55: The Burned Patient

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CHAPTER 55 The Burned Patient

Philip R. Levin, MD, Alma N. Juels, MD

1 Who gets burned?

Approximately 2 million fires are reported each year, which result in 1.2 million people with burn injuries. Approximately 45,000 people are hospitalized in the United States for thermal injury. There are about 5000 fire and burn deaths per year. The majority of burns are thermal injuries. Electrical burns usually cause tissue destruction by thermal and associated injuries. In chemical burns the degree of injury depends on the particular chemical, its concentration, and duration of exposure. Seventy percent of burn patients are men. Mean age for all cases is 35 years old. Scalds are the most common in those below 5 years of age, whereas fire injuries are more common in older patients.

2 What are the three main factors that correlate with increased mortality with burn injury?

Advanced age, burn size, and presence of inhalation injury correlate with increased mortality.

3 What are the consequences of skin damage?

The skin is the largest organ of the human body. It has three principal functions, all of which are disrupted by burn injury:

image The skin is an important sensory organ.
image It performs a major role in thermoregulation for the dissipation of metabolic heat.
image The skin acts as a barrier to protect the body against the entrance of microorganisms in the environment. A burn patient may have extensive evaporative heat and water loss, and loss of thermoregulation may lead to hypothermia. Burn patients have a profound risk of infection and sepsis.

4 How are burns classified?

The severity of the burn is graded by its depth, which depends on the extent of tissue destruction.

image Superficial burns involve the upper layers of the epidermis; the skin is painful and appears red and slightly edematous, much like a sunburn.
image Superficial partial-thickness burns occur when tissue damage extends into the superficial layer of the dermis, which is still lined with intact epithelium that proliferates and regenerates new skin. These burns develop blisters and have red or whitish areas that are very painful.
image Deep partial-thickness burns extend downward into the deeper layer of the dermis. Edema is marked, and sensation is altered.
image Full-thickness and subdermal burns affect every body system and organ. A full-thickness burn extends through the epidermis and dermis and into the subcutaneous tissue layer. A subdermal burn damages muscle, bone, and interstitial tissue. Some centers are now using laser Doppler imaging to better determine burn depth.

5 What systems are affected by burns?

All physiologic functions can be affected by burns, including the cardiovascular and respiratory systems; hepatic, renal, and endocrine function; the gastrointestinal tract; hematopoiesis; coagulation; and immunologic response.

6 How is the cardiovascular system affected?

A transient decrease in cardiac output, as much as 50% from baseline, is followed by a hyperdynamic response. In the acute phase organ and tissue perfusion decreases because of hypovolemia, depressed myocardial function, increased blood viscosity, and release of vasoactive substances. The acute phase starts immediately after injury; the second phase of burn injury, termed the metabolic phase, begins about 48 hours after injury and involves increased blood flow to organs and tissues. Geriatric patients may have a delayed or nonexisting second phase. Hypertension of unknown cause develops and may be quite extensive.

7 How is the respiratory system affected?

Pulmonary complications can be divided into three distinct syndromes based on clinical features and temporal relationship to the injury. Early complications, occurring 0 to 24 hours postburn, include carbon monoxide (CO) poisoning and direct inhalation injury and can lead to airway obstruction and pulmonary edema. Delayed injury, occurring 2 to 5 days after injury, includes adult respiratory distress syndrome. Late complications, occurring days to weeks after the injury, include pneumonia, atelectasis, and pulmonary emboli. The two most common complications of burn injury are pneumonia and respiratory failure.

8 What is inhalation injury?

Inhalation injury occurs when hot gases, toxic substances, and reactive smoke particles reach the tracheobronchial tree. These substances result in wheezing, bronchospasm, corrosion, and airway edema and should be suspected if the burn was sustained in a closed space. The presence of carbonaceous sputum, perioral soot, burns to the face and neck, stridor, dyspnea, or wheezing are indications for complete respiratory tract evaluation. Inhalation injury can cause damage to the upper airway (i.e., airway compromise, nasal obstruction, and acute laryngitis with varying degrees of laryngeal edema), damage to the conducting airway (i.e., tracheitis and bronchitis), and injury to the lower respiratory tract (i.e., pneumonitis, pulmonary edema, and adult respiratory distress syndrome). Chest radiographs during the initial phase usually underestimate the severity of lung damage because the injury is usually confined to the airways. Fiber-optic bronchoscopy has been quite useful in diagnosis of inhalation injury.

9 What is the best way to treat inhalation injury?

Management is generally supportive. Oxygen should be provided as necessary to ensure adequate oxygenation. Bronchospasm usually responds to β-agonists. Patients with smoke inhalation can require greater fluid resuscitation than other patients with burns. Pulmonary toilet may be important if there is excessive carbonaceous material in the lungs. Intubation or tracheotomy may be necessary if there is significant upper airway compromise. Patients with heat and smoke injury plus extensive face and neck burns usually all require intubation. Patients with oral burns but no smoke injury should still be intubated early because these patients have significant edema and secretions and it may be nearly impossible to intubate at a later date. If intubation occurs, make sure to secure the endotracheal tube because it may be extremely difficult to replace it if it becomes dislodged. High-frequency percussive ventilation has also been shown to be effective in clearing secretions.

10 What are the features of carbon monoxide poisoning?

CO toxicity is one of the leading causes of death in fires. CO is produced by incomplete combustion associated with fires, exhaust from internal combustion engines, cooking stoves, and charcoal stoves. Its affinity for hemoglobin is 200 times that of oxygen. When CO combines with hemoglobin, forming carboxyhemoglobin (COHb), the pulse oximeter may overestimate hemoglobin saturation. Symptoms are caused by tissue hypoxia, shift in the oxygen-hemoglobin dissociation curve, direct cardiovascular depression, and cytochrome inhibition. The persistence of a metabolic acidosis in the patient with adequate volume resuscitation and cardiac output suggests the persistent CO impairment of oxygen delivery and use. Treatment is initiated with 100% oxygen, which decreases the serum half-life of COHb. Hyperbaric oxygen (2 to 3 ATM) produces an even more rapid displacement and is most useful in cases of prolonged exposure, when it is more difficult to displace CO from the cytochrome system. The drawback of hyperbaric oxygen use is the inability to get to the burn patient during the crucial period of hemodynamic and pulmonary instability. The vast majority of cases can be managed simply by using 100% oxygen.

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