Prior laboratory work indicates that lower endogenous opioid function is associated with greater analgesic and subjective responses to opioid analgesics. We evaluated whether preoperative cerebrospinal fluid (CSF) concentrations of the analgesic endogenous opioid β-Endorphin (BE) were associated with extent of opioid use after cesarean delivery (CD). We enrolled 136 pregnant women without opioid use or chronic pain who were undergoing CD under spinal or combined spinal-epidural anesthesia. Preoperatively, participants completed validated pain measures and biospecimens were collected to assess BE concentrations in plasma and CSF. Postoperatively, pain intensity at 48 h and 2 weeks postpartum were assessed. We evaluated the association between CSF BE concentrations and total opioid use (in morphine milligram equivalents; MMEs) using linear regression controlling for confounding factors (primary analysis). In secondary analyses, we examined: 1) associations between plasma BE concentrations and total opioid use, and 2) associations between CSF and plasma BE concentrations and secondary outcomes (inpatient versus outpatient opioid use, pain intensity). Participants completed surveys with 100

BACKGROUND:We conducted a randomized trial of open lung protective ventilation (OLPV) compared to conventional ventilation (CV) in deceased donors. The primary outcome was lung utilization for transplantation. METHODS:Eligible donors were ≥13 years with PaO2/FiO2 between 150 and 400 mmHg. Donors were randomized to volume control with OLPV [tidal volume (TV) 8 ml/kg, PEEP 10 cmH2O, protocolized recruitment maneuvers (RM)] or CV [TV 10 ml/kg, PEEP 5 cm H2O, RM only after vent disconnect] for duration of donor management. Lungs were evaluated for transplantation on standardized ventilator settings in both arms [TV 10 ml/kg, PEEP 5 cm H2O, FiO2 1.0]. RESULTS:One hundred and fifty three donors were randomized (74 to OLPV, 79 to CV) and included in the final analysis. Median duration of treatment was 50 hours and did not differ by arm. Donor lung utilization was 23% in the OLPV arm and 22% in the CV arm, p = 0.85. Change in PaO2/FiO2 from randomization to procurement did not differ by treatment; median increase (quartiles) in OLPV versus CV was 68 mmHg (18, 127) vs 74 (-27, 170), p = 0.72. There was no difference in need for vasopressors or serious adverse events between arms. Among 28 lung recipients in whom detailed outcomes were available, duration of mechanical ventilation, ICU stay and hospital stay were not different by treatment arm. CONCLUSIONS:An open lung protective ventilator strategy was safe but did not improve donor lung utilization or oxygenation compared to a conventional ventilator strategy in a population of US organ donors. NCT03439995.

BATIONALE: Widespread endothelial dysfunction and injury are pivotal in the pathogenesis of sepsis, resulting in vascular hyperpermeability, hypotension, and organ dysfunction. Endocan, also known as endothelial-specific molecule-1, is a soluble dermatan sulfate proteoglycan secreted predominantly by activated endothelial cells. Endocan expression is upregulated by pro-inflammatory cytokines such as TNF-alpha and IL-1beta that have also been implicated in the pathogenesis of sepsis. Although endocan has been studied as a biomarker in various diseases including malignancy and atherosclerosis, it is unknown whether plasma endocan is as a marker for endothelial hyperpermeability, organ dysfunction, or clinical outcomes in sepsis. METHODS: This prospective observational study involved 243 ICU patients with sepsis, acute respiratory failure, and an APACHE-II score of 25 or higher. Plasma endocan levels were measured on day 1 after enrollment by ELISA. The primary objective of the study was to test the association between plasma endocan levels and the development of organ dysfunction (as defined by the Brussels organ failure criteria), fluid accumulation, and in-hospital mortality. The secondary objective was to determine whether plasma endocan levels could independently predict clinical outcomes in patients with septic shock. RESULTS: Patients with sepsis and acute respiratory failure who died during hospitalization had notably higher plasma endocan levels compared to survivors (3.11 ng/ml, IQR 2.00 – 5.40 ng/ml vs. 2.25 ng/ml, IQR 1.18 – 4.32 ng/ml, p = 0.002). Multivariable logistic regression analysis indicated that plasma endocan levels are an independent predictor of hospital mortality. Furthermore, higher plasma endocan levels by quartile were strongly linked with APACHE scores (p = 0.026), circulatory failure (p = 0.006), and renal failure at enrollment (p = 0.008) (Figure A-C). Elevated plasma endocan levels were also significantly associated with a positive net fluid balance on ICU admission day (p = 0.002) and in the subsequent 24 (p < 0.001), 48 (p < 0.001), and 72 (p < 0.001) hours after enrollment (Figure D-F). Additionally, plasma endocan levels were an independent predictor of mortality in the subset of patients with septic shock. CONCLUSIONS: Endocan is a robust predictor of clinical outcomes and organ dysfunction in sepsis and septic shock patients with acute respiratory failure. Whether endocan is simply a marker of endothelial activation and injury or contributes to the pathophysiology of organ dysfunction in sepsis is an important topic for future research.

Rationale Endothelial injury is a hallmark of sepsis pathophysiology. Endothelial barrier integrity is partially regulated by the endothelial glycocalyx, a matrix of proteoglycans and glycosaminoglycans (GAGs) lining the vascular lumen. However, in sepsis, this glycocalyx is degraded by heparanase; glycocalyx breakdown is linked to worse sepsis outcomes, but the mechanisms inducing heparanase activity in sepsis are unknown. We previously found that plasma levels of hemoglobin released from red blood cells (cell-free hemoglobin, CFH) are elevated in clinical sepsis and associate with worse outcomes. We also showed that CFH is associated with increased glycocalyx degradation in septic humans and mice (Bogart, ATS 2024). We therefore hypothesized that CFH upregulates heparanase production to drive glycocalyx shedding in sepsis. Methods To test the effect of CFH on heparanase expression in mice after 24 hours of intraabdominal polymicrobial sepsis with elevated CFH (CS [cecal slurry, 2.0mg/g] + intravenous [IV] CFH, 0.15mg/g), we quantified total plasma heparanase (ELISA). We also measured heparanase transcript abundance (RT-qPCR) and active enzyme levels (western blot, WB) in pulmonary endothelial cells isolated from these animals. Additionally, primary human lung microvascular endothelial cells (HLMVECs) treated with tumor necrosis factor alpha (TNFα, 50ng/mL) to simulate sepsis were exposed to CFH (1.0mg/mL) with or without the hemoprotein reductant acetaminophen (APAP, 24mcg/mL) for 24 hours to investigate the mechanism by which CFH may induce heparanase synthesis. Results Total plasma heparanase levels were higher in the CS+CFH treated animals compared to CS alone (430.5±98.9 vs. 61.8±9.6 pg/mL, p=0.001, Figure A), consistent with our prior data that circulating glycocalyx components are elevated in these animals. Heparanase transcript abundance (Relative expression [RE]: 3.57±0.20 vs. 1.00±0.02, p=0.022) and active enzyme levels (RE: 1.55±0.07 vs. 0.73±0.09, p=0.024, Figure B) were also increased in mice receiving CS+CFH. HLMVECs treated with TNFα+CFH had elevated heparanase mRNA (RE vs. TNFα control: 3.26±0.47 vs. 0.40±0.10, p=0.046) and active protein production (RE vs. TNFα control: 2.70±0.43 vs. 0.42±0.15, p=0.033, Figure C). The effect of CFH on heparanase transcription (RE: 0.57±0.16, p=0.047) and enzyme activation (RE: 0.23±0.07, p=0.046, Figure C) was blocked by APAP. Conclusions In sepsis, CFH induces heparanase transcription in lung microvascular endothelial cells, leading to active enzyme synthesis and subsequent endothelial glycocalyx degradation, which may disrupt the endothelial barrier and cause downstream organ injury. Heparanase induction can be blocked by APAP, a hemoprotein reductant, indicating that the effects of CFH on heparanase induction are driven by the oxidant effects of CFH.

BACKGROUND:Access to life-saving lung transplantation remains limited by a shortage of donor organs. We have previously described rehabilitation of discarded human donor lungs to a quality suitable for transplantation using cross-circulation of whole blood between xeno-support swine and human lungs. However, the immunologic implications of transplanting rehabilitated lungs remain unknown. METHODS:Human donor lungs declined for clinical transplantation (N = 5) and underwent xenogeneic cross-circulation (XC) for up to 12 hours. To model subsequent human transplantation, lungs were re-exposed to autologous human whole blood via normothermic ex vivo machine perfusion for up to 6 hours. Upon human blood re-exposure (HBR), lungs were evaluated for evidence of hyperacute rejection (HAR) through physiologic assessments and tissue analyses including histology, immunostaining, and flow cytometry. RESULTS:Upon HBR, lungs showed no significant change in physiologic function relative to the end of cross-circulation (PaO2/FiO2: p = 0.41; vascular resistance: p = 0.27; dynamic compliance: p = 0.24) and histologic features of HAR were absent in all lungs. Despite pulmonary deposition of porcine IgG during cross-circulation, HBR resulted in decreased complement deposition (p = 0.019) with no change in membrane attack complex formation (p = 0.65) or apoptotic signaling (p = 0.93). Endothelial integrity was maintained after HBR with preservation of microvascular tight junctions, decreasing endothelial injury marker p-selectin (p = 0.34), and intact vascular response to alpha-adrenergic stimulation. CONCLUSIONS:Our findings indicate that transient exposure of human donor lungs to XC does not result in HAR upon simulated human transplantation, representing an important step toward clinical translation of this donor organ rehabilitation platform.

Rationale: Endothelial injury is a hallmark of sepsis-induced acute respiratory distress syndrome (ARDS). Endothelial barrier integrity is regulated by the endothelial glycocalyx, a matrix of proteoglycans and glycosaminoglycans (GAGs) that lines the vascular lumen. In sepsis, this glycocalyx is degraded by heparanase, which cleaves heparan sulfate, the primary glycocalyx GAG. Glycocalyx breakdown is linked to worse sepsis outcomes, but the mechanisms inducing heparanase activity in sepsis are unknown. We previously found that plasma levels of hemoglobin released from red blood cells (cell-free hemoglobin, CFH) are elevated in clinical sepsis and correlate with higher rates of ARDS and death. CFH also worsens endothelial injury and microvascular permeability in murine sepsis. We therefore hypothesized that CFH upregulates heparanase production to drive glycocalyx shedding and inflammation in sepsis. Methods: To test the association between CFH levels, heparanase expression, and glycocalyx degradation, circulating levels of heparanase, heparan sulfate, and total GAGs were measured in 77 sepsis patients and compared across CFH quartiles. In mice with intraabdominal polymicrobial sepsis with elevated CFH (CS [cecal slurry] + intravenous [IV] CFH), plasma heparanase, total GAGs, and syndecan-1 were quantified. Whole lung and plasma pro-inflammatory cytokines were also determined to investigate the impact of CFH on inflammation in sepsis. Results: In sepsis patients, higher circulating CFH levels were associated with increased plasma heparanase (p=0.0304), total GAGs (p=0.0178), and heparan sulfate (p=0.0112). CFH also exacerbated glycocalyx degradation in murine sepsis; circulating syndecan-1 (p=0.0152) and total GAGs (p=0.0094) were elevated in animals that received CS+IV CFH compared to CS alone. This effect may be mediated by upregulation of active heparanase, which was higher in the plasma of CS+IV CFH treated animals (p=0.1333). CFH also worsened illness severity, as CS+IV CFH animals had worse sepsis severity scores (p=0.0074). Whole lung tumor necrosis factor-alpha (TNF-a; p=0.0129) and interferon-gamma (IFN-g; p=0.0264) transcript levels were increased in the CS+IV CFH group, indicating greater lung inflammation. Systemic inflammation was also enhanced in the CS+IV CFH animals, demonstrated by higher plasma TNF-a (p<0.001) and IFN-g (p=0.0221) concentrations. Conclusions: In sepsis, CFH is associated with upregulation of heparanase and endothelial glycocalyx degradation, which may disrupt the endothelial barrier, causing downstream organ injury. Future studies to define the molecular pathways that underlie these findings and their effect on endothelial permeability will be an important next step towards identifying novel treatment targets to improve outcomes for patients with sepsis-associated ARDS. Funding F30HL170483, R01HL164937, R01HL158906, R01HL150783, R01HL125371. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Both endocannabinoid (EC) and endogenous opioid systems are involved in nociceptive processing and may work together synergistically based on preclinical models. This study evaluated the interactive effects of preoperative beta-endorphin concentrations (a key analgesic endogenous opioid) in cerebrospinal fluid (CSF) and ECs (CSF and plasma 2-arachidonoylglycerol [2-AG] and plasma anandamide [AEA]) on postoperative opioid use and pain intensity in a prospective cohort of n = 112 pregnant patients undergoing scheduled cesarean delivery. Maternal blood and CSF samples were collected preoperatively for beta-endorphin and EC assays. Patients completed measures of outpatient opioid use (number of tablets used and days of use) and average pain intensity at 2 weeks postoperatively. Results of general linear model analyses controlling for maternal age, BMI at time of delivery, and race revealed significant multiplicative interactions between EC and beta-endorphin concentrations on number of opioid tablets used (based on pill count), days of opioid use, and total milligram morphine equivalents used in the 2 week follow-up period. Elevated preoperative plasma and CSF 2-AG predicted reduced outpatient opioid analgesic use particularly for patients low in CSF beta-endorphin. Similar analyses for pain intensity at 2-week follow-up indicated a significant interaction (p<.02) characterized by higher preoperative beta-endorphin concentrations being associated with lower subsequent pain only for individuals with low preoperative plasma AEA concentrations. Further exploration of interactions between EC and endogenous opioid inhibitory systems as they influence responses to opioid analgesics in other clinical pain populations may help guide development of precision pain management approaches.PerspectiveIn the postoperative setting of patients undergoing cesarean delivery, elevated endocannabinoids were linked to reduced outpatient opioid analgesic use in individuals who had low endogenous opioid concentrations in cerebrospinal fluid. Further exploration of interactions between these two inhibitory systems as they impact on responses to pain management interventions appears warranted.

Background In sepsis and acute respiratory distress syndrome (ARDS), heterogeneity has contributed to difficulty identifying effective pharmacotherapies. In ARDS, two molecular phenotypes (hypoinflammatory and hyper inflammatory) have consistently been identified, with divergent outcomes and treatment responses. In this study, we sought to derive molecular phenotypes in critically ill adults with sepsis, determine their overlap with previous ARDS phenotypes, and evaluate whether they respond differently to treatment in completed sepsis trials. Methods We used clinical data and plasma biomarkers from two prospective sepsis cohorts, the Validating Acute Lung Injury biomarkers for Diagnosis (VALID) study (N=1140) and the Early Assessment of Renal and Lung Injury (EARLI) study (N=818), in latent class analysis (LCA) to identify the optimal number of classes in each cohort independently. We used validated models trained to classify ARDS phenotypes to evaluate concordance of sepsis and ARDS phenotypes. We applied these models retrospectively to the previously published Prospective Recombinant Human Activated Protein C Worldwide Evaluation in Severe Sepsis and Septic Shock (PROWESSSHOCK) trial and Vasopressin and Septic Shock Trial (VASST) to assign phenotypes and evaluate heterogeneity of treatment effect. Findings A twoclass model best fit both VALID and EARLI (p<00001). In VALID, 804 (705%) of the 1140 patients were classified as hypoinflammatory and 336 (295%) as hyperinflammatory; in EARLI, 530 (648%) of 818 were hypoinflammatory and 288 (352%) hyperinflammatory. We observed higher plasma proinflammatory cytokines, more vasopressor use, more bacteraemia, lower protein C, and higher mortality in the hyperinflammatory than in the hypoinflammatory phenotype (p<00001 for all). Classifier models indicated strong concordance between sepsis phenotypes and previously identified ARDS phenotypes (area under the curve 087-096, depending on the model). Findings were similar excluding participants with both sepsis and ARDS. In PROWESSSHOCK, 1142 (680%) of 1680 patients had the hypoinflammatory phenotype and 538 (320%) had the hyperinflammatory phenotype, and response to activated protein C differed by phenotype (p=00043). In VASST, phenotype proportions were similar to other cohorts; however, no treatment interaction with the type of vasopressor was observed (p=072). Interpretation Molecular phenotypes previously identified in ARDS are also identifiable in multiple sepsis cohorts and respond differently to activated protein C. Molecular phenotypes could represent a treatable trait in critical illness beyond the patient's syndromic diagnosis.

Prior work indicates that responsiveness to opioid analgesics is influenced by endogenous opioid system function in the lab. We evaluated whether preoperative levels of β-Endorphin (BE), an endogenous opioid agonist, in cerebrospinal fluid (CSF) and plasma are associated with opioid use after cesarean. We enrolled 136 pregnant patients without opioid use disorder or chronic pain undergoing scheduled cesarean with regional anesthesia. In the preoperative period, participants completed surveys with validated pain measures (Table 2) and we analyzed BE levels from plasma and CSF using ELISA assay. In the postoperative period, participants completed pain measures again at 48 hours and 2 weeks and reported total opioid use. Our primary outcome was total opioid use summed from both inpatient and outpatient periods. We studied the association between preoperative CSF BE levels and our primary outcome using linear regression and controlling for age, BMI, and race. Secondary outcomes included inpatient and outpatient opioid use examined individually. In a second analysis, we examined associations between preoperative plasma BE levels and the primary outcome, and associations between preoperative BE levels and pre and postoperative pain measures. All participants completed pre and postoperative surveys and demographics are reported (Table 1). Neither CSF nor plasma BE levels were associated with total opioid use. CSF BE levels weakly correlated with plasma BE levels (r = 0.28, p < .01). CSF BE levels were associated positively with preoperative and 48-hour postoperative pain intensity scores. Plasma BE levels were associated positively with 48-hour and 2-week postpartum pain intensity scores (Table 2). Preoperative CSF levels of β-endorphin are not associated with opioid analgesic use after scheduled cesarean but are associated with higher pre and postoperative pain intensity scores. It is possible that variability in opioid receptor sensitivity modifies these associations.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

Loss of secretory IgA (SIgA) is common in chronic obstructive pulmonary disease (COPD) small airways and likely contributes to disease progression. We hypothesized that loss of SIgA results from reduced expression of pIgR (polymeric immunoglobulin receptor), a chaperone protein needed for SIgA transcytosis, in the COPD small airway epithelium. pIgR-expressing cells were defined and quantified at single-cell resolution in human airways using RNA in situ hybridization, immunostaining, and single-cell RNA sequencing. Complementary studies in mice used immunostaining, primary murine tracheal epithelial cell culture, and transgenic mice with secretory or ciliated cell-specific knockout of pIgR. SIgA degradation by human neutrophil elastase or secreted bacterial proteases from nontypeable Haemophilus influenzae was evaluated in vitro. We found that secretory cells are the predominant cell type responsible for pIgR expression in human and murine airways. Loss of SIgA in small airways was not associated with a reduction in secretory cells but rather a reduction in pIgR protein expression despite intact PIGR mRNA expression. Neutrophil elastase and nontypeable H. influenzae-secreted proteases are both capable of degrading SIgA in vitro and may also contribute to a deficient SIgA immunobarrier in COPD. Loss of the SIgA immunobarrier in small airways of patients with severe COPD is complex and likely results from both pIgR-dependent defects in IgA transcytosis and SIgA degradation.

Rationale Using latent class analysis (LCA), two subphenotypes of acute respiratory distress syndrome (ARDS) have consistently been identified in five randomised controlled trials (RCTs), with distinct biological characteristics, divergent outcomes and differential treatment responses to randomised interventions. Their existence in unselected populations of ARDS remains unknown. We sought to identify subphenotypes in observational cohorts of ARDS using LCA. Methods LCA was independently applied to patients with ARDS from two prospective observational cohorts of patients admitted to the intensive care unit, derived from the Validating Acute Lung Injury markers for Diagnosis (VALID) (n=624) and Early Assessment of Renal and Lung Injury (EARLI) (n=335) studies. Clinical and biological data were used as class-defining variables. To test for concordance with prior ARDS subphenotypes, the performance metrics of parsimonious classifier models (interleukin 8, bicarbonate, protein C and vasopressor-use), previously developed in RCTs, were evaluated in EARLI and VALID with LCA-derived subphenotypes as the gold-standard. Results A 2-class model best fit the population in VALID (p=0.0010) and in EARLI (p<0.0001). Class 2 comprised 27% and 37% of the populations in VALID and EARLI, respectively. Consistent with the previously described ‘hyperinflammatory’ subphenotype, Class 2 was characterised by higher proinflammatory biomarkers, acidosis and increased shock and worse clinical outcomes. The similarities between these and prior RCT-derived subphenotypes were further substantiated by the performance of the parsimonious classifier models in both cohorts (area under the curves 0.92–0.94). The hyperinflammatory subphenotype was associated with increased prevalence of chronic liver disease and neutropenia and reduced incidence of chronic obstructive pulmonary disease. Measurement of novel biomarkers showed significantly higher levels of matrix metalloproteinase-8 and markers of endothelial injury in the hyperinflammatory subphenotype, whereas, matrix metalloproteinase-9 was significantly lower. Conclusion Previously described subphenotypes are generalisable to unselected populations of non-trauma ARDS.

Women have higher prevalence of asthma compared with men. In asthma, allergic airway inflammation is initiated by IL-33 signaling through ST2, leading to increased IL-4, IL-5, and IL-13 production and eosinophil infiltration. Foxp3+ Tregs suppress and ST2+ Tregs promote allergic airway inflammation. Clinical studies showed that the androgen dehydroepiandrosterone (DHEA) reduced asthma symptoms in patients, and mouse studies showed that androgen receptor (AR) signaling decreased allergic airway inflammation. Yet the impact of AR signaling on lung Tregs remains unclear. Using AR-deficient and Foxp3 fate-mapping mice, we determined that AR signaling increased Treg suppression during Alternaria extract (Alt Ext; allergen) challenge by stabilizing Foxp3+ Tregs and limiting the number of ST2+ ex-Tregs and IL-13+ Th2 cells and ex-Tregs. AR signaling also decreased Alt Ext-induced ST2+ Tregs in mice by limiting expression of Gata2, a transcription factor for ST2, and by decreasing Alt Ext-induced IL-33 production from murine airway epithelial cells. We confirmed our findings in human cells where 5α-dihydrotestosterone (DHT), an androgen, decreased IL-33-induced ST2 expression in lung Tregs and decreased Alt Ext-induced IL-33 secretion in human bronchial epithelial cells. Our findings showed that AR signaling stabilized Treg suppressive function, providing a mechanism for the sex difference in asthma.

Background Two acute respiratory distress syndrome (ARDS) subphenotypes (hyperinflammatory and hypoinflammatory) with distinct clinical and biological features and differential treatment responses have been identified using latent class analysis (LCA) in seven individual cohorts. To facilitate bedside identification of subphenotypes, clinical classifier models using readily available clinical variables have been described in four randomised controlled trials. We aimed to assess the performance of these models in observational cohorts of ARDS. Methods In this observational, multicohort, retrospective study, we validated two machine-learning clinical classifier models for assigning ARDS subphenotypes in two observational cohorts of patients with ARDS: Early Assessment of Renal and Lung Injury (EARLI; n=335) and Validating Acute Lung Injury Markers for Diagnosis (VALID; n=452), with LCA-derived subphenotypes as the gold standard. The primary model comprised only vital signs and laboratory variables, and the secondary model comprised all predictors in the primary model, with the addition of ventilatory variables and demographics. Model performance was assessed by calculating the area under the receiver operating characteristic curve (AUC) and calibration plots, and assigning subphenotypes using a probability cutoff value of 0.5 to determine sensitivity, specificity, and accuracy of the assignments. We also assessed the performance of the primary model in EARLI using data automatically extracted from an electronic health record (EHR; EHR-derived EARLI cohort). In Large Observational Study to Understand the Global Impact of Severe Acute Respiratory Failure (LUNG SAFE; n=2813), a multinational, observational ARDS cohort, we applied a custom classifier model (with fewer variables than the primary model) to determine the prognostic value of the subphenotypes and tested their interaction with the positive end-expiratory pressure (PEEP) strategy, with 90-day mortality as the dependent variable. Findings The primary clinical classifier model had an area under receiver operating characteristic curve (AUC) of 0.92 (95% CI 0.90-0.95) in EARLI and 0.88 (0.84-0.91) in VALID. Performance of the primary model was similar when using exclusively EHR-derived predictors compared with manually curated predictors (AUC=0.88 [95% CI 0.81-0.94] vs 0.92 [0.88-0.97]). In LUNG SAFE, 90-day mortality was higher in patients assigned the hyperinflammatory subphenotype than in those with the hypoinflammatory phenotype (414 [57%] of 725 vs 694 [33%] of 2088; p<0.0001). There was a significant treatment interaction with PEEP strategy and ARDS subphenotype (p=0.041), with lower 90-day mortality in the high PEEP group of patients with the hyperinflammatory subphenotype (hyperinflammatory subphenotype: 169 [54%] of 313 patients in the high PEEP group vs 127 [62%] of 205 patients in the low PEEP group; hypoinflammatory subphenotype: 231 [34%] of 675 patients in the high PEEP group vs 233 [32%] of 734 patients in the low PEEP group). Interpretation Classifier models using clinical variables alone can accurately assign ARDS subphenotypes in observational cohorts. Application of these models can provide valuable prognostic information and could inform management strategies for personalised treatment, including application of PEEP, once prospectively validated. Copyright (C) 2021 Elsevier Ltd. All rights reserved.

Acute respiratory distress syndrome (ARDS) is a common cause of respiratory failure yet has few pharmacologic therapies, reflecting the mechanistic heterogeneity of lung injury. We hypothesized that damage to the alveolar epithelial glycocalyx, a layer of glycosaminoglycans interposed between the epithelium and surfactant, contributes to lung injury in patients with ARDS. Using mass spectrometry of airspace fluid noninvasively collected from mechanically ventilated patients, we found that airspace glycosaminoglycan shedding (an index of glycocalyx degradation) occurred predominantly in patients with direct lung injury and was associated with duration of mechanical ventilation. Male patients had increased shedding, which correlated with airspace concentrations of matrix metalloproteinases. Selective epithelial glycocalyx degradation in mice was sufficient to induce surfactant dysfunction, a key characteristic of ARDS, leading to microatelectasis and decreased lung compliance. Rapid colorimetric quantification of airspace glycosaminoglycans was feasible and could provide point-of-care prognostic information to clinicians and/or be used for predictive enrichment in clinical trials.

Background Endothelial dysfunction and injury is a major pathophysiologic feature of sepsis. Sepsis is also the most frequent cause of acute kidney injury (AKI) in critically ill patients. Though most studies of AKI in sepsis have focused on tubular epithelial injury, the role of endothelial dysfunction and injury is less well studied. The goal of this study was first to investigate whether endothelial dysfunction and injury biomarkers were associated with severe AKI in sepsis patients. The second goal was to determine the best performing biomarker for severe AKI and whether this biomarker was associated with severe AKI across different etiologies of sepsis and clinical outcomes. Methods We studied adults with severe sepsis and acute respiratory failure (ARF) enrolled in the prospective observational Validating Acute Lung Injury markers for Diagnosis (VALID) study. Plasma endothelial dysfunction and injury biomarkers, including angiopoietin-2, soluble vascular endothelial cadherin (sVE-cadherin), endocan and syndecan-1, were measured at study enrollment. Primary analysis focused on the association between endothelial biomarker levels with severe AKI (defined as Kidney Disease: Improving Global Outcomes [KDIGO] AKI stage 2 or 3), other organ dysfunctions (defined by Brussels organ failure scores), and comparison of pulmonary versus non-pulmonary sepsis. Results Among 228 sepsis patients enrolled, 141 developed severe AKI. Plasma levels of angiopoietin-2, endocan, sVE-cadherin, and syndecan-1 were significantly higher in sepsis patients with severe AKI compared to those without severe AKI. Among four endothelial biomarkers, only angiopoietin-2 was independently associated with severe AKI (odds ratio 6.07 per log increase, 95% CI 2.34–15.78, p < 0.001). Plasma angiopoietin-2 levels by quartile were significantly higher in sepsis patients with hepatic, coagulation, and circulatory failure. Plasma angiopoietin-2 levels were also significantly higher in patients with non-pulmonary sepsis compared to subjects with pulmonary sepsis. Conclusion Among four biomarkers of endothelial dysfunction and injury, angiopoietin-2 had the most robust independent association with development of severe AKI in patients with severe sepsis and ARF. Plasma angiopoietin-2 levels were also associated with other organ dysfunctions, non-pulmonary sepsis, and death. These findings highlight the importance of early endothelial dysfunction and injury in the pathogenesis of sepsis-induced AKI.

Abstract Background Recent trials have suggested use of balanced crystalloids may decrease the incidence of major adverse kidney events compared to saline in critically ill adults. The effect of crystalloid composition on biomarkers of early acute kidney injury remains unknown. Methods From February 15 to July 15, 2016, we conducted an ancillary study to the Isotonic Solutions and Major Adverse Renal Events Trial (SMART) comparing the effect of balanced crystalloids versus saline on urinary levels of neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1) among 261 consecutively-enrolled critically ill adults admitted from the emergency department to the medical ICU. After informed consent, we collected urine 36 ± 12 h after hospital admission and measured NGAL and KIM-1 levels using commercially available ELISAs. Levels of NGAL and KIM-1 at 36 ± 12 h were compared between patients assigned to balanced crystalloids versus saline using a Mann-Whitney U test. Results The 131 patients (50.2%) assigned to the balanced crystalloid group and the 130 patients (49.8%) assigned to the saline group were similar at baseline. Urinary NGAL levels were significantly lower in the balanced crystalloid group (median, 39.4 ng/mg [IQR 9.9 to 133.2]) compared with the saline group (median, 64.4 ng/mg [IQR 27.6 to 339.9]) (P < 0.001). Urinary KIM-1 levels did not significantly differ between the balanced crystalloid group (median, 2.7 ng/mg [IQR 1.5 to 4.9]) and the saline group (median, 2.4 ng/mg [IQR 1.3 to 5.0]) (P = 0.36). Conclusions In this ancillary analysis of a clinical trial comparing balanced crystalloids to saline among critically ill adults, balanced crystalloids were associated with lower urinary concentrations of NGAL and similar urinary concentrations of KIM-1, compared with saline. These results suggest only a modest reduction in early biomarkers of acute kidney injury with use of balanced crystalloids compared with saline. Trial registration ClinicalTrials.gov number: NCT02444988 . Date registered: May 15, 2015.