Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by a disruption of the endothelium and alveolar epithelial barriers involving increased microvascular permeability, thus resulting in the set of protein-rich pulmonary edema. Angiogenic factors and their receptors, including vascular endothelial growth factor (VEGF)/VEGF-receptor (VEGFR) and the angiopoietin (Ang)/Tie2 signaling pathways, play pivotal roles in both angiogenesis and microvascular permeability. The aim of the study was to assess the relationship between angiogenic factors, their soluble receptors and ALI/ARDS associated with critically ill patients, including sepsis, severe trauma, and post-cardiac arrest syndrome (PCAS).
One hundred fifty-nine critically ill patients, including 50 patients with sepsis, 57 patients with severe trauma and 52 resuscitated after out-of-hospital cardiac arrest, were divided into three subgroups: including 25 ALI patients, 101 ARDS patients and 22 non-ALI/ARDS patients. The serum levels of angiogenic factors were measured at the time of admission (day 1), as well as day 3 and day 5 and then were compared among the ALI, ARDS and non-ALI/ARDS groups. Their predictive values for developing ALI/ARDS and 28-day mortality were evaluated.
Higher levels of sVEGFR1 and Ang2 were observed in the ALI and ARDS patients than in the non-ALI/ARDS patients during the entire study period. The Ang2/Ang1 ratio in the ARDS group was also significantly higher than that in the non-ALI/ADRS group. The sVEGFR2 levels in the ARDS group on day 1 were significantly lower than those of the non-ALI/ADRS group. In addition, significant positive correlations were seen between the sVEGFR1, Ang2, Ang2/Ang1, and the development of ALI/ARDS in critical illness. There were also significant negative correlations between the minimal value of sVEGFR2, the maximal value of Ang1 and the ALI/ARDS group. In particular, sVEGFR2 and Ang2 were independent predictors of developing ALI/ARDS. Moreover, Ang2 and sVEGFR2 also independently predicted the mortality in ALI/ARDS patients.
Angiogenic factors and their soluble receptors, particularly sVEGFR2 and Ang2, are thus considered to be valuable predictive biomarkers in the development of ALI/ARDS associated with critical illness and mortality in ALI/ARDS patients.
Acute lung injury; Acute respiratory distress syndrome; Angiogenic factors; Vascular endothelial growth factor; Angiopoietin; Outcome
Rationale: Acute lung injury (ALI) acts as a complex genetic trait, yet its genetic risk factors remain incompletely understood. Large-scale genotyping has not previously been reported for ALI.
Objectives: To identify ALI risk variants after major trauma using a large-scale candidate gene approach.
Methods: We performed a two-stage genetic association study. We derived findings in an African American cohort (n = 222) using a cardiopulmonary disease–centric 50K single nucleotide polymorphism (SNP) array. Genotype and haplotype distributions were compared between subjects with ALI and without ALI, with adjustment for clinical factors. Top performing SNPs (P < 10−4) were tested in a multicenter European American trauma-associated ALI case-control population (n = 600 ALI; n = 2,266 population-based control subjects) for replication. The ALI-associated genomic region was sequenced, analyzed for in silico prediction of function, and plasma was assayed by ELISA and immunoblot.
Measurements and Main Results: Five SNPs demonstrated a significant association with ALI after adjustment for covariates in Stage I. Two SNPs in ANGPT2 (rs1868554 and rs2442598) replicated their significant association with ALI in Stage II. rs1868554 was robust to multiple comparison correction: odds ratio 1.22 (1.06–1.40), P = 0.0047. Resequencing identified predicted novel splice sites in linkage disequilibrium with rs1868554, and immunoblots showed higher proportion of variant angiopoietin-2 (ANG2) isoform associated with rs1868554T (0.81 vs. 0.48; P = 0.038).
Conclusions: An ANGPT2 region is associated with both ALI and variation in plasma angiopoietin-2 isoforms. Characterization of the variant isoform and its genetic regulation may yield important insights about ALI pathogenesis and susceptibility.
acute lung injury; acute respiratory distress syndrome; functional genetic polymorphism; genetic association study
Rationale: Accurate, early identification of patients at risk for developing acute lung injury (ALI) provides the opportunity to test and implement secondary prevention strategies.
Objectives: To determine the frequency and outcome of ALI development in patients at risk and validate a lung injury prediction score (LIPS).
Methods: In this prospective multicenter observational cohort study, predisposing conditions and risk modifiers predictive of ALI development were identified from routine clinical data available during initial evaluation. The discrimination of the model was assessed with area under receiver operating curve (AUC). The risk of death from ALI was determined after adjustment for severity of illness and predisposing conditions.
Measurements and Main Results: Twenty-two hospitals enrolled 5,584 patients at risk. ALI developed a median of 2 (interquartile range 1–4) days after initial evaluation in 377 (6.8%; 148 ALI-only, 229 adult respiratory distress syndrome) patients. The frequency of ALI varied according to predisposing conditions (from 3% in pancreatitis to 26% after smoke inhalation). LIPS discriminated patients who developed ALI from those who did not with an AUC of 0.80 (95% confidence interval, 0.78–0.82). When adjusted for severity of illness and predisposing conditions, development of ALI increased the risk of in-hospital death (odds ratio, 4.1; 95% confidence interval, 2.9–5.7).
Conclusions: ALI occurrence varies according to predisposing conditions and carries an independently poor prognosis. Using routinely available clinical data, LIPS identifies patients at high risk for ALI early in the course of their illness. This model will alert clinicians about the risk of ALI and facilitate testing and implementation of ALI prevention strategies.
Clinical trial registered with www.clinicaltrials.gov (NCT00889772).
respiratory distress syndrome, adult; prevention; prediction model; acute respiratory failure
Ventilator practices in patients at risk for acute lung injury (ALI) and ARDS are unclear. We examined factors associated with choice of set tidal volumes (VT), and whether VT < 8 mL/kg predicted body weight (PBW) relates to the development of ALI/ARDS.
We performed a secondary analysis of a multicenter cohort of adult subjects at risk of lung injury with and without ALI/ARDS at onset of invasive ventilation. Descriptive statistics were used to describe ventilator practices in specific settings and ALI/ARDS risk groups. Logistic regression analysis was used to determine the factors associated with the use of VT < 8 mL/kg PBW and the relationship of VT to ALI/ARDS development and outcome.
Of 829 mechanically ventilated patients, 107 met the criteria for ALI/ARDS at time of intubation, and 161 developed ALI/ARDS after intubation (post-intubation ALI/ARDS). There was significant intercenter variability in initial ventilator settings, and in the incidence of ALI/ARDS and post-intubation ALI/ARDS. The median VT was 7.96 (IQR 7.14–8.94) mL/kg PBW in ALI/ARDS subjects, and 8.45 (IQR 7.50–9.55) mL/kg PBW in subjects without ALI/ARDS (P = .004). VT decreased from 8.40 (IQR 7.38–9.37) mL/kg PBW to 7.97 (IQR 6.90–9.23) mL/kg PBW (P < .001) in those developing post-intubation ALI/ARDS. Among subjects without ALI/ARDS, VT ≥ 8 mL/kg PBW was associated with shorter height and higher body mass index, while subjects with pneumonia were less likely to get ≥ 8 mL/kg PBW. Initial VT ≥ 8 mL/kg PBW was not associated with the post-intubation ALI/ARDS (adjusted odds ratio 1.30, 95% CI 0.74–2.29) or worse outcomes. Post-intubation ALI/ARDS subjects had mortality similar to subjects intubated with ALI/ARDS.
Clinicians seem to respond to ALI/ARDS with lower initial VT. Initial VT, however, was not associated with the development of post-intubation ALI/ARDS or other outcomes.
acute lung injury; ARDS; mechanical ventilation; mortality; tidal volume
Packed Red Blood Cell (PRBC) transfusion is associated with Acute Lung Injury (ALI) development after trauma, but this risk may not be constant through time after trauma. We hypothesized the relationship between PRBC delivery and ALI risk varies through time after injury.
Data were collected prospectively from 1999–2006. Inclusion criteria: age > 13 years, SICU admission, and injury severity score (ISS) ≥ 16. Exclusion criteria included discharge/death within 24 hours of admission. Patients were followed prospectively for ALI development for 5 days after trauma. Discrete time models were fit to test the association of timing of PRBC delivery with development of ALI while controlling for patient demographics, resuscitation variables, ISS, and APACHE III scores.
At total of 602 patients were included. Median age was 33 years, 77% were male, and 50% were African American. Using a discrete time-survival model, the relation between transfusion and ALI development was found to vary by transfusion time-window (p<0.0001). The major effect of PRBC delivery on ALI risk occurred in the first 24 hours after trauma; this finding persisted in multivariable modeling (adjusted OR = 1.07 per unit; 95%CI 1.02–1.11, p<0.001). Cumulative incidence of ALI approached 50% in patients receiving ≥ 6u PRBC in the first 24 hours.
The association between PRBC transfusion and ALI development in trauma patients is time-dependent, with PRBC delivery in the first 24 hours after injury driving the overall relation. Each PRBC unit during this time period increases odds of subsequent ALI development by 7%.
The aim of this study was to determine the association between 25-hydroxyvitamin D (25-OHD) levels at the onset of critical illness and the development of acute lung injury/acute respiratory distress syndrome (ALI/ARDS) in patients with sepsis or trauma.
We performed two nested case-control studies of 478 patients with sepsis and trauma with or without ALI/ARDS admitted to the medical, surgical and trauma ICUs of a tertiary-care center. Cases consisted of patients with either sepsis or trauma and ALI/ARDS; controls consisted of equivalent numbers of matched patients with either sepsis or trauma alone. We measured serum 25-OHD levels the morning after ICU admission and used multivariable regression to assess the relationship between 25-OHD and diagnosis of ALI/ARDS during the first four ICU days, controlling for age, gender, diabetes, smoking status and season.
25-OHD levels did not differ between cases with ALI/ARDS and controls in either the sepsis or trauma cohorts. Using a conditional logistic regression model, sepsis patients during the winter season with higher 25-OHD levels were more likely to develop acute lung injury (odds ratio 1.68, 95% confidence interval of 1.05 to 2.69, P = 0.03). This association did not hold for the trauma cohort in either season. Sepsis and trauma patients had a lower risk of hospital mortality at higher 25-OHD levels but neither relationship reached significance. Higher one-year mortality after trauma was associated with lower 25-OHD levels (HR 0.50, CI 0.35,0.72 P = 0.001).
Serum 25-OHD measured early after admission to intensive care is not associated with the development of acute lung injury, hospital or one-year mortality in critically ill patients with sepsis although lower 25-OHD levels were associated with higher one-year mortality in patients with severe trauma.
Vitamin D; Sepsis; Trauma; Acute lung injury; Critical illness
Endocan is a proteoglycan expressed by endothelial cells in the lung which may inhibit leukocyte recruitment and thus prevent the development of acute lung injury (ALI). We tested the association of serum endocan levels with subsequent development of ALI after major trauma.
Materials and Methods
Single-center nested case control study within a prospective cohort study of major trauma patients. Using an ELISA test, we measured endocan levels from admission serum in 24 controls (no ALI) and 24 cases (ALI within 5 days of trauma). Multivariable logistic regression was used to test the association of admission serum endocan levels with subsequent ALI.
Patients who developed ALI had lower levels of endocan on admission (mean 3.5 ± 1.4 ng/mL vs. 4.9 ± 2.6 ng/mL in controls, p=0.02). For each 1-unit increase in serum endocan level, the odds ratio for ALI development decreased (0.69, 95% confidence interval (CI): 0.49, 0.97, p=0.03). Lower endocan levels remained associated with a higher incidence of ALI after adjustment for age and illness severity.
Lower levels of serum endocan on admission are associated with subsequent development of ALI in trauma patients. These observations may be explained by endocan-mediated blockade of leukocyte recruitment in the lung.
Trauma; acute respiratory distress syndrome; acute lung injury; biomarkers; endothelium
Although acute lung injury (ALI) is a common complication of severe malaria, little is known about the underlying molecular basis of lung dysfunction. Animal models have provided powerful insights into the pathogenesis of severe malaria syndromes such as cerebral malaria (CM); however, no model of malaria-induced lung injury has been definitively established. This study used bronchoalveolar lavage (BAL), histopathology and gene expression analysis to examine the development of ALI in mice infected with Plasmodium berghei ANKA (PbA). BAL fluid of PbA-infected C57BL/6 mice revealed a significant increase in IgM and total protein prior to the development of CM, indicating disruption of the alveolar–capillary membrane barrier—the physiological hallmark of ALI. In contrast to sepsis-induced ALI, BAL fluid cell counts remained constant with no infiltration of neutrophils. Histopathology showed septal inflammation without cellular transmigration into the alveolar spaces. Microarray analysis of lung tissue from PbA-infected mice identified a significant up-regulation of expressed genes associated with the gene ontology categories of defense and immune response. Severity of malaria-induced ALI varied in a panel of inbred mouse strains, and development of ALI correlated with peripheral parasite burden but not CM susceptibility. Cd36−/− mice, which have decreased parasite lung sequestration, were relatively protected from ALI. In summary, parasite burden and CD36-mediated sequestration in the lung are primary determinants of ALI in experimental murine malaria. Furthermore, differential susceptibility of mouse strains to malaria-induced ALI and CM suggests that distinct genetic determinants may regulate susceptibility to these two important causes of malaria-associated morbidity and mortality.
Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) can occur in adult malaria infections with a case fatality rate of 70%–100%. ALI and ARDS are characterized by protein-rich fluid in the lungs, with reduced gas exchange, and in malaria, often accompany high parasite levels and severe or cerebral disease. In this work we have examined lung physiology, pathology and genomics in mouse malaria—Plasmodium berghei ANKA—to show that mice develop malaria-induced ALI. Infected mice have proteinaceous fluid in their lungs, have a migration of inflammatory cells from the blood into the lung walls, and express immune response–related genes. We also found that severity of ALI depended on high parasite levels, both overall and specifically in the lung tissue, but was not consistent with whether the mice developed cerebral malaria. ALI due to Plasmodium berghei ANKA infection models prominent characteristics of human malaria-associated ALI, and we have better defined this model of malaria ALI so it may be used to further explore disease mechanisms and eventual treatment.
The role of thyroid hormone metabolism in clinical outcomes of the critically ill remains unclear. Using preclinical models of acute lung injury (ALI), we assessed the gene and protein expression of type 2 deiodinase (DIO2), a key driver for synthesis of biologically active triiodothyronine, and addressed potential association of DIO2 genetic variants with ALI in a multiethnic cohort. DIO2 gene and protein expression levels in murine lung were validated by microarrays and immunoblotting. Lung injury was assessed by levels of bronchoalveolar lavage protein and leukocytes. Single-nucleotide polymorphisms were genotyped and ALI susceptibility association assessed. Significant increases in both DIO2 gene and D2 protein expression were observed in lung tissues from murine ALI models (LPS- and ventilator-induced lung injury), with expression directly increasing with the extent of lung injury. Mice with reduced levels of DIO2 expression (by silencing RNA) demonstrated reduced thyroxine levels in plasma and increased lung injury (increased bronchoalveolar lavage protein and leukocytes), suggesting a protective role for DIO2 in ALI. The G (Ala) allele of the Thr92Ala coding single-nucleotide polymorphism (rs225014) was protective in severe sepsis and severe sepsis–associated ALI after adjustments for age, sex, and genetic ancestry in a logistic regression model in European Americans. Our studies indicate that DIO2 is a novel ALI candidate gene, the nonsynonymous Thr92Ala coding variant of which confers ALI protection. Increased DIO2 expression may dampen the ALI inflammatory response, thereby strengthening the premise that thyroid hormone metabolism is intimately linked to the integrated response to inflammatory injury in critically ill patients.
acute respiratory distress syndrome; hypothyroidism; mechanical ventilation; sepsis
Activation of adenosine A2A receptor aggravates lung damage in a neurogenic mouse model of acute lung injury (ALI) but protects against nonneurogenic ALI.
The bone marrow–derived cell (BMDC)–associated inflammatory response plays a key role in the development of acute lung injury (ALI). Activation of adenosine A2A receptor (A2AR) is generally considered to be antiinflammatory, inhibiting BMDC activities to protect against ALI. However, in the present study, we found that in a mouse model of neurogenic ALI induced by severe traumatic brain injury (TBI), BMDC A2AR exerted a proinflammatory effect, aggravating lung damage. This is in contrast to the antiinflammatory effect observed in the mouse oleic acid–induced ALI model (a nonneurogenic ALI model.) Moreover, the A2AR agonist CGS21680 aggravated, whereas the antagonist ZM241385 attenuated, the severe TBI-induced lung inflammatory damage in mice. Further investigation of white blood cells isolated from patients or mouse TBI models and of cultured human or mouse neutrophils demonstrated that elevated plasma glutamate after severe TBI induced interaction between A2AR and the metabotropic glutamate receptor 5 (mGluR5) to increase phospholipase C–protein kinase C signaling, which mediated the proinflammatory effect of A2AR. These results are in striking contrast to the well-known antiinflammatory and protective role of A2AR in nonneurogenic ALI and indicate different therapeutic strategies should be used for nonneurogenic and neurogenic ALI treatment when targeting A2AR.
Sepsis-induced acute lung injury (ALI) has been reported to have a higher case fatality rate than other causes of ALI. However, differences in the severity of illness in septic vs. non-septic ALI patients might explain this finding.
520 patients enrolled in the Improving Care of ALI Patients Study (ICAP) were prospectively characterized as having sepsis or non sepsis-induced ALI. Biologically plausible risk factors for in-hospital death were considered in multiple logistic regression models to evaluate the independent association of sepsis vs. non-sepsis ALI risk factors with mortality.
Patients with sepsis-induced ALI had greater illness severity and organ dysfunction (APACHE II and SOFA scores) at ALI diagnosis and higher crude in-hospital mortality rates compared with non-sepsis ALI patients. Patients with sepsis-induced ALI received similar tidal volumes, but higher levels of positive end expiratory pressure, and had a more positive net fluid balance in the first week after ALI diagnosis. In multivariable analysis, the following variables (odds ratio, 95% confidence interval) were significantly associated with hospital mortality: age (1.04, 1.02 to 1.05), admission to a medical intensive care unit (ICU) (2.76, 1.42 to 5.36), ICU length of stay prior to ALI diagnosis (1.15, 1.03 to 1.29), APACHE II (1.05, 1.02 to 1.08), SOFA at ALI diagnosis (1.17, 1.09 to 1.25), Lung Injury Score (2.33, 1.74 to 3.12) and net fluid balance in liters in the first week after ALI diagnosis (1.06, 1.03 to 1.09). Sepsis did not have a significant, independent association with mortality (1.02, 0.59 to 1.76).
Greater severity of illness contributes to the higher case fatality rate observed in sepsis-induced ALI. Sepsis was not independently associated with mortality in our study.
Rationale: Acute lung injury (ALI) that develops 6 hours after transfusion (TRALI) is the leading cause of transfusion-related mortality. Several transfusion characteristics have been postulated as risk factors for TRALI, but the evidence is limited to retrospective studies.
Objectives: To compare patient and transfusion risk factors between patients who do and do not develop ALI.
Methods: In this prospective cohort study, consecutive transfused critically ill patients were closely observed for development of ALI. Donor samples were collected from the transfusion bags. Risk factors were compared between patients who developed ALI after transfusion and transfused control patients, matched by age, sex, and admission diagnosis.
Measurements and Main Results: Seventy-four of 901 transfused patients developed ALI within 6 hours of transfusion (8%). Compared with transfused control subjects, patients with ALI were more likely to have sepsis (37 vs. 22%, P = 0.016) and a history of chronic alcohol abuse (37 vs. 18%, P = 0.006). When adjusted for patient characteristics, transfusion of plasma from female donors (odds ratio [OR], 5.09; 95% confidence interval [95% CI], 1.37–18.85) rather than male donors (OR, 1.60; 95% CI, 0.76 to 3.37), number of pregnancies among the donors (OR, 1.19; 95% CI, 1.05 to 1.34), number of donor units positive for anti-granulocyte antibodies (OR, 4.85; 95% CI, 1.32–17.86) and anti–HLA class II antibodies (OR, 3.08; 95% CI, 1.15–8.25), and concentration of lysophosphatidylcholine in the donor product (OR, 1.69; 95% CI, 1.10 to 2.59) were associated with the development of ALI.
Conclusions: Both patient and transfusion risk factors determine the probability of ALI after transfusion. Transfusion factors represent attractive targets for the prevention of ALI.
fresh-frozen plasma; platelet transfusion; pulmonary edema; female; blood donors
The diagnosis of acute lung injury (ALI) is based on a consensus clinical definition. Despite the simplicity of this definition, ALI remains underdiagnosed and undertreated. Severe trauma is a well-described cause of ALI that represents a relatively homogeneous subset of ALI patients. The goals of this study were to develop a panel of plasma biomarkers to facilitate diagnosis of trauma-induced ALI and to enhance our understanding of the pathogenesis of human ALI.
A retrospective nested case control of 192 patients admitted to the trauma intensive care unit (ICU) at a university hospital between 2002 and 2006. We compared 107 patients with ALI to 85 patients without ALI. Plasma was collected within 72 h of ICU admission. Twenty-one plasma biomarkers were measured in duplicate in each plasma sample.
Patients with ALI had higher severity of illness scores, more days of mechanical ventilation, longer hospital stays and higher mortality versus controls. Seven biomarkers (RAGE, PCPIII, BNP, ANG2, IL10, TNF-α, and IL8) had a high diagnostic accuracy as reflected by the area under the receiver operating characteristic curve of 0.86 (95% CI 0.82 – 0.92) in differentiating ALI from controls.
A model utilizing seven plasma biomarkers had a high diagnostic accuracy in differentiating patients with trauma-induced ALI from trauma patients without ALI. In addition, use of a panel of biomarkers provides insight into the likely importance of alveolar epithelial injury in the pathogenesis of early acute lung injury.
Acute respiratory distress syndrome; acute pulmonary edema; pulmonary contusion; alveolar epithelium
Acute lung injury (ALI) is a common and frequently devastating illness characterized by acute hypoxemic respiratory failure, profound inflammation, and flooding of the alveoli. Despite recent advances in ALI care, the morbidity and mortality of ALI continues to be unacceptably high. ALI-inciting events (e.g., sepsis, trauma, aspiration, pneumonia) are quite common, yet only a fraction of patients develop the syndrome. This heterogeneity of patients presenting with ALI has sparked interest in identifying the role of genetic factors that contribute to ALI susceptibility and prognosis. Recent advances in high-throughput sequencing and expression technologies now provide the tools to perform large-scale genomic analyses in complex disorders such as ALI; gene expression profiling and pathway analysis provide further insight into previously described molecular pathways involved in the syndrome. In this article, we describe the use of genomewide association studies, ortholog in silico techniques, utility of consomic rat methods, and candidate gene approaches using expression profiling and pathway analyses. These methods have confirmed suspected ALI candidate genes (e.g., IL-6 and MIF), but more impressively have identified novel genes (e.g., GADD45α and PBEF) not previously suspected in ALI. The analysis of the molecular pathways (e.g., the cytoskeleton in vascular barrier regulation) has identified additional genes contributing to the development and severity of ALI (e.g., MLCK), thereby providing therapeutic targets in this devastating illness.
acute lung injury; genetics; ventilator-induced lung injury
Recent studies showed that overwhelming inflammatory response mediated by the toll-like receptor (TLR)-related pathway was important in the development of acute lung injury (ALI). The aim of this study was to determine whether common genetic variation in four genes of the TLR signaling pathway were associated with sepsis-induced ALI susceptibility and risk of death in Chinese Han population.
Fourteen tag single nucleotide polymorphisms (tagSNPs) in MyD88, IRAK1, IRAK4 and TRAF6 were genotyped in samples of sepsis-induced ALI (n = 272) and sepsis alone patients (n = 276), and tested for association in this case-control collection. Then, we investigated correlation between the associated SNP and the mRNA expression level of the corresponding gene. And we also investigated correlation between the associated SNP and tumor necrosis factor alpha (TNF-α) as well as interleukin-6 (IL-6) concentrations in peripheral blood mononuclear cells (PBMCs) exposed to lipopolysaccharides (LPS) ex vivo. The mRNA expression level was determined using real-time quantitative Polymerase Chain Reaction (PCR) assays, and concentrations of TNF-α and IL-6 were measured by enzyme-linked immunosorbent assay (ELISA).
The association analysis revealed that rs4755453, an intronic SNP of TRAF6, was significantly associated with susceptibility to sepsis-induced ALI. The C allele frequency of rs4755453 in the sepsis alone group was significantly higher than that in the sepsis-induced ALI group (P = 0.00026, odds ratio (OR) = 0.52, 95% confidence interval (CI) 0.37–0.74). These associations remained significant after adjustment for covariates in multiple logistic regression analysis and for multiple comparisons. TRAF6 mRNA expression levels in PBMCs from homozygotes of the rs4755453G allele were significantly higher than that in heterozygotes and homozygotes of the rs4755453C allele at baseline (P = 0.012 and P = 0.003, respectively) as well as after LPS stimulation (P = 0.009 and P = 0.005). Moreover, the concentrations of TNF-α and IL-6 in cell culture supernatants were also significantly higher in the subjects with rs4755453GG genotype than in subjects with CG and CC genotype. None of the 14 tagSNPs showed associations with risk of death and severity among ALI cases.
Our findings indicated that common genetic variants in TRAF6 were significantly associated with susceptibility to sepsis-induced ALI in Chinese Han population. This was the first genetic evidence supporting a role for TRAF6 in ALI.
Acute lung injury; Genetic variation; TRAF6; TLR signaling pathway
Deposition of fibrin in the alveolar space is a hallmark of acute lung injury (ALI). Plasminogen activator inhibitor-1 (PAI-1) is an antifibrinolytic agent that is activated during inflammation. Increased plasma and pulmonary edema fluid levels of PAI-1 are associated with increased mortality in adults with ALI. This relationship has not been examined in children. The objective of this study was to test whether increased plasma PAI-1 levels are associated with worse clinical outcomes in pediatric patients with ALI.
We measured plasma PAI-1 levels on the first day of ALI among 94 pediatric patients enrolled in two separate prospective, multicenter investigations and followed them for clinical outcomes. All patients met American European Consensus Conference criteria for ALI.
A total of 94 patients were included. The median age was 3.2 years (range 16 days–18 years), the PaO2/FiO2 was 141 ± 72 (mean ± SD), and overall mortality was 14/94 (15%). PAI-1 levels were significantly higher in nonsurvivors compared to survivors (P < 0.01). The adjusted odds of mortality doubled for every log increase in the level of plasma PAI-1 after adjustment for age and severity of illness.
Higher PAI-1 levels are associated with increased mortality and fewer ventilator-free days among pediatric patients with ALI. These findings suggest that impaired fibrinolysis may play a role in the pathogenesis of ALI in pediatric patients and suggest that PAI-1 may serve as a useful biomarker of prognosis in patients with ALI.
Accurate respiratory distress syndrome; Acute lung injury; Clinical studies; Pediatrics; Plasminogen activator inhibitor-1 (PAI-1)
Although pneumonia has been identified as the single most common risk factor for acute lung injury (ALI), we have a limited knowledge as to why ALI develops in some patients with pneumonia and not in others. The objective of this study was to determine frequency, risk factors, and outcome of ALI in patients with infectious pneumonia.
A retrospective cohort study of adult patients with microbiologically positive pneumonia, hospitalized at two Mayo Clinic Rochester hospitals between January 1, 2005, and December 31, 2007. In a subsequent nested case-control analysis, we evaluated the differences in prehospital and intrahospital exposures between patients with and without ALI/acute respiratory distress syndrome (ARDS) matched by specific pathogen, isolation site, gender, and closest age in a 1:1 manner.
The study included 596 patients; 365 (61.2%) were men. The median age was 65 (IQR, 53 to 75) years. In total, 171 patients (28.7%) were diagnosed with ALI. The occurrence of ALI was less frequent in bacterial (n = 99 of 412, 24%) compared with viral (n = 19 of 55, 35%), fungal (n = 39 of 95, 41%), and mixed isolates pneumonias (n = 14 of 34, 41%; P = 0.002). After adjusting for baseline severity of illness and comorbidities, patients in whom ALI developed had a markedly increased risk of hospital death (ORadj 9.7; 95% CI, 6.0 to 15.9). In a nested case-control study, presence of shock (OR, 8.9; 95% CI, 2.8 to 45.9), inappropriate initial antimicrobial treatment (OR, 3.2; 95% CI, 1.3 to 8.5), and transfusions (OR, 4.8; 95% CI, 1.5 to 19.6) independently predicted ALI development.
The development of ALI among patients hospitalized with infectious pneumonia varied among pulmonary pathogens and was associated with increased mortality. Inappropriate initial antimicrobial treatment and transfusion predict the development of ALI independent of pathogen.
To characterize the use of mechanical ventilation in the emergency department (ED), with respect to ventilator settings, monitoring, and titration; and to determine the incidence of progression to acute lung injury (ALI) after admission, examining the influence of factors present in the ED on ALI progression.
This was a retrospective, observational cohort study of mechanically ventilated patients with severe sepsis and septic shock (June 2005 to May 2010), presenting to an academic ED with an annual census of >95,000 patients. All patients in the study (n = 251) were analyzed for characterization of mechanical ventilation use in the ED. The primary outcome variable of interest was the incidence of ALI progression after ICU admission from the ED and risk factors present in the ED associated with this outcome. Secondary analyses included ALI present in the ED and clinical outcomes comparing all patients progressing to ALI versus no ALI. To assess predictors of progression to ALI, statistically significant variables in univariable analyses at a p ≤ 0.10 level were candidates for inclusion in a bidirectional, stepwise, multivariable logistic regression analysis.
Lung-protective ventilation was used in 68 patients (27.1%), and did not differ based on ALI status. Delivered tidal volume was highly variable, with a median tidal volume delivered of 8.8 mL/kg ideal body weight (IBW) (IQR 7.8 to 10.0), and a range of 5.2 to 14.6 mL/kg IBW. Sixty-nine patients (27.5%) in the entire cohort progressed to ALI after admission to the hospital, with a mean onset of 2.1 days (SD ± 1 day). Multivariable logistic regression analysis demonstrated that a higher body mass index, higher Sequential Organ Failure Assessment score, and ED vasopressor use were associated with progression to ALI. There was no association between ED ventilator settings and progression to ALI. Compared to patients who did not progress to ALI, patients progressing to ALI after admission from the ED had an increase in mechanical ventilator duration, vasopressor dependence, and hospital length of stay.
Lung-protective ventilation is uncommon in the ED, regardless of ALI status. Given the frequency of ALI in the ED, the progression shortly after ICU admission, and the clinical consequences of this syndrome, the effect of ED-based interventions aimed at reducing the sequelae of ALI should be investigated further.
Von Willebrand factor antigen (vWF-Ag) is a marker of pulmonary and systemic endothelial activation and injury. Adult studies indicate that patients with plasma vWF-Ag levels ≥450% of control early in the course of acute lung injury (ALI) have an increased risk of death. The objective of this study was to evaluate whether vWF-Ag is elevated in the early phase of ALI in children and whether the magnitude of the increase was predictive of two important outcomes: mortality or duration of mechanical ventilation.
Two-center, prospective observational study.
Two pediatric intensive care units: one in an academic university setting and one in a major community children's hospital.
After appropriate consent, plasma was collected from 48 pediatric patients on day 1 of ALI, 45 patients on day 2 of ALI, and four intubated controls.
Measurements and Main Results
Mean Pao2/Fio2 at the onset of ALI was 140 ± 70, and mortality rate was 17%. vWF-Ag levels on day 1 of ALI were higher in patients compared with controls (287 ±183 vs. 87 ± 84% of control [mean ± sd], p < .05). Patients with vWF-Ag levels ≥450% of control on day 1 of ALI had a markedly greater risk of death (odds ratio, 7.0; confidence interval, 1.31, 37.30; p < .05). Multivariate analysis revealed that elevated vWF-Ag level and either presence of multiple organ system failure or Pediatric Risk of Mortality III score independently predict increased risk of death. vWF-Ag levels on day 2 of ALI were significantly higher in patients who required prolonged mechanical ventilation (316 ±173 vs. 191 ± 89% of control, p < .05).
Early injury to the systemic and pulmonary endothelium, as measured by plasma vWF-Ag levels, is associated with an increased risk of death and prolonged mechanical ventilation in pediatric patients with ALI. (Pediatr Crit Care Med 2007; 8:96–101)
pediatric acute lung injury; von Willebrand factor antigen; mortality; mechanical ventilation; acute respiratory distress syndrome; biological markers
The authors designed an automated electronic system that incorporates data from multiple hospital information systems to screen for acute lung injury (ALI) in mechanically ventilated patients. The authors evaluated the accuracy of this system in diagnosing ALI in a cohort of patients with major trauma, but excluding patients with congestive heart failure (CHF).
Single-center validation study. Arterial blood gas (ABG) data and chest radiograph (CXR) reports for a cohort of intensive care unit (ICU) patients with major trauma but excluding patients with CHF were screened prospectively for ALI requiring intubation by an automated electronic system. The system was compared to a reference standard established through consensus of two blinded physician reviewers who independently screened the same population for ALI using all available ABG data and CXR images. The system's performance was evaluated (1) by measuring the sensitivity and overall accuracy, and (2) by measuring concordance with respect to the date of ALI identification (vs. reference standard).
One hundred ninety-nine trauma patients admitted to our level 1 trauma center with an initial injury severity score (ISS) ≥ 16 were evaluated for development of ALI in the first five days in an ICU after trauma.
The system demonstrated 87% sensitivity (95% confidence interval [CI] 82.3–91.7) and 89% specificity (95% CI 84.7–93.4). It identified ALI before or within the 24-hour period during which ALI was identified by the two reviewers in 87% of cases.
An automated electronic system that screens intubated ICU trauma patients, excluding patients with CHF, for ALI based on CXR reports and results of ABGs is sufficiently accurate to identify many early cases of ALI.
Rationale: Current clinical prediction scores for acute lung injury (ALI) have limited positive predictive value. No studies have evaluated predictive plasma biomarkers in a broad population of critically ill patients or as an adjunct to clinical prediction scores.
Objectives: To determine whether plasma angiopoietin-2 (Ang-2), von Willebrand factor (vWF), interleukin-8 (IL-8), and/or receptor for advanced glycation end products (sRAGE) predict ALI in critically ill patients.
Methods: Plasma samples were drawn from critically ill patients (n = 230) identified in the emergency department. Patients who had ALI at baseline or in the subsequent 6 hours were excluded, and the remaining patients were followed for development of ALI.
Measurements and Main Results: Nineteen patients developed ALI at least 6 hours after the sample draw. Higher levels of Ang-2 and IL-8 were significantly associated with increased development of ALI (P = 0.0008, 0.004, respectively). The association between Ang-2 and subsequent development of ALI was robust to adjustment for sepsis and vasopressor use. Ang-2 and the Lung Injury Prediction Score each independently discriminated well between those who developed ALI and those who did not (area under the receiver operating characteristic curve, 0.74 for each), and using the two together improved the area under the curve to 0.84 (vs. 0.74, P = 0.05). In contrast, plasma levels of sRAGE and vWF were not predictive of ALI.
Conclusions: Plasma biomarkers such as Ang-2 can improve clinical prediction scores and identify patients at high risk for ALI. In addition, the early rise of Ang-2 emphasizes the importance of endothelial injury in the early pathogenesis of ALI.
acute respiratory distress syndrome; acute lung injury; receptor for advanced glycation end products; angiopoietin-2; Lung Injury Prediction Score
Rationale: Oxygen supplementation (e.g., hyperoxia) is used to support critically ill patients with noninfectious and infectious acute lung injury (ALI); however, hyperoxia exposure can potentially further contribute to and/or perpetuate preexisting ALI. Thus, developing novel therapeutic agents to minimize the side effects of hyperoxia is essential to improve the health of patients with severe ALI and respiratory dysfunction. We have previously shown that mice with a genetic disruption of the Nrf2 transcription factor, which squelches cellular stress by up-regulating the induction of several antioxidant enzymes and proteins, have greater susceptibility to hyperoxic lung injury. Moreover, we have recently demonstrated that Nrf2-deficiency impairs the resolution of lung injury and inflammation after nonlethal hyperoxia exposure.
Objectives: To test the hypothesis that amplification of endogenous Nrf2 activity would prevent or dampen ALI induced by hyperoxia.
Methods: Here, we tested our hypothesis using a synthetic triterpenoid compound CDDO-imidazole (CDDO-Im) (1-[2-cyano-3-,12-dioxooleana-1,9(11)-dien-28-oyl] imidazole) in Nrf2-sufficient and Nrf2-deficient mice subjected to hyperoxia-induced ALI.
Measurements and Main Results: We demonstrate that oral administration of CDDO-Im at a dose of 30 μmol/kg body weight during the hyperoxic exposure is sufficient to markedly attenuate hyperoxia-induced ALI in Nrf2-sufficient but not Nrf2-deficient mice. This protection by the CDDO-Im against hyperoxic insult was accompanied by increased levels of Nrf2-regulated cytoprotective gene expression and reduced levels of DNA damage in the lung.
Conclusions: These results suggest that up-regulation of Nrf2 signaling by CDDO-Im or its analogs may provide a novel therapeutic strategy to minimize the adverse effects of hyperoxia.
Nrf2; Keap1; antioxidants; stress response
Acute lung injury (ALI) is a frequent complication of sepsis. It is unclear if a pulmonary vs nonpulmonary source of sepsis affects mortality in patients with sepsis-induced ALI.
Two hundred eighty-eight consecutive patients with sepsis-induced ALI from 14 ICUs at four hospitals in Baltimore,MDwere prospectively classified as having a pulmonary vs nonpulmonary source of sepsis. Multiple logistic regression was conducted to evaluate the independent association of a pulmonary vs nonpulmonary source of sepsis with inpatient mortality.
In an unadjusted analysis, in-hospital mortality was lower for pulmonary vs nonpulmonary source of sepsis (42% vs 66%, p < 0.0001). Patients with pulmonary sepsis had lower acute physiology and chronic health evaluation (APACHE) II and sequential organ failure assessment (SOFA) scores, shorter ICU stays prior to the development of ALI, and higher lung injury scores. In the adjusted analysis, several factors were predictive of mortality: age (odds ratio [OR], 1.03; 95% confidence interval [CI], 1.01 to 1.06), Charlson comorbidity index (OR, 1.15; 95% CI, 1.02 to 1.30), ICU length of stay prior to ALI diagnosis (OR, 1.19; 95% CI, 1.01 to 1.39), APACHE II score (OR, 1.07; 95% CI, 1.03 to 1.12), lung injury score (OR, 1.64; 95% CI, 1.11 to 2.43), SOFA score (OR, 1.15; 95% CI, 1.06 to 1.26), and cumulative fluid balance in the first 7 days after ALI diagnosis (OR, 1.06; 95% CI, 1.03 to 1.10). A pulmonary vs nonpulmonary source of sepsis was not independently associated with mortality (OR, 0.72; 95% CI, 0.38 to 1.35).
Although lower mortality was observed for ALI patients with a pulmonary vs nonpulmonary source of sepsis, this finding is likely due to a lower severity of illness in those with pulmonary sepsis. Pulmonary vs nonpulmonary source of sepsis was not independently predictive of mortality for patients with ALI.
ARDS; critical illness; mortality; sepsis
Toll like receptors (TLRs) signaling pathways, including the adaptor protein Mal encoded by the TIRAP gene, play a central role in the development of acute lung injury (ALI). Recently, the TIRAP variants have been described association with susceptibility to inflammatory diseases. The aim of this study was to investigate whether genetic variants in TIRAP are associated with the development of ALI.
A case-control collection from Han Chinese of 298 healthy subjects, 278 sepsis-associated ALI and 288 sepsis alone patients were included. Three tag single nucleotide polymorphisms (SNPs) of the TIRAP gene and two additional SNPs that have previously showed association with susceptibility to other inflammatory diseases were genotyped by direct sequencing. The differences of allele, genotype and haplotype frequencies were evaluated between three groups.
The minor allele frequencies of both rs595209 and rs8177375 were significantly increased in ALI patients compared with both healthy subjects (odds ratio (OR) = 1.47, 95% confidence interval (CI):1.15-1.88, P = 0.0027 and OR = 1.97, 95% CI: (1.38-2.80), P = 0.0001, respectively) and sepsis alone patients (OR = 1.44, 95% CI: 1.12-1.85, P = 0.0041 and OR = 1.82, 95% CI: 1.28-2.57, P = 0.00079, respectively). Haplotype consisting of these two associated SNPs strengthened the association with ALI susceptibility. The frequency of haplotype AG (rs595209A, rs8177375G) in the ALI samples was significantly higher than that in the healthy control group (OR = 2.13, 95% CI: 1.46-3.09, P = 0.00006) and the sepsis alone group (OR = 2.24, 95% CI: 1.52-3.29, P = 0.00003). Carriers of the haplotype CA (rs595209C, rs8177375A) had a lower risk for ALI compared with healthy control group (OR = 0.69, 95% CI: 0.54-0.88, P = 0.0003) and sepsis alone group (OR = 0.71, 95% CI: 0.55-0.91, P = 0.0006). These associations remained significant after adjustment for covariates in multiple logistic regression analysis and for multiple comparisons.
These results indicated that genetic variants in the TIRAP gene might be associated with susceptibility to sepsis-associated ALI in Han Chinese population. However, the association needs to be replicated in independent studies.
Neutral endopeptidase (NEP), an enzyme that cleaves inflammatory bioactive peptides, may play a protective role in the pathogenesis of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). However, its low extracellular activity hinders the precise measurement of changes that take place during ALI/ARDS. The main objective of this study was to clarify the regulation of NEP activity and its expression during ALI/ARDS.
In a clinical study, we measured plasma NEP activity in patients who developed postoperative ALI/ARDS, using a HPLC fluorometric system. In an experimental study, we induced ALI by intratracheal instillation of hydrochloric acid (HCl) or lipopolysaccharide (LPS) in mice, and similarly measured NEP activity in plasma, lung tissue, and broncho-alveolar lavage fluid (BALF). We also studied the distribution and measured the amounts of NEP protein, using immuno-histochemical and immunoblot analyses, and measured the levels of NEP mRNA, using real-time reverse transcription-polymerase chain reaction, in the lungs of mice with ALI.
The plasma NEP activity was significantly lower in patients presenting with ALI/ARDS than in controls. Similarly, the NEP activity in plasma and lung tissue was markedly lower, and lung injuries more severe in LPS- than in HCl-treated mice. In contrast, the activity of NEP in the BALF of LPS-treated mice was increased. The intratracheal instillation of LPS decreased the gene expression of NEP in the lung. Immuno-histochemical and Western immunoblot studies in mice confirmed a) the presence of NEP in the alveolar wall, a critical target in ALI/ARDS, and b) a decrease in its expression in HCl- and LPS-induced ALI.
In this experimental and clinical study of ALI/ARDS, the activity of NEP was significantly decreased in plasma and increased in the alveolar air space.