Predictive Value of Bronchoscopy in Assessing the Severity of Inhalation Injury:

Severity of Inhalation Injury and Risk of Nosocomial Pneumonia: A Retrospective Cohort Study

BACKGROUND

The impact of inhalation injury on risk of nosocomial pneumonia (NP), an important complication in patients with burns, is not well established.

RESEARCH QUESTION

Is more severe inhalation injury associated with increased risk of NP?

STUDY DESIGN AND METHODS

We performed a retrospective cohort study of patients with suspected inhalation injury admitted to a regional burn center from 2011 to 2022 who underwent diagnostic bronchoscopy within 48 h of admission. We estimated the association of high-grade inhalation injury (Abbreviated Injury Scale grade 3 and 4) vs low-grade inhalation injury (Abbreviated Injury Scale grade 1 and 2) with NP adjusted for age, burn size, and comorbid obstructive lung disease. Death and hospital discharge were considered competing risks.

RESULTS

Of the 245 patients analyzed, 51 (21%) had high-grade injury, 180 (73%) had low-grade injury, and 14 (6%) had no inhalation injury. Among the 236 patients hospitalized for ≥ 48 h, NP occurred in 24 of 50 patients (48%) in the high-grade group, 54 of 172 patients (31%) in the low-grade group, and two of 14 patients (14%) in the no inhalation injury group. High-grade (vs low-grade) inhalation injury was associated with higher hazard of NP in both the proportional cause-specific hazard model (cause-specific hazard ratio, 2.04; 95% CI, 1.26-3.30; P = .004) and Fine-Gray subdistribution hazard model (subdistribution hazard ratio for NP, 2.24; 95% CI, 1.38-3.64; P = .001).

INTERPRETATION

In this study, among patients with inhalation injury, more severe injury was associated with higher hazard of NP in competing risk analysis. Additional research is needed to investigate mechanisms that may explain the relationship between inhalation injury and NP and to identify more effective risk reduction strategies.

An atypical airway cast

A 60-year-old man intubated for airway protection after smoke inhalation was found to have decompensated hypercapnic respiratory failure. Fiberoptic bronchoscopy revealed obstructive airway slough and pseudomembrane, a manifestation of severe inhalation injury. Veno-venous extracorporeal membrane oxygenation was established for stabilization. The airway casts were removed successfully with periprocedural veno-venous extracorporeal membrane oxygenation support.

Inhalation Injury Severity Score on Admission Predicts Overall Survival in Burn Patients

Inhalation injury is diagnosed in up to one-third of burn patients and is associated with increased morbidity and mortality. There are multiple scoring systems to grade inhalation injury, but no study has evaluated the ability of these scoring systems to predict outcomes of interest such as overall survival. We conducted a prospective, observational study of 99 intubated burn patients who underwent fiberoptic bronchoscopy within 24 hr of admission and graded inhalation injury using three scoring systems: abbreviated injury score (AIS), inhalation injury severity score (I-ISS), and mucosal score (MS). Agreement between scoring systems was assessed with Krippendorff's alpha (KA). Multivariable analyses were conducted to determine if variables were associated with overall survival. At admission, median AIS, I-ISS, and MS scores were 2 for all scoring systems. Patients who died had higher overall injury burden than those who survived and had similar median admission AIS and MS scores, but higher I-ISS scores. There was strong correlation between the inhalation injury grade at admission using the three scoring systems (KA = 0.85). On regression analysis, the only scoring system independently associated with overall survival was I-ISS (score 3 compared to scores 1-2: OR 13.16, 95% CI 1.65-105.07; P = .02). Progression of injury after initial assessment may contribute to the poor correlation between admission score and overall survival for injuries graded with AIS and MS. Repeated assessment may more accurately identify patients at increased risk for mortality.

Assessment and Management of Acute Burn Injuries

Burn injuries can affect patients from all walks of life and represent a significant healthcare problem globally. The skin is the largest organ of the body and consequences of injury range of minor pain to severe end-organ dysfunction and even death. The acute assessment and management of burn-injured patients is a critical part of their short-term and long-term outcomes and often benefit from specialty, multidisciplinary care. Local wound care and appropriate excision and grafting are important parts of managing the functional, cosmetic, and physiologic derangements caused by burn injuries. Large burns also require judicious fluid resuscitation. Electrical, chemical, and inhalational injuries are less common than thermal burns but require additional care and are often associated with increased morbidity.

A Rare Mechanism of Inhalation Injury: Direct Thermal Damage to the Lower Airway

In patients with inhalation injury associated with major burns, the primary mechanism of tissue harm depends on the location within the respiratory tract. Proximal to the trachea, the upper respiratory tract epithelium is classically injured via direct thermal injury. Such injury occurs due to the inhalation of high-temperature air. These upper airway structures and the tracheobronchial tree's dense vasculature protect the lower airways and lung parenchyma from direct thermal damage. The lower respiratory tract epithelium and lung parenchyma typically become injured secondary to the cytotoxic effects of chemical irritants inhaled in smoke as well as delayed inflammatory host responses. This paper documents a rare case in which a patient demonstrated evidence of direct thermal injury to the lower respiratory tract epithelium. A 26-year-old Caucasian male presented to the emergency room with 66% total body surface area thermal burns and grade 4 inhalation injury after a kitchen fire. Instead of visualizing carbonaceous deposits in the bronchi, a finding common in inhalation injury, initial bronchoscopy revealed bronchial mucosa carpeted with hundreds of bullae. Despite the maximum grade of inhalation injury per the abbreviated injury score and a 100% chance of mortality predicted with the revised Baux score, as well as a clinical course complicated by pneumonia development, bacteremia, and polymicrobial external wound infection, this patient survived. This dissonance between his expected and observed clinical outcome suggests that the applicability of current inhalation injury classification systems depends on the precise mechanism of injury to the respiratory tract. The flaws of these grading scales and prognostic indicators may be rooted in their failure to account for other pathophysiologic processes involved in inhalation injury. It may be necessary to develop new grading and prognostic systems for inhalation injury that acknowledge and better account for unusual pathophysiologic mechanisms of tissue damage.

Inhalation Injury Grading Using Transfer Learning Based on Bronchoscopy Images and Mechanical Ventilation Period

The abbreviated injury score (AIS) is commonly used as a grading system for inhalation injuries. While inhalation injury grades have inconsistently been shown to correlate positively with the time mechanical ventilation is needed, grading is subjective and relies heavily on the clinicians' experience and expertise. Additionally, no correlation has been shown between these patients' inhalation injury grades and outcomes. In this paper, we propose a novel inhalation injury grading method which uses deep learning algorithms in bronchoscopy images to determine the injury grade from the carbonaceous deposits, blistering, and fibrin casts in the bronchoscopy images. The proposed method adopts transfer learning and data augmentation concepts to enhance the accuracy performance to avoid overfitting. We tested our proposed model on the bronchoscopy images acquired from eighteen patients who had suffered inhalation injuries, with the degree of severity 1, 2, 3, 4, 5, or 6. As performance metrics, we consider accuracy, sensitivity, specificity, F-1 score, and precision. Experimental results show that our proposed method, with both transfer learning and data augmentation components, provides an overall 86.11% accuracy. Moreover, the experimental results also show that the performance of the proposed method outperforms the method without transfer learning or data augmentation.

Impact of inhalation injury on outcomes in critically ill burns patients: 12-year experience at a regional burns centre

INTRODUCTION

Burns inhalation injury increases the attributable mortality of burns related trauma. However, diagnostic uncertainties around bronchoscopically graded severity, and its effect on outcomes, remain. This study evaluated the impact of different bronchoscopic burns inhalation injury grades on outcomes.

METHODS

A single-centre cohort study of all patients admitted to the London Burns centre intensive care unit (BICU) over 12 years. Demographic data, burn and burns inhalation injury characteristics, and ICU-related parameters were collected retrospectively. The primary outcome was mortality. Secondary outcomes were hospital and ICU lengths of stay. The impact of pneumonia was determined. Univariate and multivariable Cox's proportional hazards regression analyses informed factors predicting mortality.

RESULTS

Burns inhalation injury was diagnosed in 84 of 231 (36%) critically ill burns patients; 20 mild (grade 1), 41 severe (grades 2/3) and 23 unclassified bronchoscopically. Median (IQR) total body surface area burned (TBSA) was 20% (10-40). Mortality was significantly higher in patients with burns inhalation injury vs those without burns inhalation injury (38/84 [45%] vs 35/147 [24%], p < 0.001). Patients with pneumonia had a higher mortality than those without (34/125 [27%] vs 8/71 [11%], p = 0.009). In multivariable analysis, severe burns inhalation injury significantly increased mortality (adjusted HR=2.14, 95%CI: 1.12-4.09, p = 0.022), compared with mild injury (adjusted HR=0.58, 95% CI: 0.18-1.86, p = 0.363). Facial burns (adjusted HR=3.13, 95%CI: 1.69-5.79, p < 0.001), higher TBSA (adjusted HR=1.05, 95%CI: 1.04-1.06, p < 0.001) and older age (adjusted HR=1.04, 95%CI: 1.02-1.07, p < 0.001) also independently predicted mortality, though pneumonia did not.

CONCLUSIONS

Severe burns inhalation injury is a significant risk factor for mortality in critically ill burns patients. However, pneumonia did not increase mortality from burns inhalation injury. This work confirms prior implications of bronchoscopically graded burns inhalation injury. Further study is suggested, through registries, into the diagnostic accuracy and reliability of bronchoscopy in burns related lung injury.

Outcomes following traumatic inhalational airway injury - Predictors of mortality and effect of procedural intervention

OBJECTIVE

Study outcomes, predictors of mortality, and effects of procedural interventions on patients following traumatic inhalational airway injury.

STUDY

Design: Retrospective study.

SETTING

National Trauma Data Bank METHODS: Patients over the age of eighteen admitted between 2008 and 2016 to NTDB-participating sites were included. In-hospital mortality and length of stay were the primary outcomes.

RESULTS

The final study cohort included 13,351 patients. History of active smoking was negatively associated with in-house mortality with an OR of 0.33 (0.25-0.44). History of alcohol use, and presence of significant medical co-morbidities were positively associated with in-house mortality with OR of 5.28 (4.32-6.46) 2.74 (19.4-3.86) respectively. There was little to no association between procedural interventions and in-house mortality. Intubation, laryngobronchoscopy, and tracheostomy had OR of 0.90 (0.67-1.20), 1.02 (0.79-1.30), and 0.94 (0.58-1.51), respectively. However, procedural intervention did affect both the median hospital and ICU lengths of stay of patients. Median hospital and ICU length of stay were shorter for patients receiving endotracheal intubation. Median hospital length of stay was longer for patients undergoing bronchoscopy and laryngoscopy, but median ICU length of stay was shorter for patients undergoing bronchoscopy and laryngoscopy. Patients receiving a tracheostomy have both significantly increased median hospital and ICU lengths of stay.

CONCLUSIONS

Active smoking was associated with decreased odds of in-hospital mortality, while presence of pre-existing medical comorbidities and history of alcohol use disorder was associated with increased odds of in-hospital mortality. Procedural intervention had little to no association with in-hospital mortality but did affect overall hospital and ICU LOS.

Acute respiratory failure and burn patient outcomes

PURPOSE OF REVIEW

Advances in the care of inhalational injuries have not kept pace with advances that have been seen in the treatment of cutaneous burns. There is not yet a standard of care for best outcomes for airway management of patients with known or suspected inhalational injuries. Clinicians must decide if to intubate the patient, and if so, whether to intubate early or late in their presentation. Unnecessary intubation affects morbidity and mortality. This review will summarize literature that highlights present practices in the treatment of patients with inhalation injuries.

RECENT FINDINGS

There have been promising investigations into biomarkers that can be used to quantify a patient's risk and better target therapies. Grading systems serve to better stratify the burn victim's prognosis and then direct their care. Special ventilator modes can assist in ventilating burn patients with inhalation injuries that experience difficulties in oxygenating.

SUMMARY

Inhalational injuries are a significant source of morbidity and mortality in thermally injured patients. Treatment modalities, such as modified ventilator settings, alteration in fluid resuscitation, and a standardized grading system may improve morbidity and mortality.

Inpatient and post-discharge outcomes following inhalation injury among critically injured burn patients

Inhalation injury is associated with high inpatient mortality, but the impact of inhalation injury after discharge and on non-mortality outcomes are poorly characterized. To address this gap, we evaluated the effect of inhalation injury on post-discharge morbidity, mortality and hospital readmissions among patients who sustained burn injury, as well as on in-hospital outcomes for context.This was a retrospective cohort study of patients with cutaneous fire/flame burns admitted to a burn center intensive care unit from 1/1/2009-12/31/2015, with or without inhalation injury. Records were linked to statewide hospital admission and vital statistics databases to assess post-discharge outcomes. Mixed-effects Poisson regression was used to assess mortality, complications, and readmissions. The overall cohort included 830 patients with cutaneous burns; of these, 201 patients had inhalation injury. In-hospital mortality was 31% among inhalation injury patients versus 6% in patients without inhalation injury (adjusted OR 2.35; 95% CI 1.66-3.31). Inhalation injury was also associated with an increased risk of in-hospital pneumonia and tracheostomy (p<0.05 for all). Inhalation injury was not associated with greater post-discharge mortality, all-cause readmission, readmission for pulmonary diagnosis, or readmission requiring intubation. Among the subset of patients with bronchoscopy-confirmed inhalation injury (n=124; 62% of inhalation injuries), higher injury grade was not associated with greater inpatient or post-discharge mortality. Inhalation injury was associated with increased early morbidity and mortality, but did not contribute to post-discharge mortality or readmission. These findings have implications for shared decision-making with patients and families, and for estimating healthcare utilization after initial hospitalization.

Inhalation Injury: Unmet Clinical Needs and Future Research

Pulmonary and systemic insults from inhalation injury can complicate the care of burn patients and contribute to significant morbidity and mortality. However, recent progress in diagnosis and treatment of inhalation injury has not kept pace with the care of cutaneous thermal injury. There are many challenges unique to inhalation injury that have slowed advancement, including deficiencies in our understanding of its pathophysiology, the relative difficulty and subjectivity of bronchoscopic diagnosis, the lack of diagnostic biomarkers, the necessarily urgent manner in which decisions are made about intubation, and the lack of universal recommendations for the application of mucolytics, anticoagulants, bronchodilators, modified ventilator strategies, and other measures. This review represents a summary of critical shortcomings in our understanding and management of inhalation injury identified by the American Burn Association's working group on Cutaneous Thermal Injury and Inhalation Injury in 2018. It addresses our current understanding of the diagnosis, pathophysiology, and treatment of inhalation injury and highlights topics in need of additional research, including 1) airway repair mechanisms; 2) the airway microbiome in health and after injury; and 3) candidate biomarkers of inhalation injury.

Serious Inhalation Injuries From Military Operations in Afghanistan, Iraq, and Syria

OBJECTIVE

To characterize serious inhalation injuries seen during recent military operations, and assess whether bronchoscopic severity findings were associated with clinical presentation and outcomes.

METHODS

Service members who suffered inhalation injuries while deployed to Iraq, Afghanistan, or Syria from 2001-2018 were identified using ICD-9 and 10 codes from the Expeditionary Medical Encounter Database (EMED), which is abstracted from patient records in forward-deployed medical facilities. Further information including demographics, mechanism of injury, mortality, total burn surface area (TBSA), degree of facial burn, total Injury Severity Score (ISS), and first post-injury bronchoscopy notes were collected. Patients were excluded with ISS less than 16 or without sufficient details regarding bronchoscopy. Injuries were grouped based on bronchoscopic Abbreviated Injury Scores (AIS) into low-grade (AIS of 1), moderate-grade (AIS of 2), or high-grade (AIS of 3 or 4).

RESULTS

91 patients met inclusion criteria, with no significant differences in age, gender, paygrade, or service branch between degrees of injury. There were no statistical correlations between grade of injury and battle versus non-battle injury, blast versus non-blast mechanism, TBSA, or degree of facial burn. High-grade injuries had significantly higher ISS than low or moderate-grade injuries. After adjusting for ISS, the odds ratio of death was 10.4 (95% CI 1.47 to 74.53) for those with high-grade and 3.7 (95% CI 0.45 to 32.30) for those with moderate-grade compared to low-grade injuries.

CONCLUSION

In this cohort of deployed military members with inhalation injuries, initial bronchoscopic severity findings are strongly associated with mortality even after adjusting for ISS. The AIS may be an important prognostic tool in all of those with serious inhalation injuries.

Injury Characteristics and von Willebrand Factor for the Prediction of Acute Respiratory Distress Syndrome in Patients With Burn Injury: Development and Internal Validation

OBJECTIVE

To derive and validate a prediction model for the development of ARDS in burn-injured patients.

SUMMARY BACKGROUND DATA

Burn injury carries the highest incidence of acute respiratory distress syndrome (ARDS) among all predisposing conditions, but few studies exist on risk factors in these patients. Studies employing biomarkers and clinical risk factors for predicting ARDS mortality have recently been examined but none exist for onset of ARDS nor in patients with burn injury.

METHODS

This was a prospective multicenter study of 113 patients with isolated burn injury or inhalation injury. Clinical variables and plasma biomarkers representative of endothelial injury, epithelial injury, or inflammation were collected within 24 hours of admission. The most parsimonious model was chosen by considering discrimination, calibration, and model fit.

RESULTS

Among the biomarkers measured in patients with burn injuries, a one-standard deviation increase in log-transformed levels of the A2 domain of von Willebrand factor in the first 24 hours was most strongly associated with the development of ARDS (OR 7.72; 95% CI: 1.64-36.28, P = 0.03). Of candidate models, a 3-variable model with %TBSA, inhalation injury, and von Willebrand factor-A2 had comparable discrimination to more complex models (area under the curve: 0.90; 95% CI 0.85-0.96). The 3-variable model had good model fit by Hosmer-Lemeshow test (P = 0.74) and maintained similar discrimination after accounting for performance optimism (Bootstrapped area under the curve: 0.90; 95% CI: 0.84-0.95).

CONCLUSIONS

The 3-variable model with %TBSA, inhalation injury, and von Willebrand factor could be used to better identify at-risk patients for both the study and prevention of ARDS in patients with burn injury.

Management of severe thermal burns in the acute phase in adults and children

OBJECTIVES

To provide recommendations to facilitate the management of severe thermal burns during the acute phase in adults and children.

DESIGN

A committee of 20 experts was asked to produce recommendations in six fields of burn management, namely, (1) assessment, admission to specialised burns centres, and telemedicine; (2) haemodynamic management; (3) airway management and smoke inhalation; (4) anaesthesia and analgesia; (5) burn wound treatments; and (6) other treatments. At the start of the recommendation-formulation process, a formal conflict-of-interest policy was developed and enforced throughout the process. The entire process was conducted independently of any industry funding. The experts drew up a list of questions that were formulated according to the PICO model (Population, Intervention, Comparison, and Outcomes). Two bibliography experts per field analysed the literature published from January 2000 onwards using predefined keywords according to PRISMA recommendations. The quality of data from the selected literature was assessed using GRADE® methodology. Due to the current paucity of sufficiently powered studies regarding hard outcomes (i.e. mortality), the recommendations are based on expert opinion.

RESULTS

The SFAR guidelines panel generated 24 statements regarding the management of acute burn injuries in adults and children. After two scoring rounds and one amendment, strong agreement was reached for all recommendations.

CONCLUSION

Substantial agreement was reached among a large cohort of experts regarding numerous strong recommendations to optimise the management of acute burn injuries in adults and children.

Assessment and treatment of acute toxic inhalations

PURPOSE OF REVIEW

Acute toxic inhalation exposures affect thousands of individuals worldwide each year. The acute evaluation of these inhaled exposures is often fraught with difficulty in identifying a specific agent, may involve multiple compounds, and a wide variety of responses are seen depending on the physical properties of the specific toxicant, the length of time of inhalation, and the concentration of the exposure. Recognizing key aspects of the most common acute toxic inhalations is useful in developing a diagnosis and treatment strategy.

RECENT FINDINGS

Use of sequential observations with flexible bronchoscopy has been the standard of care for assessing airway injury, and virtual bronchoscopy using computed tomographic images in a three-dimensional reconstructed image can now better identify airway narrowing. Use of [F]-fluorodeoxyglucose uptake, as measured by PET, has the potential for early recognition of delayed acute lung injury in toxic inhalation exposures. Development of a standardized respiratory injury grading system is ongoing with a recent multicenter trial nearly complete, allowing for more accurate estimates of eventual outcomes and guide levels of intensity of care for patients with acute inhalation injury. Removal from the source of exposure and airway support remain the first critical aspect of treatment, and additional therapies have been studied recently that focus on altering molecular mechanisms of acute cellular injury, expanding potential treatments beyond other pharmacotherapeutic strategies utilized previously such as mucolytics, bronchodilators, and inhaled anticoagulants.

SUMMARY

Although a prevalent source of airway injury, exposure to acute toxic inhalants is often difficult to assess and prognosticate, and challenging to treat.

Impact of diagnostic bronchoscopy in burned adults with suspected inhalation injury

INTRODUCTION

Inhalation injury is a common complication of thermal trauma. Fiberoptic bronchoscopy (FOB) is regarded as current standard practice in diagnosing and grading inhalation injury. Nonetheless, its predictive value in terms of therapeutic decision-making and clinical outcome is controversial.

METHODS

Adult burn patients with inhalation injury (InI) were selected from the National Burn Repository of the American Burn Association. Subjects were propensity score pair-matched based on injury severity and grouped based on whether or not FOB had been performed (FOB, CTR, respectively). Mortality, incidence of pneumonia, length of hospitalization, length of ICU stay and dependency on mechanical ventilation were compared between the two groups.

RESULTS

3014 patients were matched in two groups with a mean TBSA of 22.4%. There was no significant difference in carboxyhemoglobin fraction at admission. Patients, who underwent FOB on admission had a significantly increased incidence of pneumonia (p < 0.001), mortality (p < 0.05), length of hospitalization (p = 0.002), ICU stay (p < 0.001) and duration of mechanical ventilation (p = 0.006). In a subgroup analysis of patients with TBSA of at least 20%, incidence of pneumonia was significantly higher in the FOB group (p < 0.001) and longer mechanical ventilation was required (p = 0.036).

DISCUSSION

Diagnosis and grading of InI through FOB is the current standard, although its predictive value regarding key outcome parameters and therapeutic decision-making, remains unclear. The potential procedural risk of FOB itself should be considered. This study demonstrates correlations of FOB with major clinical outcomes in both a general collective of burned adults as well as severely burned adults. Although these findings must be interpreted with caution, they may induce further research into potential harm of FOB and critical review of routine diagnostic FOB in suspected inhalation injury in thermally injured patients.

Airway management in inhalation injury: a case series

Inhalation injury is a serious consequence of a fire or an explosion, with potential airway compromise and respiratory complications. We present a case series of five patients with inhalational burns who presented to Singapore General Hospital and discuss our approach to their early management, including early evaluation and planning for the upper and lower airway, coexisting cutaneous burns, and monitoring their ICU (intensive care unit) severity of illness, sepsis and acute respiratory distress syndrome. All five patients suffered various grades of inhalation injury. The patients were initially assessed by nasolaryngoscopy, and three patients were prophylactically intubated before being sent to the emergency operating theatre for definitive airway and burns management with fibreoptic bronchoscopy. All patients were successfully extubated and discharged stable. Various complications can arise as a result of an inhalation injury. Based on our cases and literature review, we propose a standardised workflow for patients with inhalation injury.

Changes in ventilator settings and ventilation-induced lung injury in burn patients-A systematic review

OBJECTIVE

Ventilation strategies aiming at prevention of ventilator-induced lung injury (VILI), including low tidal volumes (V_T) and use of positive end-expiratory pressures (PEEP) are increasingly used in critically ill patients. It is uncertain whether ventilation practices changed in a similar way in burn patients. Our objective was to describe applied ventilator settings and their relation to development of VILI in burn patients.

DATA SOURCES

Systematic search of the literature in PubMed and EMBASE using MeSH, EMTREE terms and keywords referring to burn or inhalation injury and mechanical ventilation.

STUDY SELECTION

Studies reporting ventilator settings in adult or pediatric burn or inhalation injury patients receiving mechanical ventilation during the ICU stay.

DATA EXTRACTION

Two authors independently screened abstracts of identified studies for eligibility and performed data extraction.

DATA SYNTHESIS

The search identified 35 eligible studies. V_T declined from 14 ml/kg in studies performed before to around 8 ml/kg predicted body weight in studies performed after 2006. Low-PEEP levels (<10 cmH₂O) were reported in 70% of studies, with no changes over time. Peak inspiratory pressure (PIP) values above 35 cmH₂O were frequently reported. Nevertheless, 75% of the studies conducted in the last decade used limited maximum airway pressures (≤35 cmH₂O) compared to 45% of studies conducted prior to 2006. Occurrence of barotrauma, reported in 45% of the studies, ranged from 0 to 29%, and was more frequent in patients ventilated with higher compared to lower airway pressures.

CONCLUSION

This systematic review shows noticeable trends of ventilatory management in burn patients that mirrors those in critically ill non-burn patients. Variability in available ventilator data precluded us from drawing firm conclusions on the association between ventilator settings and the occurrence of VILI in burn patients.

Severity of Inhalation Injury is Predictive of Alterations in Gas Exchange and Worsened Clinical Outcomes

Inhalation injury (INH) is present in one third of large burn injuries and increases oxygenation and fluid resuscitation requirements, incidences of pulmonary complications, risk for multiple organ dysfunction syndrome (MODS), and overall mortality. Previous studies have demonstrated inconsistent correlation between bronchoscopic evaluation and clinical outcomes. The authors reviewed 161 patients admitted with a diagnosis of INH or underwent diagnostic bronchoscopy for suspected INH over a period of 8.5 years. One hundred one patients had concomitant burn injury and 60 had isolated INH. Seventeen patients had abbreviated injury score (AIS) 0, 81 patients had low-grade injury (AIS 1 and 2), and 63 patients had high-grade injury (AIS 3 and 4). Patients with high-grade INH had worse pulmonary dysfunction, worse oxygenation indices (P = 0.01) and plasma carboxyhemoglobin (COHgb; P < 0.01) on admission, increased fluid requirements (P < 0.01 at 24 hours; P = 0.04 at 48 hours), MODS (P = 0.04), pneumonia (P < 0.01), acute respiratory distress syndrome (P = 0.01 at 48 hours), fewer 28-day ventilator-free days (P < 0.01), greater ventilator dependence (P = 0.03), and longer length of stay (P < 0.01). Multivariate analyses demonstrated increased risk of MODS (P = 0.03), acute respiratory distress syndrome at 48 hours (P < 0.01), pneumonia (P = 0.01), prolonged ventilator dependence (P = 0.03), and a trend toward mortality (P = 0.08) with higher AIS groups. More severe INH correlates with early oxygenation impairments and is associated with more complicated hospitalization, fluid resuscitation requirements, and ventilation demands. Severe INH is associated with and predictive of increased morbidity and mortality.

The use of a simple three-level bronchoscopic assessment of inhalation injury to predict in-hospital mortality and duration of mechanical ventilation in patients with burns

Major burn centres in Australia use bronchoscopy to assess severity of inhalation injuries despite limited evidence as to how best to classify severity of inhalational injury or its relationship to patient outcomes. All patients with burns who were admitted to the intensive care unit (ICU) at The Alfred Hospital between February 2010 and July 2014 and underwent bronchoscopy to assess inhalational injury, were reviewed. Age, total body surface area burnt, severity of illness indices and mechanisms of injury were extracted from medical histories and local ICU and burns registries. Inhalational injury was classified based on the Abbreviated Injury Score and then grouped into three categories (none/mild, moderate, or severe injury). Univariable and multivariable analyses were undertaken to examine the relationship between inhalational injury and outcomes (in-hospital mortality and duration of mechanical ventilation). One hundred and twenty-eight patients were classified as having none/mild inhalational injury, 81 moderate, and 13 severe inhalation injury. Mortality in each group was 2.3% (3/128), 7.4% (6/81) and 30.7% (4/13) respectively. Median (interquartile range) duration of mechanical ventilation in each group was 26 (11-82) hours, 84 (32-232) hours and 94 (21-146) hours respectively. After adjusting for age, total body surface area burnt and severity of illness, only the severe inhalation injury group was independently associated with increased mortality (odds ratio 20.4 [95% confidence intervals {CI} 1.74 to 239.4], <i>P</i>=0.016). Moderate inhalation injury was independently associated with increased duration of ventilation (odds ratio 2.25 [95% CI 1.53 to 3.31], <i>P</i> <0.001), but not increased mortality. This study suggests that stratification of bronchoscopically-assessed inhalational injury into three categories can provide useful prognostic information about duration of ventilation and mortality. Larger multicentre prospective studies are required to validate these findings.

Multiple-Drug Resistance in Burn Patients: A Retrospective Study on the Impact of Antibiotic Resistance on Survival and Length of Stay

Despite improvements in early treatment, survival following burn injury remains challenged by sepsis and multiple organ dysfunction syndrome (MODS). Additionally, susceptibility to infections and growing antibiotic resistance places burn patients at increased risk for infections with multiple-drug resistant organisms (MDROs). We therefore aimed to evaluate the impact of MDRO infections on survival and hospital length of stay, as well as examine the role of these organisms in the development of complications, such as acute kidney injury, sepsis, and MODS. To study this, we included all burn patients with infections, admitted between January 1, 2012, and December 31, 2013. Patients were divided into two groups: patients with infections caused by MDROs and patients with infections caused by susceptible organisms. Data were collected on all available cultures, as well as demographic, injury, and treatment-related variables from the medical record. The number of operative procedures (median: 2 vs 1, P < .0001), ventilator days (21 vs 0 days, P < .0001), total antibiotic days (21 vs 7days, P < .0001), and length of hospitalization (39 vs 14 days, P < .0001) were significantly different in the MDRO group vs the nonresistant group. While MDRO infection was not associated with patient mortality, univariable logistic regression analyses demonstrated >20% TBSA (odds ratio [OR] = 4.30, 95% confidence interval [CI]: 1.14-16.29, P = .03), acute kidney injury (OR = 10.93, 95% CI: 2.74-43.57, P = .001), sepsis (OR = 19.20, 95% CI: 3.79-97.27, P < .001), and MODS (OR = 85.49, 95% CI: 12.97-563.28, P < .0001) significantly increased the odds of patient mortality. These findings suggest that infections with MDROs are associated with a greater number of surgical procedures, longer duration of mechanical ventilation, more antibiotic days, and longer hospitalization.

Inhalation Injury: State of the Science 2016

This article summarizes research conducted over the last decade in the field of inhalation injury in thermally injured patients. This includes brief summaries of the findings of the 2006 State of the Science meeting with regard to inhalation injury, and of the subsequent 2007 Inhalation Injury Consensus Conference. The reviewed studies are categorized in to five general areas: diagnosis and grading; mechanical ventilation; systemic and inhalation therapy; mechanistic alterations; and outcomes.

Smoke Inhalation Injury: Etiopathogenesis, Diagnosis, and Management

Smoke inhalation injury is a major determinant of morbidity and mortality in fire victims. It is a complex multifaceted injury affecting initially the airway; however, in short time, it can become a complex life-threatening systemic disease affecting every organ in the body. In this review, we provide a summary of the underlying pathophysiology of organ dysfunction and provide an up-to-date survey of the various critical care modalities that have been found beneficial in caring for these patients. Major pathophysiological change is development of edema in the respiratory tract. The tracheobronchial tree is injured by steam and toxic chemicals, leading to bronchoconstriction. Lung parenchyma is damaged by the release of proteolytic elastases, leading to release of inflammatory mediators, increase in transvascular flux of fluids, and development of pulmonary edema and atelectasis. Decreased levels of surfactant and immunomodulators such as interleukins and tumor-necrosis-factor-α accentuate the injury. A primary survey is conducted at the site of fire, to ensure adequate airway, breathing, and circulation. A good intravenous access is obtained for the administration of resuscitation fluids. Early intubation, preferably with fiberoptic bronchoscope, is prudent before development of airway edema. Bronchial hygiene is maintained, which involves therapeutic coughing, chest physiotherapy, deep breathing exercises, and early ambulation. Pharmacological agents such as beta-2 agonists, racemic epinephrine, N-acetyl cysteine, and aerosolized heparin are used for improving oxygenation of lungs. Newer agents being tested are perfluorohexane, porcine pulmonary surfactant, and ClearMate. Early diagnosis and treatment of smoke inhalation injury are the keys for better outcome.

The Contributing Risk of Tobacco Use for ARDS Development in Burn-Injured Adults With Inhalation Injury

BACKGROUND

This study aims to determine the relationship between tobacco use, inhalation injury, and ARDS in burn-injured adults.

METHODS

This study was an observational cohort of 2,485 primary burn admissions to a referral burn center between January 1, 2008 and March 15, 2015. Subjects were evaluated by methods used to account for mediation and traditional approaches (multivariable logistic regression and propensity score analysis). Mediation analysis examined both the (1) indirect effect of tobacco use via inhalation injury as the mediator on ARDS development and (2) the direct effect of tobacco use alone on ARDS development.

RESULTS

ARDS development occurred in 6.8% (n = 170) of the cohort. Inhalation injury occurred in 5.0% (n = 125) of the cohort, and ARDS developed in 48.8% (n = 83) of the subjects with inhalation injury. Tobacco use was 2-fold more common in subjects with ARDS. In the mediated model, the direct effect of tobacco use on ARDS, including interaction between tobacco use and inhalation injury, was not significant (odds ratio [OR] 1.63, 95% CI 0.91-2.92, P = .10). However, the indirect effect of tobacco use via inhalation injury as the mediator was significant (OR 1.61, 95% CI 1.25-2.07, P < .001), and the proportion of the total effect of tobacco use operating through the mediator was 55.6%. In the non-mediation models (multivariable logistic regression and propensity score analysis), which controlled for inhalation injury and other covariables, the OR for the association between tobacco use and ARDS was 1.84 (95% CI 1.22-2.81, P < .001) and 1.69 (95% CI 1.04-2.75, P = .03), respectively.

CONCLUSIONS

In mediation analysis, inhalation injury was the overwhelming predictor for ARDS development, whereas tobacco use has its strongest effect indirectly through inhalation injury. Patients with at least moderate inhalation injury are at greatest risk for ARDS development despite baseline risk factors like tobacco use.

Inhalation Injury: Pathophysiology, Diagnosis, and Treatment

The classic determinants of mortality from severe burn injury are age, size of injury, delays of resuscitation, and the presence of inhalation injury. Of the major determinants of mortality, inhalation injury remains one of the most challenging injuries for burn care providers. Patients with inhalation injury are at increased risk for pneumonia (the leading cause of death) and multisystem organ failure. There is no consensus among leading burn care centers in the management of inhalation injury. This article outlines the current treatment algorithms and the evidence of their efficacy.

Orange-Pigmented Sputum as a Manifestation of Smoke Grenade Inhalation Injury

A 34-year-old man presented with scanty hemoptysis, orange-colored expectoration, and mild dyspnea. He was in an enclosed building taking part in a military training exercise inhaling an orange-colored smoke from a smoke grenade ignition. His symptoms developed immediately after the initial exposure but he sought medical assistance 20 hours later because of their persistence. Fiberoptic bronchoscopy was performed revealing diffuse inflammatory tracheobronchial tree with streaky orange-pigmented secretions in the trachea and both main-stem bronchi. Acute tracheobronchitis was diagnosed and the patient was treated with nebulized bronchodilators and intravenous corticosteroids showing complete recovery. To our knowledge, this is the first well-documented report of inhalation injury induced by a smoke bomb explosion including potassium chlorate oxidizer and Sudan I and presenting with orange-pigmented sputum production. Smoke inhalation injury is associated with significant morbidity and mortality. The heterogeneity of the smoke and the large variety of the resulting symptoms may be the reason why a definition, specific diagnostic criteria, and therapeutic guidelines are still lacking.

Utility and outcomes of hydroxocobalamin use in smoke inhalation patients

INTRODUCTION

Hydroxocobalamin has been available for use for suspected cyanide toxicity in smoke inhalation patients in the United States since 2006. Our study compares outcomes of patients who received hydroxocobalamin to historical controls who did not.

METHODS

In this retrospective review, patients administered hydroxocobalamin (2008-2014) were compared to historical controls (2002-2008). Patients <18 years, patients who received an alternate antidote, and patients without suspicion of smoke inhalation injury were excluded. Mortality was the primary outcome. Secondary outcomes evaluated were 7-day change in creatinine, culture-proven pneumonia, days on mechanical ventilation, ventilator- free days (VFD), ICU length of stay (ICU LOS), and hospital length of stay (HLOS).

RESULTS

A total of 138 patients in the hydroxocobalamin group and 135 in the control group were identified. Mortality rate was similar between both groups (29% vs. 28%, p=0.90). Hydroxocobalamin was associated with lower pneumonia rate (23% vs. 49%, p<0.01), less ventilator days (4 days vs. 7 days, p<0.01), and increased VFD (20 days vs. 11 days, p=0.01) compared to controls. Shorter ICU LOS (6 days vs. 10 days, p=0.03) and a trend toward lower HLOS (7 day vs. 11 days, p=0.06) were also found in patients who received hydroxocobalamin.

CONCLUSIONS

Routine administration was associated with lower rate of pneumonia, faster liberation from the ventilator, and reductions in intensive care unit stay. Burn centers should consider its empiric use in suspected smoke inhalation patients.

Inhalation injury after exposure to indoor fire and smoke: The Brazilian disaster experience

OBJECTIVE

To describe the pre-hospital, emergency department, and intensive care unit (ICU) care and prognosis of patients with inhalation injury after exposure to indoor fire and smoke.

MATERIALS AND METHODS

This is a prospective observational cohort study that includes patients admitted to seven ICUs after a fire disaster. The following data were collected: demographic characteristics; use of fiberoptic bronchoscopy; degree of inhalation injury; percentage of burned body surface area; mechanical ventilation parameters; and subsequent events during ICU stay. Patients were followed to determine the ICU and hospital mortality rates.

RESULTS

Within 24h of the incident, 68 patients were admitted to seven ICUs. The patients were young and had no comorbidities. Most patients (n=35; 51.5%) only had an inhalation injury. The mean ventilator-free days for patients with an inhalation injury degree of 0 or I was 12.5±8.1 days. For patients with an inhalation injury degree of II or III, the mean ventilator-free days was 9.4±5.8 days (p=0.12). In terms of the length of ICU stay for patients with degrees 0 or I, and patients with degrees II or III, the median was 7.0 days (5.0-8.0 days) and 12.0 days (8.0-23.0 days) (p<0.001), respectively. In addition, patients with a larger percentage of burned surface areas also had a longer ICU stay; however, no association with ventilator-free days was found. The patients with <10% of burned body surface area showed a mean of 9.2±5.4 ventilator-free days. The mean ventilator-free days for patients who had >10% burned body surface area was 11.9±9.5 (p=0.26). The length of ICU stay for the <10% and >10% burned body surface area patients was 7.0 days (5.0-10.0 days) and 23.0 days (11.5-25.5 days) (p<0.001), respectively.

CONCLUSIONS

We conclude that burn patients with inhalation injuries have different courses of disease, which are mainly determined by the percentage of burned body surface area.

Diagnosis and management of inhalation injury: an updated review

In this article we review recent advances made in the pathophysiology, diagnosis, and treatment of inhalation injury. Historically, the diagnosis of inhalation injury has relied on nonspecific clinical exam findings and bronchoscopic evidence. The development of a grading system and the use of modalities such as chest computed tomography may allow for a more nuanced evaluation of inhalation injury and enhanced ability to prognosticate. Supportive respiratory care remains essential in managing inhalation injury. Adjuncts still lacking definitive evidence of efficacy include bronchodilators, mucolytic agents, inhaled anticoagulants, nonconventional ventilator modes, prone positioning, and extracorporeal membrane oxygenation. Recent research focusing on molecular mechanisms involved in inhalation injury has increased the number of potential therapies.

Assessing inhalation injury in the emergency room

Respiratory tract injuries caused by inhalation of smoke or chemical products are related to significant morbidity and mortality. While many strategies have been built up to manage cutaneous burn injuries, few logical diagnostic strategies for patients with inhalation injuries exist and almost all treatment is supportive. The goals of initial management are to ensure that the airway allows adequate oxygenation and ventilation and to avoid ventilator-induced lung injury and substances that may complicate subsequent care. Intubation should be considered if any of the following signs exist: respiratory distress, stridor, hypoventilation, use of accessory respiratory muscles, blistering or edema of the oropharynx, or deep burns to the face or neck. Any patients suspected to have inhalation injuries should receive a high concentration of supplemental oxygen to quickly reverse hypoxia and to displace carbon monoxide from protein binding sites. Management of carbon monoxide and cyanide exposure in smoke inhalation patients remains controversial. Absolute indications for hyperbaric oxygen therapy do not exist because there is a low correlation between carboxyhemoglobin levels and the severity of the clinical state. A cyanide antidote should be administered when cyanide poisoning is clinically suspected. Although an ideal approach for respiratory support of patients with inhalation injuries do not exist, it is important that they are supported using techniques that do not further exacerbate respiratory failure. A well-organized strategy for patients with inhalation injury is critical to reduce morbidity and mortality.

Computed tomographic assessment of airflow obstruction in smoke inhalation injury: Relationship with the development of pneumonia and injury severity

PURPOSE

The prediction of pulmonary deterioration in patients with smoke inhalation injury is important because this influences the strategy for patient management. We hypothesized that narrowing of the luminal bronchus due to bronchial wall thickening correlates to respiratory deterioration in smoke inhalation injury patients.

METHODS

In a prospective observational study, all patients were enrolled at a single tertiary trauma and critical care center. In 40 patients, chest computed tomographic images were obtained within a few hours after smoke inhalation injury. We assessed bronchial wall thickness and luminal area % on chest computed tomographic images. Airway wall thickness to total bronchial diameter (T/D) ratio, percentage of luminal area, and clinical indices were compared between patients with smoke inhalation injury and control patients.

RESULTS

The T/D ratio of patients with smoke inhalation was significantly higher than that of control patients (p<0.001), and the luminal area of these patients was significantly smaller than that of control patients (p<0.001). The number of mechanical ventilation days correlated with the initial infusion volume, T/D ratio, and luminal area %. ROC analysis showed a cut-off value of 0.26 for the T/D ratio, with a sensitivity of 79.0% and specificity of 73.7%, and a value of 23.4% for luminal area %, with a sensitivity of 68.4% and specificity of 84.2%.

CONCLUSIONS

These data revealed the utility of computed tomography scanning on admission to show that the patients with smoke inhalation injury had airway wall thickening compared to control patients without smoke inhalation injury. Airflow narrowing due to airway wall thickening was related to the development of pneumonia and the number of mechanical ventilation days in patients with smoke inhalation injury. Airflow narrowing is one important factor of respiratory deterioration in smoke inhalation injury.

Overview of current pediatric burn care

Burn injuries affect approximately a million children in the United States on an annual basis. Moderate to severe burns require hospitalization, usually under the direction of a Pediatric Surgical service. Despite advancements in burn treatment, pediatric burn injuries account for approximately 2500 deaths annually. This article provides an overview of the initial evaluation and resuscitative measures for pediatric burn patients, most current wound care, indications for grafting, and the role of nutrition, including use of pharmacologic adjuncts. Use of colloid solutions, indications for use of skin substitutes, and transfer criteria will also be addressed.

Inhalation injury in burn patients: establishing the link between diagnosis and prognosis

This study was to re-evaluate inhalation injury as a prognostic factor in burn patients and to determine the factors that should be considered when refining the definition of inhalation injury. A total of 192 burn patients (152 men, 40 women; mean age, 46.1±13.8 years) who were suspected to have an inhalation injury and underwent bronchoscopy between January 2010 and June 2012 were included in this prospective observational study. All patients underwent bronchoscopy within 24h of sustaining the burn. The bronchoscopic findings were classified as normal, mild, moderate, and severe. Mechanical ventilation was administered, when required. Age, percentage of TBSA burned, ABSI score, requirement of mechanical ventilation and PF ratio, but not inhalation injury, COHb level, and bronchoscopic grades, significantly differed between the survivors and non-survivors (p<0.05). Mechanical ventilation (adjusted odds ratio [OR]: 9.787) and severe inhalation injury on bronchoscopy (adjusted OR: 45.357) were independent predictors of mortality on multivariate logistic regression analysis. Inhalation injury diagnosed through history does not predict mortality from burns. Other components such as severity of inhalation injury determined using bronchoscopy, and administration of mechanical ventilation might help predict the morbidity and mortality of burn patients with inhalation injury and all of the factors should be considered when the definition of inhalation injury is refined.

Comparison of virtual bronchoscopy to fiber-optic bronchoscopy for assessment of inhalation injury severity

PURPOSE

Compare virtual bronchoscopy (VB) to fiberoptic bronchoscopy (FOB) for scoring smoke inhalation injury (SII).

METHODS

Swine underwent computerized tomography (CT) with VB and FOB before (0) and 24 and 48 h after SII. VB and FOB images were scored by 5 providers off line.

RESULTS

FOB and VB scores increased over time (p<0.001) with FOB scoring higher than VB at 0 (0.30±0.79 vs. 0.03±0.17), 24 h (4.21±1.68 vs. 2.47±1.50), and 48h (4.55±1.83 vs. 1.94±1.29). FOB and VB showed association with PaO2-to-FiO2 ratios (PFR) with areas under receiver operating characteristic curves (ROC): for PFR≤300, VB 0.830, FOB 0.863; for PFR≤200, VB 0.794, FOB 0.825; for PFR≤100, VB 0.747, FOB 0.777 (all p<0.001). FOB showed 80.3% specificity, 77% sensitivity, 88.8% negative-predictive value (NPV), and 62.3% positive-predictive value (PPV) for PFR≤300 and VB showed 67.2% specificity, 85.5% sensitivity, 91.3% NPV, and 53.4% PPV.

CONCLUSIONS

VB provided similar injury severity scores to FOB, correlated with PFR, and reliably detected airway narrowing. VB performed during admission CT may be a useful screening tool specifically to demonstrate airway narrowing induced by SII.

Smoke inhalation injury during enclosed-space fires: an update

In view of the tragic fire at a nightclub in the city of Santa Maria, Brazil, which culminated in the sudden death of 232 young people, we decided to review the literature regarding smoke inhalation injury caused by enclosed-space fires, which can be divided into direct thermal damage, carbon monoxide poisoning, and cyanide poisoning. Such injuries often call for immediate orotracheal intubation, either due to acute airway obstruction or due to a reduced level of consciousness. The diagnosis and the severity of the thermal injury can be determined by fiberoptic bronchoscopy. The levels of gases and gas by-products in the bloodstream should be assessed as rapidly as possible, even while still at the scene of the incident. First responders can also treat carbon monoxide poisoning, with immediate administration of oxygen at 100%, as well as cyanide poisoning, with oxygen therapy and hydroxocobalamin injection.

Lung [(18)F]fluorodeoxyglucose uptake and ventilation-perfusion mismatch in the early stage of experimental acute smoke inhalation

BACKGROUND

Acute lung injury occurs in a third of patients with smoke inhalation injury. Its clinical manifestations usually do not appear until 48-72 h after inhalation. Identifying inflammatory changes that occur in pulmonary parenchyma earlier than that could provide insight into the pathogenesis of smoke-induced acute lung injury. Furthermore, noninvasive measurement of such changes might lead to earlier diagnosis and treatment. Because glucose is the main source of energy for pulmonary inflammatory cells, the authors hypothesized that its pulmonary metabolism is increased shortly after smoke inhalation, when classic manifestations of acute lung injury are not yet expected.

METHODS

In five sheep, the authors induced unilateral injury with 48 breaths of cotton smoke while the contralateral lung served as control. The authors used positron emission tomography with: (1) [F]fluorodeoxyglucose to measure metabolic activity of pulmonary inflammatory cells; and (2) [N]nitrogen in saline to measure shunt and ventilation-perfusion distributions separately in the smoke-exposed and control lungs.

RESULTS

The pulmonary [F]fluorodeoxyglucose uptake rate was increased at 4 h after smoke inhalation (mean ± SD: 0.0031 ± 0.0013 vs. 0.0026 ± 0.0010 min; P < 0.05) mainly as a result of increased glucose phosphorylation. At this stage, there was no worsening in lung aeration or shunt. However, there was a shift of perfusion toward units with lower ventilation-to-perfusion ratio (mean ratio ± SD: 0.82 ± 0.10 vs. 1.12 ± 0.02; P < 0.05) and increased heterogeneity of the ventilation-perfusion distribution (mean ± SD: 0.21 ± 0.07 vs. 0.13 ± 0.01; P < 0 .05).

CONCLUSION

Using noninvasive imaging, the authors demonstrated that increased pulmonary [F]fluorodeoxyglucose uptake and ventilation-perfusion mismatch occur early after smoke inhalation.

The year in burns 2012

Approximately 2457 research articles were published with burns in the title, abstract, and/or keyword in 2012. This number continues to rise through the years; this article reviews those selected by the Editor of one of the major journals in the field (Burns) and his colleague that are most likely to have the greatest likelihood of affecting burn care treatment and understanding. As done previously, articles were found and divided into these topic areas: epidemiology of injury and burn prevention, wound and scar characterization, acute care and critical care, inhalation injury, infection, psychological considerations, pain and itching management, rehabilitation, long-term outcomes, and burn reconstruction. Each selected article is mentioned briefly with comment from the authors; readers are referred to the full papers for further details.