Inflammation induces a procoagulant phenotype of endothelial cells (EC) with the exposure of tissue factor (TF), a potent initiator of the extrinsic coagulation cascade. Although systemic inflammation affects the whole vascular system, thrombotic lesions occur particularly in microcirculation. This raises the question of whether TF-procoagulant activity (TF-PCA) differs between EC from arterial, venous, and microvascular beds. Functional coagulation tests, including TF-PCA, and inflammatory responses were investigated on arterial, venous and microvascular endothelial cells. Interleukin-6 (IL-6) and TF-levels were determined in cohort of 59 septic patients. We found that tumor necrosis factor alpha (TNFα), lipopolysaccharide, and interleukin-1β induce a solid, dose-dependent increase in TF-PCA, which is highest in microvascular EC. A positive correlation of interleukin-6 (IL-6) with TF levels was observed in a cohort of 59 septic patients. In contrast, TF-PCA was independent of IL-6 concentrations in vitro. Re-analysis of publicly available gene expression data revealed that among the top 50 genes annotated to coagulation, TF is one of three regulated genes common to the three investigated EC subtypes. The response to inflammatory stimuli in terms of exposure of leukocyte-endothelial- and platelet-endothelial adhesion molecules (E-selectin and PECAM-1), remodeling of adherens junctions, co-exposure of negatively charged surfaces nor breakdown of the glycocalyx was comparable between the EC subtypes and did not explain the higher TF-PCA on microvascular cells. We found that the ratio of TF and TFPI exposure on the endothelial membrane significantly differs between the EC subtypes. These findings indicate that the ratio of TF to its inhibitor TFPI is a determinant of endothelial TF-PCA, which is most pronounced on microvascular endothelial cells and might explain why the microvascular system is particularly susceptible to inflammation-induced thrombosis.

Microvesicles (MV) are extracellular vesicles known to be associated with cellular activation and inflammation. Hemofiltration is an effective blood purification technique for patients with renal failure and possibly also eliminates inflammatory mediators in the setting of sepsis. On the other hand, proinflammatory stimuli are induced by blood contacting the artificial membrane during extracorporeal blood purification. In chronic dialysis patients a systemic increase in MV has been described. The aim of the study was to investigate whether hemofilter passage of blood in continuous veno-venous hemofiltration (CVVH) alters MV composition and levels in critically ill patients with sepsis. Pre- and postfilter bloods as well as ultrafiltrate samples from intensive care unit patients with severe sepsis were obtained during CVVH with regional citrate anticoagulation. MV subtypes in blood were analyzed by high-sensitivity flow cytometry. Additionally, tissue factor (TF) levels and MV-associated TF activities as well as MV activities were quantified. All parameters were corrected for hemoconcentration applied during CVVH. Twelve patients were analyzed. A significant increase in presumably mostly leukocyte-derived CD31+/CD41− MV (1.32 (1.09–1.93)-fold [median (25th–75th quartiles)], p = 0.021) was observed post- to prefilter, whereas platelet-derived MV as well as AnnexinV-binding MV were unaltered. Increments of AnnexinV+, CD42b+ and CD31+/CD41− MV post- to prefilter correlated with filtration fraction (FF) (all p < 0.05). Significant reductions in MV activity [0.72 (0.62–0.84)-fold, p = 0.002] and TF level [0.95 (0.87–0.99)-fold, p = 0.0093] were detected postfilter compared to prefilter. No MV activity was measurable in ultrafiltrate samples. Despite clearing a fraction of small PS-exposing MV CVVH does not eliminate larger MV. Concurrently, CVVH induces the release of CD31+/CD4− MV that indicate leukocyte activation during hemofilter passage in septic patients. Increments of several MV subtypes within the hemofilter correlate with FF, which supports common recommendations to keep FF low. A fraction of TF is being cleared by CVVH via ultrafiltration.

Sepsis-induced disseminated intravascular coagulopathy (DIC) remains a challenging clinical entity associated with significant morbidity and mortality. Endothelial injury or activation and extracellular vesicles (EV) are postulated as important determinants of DIC. The aim of this study was to test the discriminatory ability of E-selectin, EV, tissue factor (TF) and TF pathway inhibitor (TFPI) in sepsis-induced coagulopathy. In this prospective, single-center study, we collected plasma samples within 24 hours after sepsis diagnosis and followed these patients for 5 consecutive days. Overt DIC was determined by the International Society on Thrombosis and Haemostasis (ISTH) DIC score. Eighty-seven sepsis patients were recruited (35 with overt DIC) who presented with increased levels of EV, EV-associated TF procoagulant activity (TF-PCA), E-selectin, TF, and TFPI at admission compared with healthy subjects. Only TFPI levels and TF-PCA discriminated between sepsis patients with or without DIC (area under the curve = 0.76; P = .0002). Increased TF-PCA was not sensitive in detecting sepsis-associated DIC; however, levels above 1.38 pg/mL showed high specificity in this cohort (sensitivity 27%, specificity 95%). The hazard ratio to progress to DIC over 5 days was 1.14 (95% CI, 0.64-2.07) for TF-PCA levels of 0.5 pg/mL or higher and 3.18 (95% CI, 1.74-5.79) for TFPI levels of 22.28 ng/mL or higher at admission. These findings highlight the pivotal roles of TF-PCA and TFPI in an early phase of sepsis-induced DIC. Only EV-associated and functionally active TF and not TF antigen levels showed a predictive potential regarding DIC. These novel results might support the improvement of diagnostic or even therapeutic strategies to mitigate the devastating consequences of DIC in septic patients.

Sepsis is defined as a dysregulated host response to an infection, leading to life-threatening organ dysfunction. While sepsis is most commonly the result of a bacterial infection, it may also be caused by viral pathogens. The aim of this study was to describe differences in organ dysfunction patterns and inflammatory markers between bacterial and viral sepsis. In this prospective multicenter cohort study, adults meeting SEPSIS-3 criteria were recruited from four Austrian ICUs between 1 August 2021 and 1 April 2024, excluding those who were immunocompromised within the preceding 12 months. Ninety patients were enrolled, of whom 57 had bacterial and 33 viral sepsis. Inflammatory markers, including IL-6 and PCT, were higher at ICU admission in bacterial sepsis. Adjusted linear regression confirmed bacterial etiology as the only significant predictor of higher 48 h peak IL-6 and PCT values. Patients with viral sepsis typically fulfilled SEPSIS-3 criteria through respiratory and cardiovascular SOFA components, while other organ dysfunctions were less frequent. Significant differences in the phenotype of bacterial and viral sepsis were observed, characterized by distinct inflammatory profiles and differing patterns of organ dysfunction. These findings may support the improved differentiation of bacterial and viral etiologies in sepsis.

Sepsis causes millions of deaths each year. Rapid, targeted therapy can reduce mortality rates. Both bacterial and viral pathogens can trigger sepsis, but the utility of commonly used inflammatory markers for differentiation remains controversial. Moreover, little is known about the time courses of alternative inflammatory parameters. The aim of this prospective, two-center observational study was to investigate the differences in the course of soluble Neuropilin-1 (sNRP-1) levels between bacterial and viral sepsis over a 7-day period. To be included, adult patients had to meet the SEPSIS-3 criteria and be diagnosed with either a bacterial or viral pathogen. Immunosuppressed patients were excluded. While IL-6, PCT, and CRP levels decreased consistently over time, sNRP-1 levels remained elevated in the bacterial group throughout the entire ICU stay. PCT (p < 0.001) and CRP (p = 0.016) levels were significantly associated with the course of sNRP-1. The AUC of sNRP-1 was 0.777 for discriminating between bacterial and viral infections on day 1. sNRP-1 remained stable and significantly higher in bacterial than in viral infections. Furthermore, the AUC values for discrimination ranged from acceptable to good, depending on the day of the ICU stay. sNRP-1 may serve as a potential tool to differentiate between bacterial and viral pathogens in sepsis.