular bed is ade- quate to support re-epithelialization. Third-degree full-thickness burns extend into the subcutaneous tissue and may involve muscle and bone. Thrombosed vessels can be seen under the burned skin, indicating that the underlying vasculature is involved. Third-degree burns vary in color from waxy white or yellow to tan, brown, deep red, or black. These burns are hard, dry, and leathery. Edema is extensive in the burn area and surrounding tissues. There is no pain because the nerve sensors have been destroyed. However, there is no such thing as a “pure” third-degree burn. Third- degree burns are almost always surrounded by second- degree burns, which are surrounded by an area of first-degree burns. The injury sometimes has an almost targetlike appearance because of the various degrees of burn. Full-thickness burns wider than 1.5 inches usu- ally require skin grafts because all the regenerative (i.e., dermal) elements have been destroyed. Smaller injuries usually heal from the margins inward toward the cen- ter, the dermal elements regenerating from the healthier margins. However, regeneration may take many weeks and leave a permanent scar, even in smaller burns. In addition to the depth of the wound, the extent of the burn also is important. Extent is measured by esti- mating the amount of total body surface area (TBSA) involved. 49,50 Several tools exist for estimating the TBSA. For example, the rule of nines counts anatomic body parts as multiples of 9% (the head and neck is 9%, each arm 9%, each leg 18%, anterior trunk 18%, posterior trunk 18%), with the perineum 1%. The Lund and Browder chart includes a body diagram table that esti- mates the TBSA by age and anatomic part. Children are more accurately assessed using this method because it takes into account the difference in relative size of body parts. The estimates of TBSA are then converted to the

American Burn Association Classification of Extent of Injury (Table 46-1). Other factors, such as age, location, other injuries, and preexisting conditions, are taken into consideration for a full assessment of burn injury. 49,50 These factors can increase the assessed severity of the burn and the length of treatment. For example, a first-degree burn is reclassified as a more severe burn if other factors are present, such as burns to the hands, face, and feet; inhalation injury; other trauma; or existence of psychosocial problems. Genital burns almost always require hospitalization because edema may cause difficulty urinating and the location complicates maintenance of a bacteria-free environment. Systemic Complications Burn victims often are confronted with hemodynamic instability, impaired respiratory function, a hypermeta- bolic response, and sepsis. 49,50 The magnitude of the response is proportional to the extent of injury, usu- ally reaching a plateau when approximately 60% of the body is burned. In addition to loss of skin, burn victims often have associated injuries or illnesses. The treatment challenge is to provide immediate resuscitation efforts and long-term maintenance of physiologic function. Pain and emotional problems are additional challenges faced by persons with burns. Hemodynamic Instability. Hemodynamic instabil- ity begins almost immediately with injury to capillar- ies in the burned area and surrounding tissue. Fluid is lost from the vascular, interstitial, and cellular compart- ments. Because of a loss of vascular volume, major burn victims often present in the emergency department in a form of hypovolemic shock (Chapter 20) known as burn shock . Because proteins from the blood are lost into the interstitial compartment, generalized edema, including pulmonary edema, can be severe.

TABLE 46-1 American Burn Association Grading System for Burn Severity and Disposition Type of Burn Minor Moderate Major

<10%TBSA in adult

10%–20%TBSA in adult

>20%TBSA in adult

Criteria

<5%TBSA in young (<10 years) or old (>50 years)

5%–10%TBSA in young or old >10%TBSA in young or old

<2% Full-thickness burn

2%–5% Full-thickness burn

>5% Full-thickness burn

High-voltage injury

High-voltage burn

Suspected inhalation injury

Known inhalation injury

Circumferential burn

Any significant burn to face, eyes, ears, genitalia, hands, feet, or major joints Significant associated injuries (e.g., major trauma)

Concomitant medical problem predisposing to infection (e.g., diabetes, sickle cell disease)

Outpatient management

Hospital admission

Referral to burn center

Disposition

TBSA, total body surface area. From American Burn Association. Hospital and prehospital resources for optimal care of patients with burn injury: guidelines for development and operation of burn centers. J Burn Care Rehabil. 1990;11:98–104.