Inhalation injury: research progress and needs

Incidence of Pneumonia Following Bronchoscopy and Bronchoalveolar Lavage in Burn Patients

The standard modality for diagnosis of smoke inhalational injury in burn patients is bronchoscopy with or without bronchoalveolar lavage (BAL). However, the risks associated with these procedures are poorly described in established literature. We sought to investigate the association between diagnostic BAL at admission and the development of pneumonia in burn patients. This retrospective analysis of intubated burn patients studied those who underwent bronchoscopy on admission, comparing patients who received BAL to those who did not. Demographics and baseline characteristics were analyzed using chi-squared or Student's t-test. Unadjusted and multivariable logistic regression studies assessed the effect of admission BAL on the development of pneumonia. Out of the 196 patients who underwent bronchoscopy, 98 met our criteria for analysis. The BAL group was more likely to be male and have a higher grade of abbreviated injury score. Patients who received BAL were more likely to develop pneumonia during the admission in both unadjusted and multivariable logistic regression models. These patients also had a longer hospital length of stay, greater number of ventilator days, and were more likely to undergo second bronchoscopy. These findings associate admission BAL with increased risk of pneumonia during the index hospitalization, suggesting a judicious use of BAL during admission bronchoscopy in burn patients.

Evaluating Determinants of Length of Stay in Burn Care: Is One Day per 1% Total Burn Surface Area Still Accurate?

Background Despite advances in burn care, morbidity and mortality remain high. There is a large gap in research focusing on resource-limited Appalachian burn victims. Appalachia is unique in many different ways. The region is well known nationally for poor healthcare outcomes, household income below the national average, ranking high in addiction and drug use crisis, and characterized with a high prevalence of comorbidities such as chronic obstructive pulmonary disease (COPD), diabetes mellitus (DM), coronary artery disease, and obesity. To complicate this devastating imbalance, Cabell Huntington Hospital is the sole burn intensive care unit in the state of West Virginia, with only six beds available. It is crucial to understand the factors that prolong the length of stay (LOS), as LOS is a key indicator for healthcare resource utilization, especially in this resource-limited population. This study aims to identify factors that influence LOS among burn patients in Appalachia, focusing on demographic and clinical variables. Methodology A retrospective analysis was conducted among 748 patients between January 1, 2017, and January 1, 2023. Demographic and clinical variables, including age, gender, COPD, DM, smoking history, inhalational injury, burn source, body mass index (BMI), total burn surface area (TBSA), and total ventilation duration (TVD), were collected. Multiple linear regression was used to identify predictors of LOS. Statistical significance was set at p-values <0.05. Results Significant predictors of prolonged LOS included TVD (β = 1.25, p < 0.001), TBSA (β = 0.60, p < 0.001), inhalational injury (β = 6.02, p < 0.001), and burn source (thermal contact with metal: β = 10.68, p = 0.003). Discharge status (dead) was associated with shorter LOS (β = -17.09, p < 0.001). For every additional day of ventilation, LOS increased by approximately 1.25 days. Each percentage increase in TBSA contributed to a 0.6-day increase in LOS. Patients who died had a hospital stay approximately 17 days shorter than those who survived. The presence of inhalational injury extended the LOS by an average of six days. Age, gender, COPD, DM, BMI, and smoking history were not significantly associated with LOS. Conclusions Newer predictor models should be used to combine TBSA with other demographics, comorbidities, and burn factors, such as inhalation injury and TVD, to provide a more accurate LOS for patients, their loved ones, and caregivers. The rule that for every 1% TBSA burned LOS increases with one day does not hold in our population. These findings provide valuable insights for optimizing burn care in resource-limited settings.

Inhalation Injury, Respiratory Failure, and Ventilator Support in Acute Burn Care

Sustaining an inhalation injury increases the risk of severe complications and mortality. Current evidential support to guide treatment of the injury or subsequent complications is lacking, as studies either exclude inhalation injury or design limit inferences that can be made. Conventional ventilator modes are most commonly used, but there is no consensus on optimal strategies. Settings should be customized to patient tolerance and response. Data for pharmacotherapy adjunctive treatments are limited.

Machine learning approach for predicting inhalation injury in patients with burns

BACKGROUND

The coronavirus disease pandemic has had a tangible impact on bronchoscopy for burn inpatients due to isolation and triage measures. We utilised the machine-learning approach to identify risk factors for predicting mild and severe inhalation injury and whether patients with burns experienced inhalation injury. We also examined the ability of two dichotomous models to predict clinical outcomes including mortality, pneumonia, and duration of hospitalisation.

METHODS

A retrospective 14-year single-centre dataset of 341 intubated patients with burns with suspected inhalation injury was established. The medical data on day one of admission and bronchoscopy-diagnosed inhalation injury grade were compiled using a gradient boosting-based machine-learning algorithm to create two prediction models: model 1, mild vs. severe inhalation injury; and model 2, no inhalation injury vs. inhalation injury.

RESULTS

The area under the curve (AUC) for model 1 was 0·883, indicating excellent discrimination. The AUC for model 2 was 0·862, indicating acceptable discrimination. In model 1, the incidence of pneumonia (P < 0·001) and mortality rate (P < 0·001), but not duration of hospitalisation (P = 0·1052), were significantly higher in patients with severe inhalation injury. In model 2, the incidence of pneumonia (P < 0·001), mortality (P < 0·001), and duration of hospitalisation (P = 0·021) were significantly higher in patients with inhalation injury.

CONCLUSIONS

We developed the first machine-learning tool for differentiating between mild and severe inhalation injury, and the absence/presence of inhalation injury in patients with burns, which is helpful when bronchoscopy is not available immediately. The dichotomous classification predicted by both models was associated with the clinical outcomes.

Clinical characteristics and predictors of burn complicated with smoke inhalation injury: A retrospective analysis

Fire smoke enters the human lungs through the respiratory tract. The damage to the respiratory tract and lung tissue is known as smoke inhalation injury (SII). Fire smoke can irritate airway epithelium cells, weaken endothelial cell adhesion and lyse alveolar type II epithelia cells, leading to emphysema, decreased lung function, pneumonia and risk of acute lung injury/acute respiratory distress syndrome (ARDS). The purpose of the present study was to analyze the clinical characteristics of patients with SII and the risk factors affecting their prognosis. A total of 103 patients with SII admitted between January 2016 to December 2021 to the Burns Unit of the Characteristic Medical Center of Chinese People's Armed Police Force and 983 Hospital of the Joint Logistics Support Force of the Chinese People's Liberation Army were selected for the present study. The demographics and clinical features between different severities of SII were analyzed. Univariate/multivariate logistic regression was used to analyze the potential predictors for severity, ARDS and mortality of patients with SII. Receiver operating characteristic (ROC) curves were used to screen independent risk factors and identify their prediction accuracy. It was concluded that total body surface area (TBSA), III burn area (of total %TBSA), cases of respiratory infections, ARDS morbidity, mortality, acute physiology and chronic health evaluation II, lung injury prediction score, lactic acid, white blood cells (WBC), alanine transaminase, blood urea nitrogen, serum creatinine and uric acid were indicators that were raised with increasing severity of SII. However red blood cells, hemoglobin, platelet count, total protein, albumin, and albumin/globulin were decreased with the increasing severity of SII (P<0.05). WBC >20.91 (10⁹/l) was a reliable indicator for severe SII. Lactic acid >9.60 (mmol/l) demonstrated a high degree of accuracy in predicting ARDS development in patients with SII. Hemoglobin <83.00 (g/l) showed a high degree of accuracy in predicting mortality. In summary, the highlighted assessment parameters could be used to contribute to devising improved treatment plans to preempt worsening conditions (such as shock, ARDS, multiple organ dysfunction syndrome and death).

Aspartate transaminase/alanine transaminase (De Ritis ratio) predicts survival in major burn patients

BACKGROUND

Although treatment of burn patients has significantly improved in recent decades, major burns remain fatal. Therefore, the evaluation of the death risk of the patients with extensive burns is very important. The ratio between the serum levels of aspartate transaminase and alanine transaminase (De Ritis ratio) was an independent predictor of poor outcomes in patients with acute ischemic stroke, cardiac surgery, non-metastatic renal cell carcinoma, and upper urinary tract urothelial carcinoma. Our aim was to determine whether the ratio between the serum levels of AST and ALT (De Ritis ratio) was useful to assess prognosis in extensively burned patients.

METHODS

We conducted a single-center cohort study at the Burns Department of Changhai Hospital. This retrospective observational analysis was performed based on the clinical data of major burn patients admitted between May 1, 2005 and April 30, 2018. Univariate and multivariate logistic regression analyses were performed on variables such as age, sex, total body surface area (TBSA), De Ritis ratio, and serum albumin level, which may affect mortality in major burn patients. We assessed their diagnostic value and found the cut-off value by receiver operative characteristic (ROC) curve analysis. We used the Kaplan-Meier curve to display the impact of the De Ritis ratio and serum albumin level on survival in burn patients.

RESULTS

A total of 351 patients with extensive burns were included in the study. The cohort predominantly consisted of males (74.64%), and most of the patients (78.35%) had been burned by a flame. Age, TBSA, inhalation, and the De Ritis ratio were found to be independent risk factors for the 30-days mortality of major burn patients, while age, TBSA, inhalation, and the De Ritis ratio were independent risk factors for 90-day mortality. Further, the De Ritis ratio was a better mortality predictor than serum albumin in severely burned patients, whose area under ROC for 30-day and 90-day mortality was 0.771 (95% confidence intervals [CI], 0.708-0.835) and 0.750 (95% CI, 0.683, 0.818).

CONCLUSIONS

The De Ritis ratio was useful as a prognostic indicator for major burn patients, which can be conveniently obtained through blood examination. Regardless of whether the prediction was for 30-day or 90-day mortality, the accuracy remained high. Moreover, compared to serum albumin level, the De Ritis ratio was superior in assessing the prognosis of extensively burned patients.

Does High-Frequency Chest Wall Oscillation Have an Impact on Improving Pulmonary Function in Patients With Smoke Inhalation Injury?

Smoke inhalation results in bronchospasm of the trachea, increasing secretion of mucus, casts formation, and improvement of blood flow of the airway. High frequency chest wall oscillation is a common modality used for clearing mucus secretion in patients suffering from hypersecretion of thick mucus and used also to help cough clearance. This study aimed to detect the effect of high frequency chest wall oscillation in improving pulmonary function in burn patients suffering from smoke inhalation. Sixty smoke inhalation injury patients were randomly distributed into two groups of equal size. Group A: received high frequency chest wall oscillation and conventional chest physical therapy (breathing exercises, early ambulation, and cough training) thrice per week for 8 weeks. Group B: received traditional chest physical therapy (breathing exercises, early ambulation, and cough training) thrice per week for 8 weeks. Pulmonary function test (forced vital capacity, forced expiratory volume in the first second and peak expiratory flow rate) was measured at enrollment and after 8 weeks by using spirometer. Pulmonary function increased significantly posttreatment when compared with that pretreatment in groups A and B (P > .001). Also, they increased significantly in group A compared with that of group B posttreatment (P > .05). High-frequency chest wall oscillation have an impact on improving pulmonary function and should be handled to be a part of the pulmonary rehabilitation plan for smoke inhalation injury patients.

The Influence of Obesity on Treatment and Outcome of Severely Burned Patients

Obesity and the related medical, social, and economic impacts are relevant multifactorial and chronic conditions that also have a meaningful impact on outcomes following a severe injury, including burns. In addition to burn-specific difficulties, such as adequate hypermetabolic response, fluid resuscitation, and early wound coverage, obese patients also present with common comorbidities, such as arterial hypertension, diabetes mellitus, or nonalcoholic fatty liver disease. In addition, the pathophysiologic response to severe burns can be enhanced. Besides the increased morbidity and mortality compared to burn patients with normal weight, obese patients present a challenge in fluid resuscitation, perioperative management, and difficulties in wound healing. The present work is an in-depth review of the current understanding of the influence of obesity on the management and outcome of severe burns.

Microbiome in the setting of burn patients: implications for infections and clinical outcomes

Burn damage can lead to a state of immune dysregulation that facilitates the development of infections in patients. The most deleterious impact of this dysfunction is the loss of the skin’s natural protective barrier. Furthermore, the risk of infection is exacerbated by protracted hospitalization, urinary catheters, endotracheal intubation, inhalation injury, arterial lines and central venous access, among other mainstays of burn care. Currently, infections comprise the leading cause of mortality after major burn injuries, which highlights the improvements observed over the last 50 years in the care provided to burn victims. The need to implement the empirical selection of antibiotic therapy to treat multidrug-resistant bacteria may concomitantly lead to an overall pervasiveness of difficult-to-treat pathogens in burn centres, as well as the propagation of antimicrobial resistance and the ultimate dysregulation of a healthy microbiome. While preliminary studies are examining the variability and evolution of human and mice microbiota, both during the early and late phase burn injury, one must consider that abnormal microbiome conditions could influence the systemic inflammatory response. A better understanding of the changes in the post-burn microbiome might be useful to interpret the provenance and subsequent development of infections, as well as to come up with inferences on the prognosis of burn patients. This review aims to summarise the current findings describing the microbiological changes in different organs and systems of burn patients and how these alterations affect the risks of infections, complications, and, ultimately, healing.

The Predictive Applicability of Liberal vs Restrictive Intubation Criteria in Adult Patients With Suspected Inhalation Injury-A Retrospective Cohort Study

This study compares the ability of liberal vs restrictive intubation criteria to detect prolonged intubation and inhalation injury in burn patients with suspected inhalation injury. Emerging evidence suggests that using liberal criteria may lead to unnecessary intubation in some patients. A single-center retrospective cohort study was conducted in adult patients with suspected inhalation injury admitted to intensive care at Queen Elizabeth Hospital, Birmingham between April 2016 and July 2019. Liberal intubation criteria, as reflected in local guidelines, were compared to restrictive intubation criteria, as outlined in the American Burn Association guidelines. The number of patients displaying positive characteristics from either guideline was compared to the number of patients who had prolonged intubation (more than 48 hours) and inhalation injury. In detecting a need for prolonged intubation (n = 85), the liberal criteria had greater sensitivity (liberal = 0.98 [0.94-1.00] vs restrictive = 0.84 [0.75-0.93]; P = .013). However, the restrictive criteria had greater specificity (restrictive = 0.96 [0.89-1.00] vs liberal = 0.48 [0.29-0.67]; P < .001). In detecting inhalation injury (n = 72), the restrictive criteria were equally sensitive (restrictive = 0.94 [0.87-1.00] vs liberal = 0.98 [0.84-1.00]; P = .48) and had greater specificity (restrictive = 0.86 [0.72-1.00] vs liberal = 0.04 [0.00-0.13]; P < .001). In patients who met liberal but not restrictive criteria, 65% were extubated within 48 hours and 90% did not have inhalation injury. Liberal intubation criteria were more sensitive at detecting a need for prolonged intubation, while restrictive criteria were more specific. Most patients intubated based on liberal criteria alone were extubated within 48 hours. Restrictive criteria were highly sensitive and specific at detecting inhalation injury.

Response of routine inflammatory biomarkers and novel Pancreatic Stone Protein to inhalation injury and its interference with sepsis detection in severely burned patients

BACKGROUND

Inhalation of thermal and chemical products of combustion evokes an immune response measurable at a systemic level. Inhalation injury related kinetics of currently available inflammatory biomarkers and novel Pancreatic Stone Protein (PSP) as well as their interference with septic events has not been addressed to literature yet.

METHODS

Analysis of the influence of inhalation injury and ARDS on biomarker kinetics (PSP, procalcitonin (PCT), C-reactive Protein (CRP), white blood cells (WBC)) in 90 patients admitted to Zurich Burn Center between May 2015 and October 2018 with burns ≥15% total body surface area (TBSA) over 14 days.

RESULTS

Twenty-five (27%) of 90 included patients presented with inhalation injury (median age 52 years [IQR 27], median TBSA 31.5% [IQR 21], mean ABSI-Score 7±3). At admission, only WBC demonstrated significantly higher values in the inhalation injury group (p=0.011). Acute respiratory distress syndrome (ARDS) was present in 32% without association to the severity of inhalation injury (p=0.11). WBC, CRP and PCT failed to delineate inhalation injury related inflammation from septic progression at most time points. PSP was the strongest marker to identify septic patients both by its higher values and steeper increase over time (p<0.001).

CONCLUSION

Inhalation injury leads to an inflammatory response at a systemic level with alterations of biomarkers. While routine inflammatory markers demonstrated strong interferences between inhalation injury with its associated ARDS and evolving sepsis, PSP reliably identified septic patients in a setting of inflammatory turbulences secondary to inhalation injury.

Variation in documented inhalation injury rates following burn injury in Australia and New Zealand

INTRODUCTION

The negative impact of inhalation injuries on in-hospital outcomes for burn patients is well known, but the burns community is yet to form a consensus on diagnostic criteria and clinical definitions. The diagnosis of inhalation injuries is consequently highly subjective. This study aimed to assess the variation in the rate of documented inhalation injury for adult patients in Australian and New Zealand burn units.

METHODS

Data for sequential admissions collected from eight adult burn centres across Australia and New Zealand between July 2009 and June 2016 were extracted from the Burns Registry of Australia and New Zealand (BRANZ). Inhalation injury was classified in two ways: (i) a field in the BRANZ data dictionary, and (ii) through a series of International Classification of Disease 10th Revision Australian Modification (ICD-10-AM) codes. Variation in inhalation injury prevalence was assessed using descriptive statistics, funnel plots, logistic regression, and predicted probabilities.

RESULTS

There were 11,206 admissions to BRANZ sites over the study period. Inhalation injury prevalence was the highest at Site D (13.1% for the BRANZ field and 11.8% for the ICD-10-AM codes), but there was significant variation between the contributing sites and the inhalation injury classification methods.

CONCLUSION

There is significant variation in the prevalence of documented inhalation injury among Australian and New Zealand burns units. The variation in the prevalence of documented inhalation injury across Australian and New Zealand sites reinforces the need for a consensus definition in the diagnosis of these injuries. Further work is required to improve data quality and reconcile the differences between clinical and ICD-10-AM coding prevalence before changes in clinical practice can be recommended from these data.

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.

1H-NMR Metabolomics Identifies Significant Changes in Metabolism over Time in a Porcine Model of Severe Burn and Smoke Inhalation

Burn injury initiates a hypermetabolic response leading to muscle catabolism and organ dysfunction but has not been well-characterized by high-throughput metabolomics. We examined changes in metabolism over the first 72 h post-burn using proton nuclear magnetic resonance (1H-NMR) spectroscopy and serum from a porcine model of severe burn injury. We sought to quantify the changes in metabolism that occur over time in response to severe burn and smoke inhalation in this preliminary study. Fifteen pigs received 40% total body surface area (TBSA) burns with additional pine bark smoke inhalation. Arterial blood was drawn at baseline (pre-burn) and every 24 h until 72 h post-injury or death. The aqueous portion of each serum sample was analyzed using 1H-NMR spectroscopy and metabolite concentrations were used for principal component analysis (PCA). Thirty-eight metabolites were quantified in 39 samples. Of these, 31 showed significant concentration changes over time (p < 0.05). PCA revealed clustering of samples by time point on a 2D scores plot. The first 48 h post-burn were characterized by high concentrations of histamine, alanine, phenylalanine, and tyrosine. Later timepoints were characterized by rising concentrations of 2-hydroxybutyrate, 3-hydroxybutyrate, acetoacetate, and isovalerate. No significant differences in metabolism related to mortality were observed. Our work highlights the accumulation of organic acids resulting from fatty acid catabolism and oxidative stress. Further studies will be required to relate accumulation of the four organic carboxylates identified in this analysis to outcomes from burn injury.

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.

Defining the criteria for intubation of the patient with thermal burns

OBJECTIVES

Recent studies demonstrate that burn patients are undergoing unnecessary intubations. We sought to determine the clinical criteria that predict intubations with benefit.

METHODS

This was a retrospective review of intubated adults admitted to our center with thermal burns 2008-2013. Criteria for intubation were defined as traditional criteria (suspected smoke inhalation, oropharynx soot, hoarseness, dysphagia, singed facial hair, oral edema, oral burn, non-full thickness facial burns), or ABA criteria as defined by the 2011 ABA guidelines (full thickness facial burns, stridor, respiratory distress, swelling on laryngoscopy, upper airway trauma, altered mentation, hypoxia/hypercarbia, hemodynamic instability). Patients with <26days free from mechanical ventilation (ventilator-free days (VFD)) out of 28, were deemed indicated long-term intubations. Those with ≥26 VFD were deemed unnecessary short-term intubations.

RESULTS

Of 218 patients, 151 had long-term and 67 had short-term intubations. Long-term intubation was strongly associated with ABA criteria (77.5%) compared to traditional criteria (22.5%) (p<0.001). Sensitivity of ABA criteria for long-term intubation was 77% and specificity 46%. Traditional criteria associated with long-term intubation included suspected smoke inhalation (OR 2.45 [95% CI, 1.18-5.11]), and singed facial hair (OR 2.53 [95% CI, 1.25-5.09]). The addition of these to ABA criteria created the Denver criteria, which exhibited an increased sensitivity for long-term intubations (95%), but decreased specificity (24%).

CONCLUSIONS

Intubation should be considered for patients displaying the Denver criteria, which includes full thickness facial burns, stridor, respiratory distress, swelling on laryngoscopy, upper airway trauma, altered mentation, hypoxia/hypercarbia, hemodynamic instability, suspected smoke inhalation, and singed facial hair. Patients lacking these criteria should not be intubated.

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.

Does inhalation injury predict mortality in burns patients or require redefinition?

Inhalation injury is known to be an important factor in predicting mortality in burns patients. However, the diagnosis is complicated by the heterogeneous presentation and inability to determine the severity of inhalation injury. The purpose of this study was to identify clinical features of inhalation injury that affect mortality and the values that could predict the outcome more precisely in burns patients with inhalation injury. This retrospective observational study included 676 burns patients who were over 18 years of age and hospitalized in the Burns Intensive Care Unit between January 2012 and December 2015. We analyzed variables that are already known to be prognostic factors (age, percentage of total body surface area (%TBSA) burned, and inhalation injury) and factors associated with inhalation injury (carboxyhemoglobin and PaO₂/FiO₂ [PF] ratio) by univariate and multivariate logistic regression. Age group (odds ratio [OR] 1.069, p<0.001), %TBSA burned (OR 1.100, p<0.001), and mechanical ventilation (OR 3.774, p<0.001) were identified to be significant predictive factors. The findings for presence of inhalation injury, PF ratio, and carboxyhemoglobin were not statistically significant in multivariate logistic regression. Being in the upper inhalation group, the lower inhalation group, and having a PF ratio <100 were identified to be significant predictors only in univariate logistic regression analysis (OR 4.438, p<0.001; OR 2.379, p<0.001; and OR 2.765, p<0.001, respectively). History and physical findings are not appropriate for diagnosis of inhalation injury and do not predict mortality. Mechanical ventilation should be recognized as a risk factor for mortality in burns patients with inhalation injury.

Inhalation injury caused by cornstarch dust explosion in intubated patients-A single center experience

BACKGROUND

Around 10%-20% of burned patients have inhalation injuries, and the severity of these injuries is correlated with mortality. Fiberoptic bronchoscopy is an important tool for the early diagnosis of inhalation injury. This study investigated correlations between the severity of inhalation injury and outcomes of patients involved in a cornstarch dust explosion in northern Taiwan in 2015.

METHODS

Patients with burns who were intubated after the explosion were enrolled. Their medical records were reviewed, and data including patient characteristics, percentage of total body surface area (%TBSA) burned, severity of the inhalation injury, mechanical ventilation settings, and outcomes were collected and analyzed.

RESULTS

Twenty patients underwent fiberoptic bronchoscopy during the first 24h to evaluate an inhalation injury. Their mean age was 22.4±5.5 years and the mean %TBSA burned was 55.7±19.4%. Fourteen patients had a grade 1 inhalation injury and six had a grade 2 injury. There was a higher %TBSA burned in the grade 1 group than in the grade 2 group, although the difference did not reach statistical significance (60.0±20.3% versus 45.5±13.5%, p=0.129). Compared to the grade 2 group, the grade 1 group had a significantly higher white blood cell count (29.4±9.3 versus 18.6±4.6, p=0.015) and frequency of facial burns (85.7% versus 33.3%, p=0.037). The overall intensive care unit mortality rate was 10% (n=2), with no significant intergroup difference (grade 1, 14.3% versus grade 2, 0%, p=0.192).

CONCLUSION

Although the explosion resulted in a high rate of inhalation injuries in critically ill patients, there was no significant correlation between mortality and the severity of the inhalation injuries.

Nebulized Epinephrine Limits Pulmonary Vascular Hyperpermeability to Water and Protein in Ovine With Burn and Smoke Inhalation Injury

OBJECTIVES

To test the hypothesis that nebulized epinephrine ameliorates pulmonary dysfunction by dual action-bronchodilation (β2-adrenergic receptor agonism) and attenuation of airway hyperemia (α1-adrenergic receptor agonism) with minimal systemic effects.

DESIGN

Randomized, controlled, prospective, and large animal translational studies.

SETTING

University large animal ICU.

SUBJECTS

Twelve chronically instrumented sheep.

INTERVENTIONS

The animals were exposed to 40% total body surface area third degree skin flame burn and 48 breaths of cooled cotton smoke inhalation under deep anesthesia and analgesia. The animals were then placed on a mechanical ventilator, fluid resuscitated, and monitored for 48 hours in a conscious state. After the injury, sheep were randomized into two groups: 1) epinephrine, nebulized with 4 mg of epinephrine every 4 hours starting 1 hour post injury, n = 6; or 2) saline, nebulized with saline in the same manner, n = 6.

MEASUREMENTS AND MAIN RESULTS

Treatment with epinephrine had a significant reduction of the pulmonary transvascular fluid flux to water (p < 0.001) and protein (p < 0.05) when compared with saline treatment from 12 to 48 hours and 36 to 48 hours, respectively. Treatment with epinephrine also reduced the systemic accumulation of body fluids (p < 0.001) with a mean of 1,410 ± 560 mL at 48 hours compared with 3,284 ± 422 mL of the saline group. Hemoglobin levels were comparable between the groups. Changes in respiratory system dynamic compliance, mean airway pressure, PaO2/FiO2 ratio, and oxygenation index were also attenuated with epinephrine treatment. No considerable systemic effects were observed with epinephrine treatment.

CONCLUSIONS

Nebulized epinephrine should be considered for use in future clinical studies of patients with burns and smoke inhalation injury.

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.

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.

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.

Inhalation injury: epidemiology, pathology, treatment strategies

Lung injury resulting from inhalation of smoke or chemical products of combustion continues to be associated with significant morbidity and mortality. Combined with cutaneous burns, inhalation injury increases fluid resuscitation requirements, incidence of pulmonary complications and overall mortality of thermal injury. While many products and techniques have been developed to manage cutaneous thermal trauma, relatively few diagnosis-specific therapeutic options have been identified for patients with inhalation injury. Several factors explain slower progress for improvement in management of patients with inhalation injury. Inhalation injury is a more complex clinical problem. Burned cutaneous tissue may be excised and replaced with skin grafts. Injured pulmonary tissue must be protected from secondary injury due to resuscitation, mechanical ventilation and infection while host repair mechanisms receive appropriate support. Many of the consequences of smoke inhalation result from an inflammatory response involving mediators whose number and role remain incompletely understood despite improved tools for processing of clinical material. Improvements in mortality from inhalation injury are mostly due to widespread improvements in critical care rather than focused interventions for smoke inhalation.

Morbidity associated with inhalation injury is produced by heat exposure and inhaled toxins. Management of toxin exposure in smoke inhalation remains controversial, particularly as related to carbon monoxide and cyanide. Hyperbaric oxygen treatment has been evaluated in multiple trials to manage neurologic sequelae of carbon monoxide exposure. Unfortunately, data to date do not support application of hyperbaric oxygen in this population outside the context of clinical trials. Cyanide is another toxin produced by combustion of natural or synthetic materials. A number of antidote strategies have been evaluated to address tissue hypoxia associated with cyanide exposure. Data from European centers supports application of specific antidotes for cyanide toxicity. Consistent international support for this therapy is lacking. Even diagnostic criteria are not consistently applied though bronchoscopy is one diagnostic and therapeutic tool. Medical strategies under investigation for specific treatment of smoke inhalation include beta-agonists, pulmonary blood flow modifiers, anticoagulants and antiinflammatory strategies. Until the value of these and other approaches is confirmed, however, the clinical approach to inhalation injury is supportive.

Admission chest CT complements fiberoptic bronchoscopy in prediction of adverse outcomes in thermally injured patients

In burned patients, inhalation injury can result in progressive pulmonary dysfunction, infection, and death. Although bronchoscopy is the standard for diagnosis, it only assesses the proximal airway and does not provide a comprehensive analysis of pulmonary insult. Chest radiographs have not been proven helpful in diagnosis of inhalation injury. Our hypothesis is that a CT scan alone or in conjunction with bronchoscopy can be used as a prognostic tool for critically ill burn patients, especially those with inhalation injury. The authors performed a retrospective study of all patients admitted to the U.S. Army Institute of Surgical Research Burn Center between 2002 and 2008 with chest CT within 24 hours of admission. They divided subjects into two groups, those with evidence of inhalation injury on bronchoscopy and those without. They used a radiologist's score to assess the degree of damage to the pulmonary parenchyma. The primary endpoint was a composite of pneumonia, acute lung injury/acute respiratory distress syndrome, and death. The inhalation injury group consisted of 25 patients and the noninhalation injury group of 19 patients. Groups were not different in age, TBSA burned, and percentage full-thickness burn. By multiple logistic regression, detection of inhalation injury on bronchoscopy was associated with an 8.3-fold increase in the composite endpoint. The combination of inhalation injury on bronchoscopy and a high radiologist's score was associated with a 12.7-fold increase in the incidence of the composite endpoint. Admission CT assists in predicting future lung dysfunction in burn patients.

Airway management and smoke inhalation injury in the burn patient

Smoke inhalation injury, a unique form of acute lung injury, greatly increases the occurrence of postburn morbidity and mortality. In addition to early intubation for upper-airway protection, subsequent critical care of patients who have this injury should be directed at maintaining distal airway patency. High-frequency ventilation, inhaled heparin, and aggressive pulmonary toilet are among the therapies available. Even so, immunosuppression, intubation, and airway damage predispose these patients to pneumonia and other complications.

Inhalation injury in southwest China--the evolution of care

AIM

This study aims to review the changes in management of inhalation injury and the associated reduction in mortality over the past 2 decades.

METHODS

The records of burn patients with inhalation injury hospitalised in our institute from 1986 to 2005 were retrospectively analysed. The incidence of inhalation injury and the associated mortality were analysed. Meanwhile, the relationship of inhalation injury with age, total burn area, tracheostomy intubation and mechanical ventilation were studied.

RESULTS

The incidence of inhalation injury was 8.01% in the total 10 608 hospitalised burn patients during the 20 years surveyed. Inhalation injury was always associated with large-sized burn and was more common in adults. The incidence of tracheostomy and mechanical ventilation increased from 39.46 and 30.28% in the period from 1986 to 1995 to 70.12 and 39.74% from 1996 to 2005, respectively. The overall mortality of inhalation-injured burn patients was 15.88% compared with 0.82% of the non-inhalation group. The mortality of the burn patients with inhalation injury dropped from 25.29% during the first 10 years to 11.71% during the second decade (p<0.01). Mortality secondary to inhalation injury as the lead cause decreased from 14.56 to 6.29% (p<0.01).

CONCLUSION

The care of inhalation injury has made significant progress over the past 2 decades. The early diagnosis of inhalation injury, early airway control and pulmonary function assistance with mechanical ventilation contribute to the reduction of mortality.

Management of burns of over 80% of total body surface area: a comparative study

The aim of this retrospective, comparative study was to analyse the management of extensive burns so as to decrease morbidity and mortality. Over 1987-1996, 24 people with burns >80% of total body surface area and >50% full-thickness burn were admitted to the burn unit of Anhui Medical University Hospital (group A); 30 similar admissions over 1997-2006 formed group B. No significant difference was found in age, male:female ratio, % total body surface or full-thickness burn area between the two groups. Severe shock developed in 19/24 cases in group A and 23/30 cases in group B, following inadequate fluid resuscitation, although group B received a higher mean resuscitation fluid volume during the first 24h after burn. Early excision and grafting was performed for 8/24 people in group A and 23/30 in group B. Inhalation injury was seen in 18/24 cases in group A and 28/30 cases in group B. Prophylactic tracheotomy was undergone by 8/24 casualties in group A and 22/30 in group B. Mortality in group A was significantly higher than in group B (95.8% vs. 63.3%, p<0.05) and survival was longer in group B. These results showed that refinements in burn shock resuscitation, and advances in early wound excision, skin grafting and respiratory management were associated with decreased morbidity and mortality after severe burn.

In vivo optical coherence tomography detection of differences in regional large airway smoke inhalation induced injury in a rabbit model

Smoke inhalation injury causes acute airway injury that may result in airway compromise with significant morbidity and mortality. We investigate the ability of high resolution endobronchial optical coherence tomography (OCT) to obtain real-time images for quantitatively assessing regional differences between upper tracheal versus lower tracheal and bronchial airway injury responses to smoke inhalation in vivo using a prototype spectral domain (SLD)-OCT system we constructed, and flexible fiber optic probes. 33 New Zealand White rabbits are intubated and mechanically ventilated. The treatment groups are exposed to inhaled smoke. The OCT probe is introduced through the endotracheal tube and maintained in place for 5 to 6 h. Images of airway mucosa and submucosa are obtained at baseline and at specified intervals postexposure. Starting within less than 15 min after smoke inhalation, there is significant airway thickening in the smoke-exposed animals. This is maintained over 5 h of imaging studies. The lower tracheal airway changes, correlating closely with carboxyhemoglobin levels, are much greater than upper tracheal changes. Significant differences are seen in lower trachea and bronchi after acute smoke inhalation compared to upper trachea as measured in vivo by minimally invasive OCT. OCT is capable of quantitatively detecting regional changes in airway swelling following inhalation injury.