Pathophysiology, research challenges, and clinical management of smoke inhalation injury

Advances in nanomaterial-targeted treatment of acute lung injury after burns

Acute lung injury (ALI) is a common complication in patients with severe burns and has a complex pathogenesis and high morbidity and mortality rates. A variety of drugs have been identified in the clinic for the treatment of ALI, but they have toxic side effects caused by easy degradation in the body and distribution throughout the body. In recent years, as the understanding of the mechanism underlying ALI has improved, scholars have developed a variety of new nanomaterials that can be safely and effectively targeted for the treatment of ALI. Most of these methods involve nanomaterials such as lipids, organic polymers, peptides, extracellular vesicles or cell membranes, inorganic nanoparticles and other nanomaterials, which are targeted to reach lung tissues to perform their functions through active targeting or passive targeting, a process that involves a variety of cells or organelles. In this review, first, the mechanisms and pathophysiological features of ALI occurrence after burn injury are reviewed, potential therapeutic targets for ALI are summarized, existing nanomaterials for the targeted treatment of ALI are classified, and possible problems and challenges of nanomaterials in the targeted treatment of ALI are discussed to provide a reference for the development of nanomaterials for the targeted treatment of ALI.

The impact of inhalation injury on fluid resuscitation in major burn patients: a 10-year multicenter retrospective study

BACKGROUND

It remains unclear whether additional fluid supplementation is necessary during the acute resuscitation period for patients with combined inhalational injury (INHI) under the guidance of the Third Military Medical University (TMMU) protocol.

METHODS

A 10-year multicenter, retrospective cohort study, involved patients with burns ≥ 50% total burn surface area (TBSA) was conducted. The effect of INHI, INHI severity, and tracheotomy on the fluid management in burn patients was assessed. Cumulative fluid administration, cumulative urine output, and cumulative fluid retention within 72 h were collected and systematically analyzed.

RESULTS

A total of 108 patients were included in the analysis, 85 with concomitant INHI and 23 with thermal burn alone. There was no significant difference in total fluid administration during the 72-h post-burn between the INHI and non-INHI groups. Although no difference in the urine output and fluid retention was shown in the first 24 h, the INHI group had a significantly lower cumulative urine output and a higher cumulative fluid retention in the 48-h and 72-h post-burn (all p < 0.05). In addition, patients with severe INHI exhibited a significantly elevated incidence of complications (Pneumonia, 47.0% vs. 11.8%, p = 0.012), (AKI, 23.5% vs. 2.9%, p = 0.037). For patients with combined INHI, neither the severity of INHI nor the presence of a tracheotomy had any significant influence on fluid management during the acute resuscitation period.

CONCLUSIONS

Additional fluid administration may be unnecessary in major burn patients with INHI under the guidance of the TMMU protocol.

Challenges in the Management of Large Burns

Large burns provoke profound pathophysiological changes. Survival rates of patients with large burns have improved significantly with the advancement of critical care and adaptation of early excision protocols. Nevertheless, care of large burn wounds remains challenging secondary to limited donor sites, prolonged time to wound closure, and immunosuppression. The development of skin substitutes and new grafting techniques decreased time to wound closure. Individually, these methods have limited success, but a combination of them may yield more successful outcomes. Early identification of patients with likely poor prognosis should prompt goals of care discussion and involvement of a palliative care team when possible.

Effect of sugammadex on postoperative complications in patients with severe burn who underwent surgery: a retrospective study

This retrospective study investigated the association of sugammadex with postoperative pulmonary complication risk between 2013 and 2021 in patients with severe burn of five hospitals. Postoperative pulmonary complications included atelectasis, pulmonary edema, pulmonary effusion, pneumothorax, pneumonia, pulmonary thromboembolism, respiratory failure and acute respiratory distress. To identify whether sugammadex reduced the risk of postoperative pulmonary complication in patients with severe burn who underwent surgery, Kaplan-Meier curve were used to check the difference of incidence according to surgical cases and time-varying Cox hazard regression were used to calculate the hazard ratio. The study included 1213 patients with severe burn who underwent 2259 surgeries. Postoperative pulmonary complications were occurred in 313 (25.8%) patients. Among 2259 surgeries, sugammadex was used in 649 (28.7%) surgeries. Cumulative postoperative pulmonary complication were 268 (16.6%) cases in surgeries without sugammadex, and 45 (6.9%) cases in surgeries with sugammadex, respectively (P < 0.005). The postoperative pulmonary complications risk was reduced significantly in patients who use sugammadex than those who did not use sugammadex. (Adjusted hazard ratio, 0.61; 95% confidence interval, 0.42-0.89; P = 0.011). In conclusion, sugammadex reduced risk of postoperative pulmonary complications compared with nonuse of sugammadex in patients with severe burn who underwent surgery.

Acute care for burn patients: fluids, surgery, and what else?

PURPOSE OF REVIEW

Recently published initiatives spanning the burn care spectrum have substantially changed the standard of care in burn care. The purpose of this article is to describe new impactful concepts in burn first aid, triage, resuscitation, and treatment as well as their impact on future research.

RECENT FINDINGS

First aid after burn injury traditionally consists of extinguishing the burn and applying dressings. Recent evidence suggests that applying 20 min of cool tap water to the burn wound in the first 3 h postburn mitigates burn injury extent. National burn center transfer criteria have been updated, impacting patient initial transfer and management. The adverse effects of hydroxocobalamin, a commonly used antidote for cyanide toxicity, have been delineated. Initial burn resuscitation recommendations for both volume and potentially fluid type are being reexamined. The emergence of innovative skin substitutes may improve burn survival by providing a physiologically stabilizing intermediate dressing. Finally, formal clinical practice guidelines for early mobility in the ICU after burn injury have been defined.

SUMMARY

These changes in burn care, triage, resuscitation, and treatment have challenged traditional burn care standards, created new standards, and are the basis for future prospective randomized trials.

Effects of nebulized adipose-derived mesenchymal stem cells on acute lung injury following smoke inhalation in sheep

INTRODUCTION

Treatment of ARDS caused by smoke inhalation is challenging with no specific therapies available. The aim of this study was to test the efficacy of nebulized adipose-derived mesenchymal stem cells (ASCs) in a well-characterized, clinically relevant ovine model of smoke inhalation injury.

MATERIAL AND METHODS

Fourteen female Merino sheep were surgically instrumented 5-7 days prior to study. After induction of acute lung injury (ALI) by cooled cotton smoke insufflation into the lungs (under anesthesia and analgesia), sheep were placed on a mechanical ventilator for 48 hrs and monitored for cardiopulmonary hemodynamics in a conscious state. ASCs were isolated from ovine adipose tissue. Sheep were randomly allocated to two groups after smoke injury: 1) ASCs group (n = 6): 10 million ASCs were nebulized into the airway at 1 hr post-injury; and 2) Control group (n = 8): Nebulized with saline into the airways at 1 hr post-injury. ASCs were labeled with green fluorescent protein (GFP) to trace cells within the lung. ASCs viability was determined in bronchoalveolar lavage fluid (BALF).

RESULTS

PaO2/FiO2 in the ASCs group was significantly higher than in the control group (p = 0.001) at 24 hrs. Oxygenation index: (mean airway pressure × FiO2/PaO2) was significantly lower in the ASCs group at 36 hr (p = 0.003). Pulmonary shunt fraction tended to be lower in the ASCs group as compared to the control group. GFP-labelled ASCs were found on the surface of trachea epithelium 48 hrs after injury. The viability of ASCs in BALF was significantly lower than those exposed to the control vehicle solution.

CONCLUSION

Nebulized ASCs moderately improved pulmonary function and delayed the onset of ARDS.

Protection of laryngeal mucosa and function in laryngeal burns by heat absorption of perilaryngeal tissue

OBJECTIVE

The laryngeal tissue carries most of the heat during inhalation injury. This study aims to explore the heat transfer process and the severity of injury inside laryngeal tissue by horizontally studying the temperature rise process at various anatomical layers of the larynx and observing the thermal damage in various parts of the upper respiratory tract.

METHODS

The 12 healthy adult beagles were randomly divided into four groups, and inhaled room temperature air (control group), dry hot air of 80 °C (group I), 160 °C (group II), and 320 °C (group III) for 20 min, respectively. The temperature changes of the glottic mucosal surface, the inner surface of the thyroid cartilage, the external surface of the thyroid cartilage, and subcutaneous tissue were measured every minute. All animals were immediately sacrificed after injury, and pathological changes in various parts of laryngeal tissue were observed and evaluated under a microscope.

RESULTS

After inhaling hot air of 80 °C, 160 °C and 320 °C, the increase of laryngeal temperature in each group was ΔT = 3.57 ± 0.25 °C, 7.83 ± 0.15 °C, 11.93 ± 0.21 °C. The tissue temperature was approximately uniformly distributed, and the difference was not statistically significant. The average laryngeal temperature-time curve showed that the laryngeal tissue temperature in group I and group II showed a trend of "first decrease and then increase", except that the temperature of group III directly increased with time. The prominent pathological changes after thermal burns mainly concluded necrosis of epithelial cells, loss of the mucosal layer, atrophy of submucosal glands, vasodilatation, erythrocytes exudation, and degeneration of chondrocytes. Mild degeneration of cartilage and muscle layers was also observed in mild thermal injury. Pathological scores indicated that the pathological severity of laryngeal burns increased significantly with the increase of temperature, and all layers of laryngeal tissue were seriously damaged by 320 °C hot air.

CONCLUSIONS

The high efficiency of tissue heat conduction enabled the larynx to quickly transfer heat to the laryngeal periphery, and the heat-bearing capacity of perilaryngeal tissue has a certain degree of protective effect on laryngeal mucosa and function in mild to moderate inhalation injury. The laryngeal temperature distribution was in accordance with the pathological severity, and the pathological changes of laryngeal burns provided a theoretical basis for the early clinical manifestations and treatment of inhalation injury.

Cryptotanshinone alleviates lipopolysaccharide and cigarette smoke-induced chronic obstructive pulmonary disease in mice via the Keap1/Nrf2 axis

Chronic obstructive pulmonary disease (COPD) is a major cause of morbidity worldwide. Cigarette smoking, which leads to abnormalities in the airways or alveoli and persistent obstruction of the airway's flow, is a significant risk factor of COPD. Cryptotanshinone (CTS) is the active ingredient in Salvia miltiorrhiza (Danshen) and has many pharmacological properties including anti-inflammatory, antitumor, and antioxidant properties, but its impact on COPD is uncertain. In the present study, the potential effect of CTS on COPD was investigated in a modified COPD mice model induced with cigarette smoke (CS) and lipopolysaccharide (LPS) exposure. CTS significantly reversed the decline in lung function, emphysema, inflammatory cell infiltration, small airway remodeling, pulmonary pathological damage, and airway epithelial cell proliferation in CS- and LPS-exposed mice. Additionally, CTS decreased inflammatory cytokines such as tumor necrosis factor α (TNF α), interleukins IL-6 and IL-1β, and keratinocyte chemoattractant (KC), increased the activities of superoxide dismutase (SOD), Catalase (CAT) and L-Glutathione (GSH), and repressed the expression of protein hydrolases matrix metalloprotein (MMP)- 9 and - 12 in pulmonary tissue and bronchoalveolar lavage fluid (BALF). The protective effects of CTS were also observed in human bronchial epithelial cell line BEAS-2B simulated with cigarette smoke condensate (CSC) and LPS. Mechanistically, CTS can repress the protein level of Keap1, resulting to activation of erythroid 2-related factor (Nrf2), finally alleviating COPD. In summary, the present findings demonstrated that CTS dramatically ameliorates COPD induced by CS and LPS via activating Keap1/Nrf2 pathway.

Circulatory HMGB1 is an early predictive and prognostic biomarker of ARDS and mortality in a swine model of polytrauma

Acute respiratory distress syndrome (ARDS) is a leading cause of morbidity and mortality in polytrauma patients. Pharmacological treatments of ARDS are lacking, and ARDS patients rely on supportive care. Accurate diagnosis of ARDS is vital for early intervention and improved outcomes but is presently delayed up to days. The use of biomarkers for early identification of ARDS development is a potential solution. Inflammatory mediators high-mobility group box 1 (HMGB1), syndecan-1 (SDC-1), and C3a have been previously proposed as potential biomarkers. For this study, we analyzed these biomarkers in animals undergoing smoke inhalation and 40% total body surface area burns, followed by intensive care for 72 h post-injury (PI) to determine their association with ARDS and mortality. We found that the levels of inflammatory mediators in serum were affected, as well as the degree of HMGB1 and Toll-like receptor 4 (TLR4) signal activation in the lung. The results showed significantly increased HMGB1 expression levels in animals that developed ARDS compared with those that did not. Receiver operating characteristic (ROC) analysis showed that HMGB1 levels at 6 h PI were significantly associated with ARDS development (AUROC=0.77) and mortality (AUROC=0.82). Logistic regression analysis revealed that levels of HMGB1 ≥24.10 ng/ml are associated with a 13-fold higher incidence of ARDS [OR:13.57 (2.76-104.3)], whereas the levels of HMGB1 ≥31.39 ng/ml are associated with a 12-fold increase in mortality [OR: 12.00 (2.36-93.47)]. In addition, we found that mesenchymal stem cell (MSC) therapeutic treatment led to a significant decrease in systemic HMGB1 elevation but failed to block SDC-1 and C3a increases. Immunohistochemistry analyses showed that smoke inhalation and burn injury induced the expression of HMGB1 and TLR4 and stimulated co-localization of HMGB1 and TLR4 in the lung. Interestingly, MSC treatment reduced the presence of HMGB1, TLR4, and the HMGB1-TLR4 co-localization. These results show that serum HMGB1 is a prognostic biomarker for predicting the incidence of ARDS and mortality in swine with smoke inhalation and burn injury. Therapeutically blocking HMGB1 signal activation might be an effective approach for attenuating ARDS development in combat casualties or civilian patients.

Introduction: The Multidisciplinary Team Approach to Burn Care

Since the first burn units were established following World War II, great advances in understanding and treating burn shock, smoke inhalation injury, pneumonia, and invasive burn wound infections, and in achieving early burn-wound closure, have greatly decreased postburn morbidity and mortality. These advances were the result of closely integrated multidisciplinary teams of clinicians and researchers. The team approach to burns is a model for success in the care of any challenging clinical problem.

A synthetic porphyrin as an effective dual antidote against carbon monoxide and cyanide poisoning

Simultaneous poisoning by carbon monoxide (CO) and hydrogen cyanide is the major cause of mortality in fire gas accidents. Here, we report on the invention of an injectable antidote against CO and cyanide (CN^-) mixed poisoning. The solution contains four compounds: iron(III)porphyrin (Fe^IIITPPS, F), two methyl-β-cyclodextrin (CD) dimers linked by pyridine (Py3CD, P) and imidazole (Im3CD, I), and a reducing agent (Na₂S₂O₄, S). When these compounds are dissolved in saline, the solution contains two synthetic heme models including a complex of F with P (hemoCD-P) and another one of F with I (hemoCD-I), both in their iron(II) state. hemoCD-P is stable in its iron(II) state and captures CO more strongly than native hemoproteins, while hemoCD-I is readily autoxidized to its iron(III) state to scavenge CN^- once injected into blood circulation. The mixed solution (hemoCD-Twins) exhibited remarkable protective effects against acute CO and CN^- mixed poisoning in mice (~85% survival vs. 0% controls). In a model using rats, exposure to CO and CN^- resulted in a significant decrease in heart rate and blood pressure, which were restored by hemoCD-Twins in association with decreased CO and CN^- levels in blood. Pharmacokinetic data revealed a fast urinary excretion of hemoCD-Twins with an elimination half-life of 47 min. Finally, to simulate a fire accident and translate our findings to a real-life scenario, we confirmed that combustion gas from acrylic cloth caused severe toxicity to mice and that injection of hemoCD-Twins significantly improved the survival rate, leading to a rapid recovery from the physical incapacitation.

NUCLEAR FACTOR-ERYTHROID-2-RELATED FACTOR REGULATES SYSTEMIC AND PULMONARY BARRIER FUNCTION AND IMMUNE PROGRAMMING AFTER BURN AND INHALATION INJURY

ABSTRACT

Major burn injury is associated with systemic hyperinflammatory and oxidative stresses that encompass the wound, vascular, and pulmonary systems that contribute to complications and poor outcomes. These stresses are exacerbated if there is a combined burn and inhalation (B+I) injury, which leads to increases in morbidity and mortality. Nuclear factor-erythroid-2-related factor (NRF2) is a transcription factor that functions to maintain homeostasis during stress, in part by modulating inflammation and oxidative injury. We hypothesized that the NRF2-mediated homeostasis after burn alone and combined B-I injury is insufficient, but that pharmacological activation of the NRF2 pathway has the potential to reduce/reverse acute hyper inflammatory responses. We found that, after burn and B+I injury, Nrf2 -/- mice have higher mortality and exhibit greater pulmonary edema, vascular permeability, and exacerbated pulmonary and systemic proinflammatory responses compared with injured wild-type (WT) controls. Transcriptome analysis of lung tissue revealed specific Nrf2 -dependent dysregulated immune pathways after injury. In WT mice, we observed that B+I injury induces cytosolic, but not nuclear, accumulation of NRF2 protein in the lung microenvironment compared with sham-injured controls. Bardoxolone methyl (CDDO-Me)-containing microparticles (CDDO-MPs) were developed that allow for dilution in saline and stable release of CDDO-Me. When delivered intraperitoneally into mice 1 hour after B+I injury, CDDO-MPs significantly reduced mortality and cytokine dysfunction compared with untreated B-I animals. These data implicate the role of NRF2 regulation of pulmonary and systemic immune dysfunction after burn and B+I injury, and also a deficiency in controlling immune dysregulation. Selectively activating the NRF2 pathway may improve clinical outcomes in burn and B+I patients.

Survival and analysis of prognostic factors for severe burn patients with inhalation injury: based on the respiratory SOFA score

BACKGROUND

It is important to determine the severity of inhalation injury in severely burned patients. The oxygenation index PaO₂/FiO₂(PF) ratio is a key clinical indicator of inhalation injury. Sequential organ failure assessment (SOFA) is developed to assess the acute incidence of critical illness in the population. We hope to provide an assessment of survival or prognostic factor for severely burned patients with inhalation injury based on the respiratory SOFA score.

METHODS

This is a retrospective cohort study of all admissions to Department of Burn and Plastic Surgery at West China Hospital of Sichuan University from July 2010 to March 2021. Data was analyzed using Cox regression models to determine significant predictors of mortality. Survival analysis with time to death event was performed using the Kaplan-Meier survival curve with the log-rank test. All potential risk factors were considered independent variables, while survival was considered the risk dependent variable.

RESULTS

One hundred eighteen severe burn patients with inhalation injury who met the inclusion and exclusion criteria were admitted, including men accounted for 76.3%. The mean age and length of stay were 45.9 (14.8) years and 44.3 (38.4) days. Flame burns are the main etiology of burn (74.6%). Patients with the respiratory SOFA score greater than 2 have undergone mechanical ventilation. Univariate Kaplan-Meier analysis identified age, total body surface area burned (TBSA), ICU admission and the respiratory SOFA score as significant factors on survival. Cox regression analysis showed that TBSA and the respiratory SOFA score were associated with patient survival (p < 0.001). In some patients with severe burns and inhalation damage, the survival probability drops to less than 10% (TBSA greater than 80%: 8.9% and respiratory SOFA score greater than 2: 5.6%). This study statistically found that the TBSA with the respiratory SOFA score model (AUROC: 0.955) and the rBaux score (AUROC: 0.927) had similar predictive value (p = 0.175).

CONCLUSION

The study indicates that a high respiratory system SOFA score was identified as a strong and independent predictor of severely burned patients with inhalation injury during hospitalization. When combined with TBSA, the respiratory SOFA scores can dynamically assess the severity of the patient's lung injury and improve the predictive level.

Protective Effect of Nebulized Heparin in the Animal Models of Smoke Inhalation Injury: A Meta-analysis and Systematic Review of Experimental Studies

The pathophysiological mechanism of abnormal coagulation can result from smoke inhalation injury (SII). Heparin nebulization is a common treatment for lung disorders. This study aimed to use meta-analysis in animal models to examine the effectiveness of atomized heparin on SII. For our online searches, we used the Cochrane Central Register of Controlled Trials, PubMed, Web of Science, Chinese National Knowledge Infrastructure, Chinese BioMedical Literature Database, and Wanfang Database up to January 2022. Data for SII were retrieved and compared to control animals. The studies' findings were determined by combining standardized mean difference (SMD) analysis with 95% confidence intervals (CIs). The findings showed that as compared to the control group, the heparin-treated group had a lower death rate (relative risk 0.42; 95% CI 0.22, 0.80; p < .05). The meta-analysis demonstrated favorable changes in lung physiology, including PaO2/FiO2 (SMD 1.04; 95% CI 0.65, 1.44; p < .001), lung wet-to-dry weight ratio (SMD -1.83; 95% CI -2.47, -1.18; p < .001), and pulmonary shunt Qs/Qt (SMD -0.69; 95% CI -1.29, -0.08; p < .05) after heparin nebulization for lung injury. The present data indicated that pulmonary artery mean pressure in the heparin therapy group was significantly lowered after 24 and 48 hours of therapy, suggesting that the cardiovascular system could recover following heparin treatment. As a result, heparin nebulization appeared to be more effective against SII and improved cardiopulmonary function compared to the control group. Graphical Abstract.

[Carbon monoxide intoxication-New aspects and current guideline-based recommendations]

Carbon monoxide poisoning is a common and potentially life-threatening intoxication, showing an interindividual variety of unspecific symptoms as well as late neurological and other sequelae. Two new German guidelines (S2k guidelines diagnosis and treatment of carbon monoxide poisoning as well as S3 guidelines oxygen therapy in the acute care of adult patients) focus on current evidence-based information on diagnostics as well as therapeutic options with considerable uncertainty remaining. This review summarizes current information and presents a flow scheme for daily practical use.

Combined biological effects and lung proteomics analysis in mice reveal different toxic impacts of electronic cigarette aerosol and combustible cigarette smoke on the respiratory system

Combustible cigarettes produce many toxic substances that have been linked to diseases, such as lung cancer and chronic obstructive pulmonary disease. For those smokers unable or unwilling to quit, electronic cigarettes (e-cigarettes) could be used as an alternative to cigarettes. However, the effects and mechanisms of e-cigarette aerosol (ECA) on respiratory function have not been fully elucidated, and in vivo studies of its safety are limited compared to cigarette smoke (CS). In this article, we chose nicotine levels as dosing references and C57BL/6 mice for a 10-week subchronic inhalation toxicity study. A comprehensive set of toxicological endpoints was used to study the effect of exposure. Both CS (6 mg/kg) and ECA (6 or 12 mg/kg) inhalation had decreased the animal’s lung function and increased levels of inflammation markers, along with pathological changes in the airways and lungs, with ECA displaying a relatively small effect at the same dose. Proteomic analysis of lung tissue showed greater overall protein changes by CS than that of ECA, with more severe inflammatory network perturbations. Compared with ECA, KEGG analysis of CS revealed upregulation of more inflammatory and virus-related pathways. Protein–protein interactions (PPI) showed that both ECA and CS significantly changed ribosome and complement system-related proteins in mouse lung tissue. The results support that e-cigarette aerosol is less harmful to the respiratory system than cigarette smoke at the same dose using this animal model, thus providing additional evidence for the relative safety of e-cigarettes.

Advantages and Disadvantages of Using Small and Large Animals in Burn Research: Proceedings of the 2021 Research Special Interest Group

Multiple animal species and approaches have been used for modeling different aspects of burn care, with some strategies considered more appropriate or translatable than others. On April 15, 2021, the Research Special Interest Group of the American Burn Association held a virtual session as part of the agenda for the annual meeting. The session was set up as a pro/con debate on the use of small versus large animals for application to four important aspects of burn pathophysiology: burn healing/conversion; scarring; inhalation injury; and sepsis. For each of these topics, 2 experienced investigators (one each for small and large animal models) described the advantages and disadvantages of using these preclinical models. The use of swine as a large animal model was a common theme due to anatomic similarities with human skin. The exception to this was a well-defined ovine model of inhalation injury; both of these species have larger airways which allow for incorporation of clinical tools such as bronchoscopes. However, these models are expensive and demanding from labor and resource standpoints. Various strategies have been implemented to make the more inexpensive rodent models appropriate for answering specific questions of interest in burns. Moreover, modelling burn-sepsis in large animals has proven difficult. It was agreed that the use of both small and large animal models have merit for answering basic questions about the responses to burn injury. Expert opinion and the ensuing lively conversations are summarized herein, which we hope will help inform experimental design of future research.

LncRNA MALAT1 Participates in Protection of High-Molecular-Weight Hyaluronan against Smoke-Induced Acute Lung Injury by Upregulation of SOCS-1

Smoke-induced acute lung injury (ALI) is a grievous disease with high mortality. Despite advances in medical intervention, no drug has yet been approved by the Food and Drug Administration (FDA) for ALI. In this study, we reported that pretreatment with high-molecular-weight hyaluronan (1600 kDa, HA1600) alleviated pulmonary inflammation and injury in mice exposed to smoke and also upregulated long non-coding RNA (lncRNA) metastasis-associated lung adenocarcinoma transcript 1 (MALAT1), as well as suppressor of cytokine signaling-1 (SOCS-1), in the lung tissues. Next, we overexpressed MALAT1 in the lungs by intratracheal administration of adenovirus cloned with MALAT1 cDNA and found that the survival of mice after smoke exposure was improved. Moreover, pulmonary overexpression of MALAT1 ameliorated smoke-induced ALI in mice and elevated the level of SOCS-1 in the lungs. In conclusion, the results pointed out that HA1600 exerted a protective effect against smoke-induced ALI through increasing the MALAT1 level and the subsequent SOCS-1 expression. Our study provides a potential therapeutic approach to smoke-induced ALI and a novel insight into the mechanism of action of HA1600.

In vitro and vivo study of tranilast protects from acute respiratory distress syndrome and early pulmonary fibrosis induced by smoke inhalation

BACKGROUND

Tranilast (N-[3＇,4＇-dimethoxycinnamoyl]-anthranilic acid) is an analog of a tryptophan metabolite. It was identified with anti-inflammatory and antifibrotic activities, and used in the treatment of a variety of diseases, such as anti - allergy, bronchial asthma, and hypertrophic scars. As a drug with few adverse reactions, tranilast has attracted great attention, but its application is limited due to the uncertainty of dosages and mechanisms. In this study, the protection effects of different doses of tranilast on smoke inhalation mediated lung injury on rats, and on the damage of three kinds of lung cells in vitro were investigated.

METHOD

In vivo, Sprague-Dawley rats were randomly divided into sham group, smoke group (rats were exposed to pine sawdust smoke three times, each time for 5 min), different doses of tranilast treatment group (doses were 100 mg/kg, 200 mg/kg and 300 mg/kg, ip.) and placebo group. After 1, 3 and 7 days, pulmonary function, pathologic injury by HE staining, cytokines and oxidative stress level by kits were determined. At 7days, lung fibrosis was assessed by Masson's trichrome staining and the level of hydroxyproline (HYP). In vitro, three kinds of lung cells from normal rats were isolated: type II alveolar epithelial cells (AT-II), pulmonary microvascular endothelial cells (PMVECs) and pulmonary fibroblasts (PFs). To investigate the potential effects of tranilast on cell proliferation, cell cycle and cytokine production of three kinds of lung cells exposed to smoke.

RESULTS

Compared with smoke group and placebo group, tranilast treatment significantly reduced histopathological changes (such as pulmonary hemorrhage, edema and inflammatory cell infiltration, etc.), significantly reduced histopathological score (p < 0.05), increased arterial oxygen partial pressure, and decreased the levels of IL-1β, TNF-α, TGF-β1 (p < 0.05), oxidative stress and the expression of nuclear transcription factor κB (NF-κB) smoke exposed rats (p < 0.01). In particular, the effect of 200 mg/kg dose was more prominent. In vitro, smoke induced AT-II and PMVECs apoptosis, improved PFs proliferation (p < 0.01), activity of SOD and decreased the content of MDA (p < 0.01). However, tranilast seems to be turning this trend well. The inflammatory factor IL-11β, TNF-α and TGF-β1, and the expression of NF-κB were significantly lower in the tranilast treatment than in the smoke group (p < 0.01).

CONCLUSION

This study indicates that tranilast had a protective effect on acute respiratory distress syndrome and early pulmonary fibrosis of rats in vivo. In addition, tranilast promotes proliferation of AT-II and PMVECs but inhibits PFs proliferation, down-regulates secretion of inflammatory cytokines and alleviates oxidative stress of AT-II, PMVECs and PFs after smoke stimuli in vitro.

A Rationale for Safe Ventilation with Inhalation Injury: An Editorial Review

Lung injury from smoke inhalation manifests as airway and parenchymal damage, at times leading to the acute respiratory distress syndrome. From the beginning of this millennium, the approach to mechanical ventilation in the patient with ARDS was based on reduction of tidal volume to 6 milliliters/kilogram of ideal body weight, maintaining a ceiling of plateau pressure, and titration of driving pressure (plateau pressure minus PEEP). Beyond these broad constraints, there is little specification for the mechanics of ventilator settings, consideration of the metabolic impact of the disease process on the patient, or interaction of patient disease and ventilator settings. Various studies suggest that inhomogeneity of lung injury, which increases the risk of regional lung trauma from mechanical ventilation, may be found in the patient with smoke inhalation. We now appreciate that energy transfer principles may affect optimal ventilator management and come into play in damaged heterogenous lungs. Mechanical ventilation in the patient with inhalation injury should consider various factors. Self-injurious respiratory demand by the patient can be reduced using analgesia and sedation. Dynamic factors beginning with rate management can reduce the incidence of potentially damaging ventilation. Moreover, preclinical study is underway to examine the flow of gas based on the ventilator mode selected, which may also be a factor triggering regional lung injury.

Analysis of risk factors of mortality for pediatric burned patients with inhalation injury and comparison of different treatment protocols

BACKGROUND

We present our approach of pediatric burned patients with the suspicion of inhalation injury.

METHODS

This retrospective study was conducted on children with the suspicion of inhalation injury admitted to our burn center from December 2009 to December 2019. We collected data on patient demographics, total burn surface area (TBSA), presence of inhalation injury, level of carboxyhemoglobin, grade of inhalation injury, duration of mechanical ventilation, reintubation rate, total length of hospital stay, and the mortality rate. We also reviewed the required treatment of patients with inhalation injury.

RESULTS

A total of sixty pediatric burn patients were suspected inhalation injury were included in this retrospective study. 40 pa-tients included in the study were male. Age average of the patients was 87.7 months. Total burned surface area average was 32%. 46 of these patients had inhalation injury. Patients with larger cutaneous burn and needed early intubation have a higher risk of inhalation injury. There was no significant relation between inhalation injury grades and mortality and treatment protocols. Higher levels of car-boxyhemoglobin and larger TBSA are the risk factors for mortality at univariate analysis. Pediatric patient with inhalation injury whose TBSA is higher than 47.5% has a 5 times higher risk of mortality at multivariate analysis.

CONCLUSION

This study demonstrated that TBSA is the risk factor that independently affects the mortality in pediatric patients with inhalation injury. Among the patients with higher than 47.5% burn surface area, the mortality rate rises 5 times.

Risk Factors For Death And Prognosis Value Of Revised Baux Score For Burn Patients With Inhalation Injury

A retrospective study was conducted on 314 burn patients with inhalation injury admitted to the National Burn Hospital during the period 2015-2019. The results showed that adult and male was predominant (81.9% and 77.7%), with burns mostly caused by flame (93.6%) and burn extent of 68.6±24.3% and deep burn area of 44.6±25.2% total body surface area. Rate of required mechanical ventilation patients was 95.22%. Common complications were multiple organ failure (41.9%), pneumonia (29.9%), ARDS (25.5%) and septic shock (23.8%), with a mortality rate of 85.4%. Multivariate logistic analysis indicated that burn extent and age were independent risk factors for death of patients with inhalation injury. SMR of rBaux score was 1.01 with AUC of 0.84, Youden index 113, sensitivity 82.09%, specificity 70.21%. The SMR of adult and elderly patients was relatively close to 1 (1 and .97 respectively). In addition, the AUC value for the elderly was highest (.95) followed by adult patients (.84). However, predicting the value of rBaux on children with inhalation injury was quite low (SMR=1.57; AUC = 0.4). There is a need to determine an optimal prognosis score for children with inhalation injury.

The expression profile of lung long non-coding RNAs and mRNAs in a mouse model of smoke inhalation injury

To study the potential expression of lung long non-coding RNAs (lncRNAs) and mRNAs during smoke inhalation injury (SII), using a SII mouse model that we created in our previous work. Microarray was used to investigate the lncRNAs and mRNAs profiles. A bioinformatics analysis was performed. Changes in the top 10 down-regulated and 10 up-regulated lncRNAs were validated using Quantitative Reverse Transcription-PCR (RT-qPCR). The acute lung injury (ALI) mouse model was successfully induced by smoke inhalation, as confirmed by the aberrantly modified cell numbers of red blood cells and neutrophils counts, increased levels of TNF-α, IL-1β, Bax, caspase-7, caspase-3, and decreased Bcl-2 content in lung tissues. When compared to the control mice, 577 lncRNAs and 517 mRNAs were found to be aberrantly expressed in the SII mice. According to the Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, the altered mRNAs were enriched in acute-phase response, oxidoreductase activity, oxidation-reduction process, glutathione metabolism, the wnt signaling pathway, and ferroptosis. A lncRNA-related competitive endogenous RNA (ceRNA) network, including 383 lncRNAs, 318 MicroRNAs (miRNAs), and 421 mRNAs specific to SII, was established. The changes in NONMMUT026843.2, NONMMUT065071.2, ENSMUST00000235858.1, NONMMUT131395.1, NONMMUT122516.1, NONMMUT057916.2, and NONMMUT013388.2 in the lung matched the microarray results. Our findings help to provide a more comprehensive understanding of the pathogenesis of SII as well as new insights into potential therapeutic targets.

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.

Environmental Factors

The acute respiratory distress syndrome (ARDS) remains a major cause of morbidity and mortality in the intensive care unit. Improving outcomes depends on not only evidence-based care once ARDS has already developed but also preventing ARDS incidence. Several environmental exposures have now been shown to increase the risk of ARDS and related adverse outcomes. How environmental factors impact the risk of developing ARDS is a growing and important field of research that should inform the care of individual patients as well as public health policy.

Acute respiratory distress syndrome caused by carbon monoxide poisoning and inhalation injury recovered after extracorporeal membrane oxygenation along with direct hemoperfusion with polymyxin B-immobilized fiber column: a case report

BACKGROUND

Inhalation injury from smoke or chemical products and carbon monoxide poisoning are major causes of death in burn patients from fire accidents. Respiratory tract injuries from inhalation injury and carbon monoxide poisoning can lead to acute respiratory distress syndrome and cytokine storm syndrome. In the case of acute respiratory failure needing mechanical ventilation accompanied by cytokine storm, mortality is high and immediate adequate treatment at the emergency department is very important.

CASE PRESENTATION

This report describes a case of acute respiratory distress syndrome and cytokine storm followed by carbon monoxide poisoning in a 34-year-old Korean male patient who was in a house fire, and was successfully treated by extracorporeal membrane oxygenation and direct hemoperfusion with polymyxin B-immobilized fiber column at emergency department.

CONCLUSIONS

To prevent mortality in acute respiratory distress syndrome with cytokine storm from inhalation injury and to promote a better prognosis, we suggest that early implication of extracorporeal membranous oxygenation along with direct hemoperfusion with polymyxin B-immobilized fiber column even at the emergency department should be considered.

Rat model of smoke inhalation-induced acute lung injury

BACKGROUND

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a lethal disease with limited therapeutic options and an unacceptably high mortality rate. Understanding the complex pathophysiological processes involved in the development of ALI/ARDS is critical for developing novel therapeutic strategies. Smoke inhalation (SI) injury is the leading cause of morbidity and mortality in patients with burn-associated ALI/ARDS; however, to our knowledge few reliable, reproducible models are available for pure SI animal model to investigate therapeutic options for ALI/ARDS without the confounding variables introduced by cutaneous burn or other pathology.

OBJECTIVE

To develop a small animal model of pure SI-induced ALI and to use this model for eventual testing of novel therapeutics for ALI.

METHODS

Rats were exposed to smoke using a custom-made smoke generator. Peripheral oxygen saturation (SpO₂), heart rate, arterial blood gas, and chest X-ray (CXR) were measured before and after SI. Wet/dry weight (W/D) ratio, lung injury score and immunohistochemical staining of cleaved caspase 3 were performed on harvested lung tissues of healthy and SI animals.

RESULTS

The current study demonstrates the induction of ALI in rats after SI as reflected by a significant, sustained decrease in SpO₂ and the development of diffuse bilateral pulmonary infiltrates on CXR. Lung tissue of animals exposed to SI showed increased inflammation, oedema and apoptosis as reflected by the increase in W/D ratio, injury score and cleaved caspase 3 level of the harvested tissues compared with healthy animals.

CONCLUSION

We have successfully developed a small animal model of pure SI-induced ALI. This model is offered to the scientific community as a reliable model of isolated pulmonary SI-induced injury without the confounding variables of cutaneous injury or other systemic pathology to be used for study of novel therapeutics or other investigation.

Edaravone combined with dexamethasone exhibits synergic effects on attenuating smoke-induced inhalation lung injury in rats

Inhalational lung injury often leads to morbidity and mortality during fire disasters. In this study, we aimed to evaluate the protective effects of edaravone combined with dexamethasone on smoke-induced inhalational lung injury. Sprague-Dawley rats were divided into five groups, namely, the control, model (inhalation), and three treatment groups (edaravone, dexamethasone, and edaravone combined with dexamethasone). After drug intervention in the acute lung injury model, arterial blood gas, wet:dry weight ratio of the lung tissue, bronchoalveolar lavage fluid, and pulmonary histopathology were determined. The production of reactive oxygen species (ROS), mitochondrial membrane potential (MMP), inflammatory cytokines, peroxidase and apoptosis were further analyzed to explore the underlying mechanisms. The results of blood gas and inflammatory cytokine analysis and the histopathological data demonstrated that edaravone combined with dexamethasone had obvious protective effects on smoke infiltration and tissue injury. Moreover, after the co-administration of edaravone and dexamethasone, malondialdehyde and myeloperoxidase levels in the lung tissue decreased, whereas those of glutathione peroxidase and superoxide dismutase were elevated. In addition, this drug combination could inhibit smoke-induced apoptosis in lung tissues by reducing the cleavage of caspase-3, caspase-9, and poly ADP-ribose polymerase (PARP), and also reverse smoke-mediated mitochondrial dysfunction, including ROS generation, loss of MMP, early release of cytochrome C, second mitochondrial activator of caspases, and apoptosis-inducing factor. In conclusion, edaravone combined with dexamethasone had a protective effect on smoke-induced inhalational lung injury in rats and can be further explored as an attractive therapeutic option for the treatment of smoke inhalation-induced pulmonary dysfunction.

Club Cell Protein, CC10, Attenuates Acute Respiratory Distress Syndrome Induced by Smoke Inhalation

OBJECTIVES

To evaluate the dose effects of Recombinant human Club cell 10-kDa protein (rhCC10) on lung function in a well-characterized ovine model of acute respiratory distress syndrome (ARDS) induced by smoke inhalation injury (SII); specifically, the potential of rhCC10 protein to control the inflammatory response and protect pulmonary tissue and function following SII.

DESIGN

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

SETTING

University large animal intensive care unit.

SUBJECTS

Thirty-six adult female sheep were surgically prepared and allocated into five groups (Sham (no SII), n = 6; 1 mg/kg/d CC10, n = 8; 3 mg/kg/d CC10, n = 7; 10 mg/kg/d CC10, n = 8; Control SII, n = 7).

INTERVENTIONS

All groups except the sham group were subjected to SII with cooled cotton smoke. Then, the animals were placed on a ventilator, treated with 1, 3, and 10 mg/kg/d of intravenous rhCC10 or vehicle, divided evenly into two administrations per day every 12 h, fluid resuscitated, and monitored for 48 h in a conscious state.

MEASUREMENTS AND MAIN RESULTS

The group treated with 10 mg/kg/d rhCC10 attenuated changes in the following variables: PaO2/FiO2 ratio, oxygenation index, and peak inspiratory pressure; neutrophil content in the airway and myeloperoxidase levels; obstruction of the large and small airways; systemic leakage of fluid and proteins, and pulmonary edema.

CONCLUSIONS

In this study, high-dose rhCC10 significantly attenuated ARDS progression and lung dysfunction and significantly reduced systemic extravasation of fluid and proteins, normalizing fluid balance. Based on these results, rhCC10 may be considered a novel therapeutic option for the treatment of SII-induced ARDS.

Development of novel nanofibers targeted to smoke-injured lungs

Smoke inhalation injury is associated with significant mortality and current therapies remain supportive. The purpose of our study was to identify proteins upregulated in the lung after smoke inhalation injury and develop peptide amphiphile nanofibers that target these proteins. We hypothesize that nanofibers targeted to angiotensin-converting enzyme or receptor for advanced glycation end products will localize to smoke-injured lungs.

METHODS

Five targeting sequences were incorporated into peptide amphiphile monomers methodically to optimize nanofiber formation. Nanofiber formation was assessed by conventional transmission electron microscopy. Rats received 8 min of wood smoke. Levels of angiotensin-converting enzyme and receptor for advanced glycation end products were evaluated by immunofluorescence. Rats received the targeted nanofiber 23 h after injury via tail vein injection. Nanofiber localization was determined by fluorescence quantification.

RESULTS

Peptide amphiphile purity (>95%) and nanofiber formation were confirmed. Target proteins were increased in smoke inhalation versus sham (p < 0.001). After smoke inhalation and injection of targeted nanofibers, we found a 10-fold increase in angiotensin-converting enzyme-targeted nanofiber localization to lung (p < 0.001) versus sham with minimal localization of non-targeted nanofiber (p < 0.001).

CONCLUSIONS

We synthesized, characterized, and evaluated systemically delivered targeted nanofibers that localized to the site of smoke inhalation injury in vivo. Angiotensin-converting enzyme-targeted nanofibers serve as the foundation for developing a novel nanotherapeutic that treats smoke inhalation lung injury.

Omega-7 oil increases telomerase activity and accelerates healing of grafted burn and donor site wounds

This study investigated the efficacy of Omega-7 isolated from the sea buckthorn oil (Polyvit Co., Ltd, Gangar Holding, Ulaanbaatar, Mongolia) in ovine burn wound healing models. In vitro, proliferation (colony-forming rate) and migration (scratch) assays using cultured primary ovine keratinocytes were performed with or without 0.025% and 0.08% Omega-7, respectively. The colony-forming rate of keratinocytes in the Omega-7 group at 72 and 96 h were significantly higher than in the control (P < 0.05). The percentage of closure in scratch assay in the Omega-7 group was significantly higher than in the control at 17 h (P < 0.05). In vivo, efficacy of 4% Omega-7 isolated from buckthorn oil was assessed at 7 and 14 days in grafted ovine burn and donor site wounds. Telomerase activity, keratinocyte growth factor, and wound nitrotyrosine levels were measured at day 14. Grafted sites: Un-epithelialized raw surface area was significantly lower and blood flow was significantly higher in the Omega-7-treated sites than in control sites at 7 and 14 days (P < 0.05). Telomerase activity and levels of keratinocyte growth factors were significantly higher in the Omega-7-treated sites after 14 days compared to those of control (P < 0.05). The wound 3-nitrotyrosine levels were significantly reduced by Omega-7. Donor sites: the complete epithelialization time was significantly shorter and blood flow at day 7 was significantly higher in the Omega-7-treated sites compared to control sites (P < 0.05). In summary, topical application of Omega-7 accelerates healing of both grafted burn and donor site wounds. Omega-7 should be considered as a cost-efficient and effective supplement therapy for burn wound healing.

ATS Core Curriculum 2020. Pediatric Pulmonary Medicine

The American Thoracic Society Core Curriculum updates clinicians annually in adult and pediatric pulmonary disease, medical critical care, and sleep medicine, in a 3- to 4-year recurring cycle of topics. These topics will be presented at the 2020 International Conference. Below is the pediatric pulmonary medicine core, including pediatric hypoxemic respiratory failure; modalities in noninvasive management of chronic respiratory failure in childhood; surgical and nonsurgical management of congenital lung malformations; an update on smoke inhalation lung injury; an update on vaporizers, e-cigarettes, and other electronic delivery systems; pulmonary complications of sarcoidosis; pulmonary complications of congenital heart disease; and updates on the management of congenital diaphragmatic hernia.

Advances in airway management and mechanical ventilation in inhalation injury

PURPOSE OF REVIEW

Airway management, mechanical ventilation, and treatment of systemic poisoning in burn patients with inhalation injury remains challenging. This review summarizes new concepts as well as open questions.

RECENT FINDINGS

Several life-threatening complications, such as airway patency impairment and respiratory insufficiency, can arise in burn patients and require adequate and timely airway management. However, unnecessary endotracheal intubation should be avoided. Direct visual inspection via nasolaryngoscopy can guide appropriate airway management decisions. In cases of lower airway injury, bronchoscopy is recommended to remove casts and estimate the extent of the injury in intubated patients. Several mechanical ventilation strategies have been studied. An interesting modality might be high-frequency percussive ventilation. However, to date, there is no sound evidence that patients with inhalation injury should be ventilated with modes other than those applied to non-burn patients. In all burn patients exposed to enclosed fire, carbon monoxide as well as cyanide poisoning should be suspected. Carbon monoxide poisoning should be treated with an inspiratory oxygen fraction of 100%, whereas cyanide poisoning should be treated with hydroxocobalamin.

SUMMARY

Burn patients need specialized care that requires specific knowledge about airway management, mechanical ventilation, and carbon monoxide and cyanide poisoning.

Pathology of Free-Ranging and Captive Brazilian Anteaters

There is little information on the anatomical pathology of Brazilian anteaters. Considering the relevance of knowledge of diseases of these species for their conservation, the aim of this study was to describe pathological changes in 99 captive and free-ranging anteaters from the Brazilian states of São Paulo, Minas Gerais, Bahia, Mato Grosso do Sul and Amazonas. Forty-two animals were killed on roads and 10 died from burns injuries. Other significant conditions included the metabolic diseases of iron storage disease, tissue mineralization and taurine deficiency, protozoan and metazoan infections, candidiasis, sporotrichosis, clostridiosis and proliferative disorders including squamous cell carcinoma.

Nebulized Heparin for Adult Patients With Smoke Inhalation Injury: A Review of the Literature

Objective: To review the clinical effects of nebulized heparin and N-acetylcysteine (NAC) in patients with smoke inhalation injury (IHI) and provide recommendations for use. Data Sources: A search of PubMed, MEDLINE, and Scopus databases was completed from database inception through April 15, 2020, using terms: heparin, acetylcysteine, smoke inhalation injury, and burn injury. Study Selection and Data Extraction: All studies pertaining to efficacy and safety of nebulized heparin and/or NAC for IHI in adult patients were evaluated. Reference lists were reviewed for additional publications. Nonhuman studies, non-English, and case report publications were excluded. Data Synthesis: Eight studies were included. Four demonstrated positive outcomes, 3 demonstrated no benefit or possible harm, and 1 assessed safety. Supporting trials treated patients within 48 hours of injury with 10 000 units of nebulized heparin with NAC for 7 days or until extubation. Two trials with negative findings treated patients within 72 hours, or unspecified, with 5000 units of nebulized heparin with NAC for 7 days, while the third used 25 000 units within 36 hours but was grossly underpowered for analysis. Clinical findings include reduced duration of mechanical ventilation and improved lung function with possible increase risk of pneumonia and no evidence of increased bleeding risk. Conclusions: Nebulized heparin may improve oxygenation and reduce duration of mechanical ventilation in IHI. If nebulized heparin is used, 10 000 units every 4 hours alternating with NAC and albuterol at 4-hour intervals is recommended. Sterile technique should be emphasized. Monitoring for bronchospasm or new-onset pneumonia should be considered.

A comparative study of a preclinical survival model of smoke inhalation injury in mice and rats

Smoke inhalation injury increases morbidity and mortality. Clinically relevant animal models are necessary for the continued investigation of the pathophysiology of inhalation injury and the development of therapeutics. The goal of our research was threefold: 1) to develop a reproducible survival model of smoke inhalation injury in rats that closely resembled our previous mouse model, 2) to validate the rat smoke inhalation injury model using a variety of laboratory techniques, and 3) to compare and contrast our rat model with both the well-established mouse model and previously published rat models to highlight our improvements on smoke delivery and lung injury. Mice and rats were anesthetized, intubated, and placed in custom-built smoke chambers to passively inhale woodchip-generated smoke. Bronchoalveolar lavage fluid (BALF) and lung tissue were collected for confirmatory tests. Lung sections were hematoxylin and eosin stained, lung edema was assessed with wet-to-dry (W/D) ratio, and inflammatory cell infiltration and cytokine elevation were evaluated using flow cytometry, immunohistochemistry, and ELISA. We confirmed that our mouse and rat models of smoke inhalation injury mimic the injury seen after human burn inhalation injury with evidence of pulmonary edema, neutrophil infiltration, and inflammatory cytokine elevation. Interestingly, rats mounted a more severe immunological response compared with mice. In summary, we successfully validated a reliable and clinically translatable survival model of lung injury and immune response in rats and mice and characterized the extent of this injury. These animal models allow for the continued study of smoke inhalation pathophysiology to ultimately develop a better therapeutic.

Modified abbreviated burn severity index as a predictor of in-hospital mortality in patients with inhalation injury: development and validation using independent cohorts

PURPOSE

The ability to accurately evaluate the severity of inhalation injury can help to optimize patient care. However, there is no accepted severity grading system, especially for inhalation injury.

METHODS

We screened a multicenter burn registry and included adult patients who required oxygen treatment or mechanical ventilation. After the patient data were divided into development and validation cohorts, missing values were replaced with multiple imputation. Twelve potential predictors were analyzed using multivariate logistic regression to identify prognostic variables for in-hospital mortality and scores were assigned to each predictor based on odds ratios to develop the Modified Abbreviated Burn Severity Index, mABSI. The mABSI was validated using c-statistics and calibration curves.

RESULTS

We randomly assigned 1377 and 919 patients to the development and validation cohorts, respectively. Age, self-inflicted injury, cutaneous burn area, and mechanical ventilation requirement were identified as independent predictors, and the mABSI (1-17 scale) was, thus, developed. The mABSI has a high discriminatory power (c-statistic = 0.94; 95% CI 0.92-0.97), and both estimated and observed in-hospital mortalities increased from 1% at score ≤ 5 to almost 100% at score ≥ 14 with linear calibration plots.

CONCLUSIONS

We developed and validated the mABSI which accurately predicts in-hospital mortality.

Chest physical therapy reduces pneumonia following inhalation injury

PURPOSE

The purpose of this study was to clarify the efficacy of chest physiotherapy (CPT) in patients with inhalation injury in the acute phase.

PATIENTS AND METHODS

This was a single-institution retrospective study of patients with inhalation injury admitted to the Chukyo Hospital Burn Center from April 2004 to March 2014 who required endotracheal intubation for respiratory care. The patients were divided into two groups: the CPT group and the conventional physical therapy group. We compared the two groups according to the incidence of pneumonia, length of ICU/hospital stay, and level of activities of daily living at discharge. To match subject backgrounds, we conducted a propensity score matching analysis, and using a Cox regression analysis, we evaluated the effect of CPT on the first pneumonia event.

RESULTS

Of 271 patients admitted to the burn center, 139 patients were included. The incidence of pneumonia in the CPT group was significantly lower and these patients required fewer days until they could sit on the edge of the bed compared with the conventional physical therapy group. In a Cox regression model, the hazard ratio for the first incidence of pneumonia in the CPT group vs. the conventional therapy group was 0.27 (95% confidence interval: 0.13-0.54, P = 0.0002) after propensity score matching.

CONCLUSIONS

CPT reduces the incidence of pneumonia and facilitates patient mobilization following inhalation injury.

Superior Effects of Nebulized Epinephrine to Nebulized Albuterol and Phenylephrine in Burn and Smoke Inhalation-Induced Acute Lung Injury

The severity of burn and smoke inhalation-induced acute lung injury (BSI-ALI) is associated with alveolar and interstitial edema, bronchospasm, and airway mucosal hyperemia. Previously, we have reported beneficial effects of epinephrine nebulization on BSI-ALI. However, the underlying mechanisms of salutary effects of nebulized epinephrine remain unclear. The present study compared the effects of epinephrine, phenylephrine, and albuterol on a model of BSI-ALI. We tested the hypothesis that both α1- and β2-agonist effects are required for ameliorating more efficiently the BSI-ALI. Forty percent of total body surface area, 3rd-degree cutaneous burn, and 48-breaths of cotton smoke inhalation were induced to 46 female Merino sheep. Postinjury, sheep were mechanically ventilated and cardiopulmonary hemodynamics were monitored for 48 h. Sheep were allocated into groups: control, n = 17; epinephrine, n = 11; phenylephrine, n = 6; and albuterol, n = 12. The drug nebulization began 1 h postinjury and was repeated every 4 h thereafter. In the results, epinephrine group significantly improved oxygenation compared to other groups, and significantly reduced pulmonary vascular permeability index, lung wet-to-dry weight ratio, and lung tissue growth factor-β1 level compared with albuterol and control groups. Epinephrine and phenylephrine groups significantly reduced trachea wet-to-dry weight ratio and lung vascular endothelial growth factor-A level compared with control group. Histopathologically, epinephrine group significantly reduced lung severity scores and preserved vascular endothelial-cadherin level in pulmonary arteries. In conclusion, the results of our studies suggest that nebulized epinephrine more effectively ameliorated the severity of BSI-ALI than albuterol or phenylephrine, possibly by its combined α1- and β2-agonist properties.

Early Surgical Management of Thermal Airway Injury: A Case Series

Inhalation injury is an independent risk factor in burn mortality, imparting a 20% increased risk of death. Yet there is little information on the natural history, functional outcome, or pathophysiology of thermal injury to the laryngotracheal complex, limiting treatment progress. This paper demonstrates a case series (n = 3) of significant thermal airway injuries. In all cases, the initial injury was far exceeded by the subsequent immune response and aggressive fibroinflammatory healing. Serial examination demonstrated progressive epithelial injury, mucosal inflammation, airway remodeling, and luminal compromise. Histologic findings in the first case demonstrate an early IL-17A response in the human airway following thermal injury. This is the first report implicating IL-17A in the airway mucosal immune response to thermal injury. Their second and third patients received Azithromycin targeting IL-17A and showed clinical responses. The third patient also presented with exposed tracheal cartilage and underwent mucosal reconstitution via split-thickness skin graft over an endoluminal stent in conjunction with tracheostomy. This was associated with rapid abatement of mucosal inflammation, resolution of granulation tissue, and return of laryngeal function. Patients who present with thermal inhalation injury should receive a thorough multidisciplinary airway evaluation, including early otolaryngologic evaluation. New early endoscopic approaches (scar lysis and mucosal reconstitution with autologous grafting over an endoluminal stent), when combined with targeted medical therapy aimed at components of mucosal airway inflammation (local corticosteroids and systemic Azithromycin targeting IL-17A), may have potential to limit chronic cicatricial complications.

Nebulized heparin for inhalation injury in burn patients: a systematic review and meta-analysis

Background

Smoke inhalation injury increases overall burn mortality. Locally applied heparin attenuates lung injury in burn animal models of smoke inhalation. It is uncertain whether local treatment of heparin is benefit for burn patients with inhalation trauma. We systematically reviewed published clinical trial data to evaluate the effectiveness of nebulized heparin in treating burn patients with inhalation injury.

Methods

A systematic search was undertaken in PubMed, the Cochrane Library, Embase, Web of Science, the Chinese Journals Full-text Database, the China Biomedical Literature Database and the Wanfang Database to obtain clinical controlled trails evaluating nebulized heparin in the treatment of burn patients with inhalation injury. Patient and clinical characteristics, interventions and physiological and clinical outcomes were recorded. Cochrane Risk of Bias Evaluation Tool and the Newcastle–Ottawa Scale were used to evaluate data quality. Potential publication bias was assessed by Egger’s test. A sensitivity analysis was conducted to assess the stability of the results. The meta-analysis was conducted in R 3.5.1 software.

Results

Nine trials were eligible for the systematic review and meta-analysis. Nebulized heparin can reduce lung injury and improve lung function in burn patients with inhalation injury without abnormal coagulation or bleeding, but the findings are still controversial. Mortality in the heparin-treated group was lower than that of the traditional treatment group (relative risk (RR) 0.75). The duration of mechanical ventilation (DOMV) was shorter in the heparin-treated group compared to the traditional treatment group (standardized mean difference (SMD) −0.78). Length of hospital stay was significantly shorter than that in the traditional treatment group (SMD −0.42), but incidence rates of pneumonia and unplanned reintubation were not significantly different in the study groups (RRs 0.97 and 0.88, respectively). No statistically significant publication biases were detected for the above clinical endpoints (p > 0.05).

Conclusions

Based on conventional aerosol therapy, heparin nebulization can further reduce lung injury, improve lung function, shorten DOMV and length of hospital stay, and reduce mortality, although it does not reduce the incidence of pneumonia and/or the unplanned reintubation rate.

Polyurethane foam for skin graft fixation in clinical-relevant ovine burn wound model for wound repair and regeneration research

The availability of clinical-relevant large animal models for research in wound healing study is limited. Although a few reports described the wound dressing fixation method using polyurethane foam in patients, no animal studies were conducted to investigate efficacy of the polyurethane foam in grafted burn wounds. In the present study, we report a simple fixation method of grafted burned skin using polyurethane foam dressing (Allevyn Non-Adhesive, smith & nephew, UK) in a clinically relevant ovine grafted burn wound model. The dressing was removed at postoperative day 7 after skin graft. The grafted skin was completely engrafted without any complications. This method was safe and easy to perform and associated with good engraftment without any complications. We believe that the polyurethane foam fixation method may be successfully used in clinical practice as well as in preclinical studies for grafted burn wound repair and regeneration research.

Emerging therapies for smoke inhalation injury: a review

Background

Smoke inhalation injury increases overall burn mortality by up to 20 times. Current therapy remains supportive with a failure to identify an optimal or targeted treatment protocol for smoke inhalation injury. The goal of this review is to describe emerging therapies that are being developed to treat the pulmonary pathology induced by smoke inhalation injury with or without concurrent burn injury.

Main body

A comprehensive literature search was performed using PubMed (1995–present) for therapies not approved by the U.S. Food and Drug Administration (FDA) for smoke inhalation injury with or without concurrent burn injury. Therapies were divided based on therapeutic strategy. Models included inhalation alone with or without concurrent burn injury. Specific animal model, mechanism of action of medication, route of administration, therapeutic benefit, safety, mortality benefit, and efficacy were reviewed. Multiple potential therapies for smoke inhalation injury with or without burn injury are currently under investigation. These include stem cell therapy, anticoagulation therapy, selectin inhibition, inflammatory pathway modulation, superoxide and peroxynitrite decomposition, selective nitric oxide synthase inhibition, hydrogen sulfide, HMG-CoA reductase inhibition, proton pump inhibition, and targeted nanotherapies. While each of these approaches shows a potential therapeutic benefit to treating inhalation injury in animal models, further research including mortality benefit is needed to ensure safety and efficacy in humans.

Conclusions

Multiple novel therapies currently under active investigation to treat smoke inhalation injury show promising results. Much research remains to be conducted before these emerging therapies can be translated to the clinical arena.

Blood carboxyhemoglobin elimination curve, half-lifetime, and arterial-venous differences in acute phase of carbon monoxide poisoning in ovine smoke inhalation injury model

Smoke inhalation injury (SII) affects more than 50,000 people annually causing carbon monoxide (CO) poisoning. Although the increased blood level of carboxyhemoglobin (CO-Hb) is frequently used to confirm the diagnosis of SII, knowledge of its elimination in the acute phase is still limited. The aim of this study is to determine CO-Hb elimination rates and their differences in arterial (aCO-Hb) and mixed-venous (vCO-Hb) blood following severe SII in a clinically relevant ovine model. Forty-three chronically instrumented female sheep were subjected to SII (12 breaths, 4 sets) through tracheostomy tube under anesthesia and analgesia. After the SII, sheep were awakened and placed on a mechanical ventilator (FiO₂ = 1.0, tidal volume 12 mL/kg, and PEEP = 5cmH₂O) and monitored. Arterial and mixed-venous blood samples were withdrawn simultaneously for blood gas analysis at various time points to determine CO-HB half-lifetime and an elimination curve. The mean of highest aCO-Hb level during SII was 70.8 ± 13.9%. The aCO-Hb elimination curve showed an approximated exponential decay during the first 60 min. Per mixed linear regression model analysis, aCO-Hb significantly (p < 0.001) declined (4.3%/minute) with a decay constant lambda of 0.044. With this lambda, mean lifetime and half-lifetime of aCO-Hb were 22.7 and 15.7 min, respectively. The aCO-Hb was significantly lower compared to vCO-Hb at all-time points (0-180 min). To our knowledge, this is the first report describing CO-Hb elimination curve in the acute phase after severe SII in the clinically relevant ovine model. Our data shows that CO-Hb is decreasing in linear manner with supportive mechanical ventilation (0-60 min). The results may help to understand CO-Hb elimination curve in the acute phase and improvement of pre-hospital and initial clinical care in patients with CO poisoning.

The Effects of Pre-Burn Center Intubation on Rates of Pneumonia, Early Extubation, and Death: A Systematic Review

Airway burns cause delayed collapse of airways due to airway edema. Transferring clinicians are trained to intubate at the first suspicion of airway collapse, which can lead to vague reasons for intubation such as "airway protection." Intubation, however, is not without risks, such as pneumonia and death. The objective of this research review is to compare pre-burn center intubations with those performed at burn centers and compare rates of pneumonia, mortality, and time to extubation. A systematic review of articles from MEDLINE and CINAHL Plus was performed to identify eligible trials and observational studies that compared pre-burn center intubations with those performed at burn centers between the years 2014 and 2018. Four studies met eligibility requirements. There were mixed results on the correlation of pre-burn center intubation with pneumonia and death; however, pre-burn center patients were more likely to have earlier extubation times, which points to potentially unnecessary intubations. Clinicians should be aware of the increased mortality and morbidity associated with intubation. Providers should use objective evidence-based tools such as the ABA (American Burn Association) and Denver criteria to determine the need for intubation to avoid unnecessary intubations and their potential complications.

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.