Shaohua Men

Prospective studies on the incidence of VTE during severe sepsis and septic shock remain absent, hindering efficacy assessments regarding VTE prevention strategies in sepsis.We prospectively studied 113 consecutively enrolled patients in the ICU with severe sepsis and septic shock at three hospitals. All patients provided informed consent. VTE thromboprophylaxis was recorded for all patients. Patients underwent ultrasonography and were followed for VTE prior to ICU discharge. All-cause 28-day mortality was recorded. Variables from univariate analyses that were associated with VTE (including central venous catheter [CVC] insertion, age, length of stay, and mechanical ventilation) were included in a multivariable logistic regression analysis using backward stepwise elimination to determine VTE predictors.Mean APACHE (Acute Physiology and Chronic Health Evaluation) II score was 18.2 ± 7.0, and age was 50 ± 18 years. Despite all patients receiving guideline-recommended thromboprophylaxis, the incidence of VTE was 37.2% (95% CI, 28.3-46.8). Most VTE events were clinically significant (defined as pulmonary embolism, proximal DVT, and/or symptomatic distal DVT) and associated with an increased length of stay (18.2 ± 9.9 days vs 13.4 ± 11.5 days, P < .05). Mortality was higher in patients with acute VTE but did not reach statistical significance. Insertion of a CVC and longer mechanical ventilation duration were significant VTE risk factors. VTE incidence did not differ by thromboprophylaxis type.To our knowledge this is the first multicenter prospective study to identify a high incidence of VTE in patients with severe sepsis and septic shock, despite the use of universal, guideline-recommended thromboprophylaxis. Our findings suggest that the systemic inflammatory milieu of sepsis may uniquely predispose patients with sepsis to VTE. More effective VTE prevention strategies are necessary in patients with sepsis.ClinicalTrials.gov; No.: NCT02353910; URL: www.clinicaltrials.gov.

Flow cytometry is often used to measure in vivo platelet activation in critically-ill patients. Variability in blood sampling techniques, which may confound these measurements, remains poorly characterized.Platelet activation was measured by flow cytometry performed on arterial and venous blood from 116 critically-ill patients. We determined how variability in vascular sampling site, processing times, and platelet counts influenced levels of platelet-monocyte aggregates (PMA), PAC-1 binding (for glycoprotein (GP) IIbIIIa), and P-selectin (P-SEL) expression.Levels of PMA, but not PAC-1 binding or P-SEL expression, were significantly affected by variability in vascular sampling site. Average PMA levels were approximately 60% higher in whole blood drawn from an arterial vessel compared to venous blood (16.2±1.8% vs. 10.7±1.2%, p<0.05). Levels of PMA in both arterial and venous blood increased significantly during ex vivo processing delays (1.7% increase for every 10 minute delay, p<0.05). In contrast, PAC-1 binding and P-SEL expression were unaffected by processing delays. Levels of PMA, but not PAC-1 binding or P-SEL expression, were correlated with platelet count quartiles (9.4±1.6% for the lowest quartile versus 15.4±1.6% for the highest quartile, p<0.05).In critically-ill patients, variability in vascular sampling site, processing times, and platelet counts influence levels of PMA, but not PAC-1 binding or P-SEL expression. These data demonstrate the need for rigorous adherence to blood sampling protocols, particularly when levels of PMA, which are most sensitive to variations in blood collection, are measured for detection of in vivo platelet activation.

Despite the improvements in LVAD technology, the balance between bleeding and thrombosis remains a vexing problem that drives significant morbidity and mortality. Blood traversing through continuous flow pumps can drive platelet dysfunction leading to both spectra of complications. Although platelets are devoid of a nucleus, their function is more than to simply aggregate and degranulate. Under stress conditions, platelets can alter their genomic DNA. We hypothesized that platelets exposed to LVADs will be reprogrammed and contribute to the development of bleeding or thrombotic complications. Peripheral blood with isolation of platelet was prospectively collected in 32 patients prior to LVAD insertion and then 3, 30, and 90 days post implant. Demographic matching and quality of RNA were used to identify 12 like-patients. These patients were further subdivided into bleeders (N=3), clotters (N=3), and no complication (N=6). For analysis, we compared the pre-implant and 3 month timepoints to avoid confounders associated with the perioperative period. Platelet activation studies and RNA-sequencing were performed. After 3 months of LVAD support, no differences were observed in platelet function as measured by PAC-1, CD41, or CD 62 activity. Compared to pre-implantation, LVADs resulted in 722 significant changes in the transcriptome, 142 related to cardiovascular disease, and 30 related to heart failure. Important pathways included cell survival, cell-to-cell interactions, growth and proliferation, and metabolism. Highly significant genes upregulated with the cohort of 12 patients included CEACAM6, MPO, ELANE, RNASE3, and MS4A3. When examining the patients that experienced rheologic complications, subgroup analysis demonstrated that FHL3 expression was significantly higher in bleeders; MAEL and METTL7A were markedly overexpressed in clotters. While classic platelet activation does not persist past the perioperative period in patients with chronic LVAD support, the platelet transcriptome is dramatically altered. We identified specific biomarkers associated with bleeding and clotting complications. While the patient number is small, our data suggest platelet phenotyping could prove useful in risk assessment, and potentially in search for therapeutic targets in chronically supported LVAD patients.

PURPOSE: Influenza A virus subtype H1N1 is a common cause of human influenza infections. Platelet activation during H1N1 sepsis may contribute to the inflammatory and thrombotic milieu in these patients but remains poorly characterized.

PURPOSE: Whole blood flow cytometry is commonly used to detect in vivo platelet activation during critical illness. Heterogeneity in blood sampling techniques, processing time, and platelet counts may significantly influence measurements and confound comparisons yet have not been adequately characterized.