Early pulmonary immune hyporesponsiveness is associated with mortality after burn and smoke inhalation injury

Burn-Induced Apoptosis in the Livers of Aged Mice Is Associated With Caspase Cleavage of Bcl-xL

INTRODUCTION

Older adult burn victims have poorer outcomes than younger burn victims. The liver is critical for the recovery of patients with burns. Postburn hepatic apoptosis in young individuals compromises liver integrity; however, this pathway has not yet been studied in older individuals. Because aged animals with burns suffer significant liver damage, we hypothesized that apoptosis is altered in these animals and may affect liver function. Understanding postburn hepatic apoptosis and its effects on liver function in aged animals may help improve outcomes in older patients.

METHODS

We compared the protein and gene expression levels in young and aged mice after a 15% total-body-surface-area burn. Liver and serum samples were collected at different time points after injury.

RESULTS

Caspase-9 expression in liver tissue was downregulated by 47% in young animals and upregulated by 62% in aged animals 9 h postburn (P < 0.05). The livers of aged mice showed a Bcl-extra-large (Bcl-xL) transcription increase only after 6 h; however, the livers of young mice exhibited 4.3-fold, 14.4-fold, and 7.8-fold Bcl-xL transcription increases at 3, 6, and 9 h postburn, respectively (P < 0.05). The livers of young mice showed no changes in Caspase-9, Caspase-3, or Bcl-xL protein levels during the early postburn period. In contrast, the livers of aged mice contained cleaved caspase-9, reduced full-length caspase-3, and an accumulation of ΔN-Bcl-x at 6 and 9 h postburn (P < 0.05). p21 expression decreased in aged mice; however, it was significantly increased in the liver tissue of young mice postburn (P < 0.05). Serum amyloid A1 and serum amyloid A2 serum protein levels were 5.2- and 3.1-fold higher in young mice than in aged mice, respectively, at 6 and 9 h postburn (P < 0.05).

CONCLUSIONS

Livers of aged mice exhibited different apoptotic processes compared to those of young mice early after burn injury. Collectively, burn-induced liver apoptosis in aged mice compromises hepatic serum protein production.

Characterization of the Basal and mTOR-Dependent Acute Pulmonary and Systemic Immune Response in a Murine Model of Combined Burn and Inhalation Injury

Severe burn injury leads to a cascade of local and systemic immune responses that trigger an extreme state of immune dysfunction, leaving the patient highly susceptible to acute and chronic infection. When combined with inhalation injury, burn patients have higher mortality and a greater chance of developing secondary respiratory complications including infection. No animal model of combined burn and inhalation injury (B+I) exists that accurately mirrors the human clinical picture, nor are there any effective immunotherapies or predictive models of the risk of immune dysfunction. Our earlier work showed that the mechanistic/mammalian target of rapamycin (mTOR) pathway is activated early after burn injury, and its chemical blockade at injury reduced subsequent chronic bacterial susceptibility. It is unclear if mTOR plays a role in the exacerbated immune dysfunction seen after B+I injury. We aimed to: (1) characterize a novel murine model of B+I injury, and (2) investigate the role of mTOR in the immune response after B+I injury. Pulmonary and systemic immune responses to B+I were characterized in the absence or presence of mTOR inhibition at the time of injury. Data describe a murine model of B+I with inhalation-specific immune phenotypes and implicate mTOR in the acute immune dysfunction observed.

Age and Injury Size Influence the Magnitude of Fecal Dysbiosis in Adult Burn Patients

Clinical studies have demonstrated that age 50 years or older is an independent risk factor associated with poor prognosis after burn injury, the second leading cause of traumatic injuries in the aged population. While mechanisms driving age-dependent postburn mortality are perplexing, changes in the intestinal microbiome, may contribute to the heightened, dysregulated systemic response seen in aging burn patients. The fecal microbiome from 22 patients admitted to a verified burn center from July 2018 to February 2019 was stratified based on the age of 50 years and total burn surface area (TBSA) size of ≥10%. Significant differences (P = .014) in overall microbiota community composition (ie, beta diversity) were measured across the four patient groups: young <10% TBSA, young ≥10% TBSA, older <10% TBSA, and older ≥10% TBSA. Differences in beta diversity were driven by %TBSA (P = .013) and trended with age (P = .087). Alpha diversity components, richness, evenness, and Shannon diversity were measured. We observed significant differences in bacterial species evenness (P = .0023) and Shannon diversity (P = .0033) between the groups. There were significant correlations between individual bacterial species and levels of short-chain fatty acids. Specifically, levels of fecal butyrate correlated with the presence of Enterobacteriaceae, an opportunistic gut pathogen, when elevated in burn patients lead to worsen outcomes. Overall, our findings reveal that age-specific changes in the fecal microbiome following burn injuries may contribute to immune system dysregulation in patients with varying TBSA burns and potentially lead to worsened clinical outcomes with heightened morbidity and mortality.

Gut Microbial Changes and their Contribution to Post-Burn Pathology

ABSTRACT

Burn injuries are a common form of traumatic injury that leads to significant morbidity and mortality worldwide. Burn injuries are characterized by inflammatory processes and alterations in numerous organ systems and functions. Recently, it has become apparent that the gastrointestinal bacterial microbiome is a key component of regulating the immune response and recovery from burn and can also contribute to significant detrimental sequelae after injury, such as sepsis and multiple organ failure. Microbial dysbiosis has been linked to multiple disease states; however, its role in exacerbating acute traumatic injuries, such as burn, is poorly understood. In this article, we review studies that document changes in the intestinal microbiome after burn injury, assess the implications in post-burn pathogenesis, and the potential for further discovery and research.

Inhalation Injury is Associated with Endotheliopathy and Abnormal Fibrinolytic Phenotypes in Burn Patients: A Cohort Study

Burn injury is associated with endothelial dysfunction and coagulopathy and concomitant inhalation injury increases morbidity and mortality. The aim of this work is to identify associations between inhalation injury (IHI), coagulation homeostasis, vascular endothelium, and clinical outcomes in burn patients. One-hundred and twelve patients presenting to a regional burn center were included in this retrospective cohort study. Whole blood was collected at set intervals from admission through 24 hours and underwent viscoelastic assay with rapid TEG (rTEG). Syndecan-1 (SDC-1) on admission was quantified by ELISA. Patients were grouped by the presence (n=28) or absence (n=84) of concomitant IHI and rTEG parameters, fibrinolytic phenotypes, SDC-1, and clinical outcomes were compared. Of the 112 thermally injured patients, 28 (25%) had IHI. Most patients were male (68.8%) with a median age of 40 (IQR, 29-57) years. Patients with IHI had higher overall mortality (42.68% vs. 8.3%; p<0.0001). rTEG LY30 was lower in patients with IHI at hours 4 and 12 (p<0.05). There was a pattern of increased abnormal fibrinolytic phenotypes among IHI patients. There was a greater proportion of IHI patients with endotheliopathy (SDC-1 > 34 ng/mL) (64.7% vs. 26.4%; p=0.008). There was a pattern of increased mortality among patients with inhalation injury and endotheliopathy (0% vs. 72.7%; p=0.004). Significant differences between patients with and without IHI were found in measures assessing fibrinolytic potential and endotheliopathy. Mortality was associated with abnormal fibrinolysis, endotheliopathy, and inhalation injury. However, the extent to which IHI associated dysfunction is independent of TBSA burn size remains to be elucidated.

Inhalation Injury: Unmet Clinical Needs and Future Research

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

Soluble suppression of tumorigenicity-2 predicts pneumonia in patients with inhalation injury: Results of a pilot study

INTRODUCTION

Several mechanisms play a role in the development of pneumonia after inhalation injury. Our aim was to analyze whether higher concentrations of inflammatory markers or of biomarkers of epithelial injury are associated with a higher incidence of pneumonia in patients with inhalation injury.

MATERIAL AND METHODS

Secondary analysis of a single-center prospective observational cohort pilot study, performed over a two-year period (2015-2017) at the Burns Unit of the Plastic and Reconstructive Surgery Department of Vall d'Hebron University Hospital. All patients aged 18 with suspected inhalation injury undergoing admission to the Burns Unit were included. Plasma biomarkers of the lung epithelium (RAGE and SP-D), inflammation markers (IL6, IL8), and IL33, as well as soluble suppression of tumorigenicity-2 (sST2) levels, were measured within the first 24 h of admission.

RESULTS

Twenty-four patients with inhalation injury were included. Eight (33.3%) developed pneumonia after a median of 7 (4-8) days of hospital stay. Patients with pneumonia presented higher plasma concentrations of sST2 (2853 [2356-3351] ng/mL vs 1352 [865-1839] ng/mL; p < 0.001), IL33 (1.95 [1.31-2.59] pg/mL vs 1.26 [1.07-1.45] pg/mL; p = 0.002) and IL8 (325.7 [221.6-430.0] pg/mL vs 174.1 [95.2-253.0] pg/mL; p = 0.017) on day 1 of inclusion. Plasma sST2 concentration in the first 24 h demonstrated excellent diagnostic accuracy for predicting the occurrence of pneumonia in patients with smoke inhalation (AUROC 0.929 [95%CI 0.818-1.000]). A cutoff point of ≥2825 ng/mL for sST2 had a sensitivity of 75% and a specificity of 100%. The risk ratio of pneumonia in patients with sST2 ≥ 2825 ng/mL was 7.14 ([95% CI 1.56-32.61]; p = 0.016).

CONCLUSIONS

Plasma sST2 in the first 24 h of admission predicts the occurrence of pneumonia in patients with inhalation injury.

Bronchoalveolar lavage and plasma Antithrombin and cytokines in inhalation and burn injury: a pilot study

Systemic inflammatory response syndrome (SIRS) is initiated during the acute phase of thermal injury. The objective was to determine the SIRS impact on cytokine and Antithrombin (AT) levels in smoke inhalation and burn injury. This observational pilot study compared plasma and bronchoalveolar lavage fluid (BAL) cytokine and AT levels in the first six days post smoke inhalation and burn injury. Twenty-five patients, 14 with inhalation + burn injury > 10% total body surface area (TBSA) and 11 with inhalation injury and ≤ 10% TBSA participated. Human Th1/Th2 cytometric bead array kit from BD Biosciences Pharmingen determined cytokine levels; AT levels with Sigma Diagnostics and spectrophotometry. Results indicated no significant age difference between the two groups (42.1 ± 7.2) versus 49.6 ± 6.4 years. On admission, the inhalation group had 5.4 ± 3.9% TBSA compared to 35.0 ± 22.2% TBSA in the inhalation + burn group, P < 0.001. Comparing groups, AT plasma levels were significantly decreased (P = 0.025) and IL-2 levels significantly increased (P = 0.025) in the inhalation + burn group compared to the inhalation group; there was no significant difference in BAL AT or cytokine levels. Combined group plasma AT levels (65.41 ± 4.44%) were significantly increased compared to BAL AT levels (1.06 ± 0.71%), P < 0.001. In contrast, BAL TNF-α levels (35.61 ± 16.01 pg/ml) were significantly increased in relation to the plasma levels (4.68 ± 1.27 pg/ml), P = 0.02. On days 1-2, AT plasma levels were significantly decreased in the inhalation + burn group (41.01 ± 5.24%) compared to the inhalation group (81.02 ± 10.99%), P = 0.002. IL-6 plasma levels were higher in the inhalation + burn group compared to the inhalation group on admission, but both levels decreased by days 3-6. IL-6 BAL levels were elevated in both groups on days 1-2 and decreased by days 3-6. In the first six days of resuscitation, all plasma cytokines were increased in the two groups compared to controls. AT plasma and BAL levels were significantly reduced in both groups, contributing to the coagulopathy. Increased BAL TNF-α and IL-6 levels may have contributed to the pulmonary perturbations during the initial SIRS response in both groups.

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

OBJECTIVE

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

METHODS

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

RESULTS

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

CONCLUSION

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

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.

Effects of Multiday Ethanol Intoxication on Postburn Inflammation, Lung Function, and Alveolar Macrophage Phenotype

Burn patients who consumed alcohol before injury have worse clinical outcomes, including longer hospital stays, increased ventilator days, and more respiratory infections. Most alcohol consumers are binge drinkers and not chronic alcoholics, and binge drinking patterns fluctuate over the week, with consecutive days of drinking over the weekend followed by relative abstinence during the week. We used a murine model simulating this drinking pattern in the context of burn injury. Mice were given ethanol for 3 days, rested for 4 days, given ethanol for 3 more days, followed by a sham or 15% total body surface area full-thickness burn. We previously demonstrated that mice exposed to the combined insult exhibited respiratory dysfunction and 50% mortality, with those that succumbed to injury dying between 24 and 72 h, thus identifying a therapeutic intervention window. Our goal herein is to characterize inflammatory and respiratory parameters during this critical time frame. We saw that mice exposed to the combined insult had the highest circulating and pulmonary cytokine levels at 24 h, which were normalized by 72 h in survivors. Alveolar macrophage activation was observed at 24 h in burned mice, regardless of intoxication (P < 0.05). However, at 72 h, alveolar macrophages from intoxicated burned mice had elevated CD206, relative to controls (P < 0.05), indicative of an anti-inflammatory phenotype. Taken together, these findings suggest that although lung function and inflammation are normalized by 72 h, the alterations in alveolar macrophage phenotype shed light on a potential mechanism underlying increased infection susceptibility in intoxicated burn patients.

Standards in Biologic Lesions: Cutaneous Thermal Injury and Inhalation Injury Working Group 2018 Meeting Proceedings

On August 27 and 28, 2018, the American Burn Association, in conjunction with Underwriters Laboratories, convened a group of experts on burn and inhalation injury in Washington, DC. The goal of the meeting was to identify and discuss the existing knowledge, data, and modeling gaps related to understanding cutaneous thermal injury and inhalation injury due to exposure from a fire environment, and in addition, address two more areas proposed by the American Burn Association Research Committee that are critical to burn care but may have current translational research gaps (inflammatory response and hypermetabolic response). Representatives from the Underwriters Laboratories Firefighter Safety Research Institute and the Bureau of Alcohol, Tobacco, Firearms and Explosives Fire Research Laboratory presented the state of the science in their fields, highlighting areas that required further investigation and guidance from the burn community. Four areas were discussed by the full 24 participant group and in smaller groups: Basic and Translational Understanding of Inhalation Injury, Thermal Contact and Resulting Injury, Systemic Inflammatory Response and Resuscitation, and Hypermetabolic Response and Healing. A primary finding was the need for validating historic models to develop a set of reliable data on contact time and temperature and resulting injury. The working groups identified common areas of focus across each subtopic, including gaining an understanding of individual response to injury that would allow for precision medicine approaches. Predisposed phenotype in response to insult, the effects of age and sex, and the role of microbiomes could all be studied by employing multi-omic (systems biology) approaches.

Mechanism of pulmonary immunosuppression: extrapulmonary burn injury suppresses bacterial endotoxin-induced pulmonary neutrophil recruitment and neutrophil extracellular trap (NET) formation

Pulmonary immunosuppression often occurs after burn injury (BI). However, the reasons for BI-induced pulmonary immunosuppression are not clearly understood. Neutrophil recruitment and neutrophil extracellular trap (NET) formation (NETosis) are important components of a robust pulmonary immune response, and we hypothesized that pulmonary inflammation and NETosis are defective after BI. To test this hypothesis, we established a mouse model with intranasal LPS instillation in the presence or absence of BI (15% of body surface burn) and determined the degree of immune cell infiltration, NETosis, and the cytokine levels in the airways and blood on d 2. Presence of LPS recruited monocytes and large numbers of neutrophils to the airways and induced NETosis (citrullinated histone H3, DNA, myeloperoxidase). By contrast, BI significantly reduced LPS-mediated leukocyte recruitment and NETosis. This BI-induced immunosuppression is attributable to the reduction of chemokine (C-C motif) ligand (CCL) 2 (monocyte chemoattractant protein 1) and CCL3 (macrophage inflammatory protein 1α). BI also suppressed LPS-induced increase in IL-17A, IL-17C, and IL-17E/IL-25 levels in the airways. Therefore, BI-mediated reduction in leukocyte recruitment and NETosis in the lungs are attributable to these cytokines. Regulating the levels of some of these key cytokines represents a potential therapeutic option for mitigating BI-mediated pulmonary immunosuppression.-Sakuma, M., Khan, M. A. S., Yasuhara, S., Martyn, J. A., Palaniyar, N. Mechanism of pulmonary immunosuppression: extrapulmonary burn injury suppresses bacterial endotoxin-induced pulmonary neutrophil recruitment and neutrophil extracellular trap (NET) formation.

Divergent humoral responses to 23-valent pneumococcal polysaccharide vaccine in critically-ill burn and neurosurgical patients

INTRODUCTION

Critically ill hospitalized patients are at increased risk of infection so we assessed the immunogenicity of 23-valent pneumococcal polysaccharide vaccine (PPSV23) administered within six days of injury.

METHODS

This prospective observational study compared the immunogenicity of PPSV23 among critically ill burn and neurosurgical patients at a tertiary, academic medical center. Patients received PPSV23 vaccination within six days of ICU admission per standard of care. Consent was obtained to measure concentrations of vaccine-specific IgG to 14 of 23 serotype capsule-specific IgG in serum prior to and 14-35 days following PPSV23. A successful immunologic response was defined as both a ≥2-fold rise in capsule-specific IgG from baseline and concentrations of >1 mcg/mL to 10 of 14 measured vaccine serotypes. Immunologic response was compared between burn and neurosurgical patients. Multiple variable regression methods were used to explore associations of clinical and laboratory parameters to immunologic responses.

RESULTS

Among the 16 burn and 27 neurosurgical patients enrolled, 87.5% and 40.7% generated a successful response to the vaccine, respectively (p = 0.004). Both median post-PPSV23 IgG concentrations (7.79 [4.56-18.1] versus 2.93 [1.49-8.01] mcg/mL; p = 0.006) and fold rises (10.66 [7.44-14.56] versus 3.48 [1.13-6.59]; p<0.001) were significantly greater in burn compared with neurosurgical patients. Presence of burn injury was directly and days from injury to immunization were inversely correlated with successful immunologic response (both p<0.03). Burn injury was associated with both increased median antibody levels post-PPSV23 and fold rise to 14 vaccine serotypes (p<0.03), whereas absolute lymphocyte count was inversely correlated with median antibody concentrations (p = 0.034).

CONCLUSION

Critically ill burn patients can generate successful responses to PPSV23 during acute injury whereas responses among neurosurgical patients is comparatively blunted. Further study is needed to elucidate the mechanisms of differential antigen responsiveness in these populations, including the role of acute stress responses, as well as the durability of these antibody responses.

Acute clinical manifestations in toxic smoke inhalation victims: systematic review of observational studies

Abstract Introduction: Lung injuries from toxic smoke inhalation are the main causes of death in fire victims; however, information regarding the acute effects on the respiratory system after smoke inhalation and its constituents in closed environments are still scarce in literature. Objective: To investigate the acute clinical manifestations observed in victims of smoke inhalation during enclosed-space fires by means of systematic review. Methods: A systematic search was conducted in the following databases: MEDLINE (via PubMed), Lilacs, Scopus and Web of Science. There were no appliedrestrictions in terms of thepublication date. In addition, a manual search was performed on the references of published studies. Observational studies assessing the prevalence of acute clinical manifestations in victims of toxic smoke inhalation in closed environments were included. Results: Of the 4,603 articles identified, eight were included, comprising a total of 233 patients. The signs and symptoms were identified and ranked according to frequency. Dyspnea (58.80%, six studies), carbonaceous sputum (54.51%, four studies), hoarseness (39.91%, three studies), wheezing (34.33%, five studies) and sore throat (33.90%, two studies) were the most frequent acute clinical manifestations of smoke inhalation. Besides these, chest pain and pulmonary edema were observed, respectively in 13.30%, 5.15% of the studies. Conclusion: The results suggest that dyspnea, carbonaceous sputum, hoarseness, wheezing and sore throat were the most frequent acute clinical manifestations in victims of smoke inhalation. Further studies of a higher level of evidence and greater methodological rigor are required.

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.

Blocking CXCL1-dependent neutrophil recruitment prevents immune damage and reduces pulmonary bacterial infection after inhalation injury

Smoke inhalation associated with structural fires, wildfires, or explosions leads to lung injury, for which innovative and clinically relevant animal models are needed to develop effective therapeutics. We have previously reported that damage-associated molecular patterns (DAMPs) and anti-inflammatory cytokines correlate with infectious complications in patients diagnosed with inhalational injury. In this study, we describe a novel and translational murine model of acute inhalational injury characterized by an accumulation of protein and neutrophils in the bronchoalveolar space, as well as histological evidence of tissue damage. Mice were anesthetized, and a cannula was placed in the trachea and exposed to smoldering plywood smoke three times for 2-min intervals in a smoke chamber. Here we demonstrate that this model recapitulates clinically relevant phenotypes, including early release of double-stranded DNA (dsDNA), IL-10, monocyte chemoattractant protein (MCP)-1, and CXCL1 along with neutrophilia early after injury, accompanied by subsequent susceptibility to opportunistic infection with Pseudomonas aeruginosa. Further investigation of the model, and in turn a reanalysis of patient samples, revealed a late release of the DAMP hyaluronic acid (HA) from the lung. Using nitric oxide synthase-deficient mice, we found that Nos2 was required for increases in IL-10, MCP-1, and HA following injury but not release of dsDNA, CXCL1 expression, early neutrophilia, or susceptibility to opportunistic infection. Depletion of CXCL1 attenuated early neutrophil recruitment, leading to decreased histopathology scores and improved bacterial clearance in this model of smoke inhalation. Together, these data highlight the potential therapeutic benefit of attenuating neutrophil recruitment in the first 24 h after injury in patients.

Smoke Inhalation Injury: Etiopathogenesis, Diagnosis, and Management

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

Age-related immune responses after burn and inhalation injury are associated with altered clinical outcomes

This prospective study aimed to address changes in inflammatory response between different aged populations of patients who sustained burn and inhalation injury. Plasma and bronchoalveolar lavage (BAL) samples were collected from 104 patients within 15h of their estimated time of burn injury. Clinical variables, laboratory parameters, and immune mediator profiles were examined in association with clinical outcomes. Older patients were at higher odds for death after burn injury (odds ratio (OR)=7.37 per 10years, p=0.004). In plasma collected within 15h after burn injury, significant increases in the concentrations of interleukin 1 receptor antagonist (IL-1RA), interleukin 2 (IL-2), interleukin 4 (IL-4), interleukin 6 (IL-6), granulocyte colony-stimulating factor (G-CSF), interferon-gamma-induced protein 10 (IP-10) and monocyte chemoattractant protein 1 (MCP-1) (p<0.05 for all) were observed in the ≥65 group. In the BAL fluid, MCP-1 was increased three-fold in the ≥65 group. This study suggests that changes in certain immune mediators were present in the older cohort, in association with in-hospital mortality.

Inhalation Injury: Pathophysiology, Diagnosis, and Treatment

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

A model of recovery from inhalation injury and cutaneous burn in ambulatory swine

Inhalation injury commonly accompanies thermal injury, increasing the likelihood of mortality and multiple organ dysfunction (MOD). Large animal models have given important insight into the pathophysiology of this injury; however recapitulating late MOD has remained difficult. The current report describes experiments using a smoke inhalation and burn model, with follow-up of ambulatory swine for 14days with bronchoscopy, CT scanning, and bronchoalveolar lavage fluid (BALF)/blood collection. Clinically, animals cleared airway damage in the first several days after-injury. This was mirrored with erythematous airways on day 2 after-injury, which resolved by the end of the experiment, as did parenchymal damage seen on CT. An initial rise in the protein content of BALF immediately after-injury was followed by a dramatic increase in the concentration of leukocytes. Circulating neutrophils increased while lymphocytes decreased; both correlated with cell counts in BALF. IL8 levels in BALF increased 30-fold and remained elevated throughout the experiment. IL1ra increased circulation immediately after-injury, and afterwards in BALF. Other cytokines (TNFα, IL12) transiently increased in BALF (and decreased in circulation) on day 2. Taken together, these results display a remarkable capability for the lungs to recover in the absence of intubation, with further evidence of the role of cytokines such as IL8 and IL1ra. The possible exacerbating effects of clinical practices such as ventilation and bronchoscopies should be considered.

The diagnostic and prognostic value of systems biology research in major traumatic and thermal injury: a review

As secondary complications remain a significant cause of morbidity and mortality amongst hospitalised trauma patients, the need to develop novel approaches by which to identify patients at risk of adverse outcome is becoming increasingly important. Centred on the idea that patients who experience “poor” outcome post trauma elicit a response to injury that is distinct from those who experience “good” outcome, tailored therapeutics is an emerging concept aimed at improving current treatment regimens by promoting patient-specific therapies. Making use of recent advancements in the fields of genomics, proteomics and metabolomics, numerous groups have undertaken a systems-based approach to analysing the acute immune and inflammatory response to major traumatic and thermal injury in an attempt to uncover a single or combination of biomarkers that can identify patients at risk of adverse outcome. Early results are encouraging, with all three approaches capable of discriminating patients with “good” outcome from those who develop nosocomial infections, sepsis and multiple organ failure, with differences apparent in blood samples acquired as early as 2 h post injury. In particular, genomic data is proving to be highly informative, identifying patients at risk of “poor” outcome with a higher degree of sensitivity and specificity than statistical models built upon data obtained from existing anatomical and physiological scoring systems. Here, focussing predominantly upon human-based research, we provide an overview of the findings of studies that have investigated the immune and inflammatory response to major traumatic and thermal injury at the genomic, protein and metabolite level, and consider both the diagnostic and prognostic potential of these approaches.

Alteration of Leukocyte Count Correlates With Increased Pulmonary Vascular Permeability and Decreased PaO2:FiO2 Ratio Early After Major Burns

Leukocytes are activated systemically and their numbers increase soon after a burn followed by a rapid decline to low normal or subnormal levels, possibly by increased extravasation. Experimental data support that an important target for such extravasation is the lungs and that leukocytes when they adhere to endothelial cells cause an increase in vascular permeability. The authors investigated a possible relation between early increased pulmonary vascular permeability or a decreased PaO2:FiO2 ratio and the dynamic change in concentration of blood leukocytes after a burn. This is a prospective, exploratory, single-center study. The authors measured the dynamic changes of leukocytes in blood starting early after the burn, pulmonary vascular permeability index by thermodilution, and PaO2:FiO2-ratios in 20 patients during the first 21 days after a major burn (>20% TBSA%). Median TBSA was 40% interquartile range (IQR, 25-52) and full thickness burn 28% (IQR, 2-39). There was a correlation between the early (<24 hours) alteration in white blood cell count and both early increased pulmonary vascular permeability (r = .63, P = .004) and the decreased oxygenation index defined as PaO2:FiO2 < 27 kPa (P = .004). The authors have documented a correlation between dynamic change of blood leukocytes and pulmonary failure early after burns.

Intraalveolar TNF-α in combined burn and inhalation injury compared with intraalveolar interleukin-6

The objective of this study was to evaluate the role of intraalveolar tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in a combination of skin burn and smoke inhalation injuries because this combined trauma is associated with an increased morbidity and mortality compared with either of these traumas alone. We used a standardized small animal model (rats n = 84) to investigate the early intraalveolar excretion of TNF-α during the first one, three, and six hours after a singular skin burn injury, singular smoke inhalation injury, and a combination involving both the traumas. The data were compared with the data from control rats that only received preparation and mechanical ventilation. The TNF-α serum levels and intraalveolar IL-6 concentrations were also measured. One hour after trauma, there was a significant difference in the TNF-α concentration between the controls and both the singular traumas (control vs burn P < .0444 and control vs smoke P < .005) and between the inhalation injury and the combined trauma (smoke vs burn + smoke P < .0084). After three and six hours, no significant differences among the groups were observed. Compared with the controls, both the singular skin burn and smoke inhalation injuries led to increased intraalveolar TNF-α excretion, whereas the combined trauma showed the least intraalveolar TNF-α levels at three and six hours post-trauma. These findings differed from the serum TNF-α levels. Compared with the IL-6 levels, we observed a negative correlation within the intraalveolar cytokine concentrations after one hour (r = -.809), three hours (r = -.627), and six hours (r = -.746). This study confirms the importance of the intraalveolar cytokine reaction in the early posttraumatic stage after a combined burn and inhalation injury. The differences between the combined and singular traumas indicate that TNF-α plays a role in the immunologic hyporesponsiveness of the lung and therefore in the systemic pathophysiological pathway, that often leads to patient mortality. In addition, an inverse correlation between TNF-α and IL-6, both classical markers of inflammation, in the intraalveolar space was observed.

Role of alveolar macrophages in the inflammatory response after trauma

Acute lung injury (ALI) and its more severe form, acute respiratory distress syndrome (ARDS), can result from both direct and indirect pulmonary damage caused by trauma and shock. In the course of ALI/ARDS, mediators released from resident cells, such as alveolar macrophages, may act as chemoattractants for invading cells and stimulate local cells to build up a proinflammatory micromilieu. Depending on the trauma setting, the role of alveolar macrophages is differentially defined. This review focuses on alveolar macrophage function after blunt chest trauma, ischemia/reperfusion, hemorrhagic shock, and thermal burns.

DNA and inflammatory mediators in bronchoalveolar lavage fluid from children with acute inhalational injuries

The aim of this study was to assess the feasibility of using serial bronchoalveolar lavage fluids (BALFs) to characterize the course of cell damage and inflammation in the airways of pediatric patients with acute burn or inhalation injury. This was a prospective, longitudinal, descriptive pilot study conducted at the Burn and Pediatric Intensive Care Units in a tertiary care medical center. Six consecutively intubated and mechanically ventilated pediatric patients with acute inhalational injuries were studied. Serial BALF specimens from clinically indicated bronchoscopies were used to measure DNA and cytokine levels. BALF DNA levels for the six pediatric burn subjects were the highest within the first 72 hours after burn injury and declined thereafter. At the early stages after injury, BALF DNA levels (median [min, max] 3789 [1170, 11,917] ng/ml) were similar to those in adult burn patients and pediatric cystic fibrosis or bronchiectasis patients and was higher than those in pediatric recurrent pneumonia patients. BALF DNA levels in children and adults with inhalation injury correlated significantly with BALF interleukin-6, interleukin-8, and transforming growth factor-β1 levels. The patient with the most severe early visible airway mucosal damage and soot pattern at bronchoscopy, as well as the most extensive burns, also had the highest average early BALF DNA level (11,917 ng/ml) and the longest ventilator course and hospital stay. Procedures were well tolerated. In children with acute burn and inhalational injury, airway cellular damage and inflammation (reflected in high BALF DNA levels) appear to peak during the first 72 hours after burn or inhalation injury followed by a slow decline. Serial analysis of factors in airway secretions is feasible and has the potential to reveal important pathophyisiologic pathways and therapeutic targets for the treatment of acute inhalational injuries.

Early detection of pneumonia as a risk factor for mortality in burn patients in Menoufiya University Hospitals, Egypt

Pneumonia is common among critically ill burn patients and is a major cause of morbidity and mortality among them. Prediction of mortality in patients with severe burns remains unreliable. The aim of this research is to study the incidence, early diagnosis and management of nosocomial pneumonia, and to discuss the relationship between pneumonia and death in burn patients. This prospective study was carried out on 80 burn patients (35 males and 45 females) admitted to Menoufiya University Hospital Burn Center and Chest Department, Egypt, from September 2011 to March 2012. Our findings showed an overall burn patient mortality rate of 26.25 % (21/80), 15% (12/80) incidence of pneumonia, and a 50% (6/12) mortality rate among patients with pneumonia compared to 22 % (15/68) for those without pneumonia. The incidence of pneumonia was twice as high in the subset of patients with inhalation injury as among those without inhalation injury (P< 0.001). It was found that the presence of pneumonia, inhalation injury, increased burn size, and advanced age were all associated with increased mortality (P< 0.001). In the late onset pneumonia, other associated factors also contributed to mortality. Severity of disease, severity of illness (APACHE score), organ failure, underlying co-morbidities, and VAP PIRO score all have significant correlations with mortality rate. Pneumonia was an important factor for predicting burn patient mortality. Early detection and management of pneumonia are absolutely essential.

Inhalation injury severity and systemic immune perturbations in burned adults

OBJECTIVE

We aimed to determine whether the severity of inhalation injury evokes an immune response measurable at the systemic level and to further characterize the balance of systemic pro- and anti-inflammation early after burn and inhalation injury.

BACKGROUND

Previously, we reported that the pulmonary inflammatory response is enhanced with worse grades of inhalation injury and that those who die of injuries have a blunted pulmonary immune profile compared with survivors.

METHODS

From August 2007 to June 2011, bronchoscopy was performed on 80 patients admitted to the burn intensive care unit when smoke inhalation was suspected. Of these, inhalation injury was graded into 1 of 5 categories (0, 1, 2, 3, and 4), with grade 0 being the absence of visible injury and grade 4 corresponding to massive injury. Plasma was collected at the time of bronchoscopy and analyzed for 28 immunomodulating proteins via multiplex bead array or enzyme-linked immunosorbent assay.

RESULTS

The concentrations of several plasma immune mediators were increased with worse inhalation injury severity, even after adjusting for age and % total body surface area (TBSA) burn. These included interleukin (IL)-1RA (P = 0.002), IL-6 (P = 0.002), IL-8 (P = 0.026), granulocyte colony-stimulating factor (P = 0.002), and monocyte chemotactic protein 1 (P = 0.007). Differences in plasma immune mediator concentrations in surviving and deceased patients were also identified. Briefly, plasma concentrations of IL-1RA, IL-6, IL-8, IL-15, eotaxin, and monocyte chemotactic protein 1 were higher in deceased patients than in survivors (P < 0.05 for all), whereas IL-4 and IL-7 were lower (P < 0.05). After adjusting for the effects of age, % TBSA burn, and inhalation injury grade, plasma IL-1RA remained significantly associated with mortality (odds ratio, 3.12; 95% confidence interval, 1.03-9.44). Plasma IL-1RA also correlated with % TBSA burn, inhalation injury grade, fluid resuscitation, Baux score, revised Baux score, Denver score, and the Sequential Organ Failure Assessment score.

CONCLUSIONS

The severity of smoke inhalation injury has systemically reaching effects, which argue in favor of treating inhalation injury in a graded manner. In addition, several plasma immune mediators measured early after injury were associated with mortality. Of these, IL-1RA seemed to have the strongest correlation with injury severity and outcomes measures, which may explain the blunted pulmonary immune response we previously found in nonsurvivors.

Chest computed tomography performed on admission helps predict the severity of smoke-inhalation injury

Introduction

Smoke-inhalation injury is a major cause of mortality in burn patients, and therefore, it is important to determine accurately the severity of such injuries in these patients. The objective of this study was to evaluate whether chest computed tomography (CT) can be used for detecting early predictors of severity and complications of smoke-inhalation injury.

Methods

We evaluated 37 patients who had sustained smoke-inhalation injuries and had undergone chest CT within a few hours of admission to a hospital. Bronchoscopy was performed according to a standardized protocol within 12 hours of admission in all smoke-inhalation injury patients. Bronchial-wall thickness (BWT) was measured 2 cm distal from the tracheal bifurcation with CT images, and the following data were collected: total number of ventilator days, duration of intensive care unit (ICU) stay, pneumonia development, and patient outcome.

Results

The mean age of the patients was 63 ± 18 years (range, 22 to 87 years), 31 (83.8%) of the patients were men, and the mortality rate was 10.8%. The causes of death in these patients were smoke inhalation (n = 1), hemorrhage (n = 1), and other factors resulting in sepsis (n = 2). The initial carboxyhemoglobin level was 13% ± 14% (range, 1% to 50%). No significant correlation was found between bronchoscopic scoring and clinical factors. However, significant correlations were noted between admission BWT and development of pneumonia (R² = 0.41; P < 0.0001) and total number of ventilator days (R² = 0.56; P < 0.0001) and ICU-stay days (R² = 0.17; P = 0.01). Receiver operating characteristic curve analysis showed that an admission BWT cutoff value of >3.0 mm predicted pneumonia development with a sensitivity of 79%, specificity of 96%, positive predictive value of 91%, and negative predictive value of 88%.

Conclusion

BWT measured by using the chest CT scans obtained within a few hours of admission was predictive of the total number of ventilator days and ICU-stay days and the development of pneumonia in patients with smoke-inhalation injuries.

Bronchoscopy-derived correlates of lung injury following inhalational injuries: a prospective observational study

Background

Acute lung injury (ALI) is a major factor determining morbidity following burns and inhalational injury. In experimental models, factors potentially contributing to ALI risk include inhalation of toxins directly causing cell damage; inflammation; and infection. However, few studies have been done in humans.

Methods

We carried out a prospective observational study of patients admitted to the NC Jaycees Burn Center who were intubated and on mechanical ventilation for burns and suspected inhalational injury. Subjects were enrolled over an 8-month period and followed till discharge or death. Serial bronchial washings from clinically-indicated bronchoscopies were collected and analyzed for markers of cell injury and inflammation. These markers were compared with clinical markers of ALI.

Results

Forty-three consecutive patients were studied, with a spectrum of burn and inhalation injury severity. Visible soot at initial bronchoscopy and gram negative bacteria in the lower respiratory tract were associated with ALI in univariate analyses. Subsequent multivariate analysis also controlled for % body surface area burns, infection, and inhalation severity. Elevated IL-10 and reduced IL-12p70 in bronchial washings were statistically significantly associated with ALI.

Conclusions

Independently of several factors including initial inhalational injury severity, infection, and extent of surface burns, high early levels of IL-10 and low levels of IL-12p70 in the central airways are associated with ALI in patients intubated after acute burn/inhalation injury. Lower airway secretions can be collected serially in critically ill burn/inhalation injury patients and may yield important clues to specific pathophysiologic pathways.

Aspiration, localized pulmonary inflammation, and predictors of early-onset bronchiolitis obliterans syndrome after lung transplantation

BACKGROUND

We hypothesized that immune mediator concentrations in the bronchoalveolar fluid (BALF) are predictive of bronchiolitis obliterans syndrome (BOS) and demonstrate specific patterns of dysregulation, depending on the presence of acute cellular rejection, BOS, aspiration, and timing of lung transplantation.

STUDY DESIGN

We prospectively collected 257 BALF samples from 105 lung transplant recipients. The BALF samples were assessed for absolute and differential white blood cell counts and 34 proteins implicated in pulmonary immunity, inflammation, fibrosis, and aspiration.

RESULTS

There were elevated BALF concentrations of interleukin (IL)-15, IL-17, basic fibroblast growth factor, tumor necrosis factor-α, and myeloperoxidase, and reduced concentrations of α1-antitrypsin, which were predictive of early-onset BOS. Patients with BOS had an increased percentage of BALF lymphocytes and neutrophils, with a reduced percentage of macrophages (p < 0.05). The BALF concentrations of IL-1β; IL-8; interferon-γ-induced protein 10; regulated upon activation, normal T-cell expressed and secreted; neutrophil elastase; and pepsin were higher in patients with BOS (p < 0.05). Among those with BOS, BALF concentrations of IL-1RA; IL-8; eotaxin; interferon-γ-induced protein 10; regulated upon activation, normal T-cell expressed and secreted; myeloperoxidase; and neutrophil elastase were positively correlated with time since transplantation (p < 0.01). Those with worse grades of acute cellular rejection had an increased percentage of lymphocytes in their BALF (p < 0.0001) and reduced BALF concentrations of IL-1β, IL-7, IL-9, IL-12, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, interferon-γ, and vascular endothelial growth factor (p ≤ 0.001). Patients with aspiration based on detectable pepsin had increased percentage of neutrophils (p < 0.001) and reduced BALF concentrations of IL-12 (p < 0.001).

CONCLUSIONS

The BALF levels of IL-15, IL-17, basic fibroblast growth factor, tumor necrosis factor-α, myeloperoxidase, and α1-antitrypsin at 6 to 12 months after lung transplantation are predictive of early-onset BOS, and those with BOS and aspiration have an augmented chemotactic and inflammatory balance of pulmonary leukocytes and immune mediators. These data justify the surgical prevention of aspiration and argue for the refinement of antirejection regimens.

Pulmonary cytokine composition differs in the setting of alcohol use disorders and cigarette smoking

Alcohol use disorders (AUDs), including alcohol abuse and dependence, and cigarette smoking are widely acknowledged and common risk factors for pneumococcal pneumonia. Reasons for these associations are likely complex but may involve an imbalance in pro- and anti-inflammatory cytokines within the lung. Delineating the specific effects of alcohol, smoking, and their combination on pulmonary cytokines may help unravel mechanisms that predispose these individuals to pneumococcal pneumonia. We hypothesized that the combination of AUD and cigarette smoking would be associated with increased bronchoalveolar lavage (BAL) proinflammatory cytokines and diminished anti-inflammatory cytokines, compared with either AUDs or cigarette smoking alone. Acellular BAL fluid was obtained from 20 subjects with AUDs, who were identified using a validated questionnaire, and 19 control subjects, matched on the basis of age, sex, and smoking history. Half were current cigarette smokers; baseline pulmonary function tests and chest radiographs were normal. A positive relationship between regulated and normal T cell expressed and secreted (RANTES) with increasing severity of alcohol dependence was observed, independent of cigarette smoking (P = 0.0001). Cigarette smoking duration was associated with higher IL-1β (P = 0.0009) but lower VEGF (P = 0.0007); cigarette smoking intensity was characterized by higher IL-1β and lower VEGF and diminished IL-12 (P = 0.0004). No synergistic effects of AUDs and cigarette smoking were observed. Collectively, our work suggests that AUDs and cigarette smoking each contribute to a proinflammatory pulmonary milieu in human subjects through independent effects on BAL RANTES and IL-1β. Furthermore, cigarette smoking additionally influences BAL IL-12 and VEGF that may be relevant to the pulmonary immune response.

Th17 cells: critical mediators of host responses to burn injury and sepsis

Th cells have long been recognized as vital components of the adaptive immune system. Until recently, CD3(+)CD4(+) Th cells were divided into cell-mediated Th1 or humoral Th2 responses. However, the Th1-Th2 hypothesis failed to accommodate the more recently described Th17 cells. Today, the major Th cell subsets include Th1, Th2, Th9, Th17, Th22, and Tregs, each of which produce specific effector cytokines under unique transcriptional regulation. Specifically, Th17 cells produce effector cytokines IL-17, IL-21, and IL-22 under the regulation of ROR-γt. Th17 lymphocytes were first described as orchestrators of neutrophil recruitment and activation and as key players in chronic inflammation and autoimmunity. More recent evidence suggest that Th17 lymphocytes and their effector cytokines play a crucial role in maintaining mucosal immunity and barrier integrity, including the skin, lung, and gut. Burn injury induces global changes to the systemic immune response, including suppressed immune function and increased susceptibility to infection. Moreover, burn trauma is associated with remote organ injury. This relationship between burn and remote organ injury supports the hypothesis that immune suppression may facilitate the development of sepsis, systemic inflammatory response syndrome, and multiple organ dysfunction syndrome in critically ill burn patients. Herein, we discuss this emerging adaptive cell subset in critical care settings, including burn injury and clinical sepsis, and highlight the potential therapeutic role of IL-22.

The acute pulmonary inflammatory response to the graded severity of smoke inhalation injury

OBJECTIVES

To determine whether the graded severity of smoke inhalation is reflected by the acute pulmonary inflammatory response to injury.

DESIGN

In a prospective observational study, we assessed the bronchoalveolar lavage fluid for both leukocyte differential and concentration of 28 cytokines, chemokines, and growth factors. Results were then compared to the graded severity of inhalation injury as determined by Abbreviated Injury Score criteria (0, none; 1, mild; 2, moderate; 3, severe; 4, massive).

SETTING

All patients were enrolled at a single tertiary burn center.

PATIENTS

The bronchoalveolar lavage fluid was obtained from 60 patients within 14 hrs of burn injury who underwent bronchoscopy for suspected smoke inhalation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Those who presented with worse grades of inhalation injury had higher plasma levels of carboxyhemoglobin and enhanced airway neutrophilia. Patients with the most severe inhalation injuries also had a greater requirement for tracheostomy, longer time on the ventilator, and a prolonged stay in the intensive care unit. Of the 28 inflammatory mediators assessed in the bronchoalveolar lavage fluid, 21 were at their highest in those with the worst inhalation injury scores (grades 3 and 4), the greatest of which was interleukin-8 (92,940 pg/mL, grade 4). When compared in terms of low inhalation injury (grades 1-2) vs. high inhalation injury (grades 3-4), we found significant differences between groups for interleukin-4, interleukin-6, interleukin-9, interleukin-15, interferon-γ, granulocyte-macrophage colony-stimulating factor, and monocyte chemotactic protein-1 (p < .05 for all).

CONCLUSIONS

These data reveal that the degree of inhalation injury has basic and profound effects on burn patient morbidity, evokes complex changes of multiple alveolar inflammatory proteins, and is a determinant of the pulmonary inflammatory response to smoke inhalation. Accordingly, future investigations should consider inhalation injury to be a graded phenomenon.

Pulmonary immune changes early after laparoscopic antireflux surgery in lung transplant patients with gastroesophageal reflux disease

BACKGROUND

The biologic mechanisms by which laparoscopic antireflux surgery (LARS) might influence the inflammatory process leading to bronchiolitis obliterans syndrome are unknown. We hypothesized that LARS alters the pulmonary immune profile in lung transplant patients with gastroesophageal reflux disease.

METHODS

In 8 lung transplant patients with gastroesophageal reflux disease, we quantified and compared the pulmonary leukocyte differential and the concentration of inflammatory mediators in the bronchoalveolar lavage fluid (BALF) 4 weeks before LARS, 4 weeks after LARS, and 12 months after lung transplantation. Freedom from bronchiolitis obliterans syndrome (graded 1-3 according to the International Society of Heart and Lung Transplantation guidelines), forced expiratory volume in 1 second trends, and survival were also examined.

RESULTS

At 4 weeks after LARS, the percentages of neutrophils and lymphocytes in the BALF were reduced (from 6.6% to 2.8%, P = 0.049, and from 10.4% to 2.4%, P = 0.163, respectively). The percentage of macrophages increased (from 74.8% to 94.6%, P = 0.077). Finally, the BALF concentration of myeloperoxide and interleukin-1β tended to decrease (from 2109 to 1033 U/mg, P = 0.063, and from 4.1 to 0 pg/mg protein, P = 0.031, respectively), and the concentrations of interleukin-13 and interferon-γ tended to increase (from 7.6 to 30.4 pg/mg protein, P = 0.078 and from 0 to 159.5 pg/mg protein, P = 0.031, respectively). These trends were typically similar at 12 months after transplantation. At a mean follow-up of 19.7 months, the survival rate was 75% and the freedom from bronchiolitis obliterans syndrome was 75%. Overall, the forced expiratory volume in 1 second remained stable during the first year after transplantation.

CONCLUSIONS

Our preliminary study has demonstrated that LARS can restore the physiologic balance of pulmonary leukocyte populations and that the BALF concentration of pro-inflammatory mediators is altered early after LARS. These results suggest that LARS could modulate the pulmonary inflammatory milieu in lung transplant patients with gastroesophageal reflux disease.