Thermal injuries are burns caused by contact with or exposure to extremes of temperature. Over the past 6 decades the incidence of burn injuries in the United States has steadily decreased, with approximately 450,000 currently occurring annually,1 resulting in approximately 40,000 hospitalizations and 3120 deaths.^7–10 The fire loss record in the United States is the worst in the industrialized world, with the fire-related mortality double that of most countries on a per capita basis. From 2005 to 2009, residential fires resulted in nearly $7 billion per year in property damage.¹¹

A half century ago, burns over 50% of the total body surface area (TBSA) resulted in a greater than 50% mortality in pediatric patients.¹² Currently, most children survive burns of this size, and more than half survive burns of more than 90% of their TBSA.¹³ Early mortality generally occurred as a result of inadequate initial resuscitation. As vigorous resuscitation protocols were developed, a significant reduction in mortality occurred. Additionally, many advances have also contributed to decreasing thermal burn–related mortality, including: a better understanding of the pathophysiologic mechanisms of burns, implementation of a multidisciplinary team–oriented approach, improvement of resuscitation strategies and infection control measures, use of early surgical excision and skin-grafting techniques, application of advances in skin substitute development, and employment of improved rehabilitation strategies.^14–18

Unfortunately, the reduction in mortality was replaced by an increased number of survivors with wound sepsis. The development of improved topical and systemic antimicrobial agents, recognition of the importance of maintaining proper nutrition, and adoption of early wound excision and grafting techniques have resulted in a significant reduction in mortality. As a result of these advances, acute mortality in patients with thermal injuries remains relatively low. The primary cause of death in this population now occurs in the subacute setting as a result of pulmonary sepsis, often developing secondary to inhalation injury. More than 80% of patients sustaining burns have involvement of less than 20% of their TBSA and are treated on an outpatient basis. Despite burn degree, the associated physical and emotional sequelae are often extensive and prolonged. As a result, this unique population requires vigilant follow-up care.

The U.S. Centers for Disease Control and Prevention (CDC) has identified the following groups as being at high risk for fire-related injuries and deaths: children younger than 4 years; adults 65 years and older; Native Americans and African Americans; economically challenged individuals; people living in rural areas; and those residing in manufactured homes or substandard housing. Children younger than 15 years old account for one third of all admissions to burn units and one third of all deaths from burns and burn-related injuries.8 Scald injuries, primarily secondary to accidental spills, or in up to 20% from an element of abuse or neglect, account for up to 65% of all burn injuries.^4,12,19 See Figure 54-1 illustrating an abuse burn.

The population older than 65 years of age accounts for approximately 29% of all burn/fire-related deaths in the United States.20 Burns in the elderly carry a high mortality rate as a result of preinjury disability, age-related immunosuppression, and impaired healing responses (Table 54-1).⁸ Environmental and lifestyle factors influence the frequency and magnitude of thermal burn injuries. Alcohol and drug abuse contributes to approximately 40% of all residential fire-related deaths. Neurologic and psychiatric disorders have also been found to increase the risk of accidental burn injury, with one study finding 3% of patients admitted to the burn unit had thermal injuries associated with neurologic disorders.

Depth of burn injury is divided into four classifications: first-degree burns, also known as superficial burns, second-degree burns, also known as superficial and deep partial-thickness, third-degree burns (full-thickness), and fourth-degree burns (full-thickness with bone or muscle involvement), based on criteria established by the American Burn Association (Table 54-2).²²

First-degree burns (also known as superficial burns) involve only superficial tissue destruction in the outermost layers of the epidermis, with no associated compromise of the function of the skin (see Table 54-2). These burns are often associated with local discomfort, erythema, and mild systemic responses such as headache, chills, nausea, and vomiting. Erythema, a thermovascular response that occurs in first-degree burns in the absence of direct trauma to the dermis, is probably related to the release of tissue contents into the superficial circulation. First-degree burns are generally self-limiting, require no fluid resuscitation, and are therefore not included in estimates of the percentage of TBSA burned. However, in infants and elderly adults, first-degree burns may lead to systemic dehydration, necessitating intravenous resuscitation. Therapy generally includes simple analgesia. These injuries typically heal in 3 to 6 days without scarring or pigmentation changes.

Second-degree (superficial partial-thickness) burns involve the epidermis to the level of the dermis and appear red to pale ivory. Moist, thin-walled blisters often form within minutes of the injury (Figure 54-2). Pain is a major clinical feature of this depth of injury because tactile and pain sensors remain intact (see Table 54-2). Injuries typically heal in 7 to 21 days in the absence of wound infection. The amount of scarring that follows is a genetically determined trait, with some groups of people tending to scar excessively (African Americans and Caucasians with red hair) or minimally (Native American and Asian groups). Hair follicles remain intact and will regrow hair in the area of injury. Hair usually reappears 7 to 10 days after injury.

Third-degree (full-thickness) burns may also involve the entire epidermis, the dermis, and the underlying subcutaneous tissue. Immediately following injury, these areas appear white, cherry red, or black. Deep blisters may be present under a dry layer of dehydrated skin. Superficial blood vessels coagulated by the heat of injury may be visible through the skin as thrombosed veins. One of the physiologic characteristics of the skin that is lost (Box 54-1) is the elasticity of the dermis, resulting in a wound with a dry, hard, leathery texture. The massive edema that accompanies major burn injury combined with the loss of elasticity may result in a tourniquet-like effect when the injury occurs circumferentially around a limb or torso. This often necessitates escharotomies or, rarely, fasciotomies to restore distal circulation.

Extent of injury refers to the percentage of TBSA burned. Estimates can be calculated with the rule of nines (Figure 54-3) or the Lund and Browder chart (Figure 54-4). The rule of nines is commonly used in prehospital settings and emergency departments, and provides a rough estimate of TBSA involved. The Lund and Browder chart, or a variation of it, is generally used in burn centers and is more precise, particularly in assessing TBSA in children under the age of 10 years (see Figure 54-4).

The severity of a burn injury is determined by the extent to which the physiologic functions of the skin are disrupted beyond the body’s normal ability to respond with compensatory mechanisms. The American Burn Association22 classifies burn injury as minor, moderate, and major (Table 54-3). The severity of the burn injury and the eventual morbidity and mortality associated with it are related to a combination of factors: the patient’s medical history, the extent and depth of the burn, the body area involved, the presence of concomitant trauma sustained at the time of the burn, and the patient’s age.

Initial management of patients with thermal burn injuries should focus on stabilizing the ABCs (airway-breathing-circulation).4 Common signs of inhalation injury include cough, stridor, hoarseness, singed nasal hair, carbonaceous sputum, oropharyngeal edema, and blisters. These injuries generally evolve over time, often progressing to complete airway obstruction secondary to edema. Unfortunately, no clinical variables accurately predict which patients will progress to airway compromise; therefore consideration should be given early to bronchoscopy and endotracheal intubation.²³ Compromise of breathing in burn patients is often attributed to underlying inhalation injury or circumferential full-thickness burns resulting in impaired chest excursion; however, breathing difficulties may also arise from associated pneumothorax, hemothorax, or chest wall instability from multiple segmental fractures (flail chest). Vascular access is preferentially obtained peripherally through unburned tissue if possible. If no such sites are available, access may be established through burned skin. The patient is then evaluated by a complete head-to-toe examination for any other associated traumatic injuries, which are identified and managed as required. TBSA is then determined using a standardized chart such as the Lund and Browder chart (see Figure 54-4). Fluid resuscitation requirements are subsequently determined and initiated while the patient is placed on clean sheets and the burned areas covered with dry clean sheets or dressings. Coverage with cool wet sheets should be avoided, because these quickly become cold wet sheets, and with the loss of the burned skin’s ability to regulate body temperature, hypothermia can quickly ensue. Application of topical agents in the acute setting outside of a burn center is not recommended. A Foley catheter is also placed to monitor urine output during resuscitation, and in patients with burns greater than 20% of the TBSA, if possible, a nasogastric tube should be placed to allow for gastric decompression and to minimize the risk of abdominal bloating and aspiration. Transfer of patients to burn units or other facilities with appropriate resources is initiated during the course of the initial assessment. The American College of Surgeons Committee on Trauma has developed a set of burn unit referral criteria to assist initial evaluators in triage (Box 54-2).

Within minutes of a burn injury, the cardiovascular system, which is normally a closed, semipermeable system, becomes an open system through which the patient’s circulating volume leaves the circulatory system. This phenomenon, known as “capillary leak,” occurs within a few minutes of injury and persists for 24 hours. Burn shock is not confined to the burn area but, rather, is a systemic process. While the capillary system throughout the body becomes leaky, fluid lost in the area of the burn leaks through the burn into the environment in an evaporative fashion, whereas fluid loss internally collects in the nearby soft tissues, producing extensive interstitial edema (Figure 54-5).

The most widely used formula to guide fluid resuscitation within the first 24 hours of burn injury is the Parkland formula (Box 54-3). The formula utilizes lactated Ringer solution as the resuscitation fluid, because it most closely approximates the fluid it is replacing and thereby minimizes the profound electrolyte imbalances often seen with large-volume resuscitation (Box 54-4). The standardized formulas provide an excellent guideline for initiating fluid resuscitation but do not ensure adequacy of resuscitation. In Cartotto’s series, 30 patients with mean TBSA burns of 27% received 6.7 ± 2.8 ml/kg/% TBSA burn in the first 24 hours to ensure adequate resuscitation.²⁴ Adequacy of resuscitation is determined by the global response of the patient to the fluid administration and not by one single variable.²⁵ Markers commonly used to reflect adequacy of resuscitation include normalization of mental status, blood pressure, pulse rate, capillary refill time, arterial pH, and base deficit and maintenance of urine output at 0.5 to1 ml/kg per hour for adults and 1 to 1.5 ml/kg per hour for children. In addition to the fluid volumes calculated by the standardized formulas, the patient should also receive appropriate maintenance fluid over the first 24-hour period.

BOX 54-3

PARKLAND FORMULA FOR FLUID RESUSCITATION IN BURN SHOCK

During the first 24 hours after a burn, administer intravenous LRS at the following rate:

4mlLRS/%TBSA burn/kg body weight

where

• Time is calculated from the time of burn injury.

• TBSA is total body surface area.

• Half of the total fluid is administered in the first 8 hr after burn.

• One fourth of the total is administered in the second 8 hr.

• One fourth of the total is administered in the third 8 hr or in quantities to maintain adult urine output at 30 ml/hr or child urine output at 1 ml/kg/hr.

Example of formula calculation in a 70-kg patient with a 50% TBSA burn:

4ml×70kg×50%TBSA burn=14,000ml(14L)LRS in24hr

• Administer 7000 ml in the first 8 hr at 875 ml/hr.

• Administer 3500 ml in the second 8 hr at 437 ml/hr.

• Administer 3500 ml in the third 8 hr at 437 ml/hr.

LRS, Lactated Ringer solution; TBSA, total body surface area.

Data from Baxter CR: Guidelines for fluid resuscitation, J Burn Care Rehabil 2:279-286, 1981.

Approximately 24 hours following the acute burn injury, the capillary leak syndrome begins to resolve as cardiovascular integrity is restored. At this time, a colloid solution such as albumin may be administered according to an appropriate formula, which differs by gender and age (see Box 54-4), in an effort to replace the protein lost during the acute burn shock phase. Resuscitation in the acute setting with colloid has been shown to decrease net volume of fluid administered and complications associated with large-volume resuscitation such as abdominal compartment syndrome.²⁶

One of the major functions of intact skin is to serve as a barrier to water evaporation. With major burn injury, this ability of the skin to regulate evaporative loss is disrupted. In a classic study conducted in 1962, Moncrief and Mason²⁷ attempted to determine the magnitude of such a loss and found that daily evaporative loss was in the range of 20 times normal during the early phase of burn injury, with gradual decreases as wound closure was achieved. Further studies revealed that the insensible water loss through burned skin is not caused by evaporation of water from sweat glands but rather by water vapor formed within the body and lost through the skin.^28,29 As the patient progresses to the subacute phase of resuscitation, it is imperative that attention be paid to these unaccountable losses.

Patients at the extremes of age groups require special considerations with respect to resuscitation. Table 54-1 summarizes the physiologic changes associated with age that increase the vulnerability of children and elderly persons.^30–32