Low to Moderate Air Pollutant Exposure and Acute Respiratory Distress Syndrome after Severe Trauma.

RATIONALE: Exposure to air pollution has molecular and physiologic effects on the lung that may increase the risk of acute respiratory distress syndrome (ARDS) after injury. OBJECTIVES: To determine the association of short- and long-term air pollutant exposures and ARDS risk after severe trauma. METHODS: We analyzed data from a prospective cohort of 996 critically ill patients presenting with acute trauma and an injury severity score greater than 15. Exposures to ozone, nitrogen dioxide, sulfur dioxide, carbon monoxide, and particulate matter less than 2.5 µm were assessed by weighted averages of daily levels from all monitors within 50 km of the geocoded location of a patient's residence. Patients were followed for 6 days for the development of ARDS according to Berlin Criteria. The association between each exposure and ARDS was determined via multivariable logistic regression adjusting for potential confounders. MEASUREMENTS AND MAIN RESULTS: ARDS developed in 243 (24%) patients. None of the short-term exposures averaged over the 3 days before presentation was associated with ARDS, except sulfur dioxide, which demonstrated a nonlinear association. Nitrogen dioxide, sulfur dioxide, and particulate matter less than or equal to 2.5 µm in aerodynamic diameter exposure over the 6 weeks before presentation was significantly associated with ARDS (P < 0.05). All long-term exposures (3 yr) were associated with ARDS (P < 0.01) in adjusted models, despite exposure levels largely below U.S. and European Union air quality standards. CONCLUSIONS: Long-term low- to moderate-level air pollutant exposure is associated with a greater risk of developing ARDS after severe trauma and represents a novel and potentially modifiable environmental risk factor for ARDS.

Plasma receptor interacting protein kinase-3 levels are associated with acute respiratory distress syndrome in sepsis and trauma: a cohort study.

BACKGROUND: Necroptosis, a form of programmed cell death mediated by receptor interacting serine/threonine-protein kinase-3 (RIPK3), is implicated in murine models of acute respiratory distress syndrome (ARDS). We hypothesized that plasma RIPK3 concentrations in sepsis and trauma would be associated with ARDS development and that plasma RIPK3 would reflect changes in lung tissue RIPK3 in a murine model of systemic inflammation. METHODS: We utilized prospective cohort studies of critically ill sepsis (n = 120) and trauma (n = 180) patients and measured plasma RIPK3 at presentation and 48 h. Patients were followed for 6 days for ARDS by the Berlin definition. We used multivariable logistic regression to determine the association of plasma RIPK3 with ARDS in each cohort, adjusting for confounders. In mice, we determined whether plasma and lung tissue RIPK3 levels rise concomitantly 4 h after injection with lipopolysaccharide and ZVAD-FMK, an apoptosis inhibitor. RESULTS: The change in plasma RIPK3 from presentation to 48 h (ΔRIPK3) was associated with ARDS in sepsis (OR 1.30, 95% CI 1.03-1.63, per ½ standard deviation) and trauma (OR 1.79, 95% CI 1.33-2.40). This association was not evident for presentation RIPK3 levels. Secondary analyses showed similar findings for the association of ΔRIPK3 with acute kidney injury and 30-day mortality. Mice injected with lipopolysaccharide and ZVAD-FMK had significantly higher plasma (p < 0.001) and lung (p = 0.005) RIPK3 than control mice. CONCLUSIONS: The change in plasma RIPK3 from presentation to 48 h in both sepsis and trauma patients is independently associated with ARDS, and plasma RIPK3 may reflect RIPK3 activity in lung tissue.

Computed tomography-defined abdominal adiposity is associated with acute kidney injury in critically ill trauma patients*.

OBJECTIVES: Higher body mass index is associated with increased risk of acute kidney injury after major trauma. Since body mass index is nonspecific, reflecting lean, fluid, and adipose mass, we evaluated the use of CT to determine if abdominal adiposity underlies the body mass index-acute kidney injury association. DESIGN: Prospective cohort study. SETTING: Level I Trauma Center of a university hospital. PATIENTS: Patients older than 13 years with an Injury Severity Score greater than or equal to 16 admitted to the trauma ICU were followed for development of acute kidney injury over 5 days. Those with isolated severe head injury or on chronic dialysis were excluded. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Clinical, anthropometric, and demographic variables were collected prospectively. CT images at the level of the L4-5 intervertebral disc space were extracted from the medical record and used by two operators to quantitate visceral adipose tissue and subcutaneous adipose tissue areas. Acute kidney injury was defined by Acute Kidney Injury Network creatinine and dialysis criteria. Of 400 subjects, 327 (81.8%) had CT scans suitable for analysis: 264 of 285 (92.6%) blunt trauma subjects and 63 of 115 (54.8%) penetrating trauma subjects. Visceral adipose tissue and subcutaneous adipose tissue areas were highly correlated between operators (intraclass correlation > 0.99, p < 0.001 for each) and within operator (intraclass correlation > 0.99, p < 0.001 for each). In multivariable analysis, the standardized risk of acute kidney injury was 15.1% (95% CI, 10.6-19.6%), 18.1% (14-22.2%), and 23.1% (18.3-27.9%) at the 25th, 50th, and 75th percentiles of visceral adipose tissue area, respectively (p = 0.001), with similar findings when using subcutaneous adipose tissue area as the adiposity measure. CONCLUSIONS: Quantitation of abdominal adiposity using CT scans obtained for clinical reasons is feasible and highly reliable in critically ill trauma patients. Abdominal adiposity is independently associated with acute kidney injury in this population, confirming that excess adipose tissue contributes to the body mass index-acute kidney injury association. Further studies of the potential mechanisms linking adiposity with acute kidney injury are warranted.

IL1RN coding variant is associated with lower risk of acute respiratory distress syndrome and increased plasma IL-1 receptor antagonist.

RATIONALE: Acute respiratory distress syndrome (ARDS) behaves as a complex genetic trait, yet knowledge of genetic susceptibility factors remains incomplete. OBJECTIVES: To identify genetic risk variants for ARDS using large scale genotyping. METHODS: A multistage genetic association study was conducted of three critically ill populations phenotyped for ARDS. Stage I, a trauma cohort study (n = 224), was genotyped with a 50K gene-centric single-nucleotide polymorphism (SNP) array. We tested SNPs associated with ARDS at P < 5 × 10(-4) for replication in stage II, a trauma case-control population (n = 778). SNPs replicating their association in stage II (P < 0.005) were tested in a stage III nested case-control population of mixed subjects in the intensive care unit (n = 2,063). Logistic regression was used to adjust for potential clinical confounders. We performed ELISA to test for an association between ARDS-associated genotype and plasma protein levels. MEASUREMENTS AND MAIN RESULTS: A total of 12 SNPs met the stage I threshold for an association with ARDS. rs315952 in the IL1RN gene encoding IL-1 receptor antagonist (IL1RA) replicated its association with reduced ARDS risk in stages II (P < 0.004) and III (P < 0.02), and was robust to clinical adjustment (combined odds ratio = 0.81; P = 4.2 × 10(-5)). Plasma IL1RA level was associated with rs315952C in a subset of critically ill subjects. The effect of rs315952 was independent from the tandem repeat variant in IL1RN. CONCLUSIONS: The IL1RN SNP rs315952C is associated with decreased risk of ARDS in three populations with heterogeneous ARDS risk factors, and with increased plasma IL1RA response. IL1RA may attenuate ARDS risk.

Distinct and replicable genetic risk factors for acute respiratory distress syndrome of pulmonary or extrapulmonary origin.

BACKGROUND: The role of genetics in the development of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) from direct or indirect lung injury has not been specifically investigated. The aim of this study was to identify genetic variants contributing to ALI/ARDS from pulmonary or extrapulmonary causes. METHODS: We conducted a multistage genetic association study. We first performed a large-scale genotyping (50K ITMAT-Broad_CARe Chip) in 1717 critically ill Caucasian patients with either pulmonary or extrapulmonary injury, to identify single nucleotide polymorphisms (SNPs) associated with the development of ARDS from direct or indirect insults to the lung. Identified SNPs (p≤0.0005) were validated in two separated populations (Stage II), with trauma (Population I; n=765) and pneumonia/pulmonary sepsis (Population II; n=838), as causes for ALI/ARDS. Genetic variants replicating their association with trauma related-ALI in Stage II were validated in a second trauma-associated ALI population (n=224, Stage III). RESULTS: In Stage I, non-overlapping SNPs were significantly associated with ARDS from direct/indirect lung injury, respectively. The association between rs1190286 (POPDC3) and reduced risk of ARDS from pulmonary injury was validated in Stage II (p<0.003). SNP rs324420 (FAAH) was consistently associated with increased risk of ARDS from extrapulmonary causes in two independent ALI-trauma populations (p<0.006, Stage II; p<0.05, Stage III). Meta-analysis confirmed these associations. CONCLUSIONS: Different genetic variants may influence ARDS susceptibility depending on direct versus indirect insults. Functional SNPs in POPDC3 and FAAH genes may be driving the association with direct and indirect ALI/ARDS, respectively.

The adult respiratory distress syndrome cognitive outcomes study: long-term neuropsychological function in survivors of acute lung injury.

RATIONALE: Cognitive and psychiatric morbidity is common and potentially modifiable after acute lung injury (ALI). However, practical measures of neuropsychological function for use in multicenter trials are lacking. OBJECTIVES: To determine whether a validated telephone-based neuropsychological test battery is feasible in a multicenter trial. To determine the frequency and risk factors for long-term neuropsychological impairment. METHODS: As an adjunct study to the Acute Respiratory Distress Syndrome Clinical Trials Network Fluid and Catheter Treatment Trial, we assessed neuropsychological function at 2 and 12 months post-hospital discharge. MEASUREMENTS AND MAIN RESULTS: Of 406 eligible survivors, we approached 261 to participate and 213 consented. We tested 122 subjects at least once, including 102 subjects at 12 months. Memory, verbal fluency, and executive function were impaired in 13% (12 of 92), 16% (15 of 96), and 49% (37 of 76) of long-term survivors. Long-term cognitive impairment was present in 41 of the 75 (55%) survivors who completed cognitive testing. Depression, post-traumatic stress disorder, or anxiety was present in 36% (37 of 102), 39% (40 of 102), and 62% (63 of 102) of long-term survivors. Enrollment in a conservative fluid-management strategy (P = 0.005) was associated with cognitive impairment and lower partial pressure of arterial oxygen during the trial was associated with cognitive (P = 0.02) and psychiatric impairment (P = 0.02). CONCLUSIONS: Neuropsychological function can be assessed by telephone in a multicenter trial. Long-term neuropsychological impairment is common in survivors of ALI. Hypoxemia is a risk factor for long-term neuropsychological impairment. Fluid management strategy is a potential risk factor for long-term cognitive impairment; however, given the select population studied and an unclear mechanism, this finding requires confirmation.

SNP-set analysis replicates acute lung injury genetic risk factors.

BACKGROUND: We used a gene - based replication strategy to test the reproducibility of prior acute lung injury (ALI) candidate gene associations. METHODS: We phenotyped 474 patients from a prospective severe trauma cohort study for ALI. Genomic DNA from subjects' blood was genotyped using the IBC chip, a multiplex single nucleotide polymorphism (SNP) array. Results were filtered for 25 candidate genes selected using prespecified literature search criteria and present on the IBC platform. For each gene, we grouped SNPs according to haplotype blocks and tested the joint effect of all SNPs on susceptibility to ALI using the SNP-set kernel association test. Results were compared to single SNP analysis of the candidate SNPs. Analyses were separate for genetically determined ancestry (African or European). RESULTS: We identified 4 genes in African ancestry and 2 in European ancestry trauma subjects which replicated their associations with ALI. Ours is the first replication of IL6, IL10, IRAK3, and VEGFA associations in non-European populations with ALI. Only one gene - VEGFA - demonstrated association with ALI in both ancestries, with distinct haplotype blocks in each ancestry driving the association. We also report the association between trauma-associated ALI and NFKBIA in European ancestry subjects. CONCLUSIONS: Prior ALI genetic associations are reproducible and replicate in a trauma cohort. Kernel - based SNP-set analysis is a more powerful method to detect ALI association than single SNP analysis, and thus may be more useful for replication testing. Further, gene-based replication can extend candidate gene associations to diverse ethnicities.

ANGPT2 genetic variant is associated with trauma-associated acute lung injury and altered plasma angiopoietin-2 isoform ratio.

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.

Early Plasma Nuclear DNA, Mitochondrial DNA, and Nucleosome Concentrations Are Associated With Acute Kidney Injury in Critically Ill Trauma Patients.

Circulating nucleic acids, alone and in complex with histones as nucleosomes, have been proposed to link systemic inflammation and coagulation after trauma to acute kidney injury (AKI). We sought to determine the association of circulating nucleic acids measured at multiple time points after trauma with AKI risk. DESIGN: We conducted a prospective cohort study of trauma patients, collecting plasma on presentation and at 6, 12, 24, and 48 hours, defining AKI over the first 6 days by Kidney Disease Improving Global Outcomes serum creatinine and dialysis criteria. We determined kinetics of plasma mitochondrial DNA (mtDNA), nuclear DNA (nDNA), and nucleosome levels across time points and associations with AKI using multivariable linear mixed-effects models, adjusted for injury characteristics and blood transfusions. We evaluated the association of presentation nucleic acid damage-associated molecular patterns (DAMP) concentrations with subsequent AKI, adjusting for injury severity using multivariable logistic regression. SETTING: Academic level I trauma center. PATIENTS: Trauma patients (n = 55) requiring intensive care for greater than or equal to 24 hours after presentation. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: AKI developed in 17 patients (31%), a median of 12.0 hours (interquartile range, 6.2-24.1 hr) after presentation. mtDNA demonstrated a time-varying association with AKI (p = 0.022, interaction with time point), with differences by AKI status not emerging until 24 hours (ß = 0.97 [95% CI, 0.03-1.90] log copies/uL; p = 0.043). Patients who developed AKI had higher nDNA across all time points (overall ß = 1.41 log copies/uL [0.86-1.95 log copies/uL]; p < 0.001), and presentation levels were significantly associated with subsequent AKI (odds ratio [OR], 2.55 [1.36-4.78] per log copy/uL; p = 0.003). Patients with AKI had higher nucleosome levels at presentation (ß = 0.32 [0.00-0.63] arbitrary unit; p = 0.048), a difference that was more pronounced at 24 hours (ß = 0.41 [0.06-0.76]; p = 0.021) and 48 hours (ß = 0.71 [0.35-1.08]; p < 0.001) (p = 0.075, interaction with time point). CONCLUSIONS: Plasma nucleic acid DAMPs have distinct kinetics and associations with AKI in critically ill trauma patients. nDNA at presentation predicts subsequent AKI and may be amenable to targeted therapies in this population.

Performance of an automated electronic acute lung injury screening system in intensive care unit patients.

OBJECTIVE: Lung protective ventilation reduces mortality in patients with acute lung injury, but underrecognition of acute lung injury has limited its use. We recently validated an automated electronic acute lung injury surveillance system in patients with major trauma in a single intensive care unit. In this study, we assessed the system's performance as a prospective acute lung injury screening tool in a diverse population of intensive care unit patients. DESIGN: Patients were screened prospectively for acute lung injury over 21 wks by the automated system and by an experienced research coordinator who manually screened subjects for enrollment in Acute Respiratory Distress Syndrome Clinical Trials Network (ARDSNet) trials. Performance of the automated system was assessed by comparing its results with the manual screening process. Discordant results were adjudicated blindly by two physician reviewers. In addition, a sensitivity analysis using a range of assumptions was conducted to better estimate the system's performance. SETTING: The Hospital of the University of Pennsylvania, an academic medical center and ARDSNet center (1994-2006). PATIENTS: Intubated patients in medical and surgical intensive care units. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of 1270 patients screened, 84 were identified with acute lung injury (incidence of 6.6%). The automated screening system had a sensitivity of 97.6% (95% confidence interval, 96.8-98.4%) and a specificity of 97.6% (95% confidence interval, 96.8-98.4%). The manual screening algorithm had a sensitivity of 57.1% (95% confidence interval, 54.5-59.8%) and a specificity of 99.7% (95% confidence interval, 99.4-100%). Sensitivity analysis demonstrated a range for sensitivity of 75.0-97.6% of the automated system under varying assumptions. Under all assumptions, the automated system demonstrated higher sensitivity than and comparable specificity to the manual screening method. CONCLUSIONS: An automated electronic system identified patients with acute lung injury with high sensitivity and specificity in diverse intensive care units of a large academic medical center. Further studies are needed to evaluate the effect of automated prompts that such a system can initiate on the use of lung protective ventilation in patients with acute lung injury.

Novel variants in the PRDX6 Gene and the risk of Acute Lung Injury following major trauma.

BACKGROUND: Peroxiredoxin 6 (PRDX6) is involved in redox regulation of the cell and is thought to be protective against oxidant injury. Little is known about genetic variation within the PRDX6 gene and its association with acute lung injury (ALI). In this study we sequenced the PRDX6 gene to uncover common variants, and tested association with ALI following major trauma. METHODS: To examine the extent of variation in the PRDX6 gene, we performed direct sequencing of the 5' UTR, exons, introns and the 3' UTR in 25 African American cases and controls and 23 European American cases and controls (selected from a cohort study of major trauma), which uncovered 80 SNPs. In silico modeling was performed using Patrocles and Transcriptional Element Search System (TESS). Thirty seven novel and tagging SNPs were tested for association with ALI compared with ICU at-risk controls who did not develop ALI in a cohort study of 259 African American and 254 European American subjects that had been admitted to the ICU with major trauma. RESULTS: Resequencing of critically ill subjects demonstrated 43 novel SNPs not previously reported. Coding regions demonstrated no detectable variation, indicating conservation of the protein. Block haplotype analyses reveal that recombination rates within the gene seem low in both Caucasians and African Americans. Several novel SNPs appeared to have the potential for functional consequence using in silico modeling. Chi2 analysis of ALI incidence and genotype showed no significant association between the SNPs in this study and ALI. Haplotype analysis did not reveal any association beyond single SNP analyses. CONCLUSIONS: This study revealed novel SNPs within the PRDX6 gene and its 5' and 3' flanking regions via direct sequencing. There was no association found between these SNPs and ALI, possibly due to a low sample size, which was limited to detection of relative risks of 1.93 and above. Future studies may focus on the role of PRDX6 genetic variation in other diseases, where oxidative stress is suspected.

The ABO histo-blood group, endothelial activation, and acute respiratory distress syndrome risk in critical illness.

BACKGROUNDThe ABO histo-blood group is defined by carbohydrate modifications and is associated with risk for multiple diseases, including acute respiratory distress syndrome (ARDS). We hypothesized that genetically determined blood subtype A1 is associated with increased risk of ARDS and markers of microvascular dysfunction and coagulation.METHODSWe conducted analyses in 3 cohorts of critically ill trauma and sepsis patients (n = 3710) genotyped on genome-wide platforms to determine the association of the A1 blood type genotype with ARDS risk. We subsequently determined whether associations were present in FUT2-defined nonsecretors who lack ABO antigens on epithelium, but not endothelium. In a patient subgroup, we determined the associations of blood type with plasma levels of endothelial glycoproteins and disseminated intravascular coagulation (DIC). Lastly, we tested whether blood type A was associated with less donor lung injury recovery during human ex vivo lung perfusion (EVLP).RESULTSThe A1 genotype was associated with a higher risk of moderate to severe ARDS relative to type O in all 3 populations. In sepsis, this relationship was strongest in nonpulmonary infections. The association persisted in nonsecretors, suggesting a vascular mechanism. The A1 genotype was also associated with higher DIC risk as well as concentrations of thrombomodulin and von Willebrand factor, which in turn were associated with ARDS risk. Blood type A was also associated with less lung injury recovery during EVLP.CONCLUSIONWe identified a replicable association between ABO blood type A1 and risk of ARDS among the critically ill, possibly mediated through microvascular dysfunction and coagulation.FUNDINGNIH HL122075, HL125723, HL137006, HL137915, DK097307, HL115354, HL101779, and the University of Pennsylvania McCabe Fund Fellowship Award.

Relationship of body mass index, serum creatine kinase, and acute kidney injury after severe trauma.

OBJECTIVES: Body mass index (BMI) is associated with acute kidney injury (AKI) after trauma, but underlying mechanisms are unclear. Body mass index correlates with both excess adiposity and increased muscle mass. Since the latter could predispose to severe rhabdomyolysis after trauma, we hypothesized that the BMI-AKI association may be partially explained by a direct relationship of BMI with serum creatine kinase (CK). METHODS: Prospective cohort study of 463 critically ill patients admitted to a level I trauma center from 2005 to 2015 with Injury Severity Score of >15 and serum CK measured in the first 7 days. We defined AKI by AKI Network creatinine criteria. We used simple linear regression to determine the association of BMI with peak CK and multivariable logistic regression to adjust the BMI-AKI association for peak CK and confounders. RESULTS: Median age was 43 years, 350 (76%) were male, 366 (79%) had blunt mechanism, and median Injury Severity Score was 24. Body mass index was associated with peak CK (R = 0.05, p < 0.001). Acute kidney injury developed in 148 patients (32%), and median time to peak CK was 29 hours (interquartile range, 15-56 hours) after presentation. Body mass index was significantly associated with AKI in multivariable models adjusted for age, race, sex, diabetes, injury mechanism and severity, and red blood cell transfusions (odds ratio [OR], 1.31 per 5 kg/m; 95% confidence interval [CI], 1.09-1.58; p = 0.004). Adding peak CK to the model partially attenuated the association of BMI with AKI (OR, 1.26 per 5 kg/m; 95% CI, 1.04-1.52; p = 0.018), and peak CK was also associated with AKI (OR, 1.19 per natural log; 95% CI, 1.00-1.41; p = 0.049). Peak CK remained associated with AKI when restricted to patients with values of <5,000 U/L (OR, 1.31 per natural log; 95% CI, 1.01-1.69; p = 0.043). CONCLUSION: Serum CK correlated with BMI and partially attenuated the association of BMI with AKI after major trauma, suggesting that excess muscle injury may contribute to the BMI-AKI association. LEVEL OF EVIDENCE: Epidemiologic study, level III.

Plasma Mitochondrial DNA Levels Are Associated With ARDS in Trauma and Sepsis Patients.

BACKGROUND: Critically ill patients who develop ARDS have substantial associated morbidity and mortality. Circulating mitochondrial DNA (mtDNA) released during critical illness causes endothelial dysfunction and lung injury in experimental models. This study hypothesized that elevated plasma mtDNA is associated with ARDS in critically ill patients with trauma and sepsis. METHODS: Plasma mtDNA concentrations were measured at ED presentation and approximately 48 h later in separate prospective cohorts of critically ill patients with trauma and sepsis. ARDS was classified according to the Berlin definition. The association of mtDNA with ARDS was tested by using multivariable logistic regression, adjusted for covariates previously shown to contribute to ARDS risk in each population. RESULTS: ARDS developed in 41 of 224 (18%) trauma patients and in 45 of 120 (38%) patients with sepsis. Forty-eight-hour mtDNA levels were significantly associated with ARDS (trauma: OR, 1.58/log copies/µL; 95% CI, 1.14-2.19 [P = .006]; sepsis: OR, 1.52/log copies/µL; 95% CI, 1.12-2.06 [P = .007]). Plasma mtDNA on presentation was not significantly associated with ARDS in either cohort. In patients with sepsis, 48-h mtDNA was more strongly associated with ARDS among those with a nonpulmonary infectious source (OR, 2.20/log copies/µL; 95% CI, 1.36-3.55 [P = .001], n = 69) than those with a pulmonary source (OR, 1.04/log copies/µL; 95% CI, 0.68-1.59 [P = .84], n = 51; P = .014 for interaction). CONCLUSIONS: Plasma mtDNA levels were associated with incident ARDS in two critical illness populations. Given supportive preclinical data, our findings suggest a potential link between circulating mtDNA and lung injury and merit further investigation as a potentially targetable mediator of ARDS.

Association of human NAD(P)H:quinone oxidoreductase 1 (NQO1) polymorphism with development of acute lung injury.

Acute lung injury (ALI) is a syndrome with significant morbidity and mortality, but its genetic susceptibility is not clearly understood. In the present study, we characterized functional promoter single nucleotide polymorphisms (SNPs) in the phase II antioxidant gene NQO1 (NAD(P)H:quinone oxidoreductase1) to evaluate its role in susceptibility to ALI. Three previously uncharacterized SNPs in the NQO1 promoter were selected for investigation. Luciferase assays were performed using constructs of each promoter polymorphism to evaluate function. Functional SNPs were genotyped in a prospective cohort of major trauma patients (N = 264) and assessed for association with development of ALI. The A/C SNP at -1221 decreased in vitro transcription of NQO1 at baseline and after exposure to hyperoxia and other oxidant stressors. Patients heterozygous for the -1221 C allele were at significantly lesser risk of ALI after major trauma compared with patients with wild-type alleles, even after adjustment for APACHE III score, and mechanism of trauma [OR, 0.46 (95% CI 0.23, 0.90); P = 0.024]. This study demonstrated that the AC genotype at position -1221 in the NQO1 gene caused decreased transcription and was associated with a lower incidence of ALI following major trauma. These novel findings may have important implications in diseases with oxidant stress aetiologies.

Efficacy and safety of corticosteroids for persistent acute respiratory distress syndrome.

BACKGROUND: Persistent acute respiratory distress syndrome (ARDS) is characterized by excessive fibroproliferation, ongoing inflammation, prolonged mechanical ventilation, and a substantial risk of death. Because previous reports suggested that corticosteroids may improve survival, we performed a multicenter, randomized controlled trial of corticosteroids in patients with persistent ARDS. METHODS: We randomly assigned 180 patients with ARDS of at least seven days' duration to receive either methylprednisolone or placebo in a double-blind fashion. The primary end point was mortality at 60 days. Secondary end points included the number of ventilator-free days and organ-failure-free days, biochemical markers of inflammation and fibroproliferation, and infectious complications. RESULTS: At 60 days, the hospital mortality rate was 28.6 percent in the placebo group (95 percent confidence interval, 20.3 to 38.6 percent) and 29.2 percent in the methylprednisolone group (95 percent confidence interval, 20.8 to 39.4 percent; P=1.0); at 180 days, the rates were 31.9 percent (95 percent confidence interval, 23.2 to 42.0 percent) and 31.5 percent (95 percent confidence interval, 22.8 to 41.7 percent; P=1.0), respectively. Methylprednisolone was associated with significantly increased 60- and 180-day mortality rates among patients enrolled at least 14 days after the onset of ARDS. Methylprednisolone increased the number of ventilator-free and shock-free days during the first 28 days in association with an improvement in oxygenation, respiratory-system compliance, and blood pressure with fewer days of vasopressor therapy. As compared with placebo, methylprednisolone did not increase the rate of infectious complications but was associated with a higher rate of neuromuscular weakness. CONCLUSIONS: These results do not support the routine use of methylprednisolone for persistent ARDS despite the improvement in cardiopulmonary physiology. In addition, starting methylprednisolone therapy more than two weeks after the onset of ARDS may increase the risk of death. (ClinicalTrials.gov number, NCT00295269.).

Association of physical examination with pulmonary artery catheter parameters in acute lung injury.

OBJECTIVE: To correlate physical examination findings, central venous pressure, fluid output, and central venous oxygen saturation with pulmonary artery catheter parameters. DESIGN: Retrospective study. SETTING: Data from the multicenter Fluid and Catheter Treatment Trial of the National Institutes of Health Acute Respiratory Distress Syndrome Network. PATIENTS: Five hundred thirteen patients with acute lung injury randomized to treatment with a pulmonary artery catheter. INTERVENTIONS: Correlation of physical examination findings (capillary refill time >2 secs, knee mottling, or cool extremities), central venous pressure, fluid output, and central venous oxygen saturation with parameters from a pulmonary artery catheter. MEASUREMENTS: We determined association of baseline physical examination findings and on-study parameters of central venous pressure and central venous oxygen saturation with cardiac index <2.5 L/min/m2 and mixed venous oxygen saturation <60%. We determined correlation of baseline central venous oxygen saturation and mixed venous oxygen saturation and predictive value of a low central venous oxygen saturation for a low mixed venous oxygen saturation. MEASUREMENTS AND MAIN RESULTS: Prevalence of cardiac index <2.5 and mixed venous oxygen saturation <60% was 8.1% and 15.5%, respectively. Baseline presence of all three physical examination findings had low sensitivity (12% and 8%), high specificity (98% and 99%), low positive predictive value (40% and 56%), but high negative predictive value (93% and 86%) for cardiac index <2.5 and mixed venous oxygen saturation <60%, respectively. Central venous oxygen saturation <70% predicted a mixed venous oxygen saturation <60% with a sensitivity 84%,specificity 70%, positive predictive value 31%, and negative predictive value of 96%. Low cardiac index correlated with cool extremities, high central venous pressure, and low 24-hr fluid output; and low mixed venous oxygen saturation correlated with knee mottling and high central venous pressure, but these correlations were not found to be clinically useful. CONCLUSIONS: In this subset of patients with acute lung injury, there is a high prior probability that cardiac index and mixed venous oxygen saturation are normal and physical examination findings of ineffective circulation are not useful for predicting low cardiac index or mixed venous oxygen saturation. Central venous oxygen saturation <70% does not accurately predict mixed venous oxygen saturation <60%, but a central venous oxygen saturation >or=70% may be useful to exclude mixed venous oxygen saturation <60%.

A simple clinical predictive index for objective estimates of mortality in acute lung injury.

OBJECTIVE: We sought to develop a simple point score that would accurately capture the risk of hospital death for patients with acute lung injury (ALI). DESIGN: This is a secondary analysis of data from two randomized trials. Baseline clinical variables collected within 24 hours of enrollment were modeled as predictors of hospital mortality using logistic regression and bootstrap resampling to arrive at a parsimonious model. We constructed a point score based on regression coefficients. SETTING: Medical centers participating in the Acute Respiratory Distress Syndrome Clinical Trials Network (ARDSnet). PATIENTS: Model development: 414 patients with nontraumatic ALI participating in the low tidal volume arm of the ARDSnet Acute Respiratory Management in ARDS study. Model validation: 459 patients participating in the ARDSnet Assessment of Low tidal Volume and elevated End-expiratory volume to Obviate Lung Injury study. Model Validation: 459 patients participating in the ARDSnet Assessment of Low tidal Volume and elevated End-expiratory volume to Obviate Lung Injury trial. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Variables comprising the prognostic model were hematocrit <26% (1 point), bilirubin >or=2 mg/dL (1 point), fluid balance >2.5 L positive (1 point), and age (1 point for age 40-64 years, 2 points for age >or=65 years). Predicted mortality (95% confidence interval) for 0, 1, 2, 3, and 4+ point totals was 8% (5% to 14%), 17% (12% to 23%), 31% (26% to 37%), 51% (43% to 58%), and 70% (58% to 80%), respectively. There was an excellent agreement between predicted and observed mortality in the validation cohort. Observed mortality for 0, 1, 2, 3, and 4+ point totals in the validation cohort was 12%, 16%, 28%, 47%, and 67%, respectively. Compared with the Acute Physiology Assessment and Chronic Health Evaluation III score, areas under the receiver operating characteristic curve for the point score were greater in the development cohort (0.72 vs. 0.67, p = 0.09) and lower in the validation cohort (0.68 vs. 0.75, p = 0.03). CONCLUSIONS: Mortality in patients with ALI can be predicted using an index of four readily available clinical variables with good calibration. This index may help inform prognostic discussions, but validation in nonclinical trial populations is necessary before widespread use.

Validation study of an automated electronic acute lung injury screening tool.

OBJECTIVE 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). DESIGN 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). MEASUREMENTS 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. Main RESULTS 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. CONCLUSIONS 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.

The impact of development of acute lung injury on hospital mortality in critically ill trauma patients.

OBJECTIVE: The additional impact of development of acute lung injury on mortality in severely-injured trauma patients beyond baseline severity of illness has been questioned. We assessed the contribution of acute lung injury to in-hospital mortality in critically ill trauma patients. DESIGN: Prospective cohort study. The contribution of acute lung injury to in-hospital mortality was evaluated in two ways. First, multivariable logistic regression models were used to test the independent association of acute lung injury with in-hospital mortality while adjusting for baseline confounding variables. Second, causal pathway models were used to estimate the amount of the overall association of baseline severity of illness with in-hospital mortality that is attributable to the interval development of acute lung injury. SETTING: Academic level 1 trauma center. PATIENTS: Two hundred eighty-three critically ill trauma patients without isolated head injury and with an Injury Severity Score > or = 16 were evaluated for development of acute lung injury in the first 5 days after trauma. MEASUREMENTS AND MAIN RESULTS: Of the 283 patients, 38 (13.4%) died. The unadjusted mortality rate was nearly three-fold greater in the acute lung injury group (23.9% vs. 8.4%; odds ratio = 3.36; 95% confidence interval 1.67-6.77; p = 0.001). Acute lung injury remained an independent risk factor for death after adjustment for age, baseline Acute Physiologic and Chronic Health Evaluation III score, Injury Severity Score, and blunt mechanism of injury (odds ratio = 2.87; 95% confidence interval 1.29-6.37; p = 0.010). Forty percent of the total association of the baseline Acute Physiologic and Chronic Health Evaluation III score with mortality occurred via an indirect association through acute lung injury, and the remaining 60% via a direct effect. CONCLUSIONS: Development of acute lung injury in critically ill trauma patients without isolated head injury contributes independently to in-hospital mortality beyond baseline severity of illness measures. In addition, a significant portion of the association between baseline illness severity and risk of death in these patients might be explained by the interval development of acute lung injury.