If you don't remember your password, you can reset it by entering your email address and clicking the Reset Password button. You will then receive an email that contains a secure link for resetting your password
If the address matches a valid account an email will be sent to __email__ with instructions for resetting your password
Airway burn injury continues to be a significant cause of morbidity and mortality in the burn patient population. It is essential to identify patients with potential airway obstruction and also to avoid potential complications of airway manipulation in those with less severe injury. In this review, the initial evaluation and management of airway burn injuries will be discussed, including indications for observation versus intubation versus tracheotomy. Additionally, the long term sequelae of upper airway burn injury and management of these consequences will be reviewed.
Despite improved treatment modalities and an overall decrease in burn severity over the past few decades, airway burn injury continues to contribute to high morbidity and mortality.
A study of 1,447 consecutive burn patients identified a 30% mortality for concomitant inhalation injury in comparison to 2% mortality rate for those without inhalation injury.
Patients with inhalation injury have a reported 20%-30% risk of developing upper airway obstruction, and early identification and treatment in this cohort is essential.
Initial airway management may include conservative monitoring, endotracheal intubation, or tracheotomy. After patients have recovered from acute injury, the sequelae from airway burns can have substantial impact on aerodigestive functions. The following review discusses the pathophysiology, evaluation, and management of upper airway burn injury.
Pathophysiology
Upper airway burn injuries are primarily due to 3 etiologies: smoke inhalation, thermal injury, and chemical exposure. Smoke inhalation is the most common etiology for laryngeal burns. Thermal injury most commonly results from steam inhalation though hot liquids, foods, and other substances such as crack cocaine can cause similar severe injury.
Thermal injury is typically limited to the supraglottis due to reflexive supraglottic and glottic closure. Chemical exposures more often affect the lower airway and cause inflammatory response, respiratory mucosal decay, and eventual sloughing of mucosa.
Latrogenic airway fire is a rare but potentially devasting cause of burn injury. This most commonly occurs during endoscopic laser airway surgery, but can also occur during tracheotomy or other pharyngeal surgeries.
For all types of burns, the severity of injury depends on a number of factors including the magnitude of exposure, composition of inhalant, presence of particles, and exposure duration.
A patient's respiratory status acts as a critical decision point in management; patients with respiratory distress should be considered for immediate nasotracheal or orotracheal intubation whereas patients with less severe respiratory symptoms may undergo a more thorough evaluation.
Certain exam findings and symptoms may indicate potential airway compromise. Airway injury should be anticipated in patients with dysphonia, shortness of breath, or odynophagia. In 1 study, symptoms of stridor, drooling and dysphagia were not associated with need for intubation.
Clinical findings such as oral commissure edema, ulceration of oral mucosa, nasal aperture sediment, and burnt hair are all signs which signal the need for airway evaluation.
reported that 2/3 of patients with inhalation injuries have facial burns, however another series of 81 patients with upper airway burns found that 85% did not have signs of facial burn. Given this variability, and risk associated with missed airway injury, airway evaluation should be considered in all burn patients. In addition to routine head and neck evaluation, fiberoptic laryngoscopy is a sensitive method for evaluating all upper airway subsites and can be completed at the time of primary survey in patients who are not in severe respiratory distress.
Bronchoscopy should be considered in symptomatic patients, those with edema or mucosal injury seen on flexible laryngoscopy, or with concerning chest x-ray (CXR) findings.
Signs of inhalation burn injury during bronchoscopy include absence of cough reflex, carbonaceous debris, mucosal erythema, ulceration, and hemorrhagic secretions (Figure 1).
Bronchoscopy has a reported 86% accuracy rate for diagnosis of inhalation injury with a risk for false negatives particularly when performed too early after an inhalation incident.
The Abbreviated Injury Score was developed by the American Burn Association as a grading system with flexible bronchoscopy for evaluating inhalation injuries (Table 1).
This score correlates with the development of acute respiratory distress syndrome as well as the need for ventilator dependence, however it requires serial bronchoscopy for complete usefulness.
In patients without general anesthesia, bronchoscopy may cause laryngospasm in the acutely inflamed airway, therefore bronchoscopy is typically performed after intubation by pulmonary or burn physician colleagues.
Figure 1Flexible bronchoscopy after inhalantion injury demonstrating (A) sloughing of mucosa and carbonaceous debris at the carina and (B) edema, erythema, and carbonaceous material in bronchioles. Photo credit: Dr. Bruce Greenstein.
Imaging modalities are useful for evaluating lower airway injury, however utility is limited for upper airway burns. The timing of the initial CXR is controversial with some studies reporting that initial CXR findings are negative for injury in 92% of cases with known smoke inhalation (Figure 2).
In contrast, Lee and O'Connell reported a 73% rate of abnormal CXR findings in 45 patients who had radiographs obtained within 1 hour of admission. The most common CXR abnormality was bronchial wall thickening, and 13/45 patients had radiographic evidence of subglottic edema.
Rates of abnormal CXR findings may increase with time from injury, as another study reported 84% of patients with CXR abnormalities at 48 hours after smoke inhalation.
Computerized tomography is not recommended for initial upper airway evaluation unless other aerodigestive sequelae are noted such as dysphagia and dysphonia.
Patients with airway burn injuries may develop digestive tract complications given the proximity of the respiratory tract to the esophagus. Tracheal necrosis may develop from high temperatures of inhaled gas and may lead to tracheoesophageal fistula formation.
In the intubated patient, increased secretions, pneumonia, and aspiration of gastric contents may indicate tracheoesophageal fistula. Patients who are not intubated may report cough with swallowing. A contrasted swallow study with water-insoluble contrast is diagnostic and a swallow evaluation should be performed in all burn patients with dysphagia complaints.
Special consideration is necessary in the pediatric population as children often have more subtle signs of airway obstruction and high level of suspicion is required. Airway obstruction may be more common in children due to their smaller trachea and relatively higher and larger epiglottis. A low threshold for intubation should be maintained, as evolving airway edema makes intubation increasingly more difficult.
In the setting of iatrogenic airway fire, the ventilation circuit should be immediately disconnected and surgeon should simultaneously remove the endotracheal tube (ETT). Any flammable material should be removed from airway and water should be used to douse fire if needed. The surgeon should re-establish ventilation with bag-masking using only air if possible to minimize concentration of oxygen delivery. Prior to re-intubation, the airway should be thoroughly examined with direct laryngoscopy and bronchoscopy and the ETT should also be evaluated for any potential residual fragments within the airway.
Practice advisory for the prevention and management of operating room fires: An updated report by the American Society of Anesthesiologists Task Force on Operating Room Fires.
Practice advisory for the prevention and management of operating room fires. American Society of Anesthesiologists Task Force on Operating Room Fires..
A critical decision in the acute management of airway burn injury patients is determining who will require intubation. Intubation risks laryngeal and subglottic injury from direct trauma, mucosal sloughing, granuloma formation, and vocal fold paralysis and should be avoided when possible. Romanski et al
suggest avoiding intubation in individuals with burns less than 20% total body surface area, no third degree facial burns, burns from causes other than flame injury, and burns that did not occur in enclosed spaces. Conservative observation should consist of head of bed elevation and frequent re-evaluation due to potential for progression of edema that may occur within hours of injury. Laryngotracheal edema can develop within 30 minutes after injury, peak between 24-48 hours, and generally resolves in 3-6 days.
Empiric treatment with antibiotics and corticosteroids is not recommended, however surveillance cultures via bronchoscopy should be obtained for targeted antimicrobial therapy given the increased risk of pneumonia in this population.
Intubation of a patient with airway burn injury requires close communication with the anesthesia team and should be performed by an experienced provider. In a nonemergent setting, transnasal intubation with a nasotracheal tube over a fiberoptic bronchoscope is preferred. The nasal cavity should be decongested with topical 0.25% phenylephrine and anesthetized with 1% lidocaine. If time allows, nasal trumpets coated with 2% viscous lidocaine can also be carefully placed in the nasal cavity to further anesthetize and dilate. A large (size 7-0) soft-cuff polyvinyl nasotracheal tube should be placed in order to facilitate bronchoscopy during the intubated period.
If the airway cannot be readily identified due to supraglottic edema, direct laryngoscopy with a rigid blade should be performed to physically displace edematous tissues and optimally visualize the airway. Direct laryngoscopy can be used to facilitate both transnasal and transoral intubation. Sedative medications such as ketamine or opioid narcotics are given in order to optimize patient comfort while maintaining spontaneous ventilation. Paralytic agents (eg, succinylcholine, rocuronium) should be avoided because paralytics stop spontaneous respirations, which may result in inability to ventilate if the airway cannot be secured by intubation. Furthermore, succinylcholine administration beyond 72 hours after burn injury can result in a hyperkalemic response.
Nasotracheal intubation is preferred to oral intubation in order to improve nursing delivery of oral care, improved patient comfort, and allow for potential patient communication through lip movement. However, transoral intubation should be readily performed in an acute airway emergency or if resistance or bleeding are encountered during attempted transnasal intubation.
After the airway is secured, the ETT should be circumferentially secured around the head and neck with umbilical ties as burnt skin cannot tolerate adhesive tape. The cuff of the ETT should contain the minimal possible amount of air to reduce mucosal ischemia.
Airway burn injury is associated with mucosal sloughing therefore frequent suction and therapeutic bronchoscopy are often required. Furthermore, during the course of intubation, attention should be given to oral cavity or nasal cavity pressure injury. Limiting tube motion with appropriate patient manipulation and sedation may limit additional airway damage related to ETT pressure. Gastroesophageal reflux contributes to development of posterior glottic stenosis after prolonged endotracheal intubation and should be aggressively managed in airway burn patients. Patients may require placement of nasogastric tube for enteral nutrition, but intervention has not been shown to decrease incidence of reflux in intubated patients.
Extubation can be considered after resolution of laryngeal edema based on laryngoscopy and when consistent with intensive care unit criteria for extubation. Importantly, a majority of airway burn victims are intubated by emergency personnel prior to hospital arrival, and these patients should undergo a complete upper airway evaluation with laryngoscopy and bronchoscopy prior to extubation at the bedside or in the operating room.
Tracheotomy
Tracheotomy is generally recommended after 10-14 days of intubation in adult patients given increased risk of laryngotracheal stenosis (LTS) with prolonged intubation.
However, in the airway burn population there remains controversy about the optimal timing of tracheotomy. After intubation, tracheal damage occurs more rapidly in patients with burn injury, 6-10 days in comparison to 3 weeks.
Tracheotomy may therefore be considered in patients who are intubated for >48 hours to avoid further laryngeal injury and in those patients with identified vocal fold damage to limit additional vocal fold injury. However, other studies report more severe and frequent airway complications after tracheostomy in comparison to translaryngeal intubation.
reported similar incidence of airway complications among patients with tracheostomy and endotracheal intubation. In another study of 99 patients with inhalation injury and tracheostomy, major airway complications occurred in 28 patients and 6 of 25 survivors developed tracheal stenosis.
Acute complications of tracheostomy are similar to those for intubation including tube malposition, tracheal ulcerations, and tracheitis.
Long-term management
After survival from initial burn injury, the treatment goal for patients with upper airway burns is to rehabilitate laryngeal function. Injuries resulting from airway burns vary widely from no sequelae, mild vocal fold scarring, to severe LTS. All patients with a history of airway burns who develop aerodigestive symptoms should undergo direct laryngoscopy and bronchoscopy, with possible esophagoscopy to assess anatomic damage.
Figure 3 demonstrates acute changes in the glottis after extubation for an inhalation injury that required intubation.
Figure 3Flexible laryngoscopy one week after intubation for inhalation injury. There is significant erythema, ulceration, and granulation at the interarytenoid region with edema and erythema of bilateral vocal cords.
Dysphonia is commonplace after inhalation injury. A study of 10 patients evaluated 16-25 years after injury revealed abnormal laryngoscopy in all patients with commonly identified pachydermia and vocal fold scar.
Patients are at increased risk for LTS with more severe thermal airway injury, longer intubation duration, and more severe initial host inflammation as measured by white cell blood count.
The position of the ETT at the posterior glottis renders this area susceptible to pressure necrosis and development of granulation. During healing, this can result in scarring and variable degrees of posterior glottic stenosis. Patients with inflammatory laryngeal and tracheal injuries may benefit from earlier endoscopic surgery to limit mature scar formation.
Once posterior glottic stenosis has developed, there are a range of potential surgical interventions including scar lysis, cordotomy, arytenoidectomy, and arytenoid lateralization.
Pressure from the ETT cuff can cause scarring and stenosis in subglottic region. For more limited subglottic stenosis, less than 2 cm in length, a range of treatments include carbon dioxide laser division of scar, balloon or bronchoscopic dilation, and intralesional steroid injection. Endoscopic procedures and dilations may require multiple procedures to accomplish symptomatic relief.
For more extensive laryngotracheal scarring, open transcervical procedures may be considered. Prior to any open laryngeal surgery, endoscopy should be performed to characterize and to evaluate the severity of stenosis.
noted that 18 patients with LTS after inhalation burn injury had more extensive stenosis in comparison to tracheal stenosis resulting from other etiologies. Stenosis related to inhalational injuries was more commonly multi-level, higher (just below vocal cords), and longer (with 12/18 stenoses measuring greater than 3 cm in length). For these patients with complex LTS, laryngotracheal reconstruction can be performed and individualized to the area of stenosis. In Grillo's series, 6-18 patients underwent either laryngofissure or laryngocricotracheal fissure. 15 patients had placement of tracheal T-tube for a mean 28 months for combined subglottic/tracheal stenosis or distal tracheal stenosis. The optimal timing for these procedures is unclear, though evidence suggests that delaying open repair until after resolution of inflammation, may decrease recurrence.
Gaissert et al report this result in a high likelihood of the recovery of a functional airway and voice.
Tracheal injury
Tracheoesophageal fistula can occur after combined esophageal and tracheal necrosis and often requires surgical closure. There are a number of repair techniques including use of pedicle muscle flaps, free tissue transfer, and primary closure. Fistula closure with an end-to-end tracheal anastomosis has good outcomes and a low recurrence rate.
Tracheal rupture is a rare but life-threatening complication after inhalation injury. Early symptoms of tracheal rupture include subcutaneous emphysema of the neck and chest, pneumomediastinum, tension pneumothorax, tracheal bleeding, or a sudden increase in ventilation pressures. Tracheal injuries smaller than 4 cm should be managed with antibiotics and adjusting ETT position distal to the site of injury. Persistent positive pressure ventilation above the injury can cause expansion of the rupture. Larger injuries and those that do not respond to conservative management will require surgical intervention.
Airway burn injury remains a substantial cause of morbidity and mortality. A high level of suspicion, rapid diagnosis, and treatment of inhalation injury are critical to improve survival. Paralysis should be avoided during intubation to maintain spontaneous ventilation and nasotracheal intubation is preferred to transoral intubation. Longterm laryngotracheal sequelae may be limited by carefully selecting those patients needing intubation and using small endotracheal tubes with lower cuff pressures.
Disclosure
The authors have nothing to disclose.
References
Colohan SM.
Predicting prognosis in thermal burns with associated inhalational injury: a systematic review of prognostic factors in adult burn victims.
Practice advisory for the prevention and management of operating room fires: An updated report by the American Society of Anesthesiologists Task Force on Operating Room Fires.
Practice advisory for the prevention and management of operating room fires. American Society of Anesthesiologists Task Force on Operating Room Fires..
30065-8&id=gr1.jpg){kind=link}
30065-8&id=gr2.jpg){kind=link}
30065-8&id=gr3.jpg){kind=link}