Early Surgical Management of Thermal Airway Injury: A Case Series

Localized delivery of therapeutics impact laryngeal mechanics, local inflammatory response, and respiratory microbiome following upper airway intubation injury in swine

BACKGROUND

Laryngeal injury associated with traumatic or prolonged intubation may lead to voice, swallow, and airway complications. The interplay between inflammation and microbial population shifts induced by intubation may relate to clinical outcomes. The objective of this study was to investigate laryngeal mechanics, tissue inflammatory response, and local microbiome changes with laryngotracheal injury and localized delivery of therapeutics via drug-eluting endotracheal tube.

METHODS

A simulated traumatic intubation injury was created in Yorkshire crossbreed swine under direct laryngoscopy. Endotracheal tubes electrospun with roxadustat or valacyclovir- loaded polycaprolactone (PCL) fibers were placed in the injured airway for 3, 7, or 14 days (n = 3 per group/time and ETT type). Vocal fold stiffness was then evaluated with normal indentation and laryngeal tissue sections were histologically examined. Immunohistochemistry and inflammatory marker profiling were conducted to evaluate the inflammatory response associated with injury and ETT placement. Additionally, ETT biofilm formation was visualized using scanning electron microscopy and micro-computed tomography, while changes in the airway microbiome were profiled through 16S rRNA sequencing.

RESULTS

Laryngeal tissue with roxadustat ETT placement had increasing localized stiffness outcomes over time and histological assessment indicated minimal epithelial ulceration and fibrosis, while inflammation remained severe across all timepoints. In contrast, vocal fold tissue with valacyclovir ETT placement showed no significant changes in stiffness over time; histological analysis presented a reduction in epithelial ulceration and inflammation scores along with increased fibrosis observed at 14 days. Immunohistochemistry revealed a decline in M1 and M2 macrophage markers over time for both ETT types. Among the cytokines, IL-8 levels differed significantly between the roxadustat and valacyclovir ETT groups, while no other cytokines showed statistically significant differences. Additionally, increased biofilm formation was observed in the coated ETTs with notable alterations in microbiota distinctive to each ETT type and across time.

CONCLUSION

The injured and intubated airway resulted in increased laryngeal stiffness. Local inflammation and the type of therapeutic administered impacted the bacterial composition within the upper respiratory microbiome, which in turn mediated local tissue healing and recovery.

Effect of continuous local dexamethasone on tissue biomechanics and histology after inhalational burn in a preclinical model

Objective

Inhalational burns frequently lead to dysphonia and airway stenosis. We hypothesize local dexamethasone delivery via a novel drug-eluting electrospun polymer-mesh endotracheal tube (ETT) reduces biomechanical and histologic changes in the vocal folds in inhalational burn.

Methods

Dexamethasone-loaded polymer mesh was electrospun onto ETTs trimmed to transglottic endolaryngeal segments and secured in nine Yorkshire Crossbreed swine with directed 150°C inhalation burns. Uncoated ETTs were implanted in nine additional swine with identical burns. ETT segments were maintained for 3 and 7 days. Vocal fold (VF) structural stiffness was measured using automated-indentation mapping and compared across groups and to four uninjured controls, and matched histologic assessment performed. Statistical analysis was conducted using two-way ANOVA with Tukey's post hoc test and Wilcoxon rank-sum test.

Results

VF stiffness after burn decreased with longer intubation, from 19.4 (7.6) mN/mm at 3 days to 11.3 (5.2) mN/mm at 7 days (p < .0001). Stiffness similarly decreased with local dexamethasone, from 25.9 (17.2) mN/mm at 3 days to 18.1 (13.0) mN/mm at 7 days (p < .0001). VF stiffness in the dexamethasone group was increased compared to tissues without local dexamethasone (p = .0002), and all groups with ETT placement had higher tissue stiffness at 3 days (p < .001). No significant change in histologic evidence of epithelial ulceration or fibrosis was noted, while an increased degree of inflammation was noted in the dexamethasone group (p = .04).

Conclusion

Local dexamethasone delivery increases VF stiffness and degree of inflammation compared to uncoated ETTs in an acute laryngeal burn model, reflected in early biomechanical and histologic changes in an inhalational burn model.

Laryngotracheal stenosis post mechanical ventilation in paediatric burns patients

INTRODUCTION

The duration of endotracheal intubation is thought to be the most important factor in the development of acquired laryngotracheal stenosis (LTS); however, there is a paucity of studies examining the incidence of LTS in the paediatric burn population. The aim of this study was to determine the incidence of LTS in paediatric burns patients requiring mechanical ventilation to develop guidelines for consideration of a tracheostomy.

METHODS

A retrospective review of all children treated at The Children's Hospital at Westmead (CHW) Burns Unit (BU) from December 2009 to December 2019 who required intubation for their burn injury.

RESULTS

During the 10-year study period 115 patients required endotracheal intubation after having sustained a burn injury. Of these 11 were excluded. The mean age was 6.2 years (0-16), with the majority of patients being male (65%). The average TBSA was 18.5% with a range of 0.1-70%. Flame was the most common mechanism of burn (n = 59). Burns to the head and/or neck were the most common indication for intubation with the mean duration of intubation 6.1 days (range 0-40). Tracheostomies were performed on two patients (1.9%). LTS was found in two patients (1.9%).

CONCLUSION

LTS in the paediatric burn population post mechanical ventilation appears to be a rare event. Endotracheal intubation can safely be used as the route of airway access in paediatric burns patients. Based on our experience, a definitive recommendation on the timing of tracheostomy in the paediatric burn patient cannot be made.

Laryngeal Thermal Injury Model

A lack of reliable laryngeal thermal injury models precludes laryngeal burn wound healing studies and investigation of novel therapeutics. We hypothesize that a swine laryngeal burn model can allow for laryngeal burn evaluation over time. Twelve Yorkshire crossbreed swine underwent tracheostomy and endoscopically directed laryngeal burns using heated air (150-160°C). Swine larynges were evaluated and sectioned/stained at 12 hours, 1, 3, 7, 14, and 21 days. A board-certified veterinary pathologist assessed anatomic regions (left and right: epiglottis, true/false vocal folds, and subglottis) using a nine criteria histological injury scoring scale. Six swine were euthanized at scheduled endpoints, three prematurely (airway concerns), and three succumbed to airway complications after 16 to 36 hours. Endoscopic and gross examination from scheduled endpoints revealed massive supraglottic edema and tissue damage, particularly around the arytenoids, extending transglottically. Swine from premature endpoints had comparatively increased edema throughout. Microscopic evaluation documented an inverse relationship between injury severity score and time from injury. Inflammation severity decreased over time, nearly resolving by 14 days. Neutrophils predominated early with histiocytes appearing at 3 days. Granulation tissue appeared at 3 days, and early epiglottic and/or subglottic fibrosis appeared by 7 days and matured by 14 days. Edema, abundant initially, decreased by day 3 and resolved by day 7. This approach is the first to provide longitudinal analysis of laryngeal thermal injuries, reflecting some of the first temporal wound healing characteristic data in laryngeal thermal injuries and providing a platform for future therapeutic studies.

Multidisciplinary Safety Recommendations After Tracheostomy During COVID-19 Pandemic: State of the Art Review

OBJECTIVE

In the chronic phase of the COVID-19 pandemic, questions have arisen regarding the care of patients with a tracheostomy and downstream management. This review addresses gaps in the literature regarding posttracheostomy care, emphasizing safety of multidisciplinary teams, coordinating complex care needs, and identifying and managing late complications of prolonged intubation and tracheostomy.

DATA SOURCES

PubMed, Cochrane Library, Scopus, Google Scholar, institutional guidance documents.

REVIEW METHODS

Literature through June 2020 on the care of patients with a tracheostomy was reviewed, including consensus statements, clinical practice guidelines, institutional guidance, and scientific literature on COVID-19 and SARS-CoV-2 virology and immunology. Where data were lacking, expert opinions were aggregated and adjudicated to arrive at consensus recommendations.

CONCLUSIONS

Best practices in caring for patients after a tracheostomy during the COVID-19 pandemic are multifaceted, encompassing precautions during aerosol-generating procedures; minimizing exposure risks to health care workers, caregivers, and patients; ensuring safe, timely tracheostomy care; and identifying and managing laryngotracheal injury, such as vocal fold injury, posterior glottic stenosis, and subglottic stenosis that may affect speech, swallowing, and airway protection. We present recommended approaches to tracheostomy care, outlining modifications to conventional algorithms, raising vigilance for heightened risks of bleeding or other complications, and offering recommendations for personal protective equipment, equipment, care protocols, and personnel.

IMPLICATIONS FOR PRACTICE

Treatment of patients with a tracheostomy in the COVID-19 pandemic requires foresight and may rival procedural considerations in tracheostomy in their complexity. By considering patient-specific factors, mitigating transmission risks, optimizing the clinical environment, and detecting late manifestations of severe COVID-19, clinicians can ensure due vigilance and quality care.

Laryngeal inhalational injuries: A systematic review

Laryngeal inhalation injury carries a significant increase in mortality rate and often indicates immediate airway evaluation. This may be difficult in the setting of clinical deterioration necessitating immediate intubation, which itself can synergistically cause mucosal damage. Prior studies do not encompass predictive factors or long-term outcomes for the laryngotracheal complex. This systemic review of PubMed, Embase, and Cochrane identified studies investigating inhalational injuries of the upper airway. Demographic data as well as presentation, physical findings, and delayed sequelae were documented. Laryngotracheal burn patients were divided into two cohorts based on timing of laryngeal injury diagnosis (before- versus after-airway intervention). 1051 papers met initial search criteria and 43 studies were ultimately included. Airway stenosis was more common in patients that were intubated immediately (50.0%, n = 18 versus 5.2%, n = 13; p = 0.57). Posterior glottic involvement was only identified in patients intubated prior to airway evaluation (71.4%, n = 15). All studies reported a closed space setting for those patients in whom airway intervention preceded laryngeal evaluation. Laryngeal inhalational injuries are a distinct subset that can have a variety of minor to severe laryngotracheal delayed sequelae, particularly for thermal injuries occurring within enclosed spaces. Given these findings, early otolaryngology referral may mitigate or treat these effects.

Incidence of Laryngotracheal Stenosis after Thermal Inhalation Airway Injury

Inhalation injury is independently associated with burn mortality, yet little information is available on the incidence, risk factors, or functional outcomes of thermal injury to the airway. In patients with thermal inhalation injury, we sought to define the incidence of laryngotracheal stenosis (LTS), delineate risk factors associated with LTS development, and assess long-term tracheostomy dependence as a proxy for laryngeal function. Retrospective cohort study of adult patients treated for thermal inhalation injury at a single institution burn critical care unit from 2012 to 2017. Eligible patients' records were assessed for LTS (laryngeal, subglottic, or tracheal stenosis). Patient characteristics, burn injury characteristics, and treatment-specific covariates were assessed. Descriptive statistics, Mann-Whitney U-tests, odds ratio, and chi-square tests compared LTS versus non-LTS groups. Of 129 patients with thermal inhalation injury during the study period, 8 (6.2%) developed LTS. When compared with the non-LTS group, patients with LTS had greater mean TBSA (mean 30.3, Interquartile Range 7-57.5 vs 10.5, Interquartile Range 0-15.12, P = .01), higher grade of inhalation injury (mean 2.63 vs 1.80, P = .05), longer duration of intubation (12.63 vs 5.44; P < .001), and greater inflammatory response (mean white blood cell count on presentation 25.8 vs 14.9, P = .02, mean hyperglycemia on presentation 176.4 vs 136.9, P = .01). LTS patients had a significantly higher rate of tracheostomy dependence at last follow-up (50 vs 1.7%, P < .001). Six percent of patients with thermal inhalation injury develop LTS. LTS was associated with more severe thermal airway injury, longer duration of intubation, and more severe initial host inflammation. Patients with inhalation injury and LTS are at high risk for tracheostomy dependence. In burn patients with thermal inhalation injury, laryngeal evaluation and directed therapy should be incorporated early into multispecialty pathways of care.

Challenges in anaesthesia and pain management for burn injuries

Burn-injured patients provide unique challenges to those providing anaesthesia and pain management. This review aims to update both the regular burn anaesthetist and the anaesthetist only occasionally involved with burn patients in emergency settings. It addresses some aspects of care that are perhaps contentious in terms of airway management, fluid resuscitation, transfusion practices and pharmacology. Recognition of pain management failures and the lack of mechanism-specific analgesics are discussed along with the opioid crisis as it relates to burns and nonpharmacological methods in the management of distressed patients.

Laryngotracheal Reconstruction in the Pediatric Burn Patient: Surgical Techniques and Decision Making

The management of laryngotracheal stenosis (LTS) in the pediatric burn patient is complex and requires a multidisciplinary approach. The mainstay of treatment for LTS is laryngotracheal reconstruction (LTR), however, limited reports of burn-specific LTR techniques exist. Here, we provide insight into the initial airway evaluation, surgical decision making, anesthetic challenges, and incision modifications based on our experience in treating patients with this pathology. The initial airway evaluation can be complicated by microstomia, trismus, and neck contractures-the authors recommend treatment of these complications prior to initial airway evaluation to optimize safety. The surgical decision making regarding pursuing single-stage LTR, double-stage LTR, and 1.5-stage LTR can be challenging-the authors recommend 1.5-stage LTR when possible due to the extra safety of rescue tracheostomy and the decreased risk of granuloma, which is especially important in pro-inflammatory burn physiology. Anesthetic challenges include obtaining intravenous access, securing the airway, and intravenous induction-the authors recommend peripherally inserted central catheter when appropriate, utilizing information from the initial airway evaluation to secure the airway, and avoidance of succinylcholine upon induction. Neck and chest incisions are often within the TBSA covered by the burn injury-the authors recommend modifying typical incisions to cover unaffected skin whenever possible in order to limit infection and prevent wound healing complications. Pediatric LTR in the burn patient is challenging, but can be safe when the surgeon is thoughtful in their decision making.