Pathobiology, Severity, and Risk Stratification of Pediatric Acute Respiratory Distress Syndrome: From the Second Pediatric Acute Lung Injury Consensus Conference.

OBJECTIVES: To review the literature for studies published in children on the pathobiology, severity, and risk stratification of pediatric acute respiratory distress syndrome (PARDS) with the intent of guiding current medical practice and identifying important areas for future research related to severity and risk stratification. DATA SOURCES: Electronic searches of PubMed and Embase were conducted from 2013 to March 2022 by using a combination of medical subject heading terms and text words to capture the pathobiology, severity, and comorbidities of PARDS. STUDY SELECTION: We included studies of critically ill patients with PARDS that related to the severity and risk stratification of PARDS using characteristics other than the oxygenation defect. Studies using animal models, adult only, and studies with 10 or fewer children were excluded from our review. DATA EXTRACTION: Title/abstract review, full-text review, and data extraction using a standardized data collection form. DATA SYNTHESIS: The Grading of Recommendations Assessment, Development, and Evaluation approach was used to identify and summarize relevant evidence and develop recommendations for clinical practice. There were 192 studies identified for full-text extraction to address the relevant Patient/Intervention/Comparator/Outcome questions. One clinical recommendation was generated related to the use of dead space fraction for risk stratification. In addition, six research statements were generated about the impact of age on acute respiratory distress syndrome pathobiology and outcomes, addressing PARDS heterogeneity using biomarkers to identify subphenotypes and endotypes, and use of standardized ventilator, physiologic, and nonpulmonary organ failure measurements for future research. CONCLUSIONS: Based on an extensive literature review, we propose clinical management and research recommendations related to characterization and risk stratification of PARDS severity.

Executive Summary of the Second International Guidelines for the Diagnosis and Management of Pediatric Acute Respiratory Distress Syndrome (PALICC-2).

OBJECTIVES: We sought to update our 2015 work in the Second Pediatric Acute Lung Injury Consensus Conference (PALICC-2) guidelines for the diagnosis and management of pediatric acute respiratory distress syndrome (PARDS), considering new evidence and topic areas that were not previously addressed. DESIGN: International consensus conference series involving 52 multidisciplinary international content experts in PARDS and four methodology experts from 15 countries, using consensus conference methodology, and implementation science. SETTING: Not applicable. PATIENTS: Patients with or at risk for PARDS. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Eleven subgroups conducted systematic or scoping reviews addressing 11 topic areas: 1) definition, incidence, and epidemiology; 2) pathobiology, severity, and risk stratification; 3) ventilatory support; 4) pulmonary-specific ancillary treatment; 5) nonpulmonary treatment; 6) monitoring; 7) noninvasive respiratory support; 8) extracorporeal support; 9) morbidity and long-term outcomes; 10) clinical informatics and data science; and 11) resource-limited settings. The search included MEDLINE, EMBASE, and CINAHL Complete (EBSCOhost) and was updated in March 2022. Grading of Recommendations, Assessment, Development, and Evaluation methodology was used to summarize evidence and develop the recommendations, which were discussed and voted on by all PALICC-2 experts. There were 146 recommendations and statements, including: 34 recommendations for clinical practice; 112 consensus-based statements with 18 on PARDS definition, 55 on good practice, seven on policy, and 32 on research. All recommendations and statements had agreement greater than 80%. CONCLUSIONS: PALICC-2 recommendations and consensus-based statements should facilitate the implementation and adherence to the best clinical practice in patients with PARDS. These results will also inform the development of future programs of research that are crucially needed to provide stronger evidence to guide the pediatric critical care teams managing these patients.

Differences in the Genomic Profiles of Immunoparalyzed and Nonimmunoparalyzed Children With Sepsis: A Pilot Study.

OBJECTIVES: Sepsis-induced immunoparalysis represents a pathologic downregulation of leukocyte function shown to be associated with adverse outcomes, although its mechanisms remain poorly understood. Our goal was to compare genome-wide gene expression profiles of immunoparalyzed and nonimmunoparalyzed children with sepsis to identify genes and pathways associated with immunoparalysis. DESIGN: Prospective observational study. PATIENTS: Twenty-six children with lower respiratory tract infection meeting criteria for sepsis, severe sepsis, or septic shock admitted to the PICU. SETTING: Two tertiary care PICUs. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Innate immune function was assayed ex vivo by measuring release of tumor necrosis factor-α from whole blood after incubation with lipopolysaccharide for 4 hours. Immunoparalysis was defined as a tumor necrosis factor-α production capacity less than 200 pg/mL. Ten of the 26 children were immunoparalyzed. There were 17 significant differentially expressed genes when comparing genome-wide gene expression profiles of immunoparalyzed and nonimmunoparalyzed children (false discovery rate < 0.05). Nine genes showed increased expression in immunoparalyzed children (+1.5- to +8.8-fold change). Several of these dampen the immune system. Eight showed decreased expression in immunoparalyzed children (-1.7- to -3.9-fold change), several of which are involved in early regulation and activation of immune function. Functional annotation clustering using differentially expressed genes with p value of less than 0.05 showed three clusters related to immunity with significant enrichment scores (2.2-4.5); the most significant gene ontology terms in these clusters were antigen processing and presentation and negative regulation of interleukin-6 production. Network analysis identified potential protein interactions that may be involved in the development of immunoparalysis in children. CONCLUSIONS: In this exploratory analysis, immunoparalyzed children with sepsis showed increased expression of genes that dampen the immune system and decreased expression of genes involved in regulation and activation of the immune system. Analysis also implicated other proteins as potentially having as yet unidentified roles in the development of immunoparalysis.

Health Resource Use in Survivors of Pediatric Septic Shock in the United States.

OBJECTIVES: To evaluate postdischarge health resource use in pediatric survivors of septic shock and determine patient and hospitalization factors associated with health resource use. DESIGN: Secondary analyses of a multicenter prospective observational cohort study. SETTING: Twelve academic PICUs. PATIENTS: Children greater than or equal to 1 month and less than 18 years old hospitalized for community-acquired septic shock who survived to 1 year. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: For 308/338 patients (91%) with baseline and greater than or equal to one postdischarge survey, we evaluated readmission, emergency department (ED) visits, new medication class, and new device class use during the year after sepsis. Using negative binomial regression with bidirectional stepwise selection, we identified factors associated with each outcome. Median age was 7 years (interquartile range, 2-13), 157 (51%) had a chronic condition, and nearly all patients had insurance (private [n = 135; 44%] or government [n = 157; 51%]). During the year after sepsis, 128 patients (42%) were readmitted, 145 (47%) had an ED visit, 156 (51%) started a new medication class, and 102 (33%) instituted a new device class. Having a complex chronic condition was independently associated with readmission and ED visit. Documented infection and higher sum of Pediatric Logistic Organ Dysfunction--2 hematologic score were associated with readmission, whereas younger age and having a noncomplex chronic condition were associated with ED visit. Factors associated with new medication class use were private insurance, neurologic insult, and longer PICU stays. Factors associated with new device class use were preadmission chemotherapy or radiotherapy, presepsis Functional Status Scale score, and ventilation duration greater than or equal to 10 days. Of patients who had a new medication or device class, most had a readmission (56% and 61%) or ED visit (62% and 67%). CONCLUSIONS: Children with septic shock represent a high-risk cohort with high-resource needs after discharge. Interventions and targeted outcomes to mitigate postdischarge resource use may differ based on patients' preexisting conditions.

Thrombomodulin is associated with increased mortality and organ failure in mechanically ventilated children with acute respiratory failure: biomarker analysis from a multicenter randomized controlled trial.

BACKGROUND: Acute respiratory failure (ARF) can progress to acute respiratory distress syndrome and death. Biomarkers may allow for risk stratification and prognostic enrichment in ARF. Thrombomodulin (TM) is a transmembrane antithrombotic mediator expressed in endothelial cells. It is cleaved into its soluble form (sTM) during inflammation and vascular injury. Levels of sTM correlate with inflammation and end organ dysfunction. METHODS: This was a prospective observational study of 432 patients aged 2 weeks-17 years requiring invasive mechanical ventilation. It was ancillary to the multicenter clinical trial, Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE). After consent, patients had up to 3 plasma samples collected at 24-h intervals within 5 days after intubation. sTM was assayed by ELISA. The Hazard ratio (HR) for 90-day mortality was determined by Cox regression. Mixed effect models (MEM) were used to test for association with extrapulmonary multiorgan failure (MOF) and oxygenation index (OI). Age, race, sex and PRISM-III scores were used as confounding variables for multivariable analyses. RESULTS: sTM values ranged from 16.6 to 670.9 ng/ml within 5 days after intubation. Higher sTM was associated with increased 90-day mortality (n = 432, adjusted HR = 1.003, p = 0.02) and worse OI in the first 5 days after intubation (n = 252, Estimate = 0.02, p < 0.01). Both initial and slope of sTM were associated with increased extrapulmonary MOF in unadjusted and adjusted analyses (Intercept, Estimate = 0.003, p < 0.0001; and slope, Estimate = 0.01, p = 0.0009, n = 386). CONCLUSIONS: Plasma sTM is associated with mortality, severity of hypoxic respiratory failure and worsening extrapulmonary MOF in children with ARF. This suggests a role of vascular injury in the pathogenesis of ARF and provides potential applicability towards targeted therapies. TRIAL REGISTRATION: https://clinicaltrials.gov/ct2/show/NCT00814099 . In healthy lung endothelium, thrombomodulin (TM) recruits thrombin to activate Protein-C (PC/APC), that inhibits plasminogen activator-1 (PAI-1) and thrombosis. In inflamed and damaged endothelium, TM is cleaved into its soluble form (sTM), precluding its usual regulation of thrombosis. In this study, we measured plasma sTM levels in pediatric patients with respiratory failure and found that sTM correlated with mortality and other clinical markers of poor outcomes.

Impact of Bilateral Infiltrates on Inflammatory Biomarker Levels and Clinical Outcomes of Children With Oxygenation Defect.

OBJECTIVES: The 2015 definition for pediatric acute respiratory distress syndrome did not require the presence of bilateral infiltrates. We tested the hypothesis that pediatric patients meeting oxygenation criteria for pediatric acute respiratory distress syndrome but without bilateral infiltrates would have different inflammatory biomarker levels and clinical outcomes than those with bilateral infiltrates. DESIGN: Secondary analysis of a prospective cohort study. SETTING: Twenty-two PICUs. PATIENTS: Four-hundred forty-six patients age 2 weeks to 17 years intubated for respiratory failure with oxygenation index greater than or equal to 4 or oxygenation saturation index greater than or equal to 5 on the day of intubation or the day after. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients with bilateral infiltrates, either on the day of intubation or within the following 2 days, were compared with children who never developed bilateral infiltrates. Two analyses were performed to test 1) whether bilateral infiltrates are associated with elevated interleukin-1 receptor antagonist or interleukin-8 and 2) whether bilateral infiltrates are associated with worse clinical outcomes. Patients with bilateral infiltrates more often had a primary diagnosis of pneumonia (41% vs 28%; p = 0.02) and less often asthma (8% vs 23%; p < 0.01). After controlling for age, gender, and primary diagnosis, interleukin-1 receptor antagonist was higher on study days 1 and 2 in patients with bilateral infiltrates. There was no difference in interleukin-8 levels. After adjusting for age, gender, Pediatric Risk of Mortality score, and severity of oxygenation defect, presence of bilateral infiltrates was associated with longer duration of mechanical ventilation in survivors (hazard ratio, 0.64; 95% CI, 0.49-0.82; p < 0.01); this association was independent of primary diagnosis. Overall mortality was 9%; mortality was higher in those without bilateral infiltrates (14% vs 8%; p = 0.04). CONCLUSIONS: Children meeting pediatric acute respiratory distress syndrome oxygenation criteria with bilateral infiltrates on chest radiograph experience a more intense early inflammatory response. Bilateral infiltrates are associated with longer time on the ventilator independent of oxygenation defect severity.

Proprotein Convertase Subtilisin/Kexin Type 9 Loss-of-Function Is Detrimental to the Juvenile Host With Septic Shock.

OBJECTIVES: Proprotein convertase subtilisin/kexin type 9 is a central regulator of lipid metabolism and has been implicated in regulating the host response to sepsis. Proprotein convertase subtilisin/kexin type 9 loss-of-function is associated with improved sepsis outcomes in the adult host through increased hepatic bacterial clearance. Thus, there is interest in leveraging proprotein convertase subtilisin/kexin type 9 inhibitors as a therapeutic strategy in adults with sepsis. We sought to validate this association in children with septic shock and in a juvenile murine model of sepsis. DESIGN: Prospectively enrolled cohort of children with septic shock; experimental mice. SETTING: Seventeen participating institutions; research laboratory. PATIENTS AND SUBJECTS: Five-hundred twenty-two children with septic shock; juvenile (14 d old) and adult (10-14 wk) mice with constitutive proprotein convertase subtilisin/kexin type 9 null and wildtype control mice (C57BL/6). INTERVENTIONS: Proprotein convertase subtilisin/kexin type 9 single-nucleotide polymorphisms, serum proprotein convertase subtilisin/kexin type 9, and lipid profiles in patients. Cecal slurry murine model of sepsis; survival studies in juvenile and adult mice, assessment of lipoprotein fractions, bacterial burden, and inflammation in juvenile mice. MEASUREMENTS AND MAIN RESULTS: PCSK9 loss-of-function genetic variants were independently associated with increased odds of complicated course and mortality in children with septic shock. PCSK9, low-density lipoprotein, and high-density lipoprotein concentrations were lower among patients with complicated course relative to those without. PCSK9 concentrations negatively correlated with proinflammatory cytokine interleukin-8. Proprotein convertase subtilisin/kexin type 9 loss-of-function decreased survival in juvenile mice, but increased survival in adult mice with sepsis. PCSK9 loss-of-function resulted in low lipoproteins and decreased hepatic bacterial burden in juvenile mice. CONCLUSIONS: In contrast to the adult host, proprotein convertase subtilisin/kexin type 9 loss-of-function is detrimental to the juvenile host with septic shock. PCSK9 loss-of-function, in the context of low lipoproteins, may result in reduced hepatic bacterial clearance in the juvenile host with septic shock. Our data indicate that children should be excluded in sepsis clinical trials involving proprotein convertase subtilisin/kexin type 9 inhibitors.

Identification of molecular signatures of cystic fibrosis disease status with plasma-based functional genomics.

Although cystic fibrosis (CF) is attributed to dysfunction of a single gene, the relationships between the abnormal gene product and the development of inflammation and progression of lung disease are not fully understood, which limits our ability to predict an individual patient's clinical course and treatment response. To better understand CF progression, we characterized the molecular signatures of CF disease status with plasma-based functional genomics. Peripheral blood mononuclear cells (PBMCs) from healthy donors were cultured with plasma samples from CF patients ( n = 103) and unrelated, healthy controls ( n = 31). Gene expression levels were measured with an Affymetrix microarray (GeneChip Human Genome U133 Plus 2.0). Peripheral blood samples from a subset of the CF patients ( n = 40) were immunophenotyped by flow cytometry, and the data were compared with historical data for age-matched healthy controls ( n = 351). Plasma samples from another subset of CF patients ( n = 56) and healthy controls ( n = 16) were analyzed by multiplex enzyme-linked immunosorbent assay (ELISA) for numerous cytokines and chemokines. Principal component analysis and hierarchical clustering of induced transcriptional data revealed disease-specific plasma-induced PBMC profiles. Among 1,094 differentially expressed probe sets, 51 genes were associated with pancreatic sufficient status, and 224 genes were associated with infection with Pseudomonas aeruginosa. The flow cytometry and ELISA data confirmed that various immune modulators are relevant contributors to the CF molecular signature. This study provides strong evidence for distinct molecular signatures among CF patients. An understanding of these molecular signatures may lead to unique molecular markers that will enable more personalized prognoses, individualized treatment plans, and rapid monitoring of treatment response.

A prospective investigation of interleukin-8 levels in pediatric acute respiratory failure and acute respiratory distress syndrome.

BACKGROUND: The association of plasma interleukin-8 (IL-8), or IL-8 genetic variants, with pediatric acute respiratory distress syndrome (PARDS) in children with acute respiratory failure at risk for PARDS has not been examined. The purpose of this study was to examine the association of early and sequential measurement of plasma IL-8 and/or its genetic variants with development of PARDS and other clinical outcomes in mechanically ventilated children with acute respiratory failure. METHODS: This was a prospective cohort study of children 2 weeks to 17 years of age with acute airways and/or parenchymal lung disease done in 22 pediatric intensive care units participating in the multi-center clinical trial, Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE). Plasma IL-8 levels were measured within 24 h of consent and 24 and 48 h later. DNA was purified from whole blood, and IL-8 single nucleotide polymorphisms, rs4073, rs2227306, and rs2227307, were genotyped. RESULTS: Five hundred forty-nine patients were enrolled; 480 had blood sampling. Plasma IL-8 levels ranged widely from 4 to 7373 pg/mL. Highest IL-8 levels were observed on the day of intubation with subsequent tapering. Levels of IL-8 varied significantly across primary diagnoses with the highest levels occurring in patients with sepsis and the lowest levels in those with asthma. Plasma IL-8 was strongly correlated with oxygenation defect and severity of illness. IL-8 was consistently higher in PARDS patients compared to those without PARDS; levels were 4-12 fold higher in non-survivors compared to survivors. On multivariable analysis, IL-8 was independently associated with death, duration of mechanical ventilation, and PICU length of stay on all days measured, but was not associated with PARDS development. There was no association between the IL-8 single nucleotide polymorphisms, rs4073, rs2227306, and rs2227307, and PARDS development or plasma IL-8 level. CONCLUSIONS: When measured sequentially, plasma IL-8 was robustly associated with multiple, relevant clinical outcomes including mortality, but was not associated with PARDS development. The wide range of plasma IL-8 levels exhibited in this cohort suggests that further study into the heterogeneity of this patient population and its impact on individual responses to PARDS treatment is warranted.

Outcomes and Patterns of Healthcare Utilization After Hospitalization for Pediatric Critical Illness Due to Respiratory Failure.

OBJECTIVES: To quantify home care needs, healthcare utilization, and 2-year mortality after pediatric critical illness due to respiratory failure, and evaluate the impact of new morbidity and abnormal function at hospital discharge on resource use and outcomes. DESIGN: Retrospective cohort study. SETTING: Quaternary care PICU. PATIENTS: Patients less than or equal to 18 years with respiratory failure from January 1, 2013, to December 31, 2014. MEASUREMENTS AND MAIN RESULTS: Patient demographics, hospitalization characteristics, and healthcare utilization were quantified and compared according to morbidity development and discharge functional status. Multivariable regression methods evaluated 2-year readmission rates and mortality by morbidity development and discharge functional status. Of 163 patients, the median age was 2.1 years (interquartile range, 0.6-10.9 yr), 61 (37.4%) had a comorbidity, and 73 (44.8%) had abnormal function at admission. Median ventilation duration was 6.0 days (interquartile range, 3.0-11.7 d), and median PICU and hospital length of stay were 8 (interquartile range, 4-15) and 14 days (interquartile range, 8-23 d), respectively. At hospital discharge, eight of 163 (4.9%) had died, and 14 of 163 (8.6%) had a new morbidity. Of the surviving 155 patients at hospital discharge, 87 (56.1%) had abnormal function, 120 (77.4%) had new medications, 24 (15.5%) had new medical devices, and 43 (27.7%) had new home care equipment. Cumulative 2-year mortality was 14 of 163 (8.6%) with six of 163 (3.7%) occurring after discharge. Within 2 years, 81 of 155 of patients (52.2%) were readmitted, often (58/81, 71.6%) to the PICU. Abnormal function at discharge was associated with elevated odds of readmission to the hospital (odds ratio, 1.49; 1.28-1.74; p < 0.0001) and PICU (odds ratio, 1.47; 1.27-1.71; p < 0.0001) within 2 years. CONCLUSIONS: After critical illness, children have significant new healthcare burdens heretofore unrecognized. Abnormal functional status at hospital discharge was associated with increased healthcare utilization up to 2 years thereafter.

Interleukin-1 Receptor Antagonist Is Associated With Pediatric Acute Respiratory Distress Syndrome and Worse Outcomes in Children With Acute Respiratory Failure.

OBJECTIVES: To test whether plasma interleukin-1 receptor antagonist or variants within the gene encoding for interleukin-1ra (IL1RN), or proteins involved in regulating interleukin-1ß levels or interleukin-1ß response, are associated with pediatric acute respiratory distress syndrome or outcomes in mechanically ventilated children with parenchymal lung disease. DESIGN: Prospective cohort study. SETTING: Twenty-two PICUs participating in the multisite clinical trial, Randomized Evaluation of Sedation Titration for Respiratory Failure (U01 HL086622). SUBJECTS: Children 2 weeks to 17 years old treated with invasive mechanical ventilation for acute airways and/or parenchymal lung disease. MEASUREMENTS AND MAIN RESULTS: Three-hundred seventy-eight of 549 patients had pediatric acute respiratory distress syndrome; DNA and plasma were obtained from 523 of 549 and 480 of 549 patients, respectively. Plasma interleukin-1ra was highest on the day of intubation (day 0) and decreased over the subsequent 3 days (p < 0.0001). Interleukin-1ra level was higher in patients with pediatric acute respiratory distress syndrome than those without pediatric acute respiratory distress syndrome (p < 0.0001). Multivariable regression analysis of data across all days demonstrated a significant association of interleukin-1ra (odds ratio, 1.30; 95% CI, 1.10-1.52; p = 0.002) and day (p < 0.05) with pediatric acute respiratory distress syndrome, independent of age and Pediatric Risk of Mortality-III score. Analysis on individual days indicated that plasma interleukin-1ra levels were associated with pediatric acute respiratory distress syndrome on days 0 and 2, independent of age and Pediatric Risk of Mortality-III score (p = 0.04 and 0.003, respectively), however did not quite reach significance on days 1 and 3 (p = 0.06 and 0.07, respectively). Interleukin-1ra was independently associated with mortality on day 1 (p = 0.02). Interleukin-1ra also correlated with length of mechanical ventilation, measures of oxygenation, and PICU length of stay. No genetic variants were associated with pediatric acute respiratory distress syndrome. CONCLUSIONS: Plasma interleukin-1ra is associated with pediatric acute respiratory distress syndrome, PICU length of stay, length of mechanical ventilation, and mortality in children with acute respiratory failure requiring mechanical ventilation.

Genetic and epigenetic factors in the regulation of the immune response.

PURPOSE OF REVIEW: The review will update readers on research examining the influence of genetic variation and epigenetics on the immune system and whether genetic variation influences the outcome of critically ill children. RECENT FINDINGS: Although there have been few recent studies examining the role of genetic variation in the severity of disease or outcome in critically ill children, studies in critically ill adults have been informative. For example, genetic variations in the genes coding for various components of the immune response, such as the Toll-like receptor 1, interleukin-1RA, proprotein convertase subtilisin/kexin type 9, adoponectin, nuclear factor erythroid 2-related factor 2, elafin, sphingosine 1-phosphate receptor 3, and sushi, von Willebrand factor type A, EGF and pentraxin domain containing 1 have been associated with various outcomes in critically ill adult populations. Many of the variants demonstrate functional consequences in the protein levels or activities. In critically ill children, there is an association with increased ICU length of stay in children with septic shock with one of the Toll-like receptor 1 variants. SUMMARY: The degree of influence of host genetic variation in the outcome in critically ill children remains a much understudied area of research. However, it remains important because it may not only help identify children at risk for worse outcomes but it may provide insight into mechanisms of critical illnesses and novel therapies.

Association of polymorphisms in genes of factors involved in regulation of splicing of cystic fibrosis transmembrane conductance regulator mRNA with acute respiratory distress syndrome in children with pneumonia.

BACKGROUND: Previous work has demonstrated a strong association between lung injury in African American children with pneumonia and a polymorphic (TG)mTn region in cystic fibrosis transmembrane conductance (CFTR) involved in the generation of a nonfunctional CFTR protein lacking exon 9. A number of splicing factors that regulate the inclusion/exclusion of exon 9 have been identified. The objective of this study was to determine whether genetic variants in these splicing factors were associated with acute respiratory distress syndrome (ARDS) in children with pneumonia. METHODS: This is a prospective cohort genetic association study of lung injury in African American and non-Hispanic Caucasian children with community-acquired pneumonia evaluated in the emergency department or admitted to the hospital. Linkage-disequilibrium-tag single nucleotide polymorphisms (LD-tag SNPs) in genes of the following splicing factors (followed by gene name) involved in exon 9 skipping PTB1 (PTBP1), SRp40 (SFRS1), SR2/ASF (SFRS5), TDP-43 (TARDBP), TIA-1 (TIA1), and U2AF(65) (U2AF2) were genotyped. SNPs in the gene of the splicing factor CELF2 (CELF2) were selected by conservation score. Multivariable analysis was used to examine association between genotypes and ARDS. RESULTS: The African American cohort (n = 474) had 29 children with ARDS and the non-Hispanic Caucasian cohort (n = 304) had 32 children with ARDS. In the African American group multivariable analysis indicated that three variants in CELF2, rs7068124 (p = 0.004), rs3814634 (p = 0.032) and rs10905928 (p = 0.044), and two in TIA1, rs2592178 (p = 0.005) and rs13402990 (p = 0.018) were independently associated with ARDS. In the non-Hispanic Caucasian group, a single variant in CELF2, rs2277212 (p = 0.014), was associated with increased risk of developing ARDS. CONCLUSIONS: The data indicate that SNPs in CELF2 may be associated with the risk of developing ARDS in both African American and non-Hispanic Caucasian children with pneumonia and suggest that the potential role of the splicing factor CELF2 in ARDS should be explored further.

Comorbidities and assessment of severity of pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference.

OBJECTIVES: To determine the impact of patient-specific and disease-related characteristics on the severity of illness and on outcome in pediatric patients with acute respiratory distress syndrome with the intent of guiding current medical practice and identifying important areas for future research. DESIGN: Electronic searches of PubMed, EMBASE, Web of Science, Cochrane, and Scopus were conducted. References were reviewed for relevance and features included in the following section. SETTINGS: Not applicable. SUBJECTS: PICU patients with evidence of acute lung injury, acute hypoxemic respiratory failure, and acute respiratory distress syndrome. INTERVENTIONS: Not applicable. MEASUREMENTS AND MAIN RESULTS: The comorbidities associated with outcome in pediatric acute respiratory distress syndrome can be divided into 1) patient-specific factors and 2) factors inherent to the disease process. The primary comorbidity associated with poor outcome is preexisting congenital or acquired immunodeficiency. Severity of disease is often described by factors identifiable at admission to the ICU. Many measures that are predictive are influenced by the underlying disease process itself, but may also be influenced by nutritional status, chronic comorbidities, or underlying genetic predisposition. Of the measures available at the bedside, both PaO2/FIO2 ratio and oxygenation index are fairly consistent and robust predictors of disease severity and outcomes. Multiple organ system dysfunction is the single most important independent clinical risk factor for mortality in children at the onset of acute respiratory distress syndrome. CONCLUSIONS: The assessment of oxygenation and ventilation indices simultaneously with genetic and biomarker measurements holds the most promise for improved risk stratification for pediatric acute respiratory distress syndrome patients in the very near future. The next phases of pediatric acute respiratory distress syndrome pathophysiology and outcomes research will be enhanced if 1) age group differences are examined, 2) standardized datasets with adequately explicit definitions are used, 3) data are obtained at standardized times after pediatric acute respiratory distress syndrome onset, and 4) nonpulmonary organ failure scores are created and implemented.

Pathobiology of acute respiratory distress syndrome.

The unique characteristics of pulmonary circulation and alveolar-epithelial capillary-endothelial barrier allow for maintenance of the air-filled, fluid-free status of the alveoli essential for facilitating gas exchange, maintaining alveolar stability, and defending the lung against inhaled pathogens. The hallmark of pathophysiology in acute respiratory distress syndrome is the loss of the alveolar capillary permeability barrier and the presence of protein-rich edema fluid in the alveoli. This alteration in permeability and accumulation of fluid in the alveoli accompanies damage to the lung epithelium and vascular endothelium along with dysregulated inflammation and inappropriate activity of leukocytes and platelets. In addition, there is uncontrolled activation of coagulation along with suppression of fibrinolysis and loss of surfactant. These pathophysiological changes result in the clinical manifestations of acute respiratory distress syndrome, which include hypoxemia, radiographic opacities, decreased functional residual capacity, increased physiologic deadspace, and decreased lung compliance. Resolution of acute respiratory distress syndrome involves the migration of cells to the site of injury and re-establishment of the epithelium and endothelium with or without the development of fibrosis. Most of the data related to acute respiratory distress syndrome, however, originate from studies in adults or in mature animals with very few studies performed in children or juvenile animals. The lack of studies in children is particularly problematic because the lungs and immune system are still developing during childhood and consequently the pathophysiology of pediatric acute respiratory distress syndrome may differ in significant ways from that seen in acute respiratory distress syndrome in adults. This article describes what is known of the pathophysiologic processes of pediatric acute respiratory distress syndrome as we know it today while also presenting the much greater body of evidence on these processes as elucidated by adult and animal studies. It is also our expressed intent to generate enthusiasm for larger and more in-depth investigations of the mechanisms of disease and repair specific to children in the years to come.

The outcomes of children with pediatric acute respiratory distress syndrome: proceedings from the Pediatric Acute Lung Injury Consensus Conference.

OBJECTIVE: To provide additional details and evidence behind the recommendations for outcomes assessment of patients with pediatric acute respiratory distress syndrome from the Pediatric Acute Lung Injury Consensus Conference. DESIGN: Consensus conference of experts in pediatric acute lung injury. METHODS: A panel of 27 experts met over the course of 2 years to develop a taxonomy to define pediatric acute respiratory distress syndrome and to make recommendations regarding treatment and research priorities. The outcomes subgroup comprised four experts. When published data were lacking, a modified Delphi approach emphasizing strong professional agreement was used. RESULTS: The Pediatric Acute Lung Injury Consensus Conference experts developed and voted on a total of 151 recommendations addressing the topics related to pediatric acute respiratory distress syndrome, seven of which related to outcomes after pediatric acute respiratory distress syndrome. All seven recommendations had strong agreement. Children with acute respiratory distress syndrome continue to have a high mortality, specifically, in relation to certain comorbidities and etiologies related to pediatric acute respiratory distress syndrome. Comorbid conditions, such as an immunocompromised state, increase the risk of mortality even further. Likewise, certain etiologies, such as non-pulmonary sepsis, also place children at a higher risk of mortality. Significant long-term effects were reported in adult survivors of acute respiratory distress syndrome: diminished lung function and exercise tolerance, reduced quality of life, and diminished neurocognitive function. Little knowledge of long-term outcomes exists in children who survive pediatric acute respiratory distress syndrome. Characterization of the longer term consequences of pediatric acute respiratory distress syndrome in children is vital to help identify opportunities for improved therapeutic and rehabilitative strategies that will lessen the long-term burden of pediatric acute respiratory distress syndrome and improve the quality of life in children. CONCLUSIONS: The Consensus Conference developed pediatric-specific recommendations for pediatric acute respiratory distress syndrome regarding outcome measures and future research priorities. These recommendations are intended to promote optimization and consistency of care for children with pediatric acute respiratory distress syndrome and identify areas of uncertainty requiring further investigation.

MAPK and JAK-STAT signaling pathways are involved in the oxidative stress-induced decrease in expression of surfactant protein genes.

Oxidative stress is generated by reactive oxygen species (ROS) including hydrogen peroxide (H(2)O(2)), hydroxyl radical (•OH ) and superoxide anion (O(2--)), which are produced as by-products of cellular metabolism. An imbalance in cellular redox status is a potent pathogenic factor that contributes to various chronic inflammatory diseases. In this study, we demonstrate that H(2)O(2 )decreases surfactant protein A, B and ABCA3 mRNA level, and increases SP-D mRNA level in human pulmonary lung epithelial cells. The decreased mRNA level of SP-A and SP-B were significant with a maximum inhibition of 79 and 87%, respectively by 150 µM H(2)O(2 )after 24 hrs of incubation. In addition, ABCA3 mRNA level was decreased with a maximum inhibition of 55% by 150 µM H(2)O(2 )after 12 hrs of incubation. In contrast, 150 µM H(2)O(2 )caused the SP-D mRNA level to increase to 200% of control after 8 hrs of incubation. The H(2)O(2)-induced gene repression or activation of SP-A, SP-B, SP-D and ABCA3 was blocked by pretreatment with the antioxidants N-acetyl-L-cysteine (NAC) and catalase. Furthermore, the inhibition of SP-A and SP-B was associated with reduced thyroid transcription factor -1 (TTF-1) DNA binding activity, and this reduced TTF-1 binding activity may be due to decreased TTF-1 protein expression level. The analyses of signal transduction pathways that may play a role in the regulation of gene expression by H(2)O(2 )using several specific inhibitors showed that U0126, an inhibitor of ERK1/2 upstream kinase MEK1/2, blocked both H(2)O(2)-induced inhibition of SP-A and SP-B gene expression, whereas SB203580, an inhibitor of p38 MAPK, partially blocked H(2)O(2)-mediated inhibition of SP-A gene expression but not SP-B expression. In contrast, AG-490, a specific inhibitor of JAK-STAT pathway, blocked H(2)O(2)-mediated inhibition of SP-B gene expression but not SP-A expression. Immunoblot analyses using specific phosphor-antibodies demonstrated that ERK1/2, p38 MAPK and STAT3 are phosphorylated by oxidative stress suggesting that H(2)O(2)-induced inhibition of SP-A and SP-B gene expression is associated with MAPK and JAKSTAT signaling pathway. These data, therefore, suggest that H(2)O(2 )affects SP-A and SP-B gene regulation by reducing TTF-1 DNA binding activity via MAPKs or STAT signaling pathways.

Association of cystic fibrosis transmembrane conductance regulator gene variants with acute lung injury in African American children with pneumonia*.

OBJECTIVES: The cystic fibrosis transmembrane conductance regulator regulates fluid balance in alveolar epithelial cells and appears to modulate the inflammatory response. To determine whether more severe lung injury in children who develop community-acquired pneumonia is associated with variations known to affect function in the gene coding for cystic fibrosis transmembrane conductance regulator. DESIGN: A prospective cohort genetic association study of lung injury in children with community-acquired pneumonia. SETTING: Three major tertiary care children's hospitals. SUBJECTS: Caucasian and African American children with community-acquired pneumonia either evaluated in the emergency department or admitted to the hospital. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Caucasian and African American children with pneumonia were genotyped for the most common variants reported to affect cystic fibrosis transmembrane conductance regulator function, the p.508del mutation, the (TG)mTn variable repeat region, and the M470V polymorphism in the cystic fibrosis transmembrane conductance regulator gene. Genotypes and haplotypes were determined, and the association of high-risk alleles or high-risk haplotypes (defined as the presence of at least one variant known to decrease the level of functional cystic fibrosis transmembrane conductance regulator) with the need for mechanical ventilation or the development of acute lung injury was evaluated. Forty-two children in the Caucasian cohort (n = 304) required mechanical ventilation; 32 developed acute lung injury. Forty-three children in the African American cohort (n = 474) required mechanical ventilation; 29 developed acute lung injury. In African American children, high-risk (TG)mTn alleles known to result in decreased levels of functional cystic fibrosis transmembrane conductance regulator were associated with the need for mechanical ventilation (p = .0013) and the development of acute lung injury (p = .0061). Multivariable analysis demonstrated that high-risk (TG)mTn alleles were independently associated with mechanical ventilation (odds ratios = 3.19; 95% confidence interval, 1.63-6.26) and acute lung injury (odds ratios = 3.36; 95% confidence interval, 1.50-7.53) in African American children. CONCLUSION: Genetic variation in cystic fibrosis transmembrane conductance regulator is associated with acute lung injury in African American children with community-acquired pneumonia.

Association of IL-1ß -511 polymorphism with severe veno-occlusive disease in pediatric-matched allogeneic hematopoietic stem cell transplantation.

Single nucleotide polymorphisms (SNPs) of the interleukin 1 (IL-1) family have been implicated in acute graft-versus-host disease and mortality postallogeneic hematopoietic stem cell transplantation (HSCT) in adults. Hepatic veno-occlusive disease (VOD) is a well-known complication of HSCT and can result in an increased risk of mortality. In this study, we sought to investigate the association of both patient and donor genotypes at the IL-1ß -511 cytidine/thymidine (C/T) polymorphic site with hepatic VOD and mortality in an exclusive pediatric cohort undergoing matched myeloablative allogeneic HSCT. Donor TT genotype was associated with higher cumulative incidence of grade III-IV hepatic VOD at 3 months after transplantation relative to donor CT and CC genotypes (25±13.1% in TT, 2.9±2.9% in CT, and 3.6±3.6% in CC; P=0.024). Neither recipient nor donor IL-1ß -511 single nucleotide polymorphisms genotypes were associated with mortality or relapse. Our findings suggest that donor, rather than host, genotype at the IL-1ß -511 polymorphic site may associate with higher risk for severe VOD after matched allogeneic HSCT. Our findings challenge the assumption that host factors are exclusively responsible for VOD and suggest a novel role for the donor inflammasome pathway in inducing injury and microvascular disease after HSCT, which merits further study in a larger cohort analysis.

Identification of phenotypes in paediatric patients with acute respiratory distress syndrome: a latent class analysis.

BACKGROUND: Previous latent class analysis of adults with acute respiratory distress syndrome (ARDS) identified two phenotypes, distinguished by the degree of inflammation. We aimed to identify phenotypes in children with ARDS in whom developmental differences might be important, using a latent class analysis approach similar to that used in adults. METHODS: This study was a secondary analysis of data aggregated from the Randomized Evaluation of Sedation Titration for Respiratory Failure (RESTORE) clinical trial and the Genetic Variation and Biomarkers in Children with Acute Lung Injury (BALI) ancillary study. We used latent class analysis, which included demographic, clinical, and plasma biomarker variables, to identify paediatric ARDS (PARDS) phenotypes within a cohort of children included in the RESTORE and BALI studies. The association of phenotypes with clinically relevant outcomes and the performance of paediatric data in adult ARDS classification algorithms were also assessed. FINDINGS: 304 children with PARDS were included in this secondary analysis. Using latent class analysis, a two-class model was a better fit for the cohort than a one-class model (p<0·001). Latent class analysis identified two classes: class 1 (181 [60%] of 304 patients with PARDS) and class 2 (123 [40%] of 304 patients with PARDS), referred to as phenotype 1 and 2 hereafter. Phenotype 2 was characterised by higher concentrations of inflammatory biomarkers, a higher incidence of vasopressor use, and more frequent diagnosis of sepsis, consistent with the adult hyperinflammatory phenotype. All levels of severity of PARDS were observed across both phenotypes. Children with the hyperinflammatory phenotype (phenotype 2) had worse clinical outcomes than those with the hypoinflammatory phenotype (phenotype 1), with a longer duration of mechanical ventilation (median 10·0 days [IQR 6·3-21·0] for phenotype 2 vs 6·6 days [4·1-10·8] for phenotype 1, p<0·0001), and higher incidence of mortality (17 [13·8%] of 123 patients vs four [2·2%] of 181 patients, p=0·0001). When using adult phenotype classification algorithms in children, the soluble tumour necrosis factor receptor-1 (sTNFr1), vasopressor use, and interleukin (IL)-6 variables gave an area under the curve (AUC) of 0·956, and the sTNFr1, vasopressor use, and IL-8 variables gave an AUC of 0·954, compared with the gold standard of latent class analysis. INTERPRETATION: Latent class analysis identified two phenotypes in children with ARDS with characteristics similar to those in adults, including worse outcomes among patients with the hyperinflammatory phenotype. PARDS phenotypes should be considered in design and analysis of future clinical trials in children. FUNDING: US National Institutes of Health.