Carolyn S. Calfee

Plasma receptor for advanced glycation end products and clinical outcomes in acute lung injury

Objectives: To determine whether baseline plasma levels of the receptor for advanced glycation end products (RAGE), a novel marker of alveolar type I cell injury, are associated with the severity and outcomes of acute lung injury, and whether plasma RAGE levels are affected by lower tidal volume ventilation. Design, setting and participants: Measurement of plasma RAGE levels from 676 subjects enrolled in a large randomised controlled trial of lower tidal volume ventilation in acute lung injury. Measurements and main results: Higher baseline plasma RAGE was associated with increased severity of lung injury. In addition, higher baseline RAGE was associated with increased mortality (OR for death 1.38 (95% CI 1.13 to 1.68) per 1 log increment in RAGE; p = 0.002) and fewer ventilator free and organ failure free days in patients randomised to higher tidal volumes. These associations persisted in multivariable models that adjusted for age, gender, severity of illness and the presence of sepsis or trauma. Plasma RAGE was not associated with outcomes in the lower tidal volume group (p = 0.09 for interaction in unadjusted analysis). In both tidal volume groups, plasma RAGE levels declined over the first 3 days; however, the decline was 15% greater in the lower tidal volume group (p = 0.02; 95% CI 2.4% to 25.0%). Conclusions: Baseline plasma RAGE levels are strongly associated with clinical outcomes in patients with acute lung injury ventilated with higher tidal volumes. Lower tidal volume ventilation may be beneficial in part by decreasing injury to the alveolar epithelium.

Subphenotypes in acute respiratory distress syndrome: latent class analysis of data from two randomised controlled trials

BACKGROUND Subphenotypes have been identified within heterogeneous diseases such as asthma and breast cancer, with important therapeutic implications. We assessed whether subphenotypes exist within acute respiratory distress syndrome (ARDS), another heterogeneous disorder. METHODS We used data from two ARDS randomised controlled trials (ARMA trial and ALVEOLI trial), sponsored by the National Heart, Lung, and Blood Institute. We applied latent class modelling to identify subphenotypes using clinical and biological data. We modelled data from both studies independently. We then tested the association of subphenotypes with clinical outcomes in both cohorts and with the response to positive end-expiratory pressure (PEEP) in the ALVEOLI cohort. FINDINGS We analysed data for 1022 patients: 473 in the ARMA cohort and 549 in the ALVEOLI cohort. Independent latent class models indicated that a two-class (ie, two subphenotype) model was the best fit for both cohorts. In both cohorts, we identified a hyperinflammatory subphenotype (phenotype 2) that was characterised by higher plasma concentrations of inflammatory biomarkers, a higher prevalence of vasopressor use, lower serum bicarbonate concentrations, and a higher prevalence of sepsis than phenotype 1. Participants in phenotype 2 had higher mortality and fewer ventilator-free days and organ failure-free days in both cohorts than did those in phenotype 1 (p<0·007 for all). In the ALVEOLI cohort, the effects of ventilation strategy (high PEEP vs low PEEP) on mortality, ventilator-free days and organ failure-free days differed by phenotype (p=0·049 for mortality, p=0·018 for ventilator-free days, p=0·003 for organ-failure-free days). INTERPRETATION We have identified two subphenotypes within ARDS, one of which is categorised by more severe inflammation, shock, and metabolic acidosis and by worse clinical outcomes. Response to treatment in a randomised trial of PEEP strategies differed on the basis of subphenotype. Identification of ARDS subphenotypes might be useful in selecting patients for future clinical trials. FUNDING National Institutes of Health.

Critical role of activated protein C in early coagulopathy and later organ failure, infection and death in trauma patients.

Background: Recent studies have identified an acute traumatic coagulopathy that is present on admission to the hospital and is independent of iatrogenic causes. We have previously reported that this coagulopathy is due to the association of severe injury and shock and is characterized by a decrease in plasma protein C (PC) levels. Whether this early coagulopathy and later propensity to infection, multiple organ failure and mortality are associated with the activation of PC pathway has not been demonstrated and constitutes the aim of this study. Methods and Findings: This was a prospective cohort study of 203 major trauma patients. Serial blood samples were drawn on arrival in the emergency department, and at 6, 12, and 24 hours after admission to the hospital. PT, PTT, Va, VIIIa, PC aPC t-PA, and D-dimer levels were assayed. Comprehensive injury, resuscitation, and outcome data were prospectively collected. A total of 203 patients were enrolled. Patients with tissue hypoperfusion and severe traumatic injury showed a strong activation of the PC which was associated with a coagulopathy characterized by inactivation of the coagulation factors V and VIII and a derepression of the fibrinolysis with high plasma levels of plasminogen activator and high D-dimers. Elevated plasma levels of activated PC were significantly associated with increased mortality, organ injury, increased blood transfusion requirements, and reduced ICU ventilator-free days. Finally early depletion of PC after trauma is associated with a propensity to posttraumatic ventilator-associated pneumonia. Conclusions: Acute traumatic coagulopathy occurs in the presence of tissue hypoperfusion and severe traumatic injury and is mediated by activation of the PC pathway. Higher plasma levels of aPC upon admission are predictive of poor clinical outcomes after major trauma. After activation, patients who fail to recover physiologic plasma values of PC have an increased propensity to later nosocomial lung infection.

Early release of high mobility group box nuclear protein 1 after severe trauma in humans: role of injury severity and tissue hypoperfusion

IntroductionHigh mobility group box nuclear protein 1 (HMGB1) is a DNA nuclear binding protein that has recently been shown to be an early trigger of sterile inflammation in animal models of trauma-hemorrhage via the activation of the Toll-like-receptor 4 (TLR4) and the receptor for the advanced glycation endproducts (RAGE). However, whether HMGB1 is released early after trauma hemorrhage in humans and is associated with the development of an inflammatory response and coagulopathy is not known and therefore constitutes the aim of the present study.MethodsOne hundred sixty eight patients were studied as part of a prospective cohort study of severe trauma patients admitted to a single Level 1 Trauma center. Blood was drawn within 10 minutes of arrival to the emergency room before the administration of any fluid resuscitation. HMGB1, tumor necrosis factor (TNF)-α, interleukin (IL)-6, von Willebrand Factor (vWF), angiopoietin-2 (Ang-2), Prothrombin time (PT), prothrombin fragments 1+2 (PF1+2), soluble thrombomodulin (sTM), protein C (PC), plasminogen activator inhibitor-1 (PAI-1), tissue plasminogen activator (tPA) and D-Dimers were measured using standard techniques. Base deficit was used as a measure of tissue hypoperfusion. Measurements were compared to outcome measures obtained from the electronic medical record and trauma registry.ResultsPlasma levels of HMGB1 were increased within 30 minutes after severe trauma in humans and correlated with the severity of injury, tissue hypoperfusion, early posttraumatic coagulopathy and hyperfibrinolysis as well with a systemic inflammatory response and activation of complement. Non-survivors had significantly higher plasma levels of HMGB1 than survivors. Finally, patients who later developed organ injury, (acute lung injury and acute renal failure) had also significantly higher plasma levels of HMGB1 early after trauma.ConclusionsThe results of this study demonstrate for the first time that HMGB1 is released into the bloodstream early after severe trauma in humans. The release of HMGB1 requires severe injury and tissue hypoperfusion, and is associated with posttraumatic coagulation abnormalities, activation of complement and severe systemic inflammatory response.

Mesenchymal stem (stromal) cells for treatment of ARDS: a phase 1 clinical trial

BACKGROUND No effective pharmacotherapy for acute respiratory distress syndrome (ARDS) exists, and mortality remains high. Preclinical studies support the efficacy of mesenchymal stem (stromal) cells (MSCs) in the treatment of lung injury. We aimed to test the safety of a single dose of allogeneic bone marrow-derived MSCs in patients with moderate-to-severe ARDS. METHODS The STem cells for ARDS Treatment (START) trial was a multicentre, open-label, dose-escalation, phase 1 clinical trial. Patients were enrolled in the intensive care units at University of California, San Francisco, CA, USA, Stanford University, Stanford, CA, USA, and Massachusetts General Hospital, Boston, MA, USA, between July 8, 2013, and Jan 13, 2014. Patients were included if they had moderate-to-severe ARDS as defined by the acute onset of the need for positive pressure ventilation by an endotracheal or tracheal tube, a PaO2:FiO2 less than 200 mm Hg with at least 8 cm H2O positive end-expiratory airway pressure (PEEP), and bilateral infiltrates consistent with pulmonary oedema on frontal chest radiograph. The first three patients were treated with low dose MSCs (1 million cells/kg predicted bodyweight [PBW]), the next three patients received intermediate dose MSCs (5 million cells/kg PBW), and the final three patients received high dose MSCs (10 million cells/kg PBW). Primary outcomes included the incidence of prespecified infusion-associated events and serious adverse events. The trial is registered with ClinicalTrials.gov, number NCT01775774. FINDINGS No prespecified infusion-associated events or treatment-related adverse events were reported in any of the nine patients. Serious adverse events were subsequently noted in three patients during the weeks after the infusion: one patient died on study day 9, one patient died on study day 31, and one patient was discovered to have multiple embolic infarcts of the spleen, kidneys, and brain that were age-indeterminate, but thought to have occurred before the MSC infusion based on MRI results. None of these severe adverse events were thought to be MSC-related. INTERPRETATION A single intravenous infusion of allogeneic, bone marrow-derived human MSCs was well tolerated in nine patients with moderate to severe ARDS. Based on this phase 1 experience, we have proceeded to phase 2 testing of MSCs for moderate to severe ARDS with a primary focus on safety and secondary outcomes including respiratory, systemic, and biological endpoints. FUNDING The National Heart, Lung, and Blood Institute.

Nonventilatory Treatments for Acute Lung Injury and ARDS

Over the past decade, advances in the ventilatory management of acute lung injury (ALI) and ARDS have improved outcomes; however, until recently the search for other therapies has been less fruitful. Recently, the Acute Respiratory Distress Syndrome Network Fluid and Catheter Treatment Trial reported that a conservative fluid management strategy, compared with a fluid liberal strategy, increased the mean (+/- SE) number of ventilator-free days in patients with ALI (14.6 +/- 0.5 vs 12.1 +/- 0.5 days, respectively; p < 0.001). In addition to this beneficial effect on outcomes, the study found that the conservative fluid strategy did not increase the incidence of renal failure or the development of shock. Other studies have demonstrated that albumin and furosemide therapy may be beneficial in hypoproteinemic patients with lung injury, though data on outcomes is still lacking. Although several pharmacologic therapies, such as corticosteroids, surfactant, and nitric oxide, have been demonstrated to be ineffective in improving outcomes, several promising new treatments are being investigated in ongoing or upcoming clinical trials. This article reviews these developments and other recent research on the optimal nonventilatory management of patients with ALI.

Therapeutic Potential of Mesenchymal Stem Cells for Severe Acute Lung Injury

Preclinical studies indicate that allogeneic human mesenchymal stem cells (MSC) may be useful for the treatment of several clinical disorders, including sepsis, acute renal failure, acute myocardial infarction, and more recently, acute lung injury (ALI). This article provides a brief review of the biologic qualities of MSC that make them suitable for the treatment of human diseases, as well as the experimental data that provide support for their potential efficacy for critically ill patients with acute respiratory failure from ALI. The article then discusses which patients with ALI might be the best candidates for cell-based therapy and provides a template for the regulatory and practical steps that will be required to test allogeneic human MSC in patients with severe ALI. There is a dual focus on how to design trials for testing both safety and efficacy.

Plasma angiopoietin-2 predicts the onset of acute lung injury in critically ill patients.

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.

Plasma biomarker profiles in acute exacerbation of idiopathic pulmonary fibrosis

Little is known about the pathobiology of acute exacerbation of idiopathic pulmonary fibrosis (IPF), a condition that shares clinical and histopathological features with acute lung injury. Plasma biomarkers have been well studied in acute lung injury and have provided insight into the underlying disease mechanism. The objective of this study was to determine the plasma biomarker profile of acute exacerbation of IPF and compare this profile with that of stable IPF and acute lung injury. Plasma was collected from patients with stable IPF, acute exacerbation of IPF, and acute lung injury for measurement of biomarkers of cellular activity/injury (receptor for advanced glycation endproducts, surfactant protein D, KL-6, von Willebrand factor), systemic inflammation (IL-6), and coagulation/fibrinolysis (protein C, thrombomodulin, plasminogen activator inhibitor-1). Plasma from patients with acute exacerbation of IPF showed significant elevations in markers of type II alveolar epithelial cell injury and/or proliferation, endothelial cell injury, and coagulation. This profile differed from the biomarker profile in patients with acute lung injury. These findings support the hypothesis that type II alveolar epithelial cells are centrally involved in the pathobiology of acute exacerbation of IPF. Furthermore, they suggest that acute exacerbation of IPF has a distinct plasma biomarker profile from that of acute lung injury.

Acute lung injury in patients with traumatic injuries: utility of a panel of biomarkers for diagnosis and pathogenesis.

BACKGROUND 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 patients with ALI. The aims 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. METHODS A retrospective nested case control of 192 patients admitted to the trauma intensive care unit at a university hospital between 2002 and 2006. We compared 107 patients with ALI to 85 patients without ALI. Plasma was collected within 72 hours of intensive care unit admission. Twenty-one plasma biomarkers were measured in duplicate in each plasma sample. RESULTS Patients with ALI had higher severity of illness scores, more days of mechanical ventilation, longer hospital stays, and higher mortality versus controls. Seven biomarkers (receptor for advanced glycation end products, procollagen peptide III, brain natriuretic peptide, angiopoietin-2, interleukin-10, tumor necrosis factor alpha, and interleukin-8) had a high diagnostic accuracy as reflected by the area under the receiver operating characteristic curve of 0.86 (95% confidence interval, 0.82-0.92) in differentiating ALI from controls. CONCLUSIONS A model using 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 ALI.