Outcomes of Tracheostomy on Burn Inhalation Injury

Inhalation injury has been described as an independent factor for increasing morbidity and mortality in burn patients. Even in isolation, it has been associated with longstanding pulmonary dysfunction. In a study of 1018 patients, Thompson et al determined that the presence of inhalation injury increases mortality in every age and burn size category.¹ Masaru et al found in their study of 5560 patients admitted to 13 burn facilities of the Tokyo Burn Unit Association that inhalation injury was an independent predictor of outcomes and the most important predictor of overall mortality among burn patients.²

Inhalation injury causes a direct thermal injury, chemical irrigation of the respiratory tract, and systemic toxicity due to carbon monoxide. This can trigger an inflammatory response that can lead to pneumonia, acute respiratory distress syndrome (ARDS), and even death. The diagnosis is made with visual inspection of the airway with bronchoscopy. Visual findings, such as mucosal erythema or charring, blistering, edema, ulceration, or fibrin casts, are all diagnostic for inhalation injury.³ 

The treatment goal of inhalation injury is to prevent further pulmonary complications by minimizing bronchospasm, managing secretions, and clearing fibrin casts and necrotic material from the airway.⁴ Tracheostomy has been proposed for patients with expected prolonged intubation, and it has been shown to be beneficial for trauma patients with severe brain injury; however, the benefit of performing tracheostomy in patients with burn inhalation injuries remains a controversial topic with no clear consensus.^3,5-9 

A retrospective review of our institutional burn registry was performed from 2011 to 2019. We compared the outcomes of all burn patients who met our inclusion criteria, which included adequate data recording of inhalation injury within the registry, ventilator support for at least 24 hours, and a burn injury involving <15% total body surface area. 

We stratified the patients into 2 groups: patients who underwent tracheostomy within 2 weeks of injury (group 1) versus patients who did not undergo tracheostomy (group 2). Demographic characteristics and outcome variables were collected and compared between each group. 

The diagnosis of inhalation injury was based on the findings reported on bronchoscopy. Noninvasive ventilation with continuous positive airway pressure was not used in any of our patients. Tracheostomy was performed within 2 weeks of injury with a median of 7.5 days. The mechanism of injury, inhalation patterns, and degree of injury were not included in our review given the inconsistencies and lack of details on the reports. 

Outcome measures included in-hospital mortality rate, hospital length of stay, intensive care unit (ICU) length of stay, ventilator days, and ventilator-associated pneumonia (VAP). Chi-square and t test analyses were used with significance defined as P < .05. 

A total of 33 burn patients met our inclusion criteria. There were 10 patients who underwent tracheostomy within 2 weeks of injury (group 1) and 23 patients who did not undergo tracheostomy (group 2). The median time for performance of tracheotomy was 7.5 days. 

Group 1 had an average age of 68.9 years while the average age in group 2 was 53.3 years (Table). There was no statistically significant difference between the 2 groups in terms of total body surface area burned (P = .24 [t test]). The ICU length of stay was 23.8 days in group 1, significantly longer than the mean ICU stay of 3.16 days (P = .0001 [chi-square]) in group 2. The length of stay in the hospital was significantly longer for patients in group 1 than for those in group 2 (mean, 28.4 days vs 5.26 days, respectively; P = .0001 [chi-square]). Ventilator days was also significantly higher in group 1 with 20.8 days compared with 2.5 days in group 2. 

There was no statistically significant difference between the 2 groups in terms of mortality; however, the incidence of VAP was significantly higher in group 1 than in group 2, with 6 cases compared with 0 cases, respectively (P = .0001 [chi-square]).

Inhalation injury refers to the direct thermal and chemical damage caused to the airways and lung parenchyma by heat, irritants, and smoke from pyrolysis.¹⁰ Many of the consequences of smoke inhalation result from an inflammatory response involving mediators following the interaction of irritant substances with lung parenchyma. This inflammatory response leads to pulmonary edema, cast formation, airway obstruction, loss of hypoxic pulmonary vasoconstriction, and ventilation/perfusion mismatch.¹¹

The degree of the inhalation injury can be graded by bronchoscopy with the Abbreviated Injury Score, which ranges from 0 (no injury) to 4 (massive injury).^3,12,13 The higher the score, the greater the need for supportive treatment with bronchodilators, airway clearance measures, and mechanical ventilation. One notable limitation of our study is that the diagnosis of inhalation injury was based only on direct visualization of the airway mucosa during bronchoscopy with poor characterization of the severity.

Tracheostomy has been shown to facilitate ventilator weaning by reducing dead space, airway resistance, work of breathing, and the need for sedation.¹⁴ The most common indication for tracheostomy is the anticipated need for prolonged mechanical ventilation in the context of respiratory failure.¹⁵ 

Although tracheostomy offers some advantages in terms of patient comfort and security, a review by Saffle et al demonstrated that routine performance of early tracheostomy in burn patients does not improve outcomes nor does it result in earlier extubation.¹⁶ A systematic review and meta-analysis performed by Griffiths et al concluded that early tracheostomy did not significantly alter mortality but reduced the duration of mechanical ventilation and length of stay in intensive care.¹⁷ In our study, the patients who underwent tracheostomy had a statistically significant higher hospital length of stay and ICU length of stay but no significant difference in mortality risk. 

VAP is an infection that affects the lower respiratory tract after more than 48 hours of mechanical ventilation. It accounts for more than 50% of infections in the ICU and affects approximately 8% to 28% of patients on mechanical ventilation.^18,19 

Compared with an endotracheal tube, tracheostomy improves patient comfort, oral hygiene, and airway management.²⁰ It has been theorized that bypassing the mouth with a tracheostomy, plus the added benefit of easy exchange of cannulas, prevents the growth of biofilm on its surface and could be considered a protective factor for the evolution of VAP.²¹ However, large trials and meta-analyses have not found any advantage of earlier timing of tracheostomy with regard to the incidence of VAP.^22-25 In our study, the group with tracheostomy had an increased incidence of VAP compared with the group that did not undergo tracheostomy, which is expected as the risk of VAP is directly proportional to the number of ventilator days. 

In summary, the ideal timing and implementation of tracheostomy with inhalation injury has yet to be determined. In our study, tracheostomy was associated with much longer lengths of ICU and hospital stays and higher incidence of pneumonia. The impact of the underlying lung injury versus the tracheostomy itself on these observations is unclear. The challenge of characterizing the severity of an inhalation injury based on early visual inspection remains. Further research is needed to determine more  and better ways to recognize and predict the severity of lung injury in patients with inhalation injury and to provide a more tailored intervention.

Affiliations: ¹Department of Surgery, HCA Florida – Kendall Hospital, Miami, Florida;²HCA Miami Burn Center, Miami, Florida; ³Department of Surgery, University of South Florida, Tampa, Florida; ⁴Department of Plastic Surgery, Tulane University, New Orleans, Louisiana

Correspondence: Samuel Ruiz, MD; samuelgruiz@gmail.com

The abstract leading to this manuscript was presented at the American Burn Association Annual Meeting in Las Vegas, Nevada in April 2022. 

Disclosures: The authors disclose no relevant conflicts of interest or financial disclosures for this manuscript.