Airway Management in Burn Patients

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Chapter 44 Airway Management in Burn Patients

I Introduction

The airway of the burn patient presents ongoing challenges and special considerations during the period of initial burn injury and throughout the patient’s hospital course. As a consequence of their injuries, some burn patients have airway difficulties throughout the remainder of their lives.

The National Burn Repository reports 181,000 hospital admissions for burn injury for 1998 through 2007 in 73 U.S. burn centers. The overall mortality rate during this period was 4.9%.1 A 2006 report of the National Burn Repository indicated an incidence of inhalational trauma of 5.7% during the previous 10 years.2 Inhalational burn trauma was associated with a 27.3% mortality rate, compared with a rate of 4.5% for burned patients without inhalational injury.2 A review of 850 children admitted with inhalational injury during a 10-year period at the four Shriner’s Pediatric Burn Centers in the United States found a mortality rate of 16.4%.3 Consequently, inhalational burns contribute significantly to mortality among the burn population. Although the outcomes for survival after burns and the quality of life of burn victims have improved, respiratory complications are an ongoing source of burn morbidity and mortality.

II Airway Management in the Acutely Burned Patient

A Evaluation of the Patient after Acute Burn Injury and Indication for Airway Management

1 Assessment at the Scene

First responders have a crucial role in the early management of burn patients. In addition to the usual trauma assessments, emergency medical service (EMS) staff must determine whether the patient’s condition warrants immediate intubation in the field or the patient can be observed. Indications for intubation at the trauma scene include the following4,5:

Patients with a flame injury from a barbecue or fire in an open space may have burns to the neck and face but no airway involvement and therefore do not require early intubation.

In addition to initial medical management of the patient, EMS staff gathers information about the type of injury and the patient’s medical history. The information should be recorded for transport with the patient to a specialized burn center.

The practice of prehospital intubation of the burned patient has been questioned. Eastman and colleagues6 reviewed the charts of 1272 patients admitted after field intubation over a period of 23 years and found that 69% of them survived. However, 30% of the survivors were extubated on admission or on the second day after the burn. None required reintubation. Klein and associates7 reviewed the charts of patients admitted to the Washington Burn Center after a transport of more than 90 miles for the period of 2000 through 2003. They examined parameters such as duration of transport, error in burn severity estimation, fluid management, appropriateness of intubation, and transport complications. Of 1877 patients, 424 were transported more than 90 miles to the burn center. No patient died during transport, and 111 patients arrived intubated, with only 61% having inhalational burns. More than 50% of patients were extubated within the first 24 hours after admission.

Failure to secure an airway was one of the most common complications occurring during patient transport. The fact that airway obstruction can develop very quickly in burn patients and that the experience and equipment of EMS are often limited supports intubation in the field before transport in the patient with a potential for respiratory compromise.

2 Assessment in the Hospital

Roughly 10% of burn patients also present with other traumatic injuries. All burn patients are considered trauma patients and consequently undergo a primary trauma survey (i.e., the ABCDE algorithm: airway, breathing, circulation, disability, and exposure).8 The extent and surface area of the burn are noted, other traumatic injuries identified and treated, and the airway secured if indicated. The incidence of inhalational trauma, length of hospital stay, and mortality rate are increased for patients presenting with burns and other traumatic nonburn injuries.9

On arrival of the patient at the burn center, the tube position is confirmed with carbon dioxide (CO2) monitoring and auscultation of the lung fields. Uncertainty about endotracheal tube (ETT) placement should be remedied by direct laryngoscopy or fiberoptic bronchoscopy. The mouth, pharynx, and larynx are examined by laryngoscopy to assess edema and identify any burned mucosa and the presence of soot (Fig. 44-1). A radiograph is obtained to verify the ETT position and identify other potential injuries, such as a pneumothorax. Lung parenchymal injuries usually are not immediately detectable by radiography immediately after injury. Patients presenting with a supralaryngeal airway (SLA) on arrival at the hospital require endotracheal intubation or a surgical airway.

In the unintubated patient, the presence of soot in the sputum, dyspnea, tachypnea, hoarseness, and stridor are signs of impending airway obstruction. Fiberoptic endoscopy is the gold standard for the diagnosis of inhalational trauma.1017 In the awake patient, a nasal fiberoptic examination under local anesthesia can be performed to evaluate the larynx and confirm the presence or absence of edema and soot. Patients with altered mental status, dyspnea, hoarseness, or stridor require immediate intubation.

A relevant history for airway management after burn injury includes the following information:

Rarely, inhalation of hot steam and hot fluids can lead to a rapidly progressive upper airway edema. Chemical fires can have more complex sequelae because the chemicals themselves can injure tissues after extinction of the fire. The circumstances of the burn injury and its duration can help to discern the likelihood of carbon monoxide (CO), cyanide (CN), and other toxicities.

6 Extensive Burns

Patients with large body surface area burns frequently have airway burns as well (Fig. 44-3). Edema after resuscitative efforts can make intubation impossible. After massive burns, patients develop a hypermetabolic state leading to increased CO2 production requiring ventilator support. Some physicians suggest prophylactic intubation for total body surface area burns greater than 30%.10,12,17,22

B Inhalational Injury

Approximately 20% to 30% of patients admitted to regional burn centers have some degree of inhalational injury and are at risk from toxic gases.19,24 Edelman and colleagues25 reviewed 829 patients admitted to a burn center between 2000 and 2004 and found that 28% had an inhalational injury. Although the mortality rate for patients with solely a thermal injury was 3% and was 12% for those with an isolated inhalational injury, patients with combined thermal and inhalational injuries had a mortality rate of 14.6%.25 Box 44-1 summarizes smoke inhalational injuries.

1 Injury to the Respiratory Tract

a Upper and Lower Airway Inhalation Smoke Injury

Inhalational injury of the airway can be caused by steam, carbenoids, chemicals, and the toxic products of combustion. In most patients, the entire airway is involved, and several toxic agents are inhaled. Inhalational injury results from thermal injury (heat) to the upper airway, toxic chemicals in the respiratory tract, and CO and CN toxicities.

Thermal injury and inhaled chemical toxins cause burn injuries by different mechanisms. In an enclosed environment, temperatures can exceed 800° C, with an O2 concentration of just 10% and CO concentrations greater than 0.5%.26,27 Injuries are often described by the area of the tracheobronchial tree affected. The upper airway lies above the vocal cords, whereas the lower airway consists of the tracheobronchial tree, including the terminal bronchi and alveoli.

The upper airway consists of the nasal and oral cavities, the pharynx, and laryngeal structures such as the epiglottis, false vocal cords, and true vocal cords. Direct injury of the upper airway with steam, superheated air, or hot liquid is rare. The heat-conducting capacity of air is low, reducing the potential for injury. Reflex closure of the glottis usually protects the structures below the vocal cords from steam injury. Signs of upper airway injury by heated air and steam include erythema, edema, ischemia, and pharyngeal ulcerations. Although the initial presentation of injury may be unimpressive, these lesions can quickly lead to airway edema and obstruction.

The lower airway includes the tracheobronchial system and the lung parenchyma. Most injuries of the upper and lower airway result from the chemical toxins produced by combustion. Burned rubber and plastics release ammonia, chloride, sulfur, and nitrogen dioxides. Cotton and wool fires produce toxic aldehydes, including formaldehyde. Laminated structures produce cyanide.16,21,22,2830