Platelets
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Randomized Controlled Trial
Cross validation of aspirin effect in healthy individuals by Impact-R and PFA-100: a double blind randomized placebo controlled trial.
The main objective of this study was to compare testing for aspirin response in healthy volunteers by two high shear methods in a randomized double blind placebo controlled study. Seventeen healthy male individuals were randomized for aspirin 160 mg per day for 7-10 days, and 20 age matched controls for placebo for the same period. At study entry and 7-10 days thereafter we determined high shear-induced platelet adhesion to polystyrene after pre-incubation with arachidonic acid using the Cone and Plate(let) analyzer (Impact-R), and the closure time of collagen/epinephrine cartridges obtained by the PFA-100 (CEPI-CT). ⋯ The response to aspirin varied considerably among healthy individuals, but both methods were suitable to demonstrate the aspirin effect. There was, however, a significant level of absent concordance between the tests. Since the trial design cannot provide data on the specificity of the different tests, only clinical experience can determine their usefulness.
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Rotational thromboelastometry ROTEM is available as point-of-care coagulation monitoring in an increasing number of European operating theatres and emergency rooms. The Platelet Mapping Assay has been described as a platelet aggregation assay for thromboelastography TEG. The aim of this experimental trial was to evaluate feasibility of the Platelet Mapping Assay on the ROTEM test system. ⋯ Differences in frequency distribution between the results obtained in ROTEM and TEG were not statistically significant. The Platelet Mapping Assay can be performed on the ROTEM. For the perioperative scenario, however, longer test duration and higher costs have to be considered compared to Multiplate analyses.
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Pre- and intraoperative platelet function monitoring is increasingly recommended in order to detect risk factors for bleeding and to target coagulation management. The ideal anticoagulant for accurate platelet aggregometry remains controversial. The aim of this experimental trial was to compare platelet aggregability in whole blood stored in citrate, heparin and direct thrombin inhibitors. ⋯ During storage the response to arachidonic acid and collagen was maintained by direct thrombin inhibitors and heparin, whereas ADP-, TRAP- and ristocetin-induced aggregation varied considerably over time in all ex vivo anticoagulants tested. Pre-analytical procedures should be standardized because storage duration and anticoagulants significantly affect platelet aggregability in whole blood. For point-of-care monitoring with immediate analysis after blood withdrawal all tested direct thrombin inhibitors as well as unfractionated heparin can be used as anticoagulants whereas citrate is not recommended.
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Platelet activation contributes to microvascular thrombosis and organ failure in systemic inflammation. We tested the hypothesis whether anti-platelet drugs might favourably affect outcome in patients at risk for organ failure as well as in a mouse model of endotoxin shock. Two hundred twenty-four consecutive patients who were admitted for community acquired pneumonia over a time period of 5 years to a University Hospital were enrolled; about 20% of whom received anti-platelet drugs (acetylsalicylic acid, thienopyridines) for secondary prevention of cardiovascular disease. ⋯ However, clopidogrel abolished the LPS-induced drop in platelet count and reduced fibrin deposition in lung tissue. Using DNA microarray technology, we could show that clopidogrel suppressed endotoxin-induced up-regulation of inflammation-relevant genes, including arachidonate-5-lipoxygenase activating protein and leukotriene B4 receptor 1. According to our data a possible benefit of anti-platelet drugs in patients on risk for systemic inflammation and organ failure should be tested in a prospective trial.
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Comparative Study
Change of platelet activation markers using flow cytometry in patients with hematology/oncology disorders after transfusion.
In spite of the frequent need of platelet transfusions, there is limited information on the association of platelet activation markers, in transfused patients with hematology/oncology disorders, with platelet function using flow cytometry. The goal of this study was to evaluate the changes of PAC-1 binding and CD62P expression, with or without agonists in patients after transfusions. Twenty-eight whole blood samples were obtained from 24 patients admitted to the department of Hematology & Oncology and transfused with platelets; these samples were compared to 30 healthy controls. ⋯ ADP and TRAP induced an increased percentage of CD62P expression and PAC-1 binding after platelet transfusions compared to the samples studied before transfusion, and these findings were lower than those of the healthy controls. However, the expression of platelets without the agonists was not significantly changed, despite the transfusions. Therefore, agonist-induced platelet activation markers, studied by flow cytometry, appear to be more useful for the evaluation of platelet function after transfusions than platelet activation markers without agonists.