To cite this article: Hillarp A, Baghaei F, Fagerberg Blixter I, Gustafsson KM, Stigendal L, Sten-Linder M, Strandberg K, Lindahl TL. Effects of the oral, direct factor Xa inhibitor rivaroxaban on commonly used coagulation assays. J Thromb Haemost 2011; 9: 133-9.Summary. Introduction: Rivaroxaban is an oral direct factor Xa inhibitor developed for prophylaxis and treatment of thromboembolic disorders. Laboratory monitoring is not necessary but the dose-dependent effects on common reagents and assay procedures are largely unknown. Objectives: To investigate the effect of rivaroxaban on commonly used coagulation assays. Materials and Methods: Rivaroxaban was added to plasma from healthy subjects in the concentration range 0-1000 lg L )1 and analyzed using different reagents for activated partial thromboplastin time (APTT), prothrombin time (PT), antithrombin, fibrinogen and activated protein C (APC) resistance assays. Results: At an expected peak concentration of rivaroxaban in clinical use, the APTTs were almost invariably prolonged but at lower concentrations the effect was weak. The concentration needed to double the APTT varied between 389 ± 106 and 617 ± 149 lg L )1 for different reagents. The PT assays showed a marked degree of difference. In general, the Quick PT type assays were more sensitive compared with the Owren type PT assays. The results from antithrombin assays were dependent on the type of reagent, with the Xa-based assay being sensitive for rivaroxaban with an estimated increase of 0.09 IU mL )1 per 100 lg L )1 rivaroxaban. There were only minor effects on fibrinogen assays based on thrombin reagents. The APTT-based assay for APC resistance is affected in a dose-dependent manner whereas an assay based on the activation of coagulation at the prothrombinase level was unaffected. Conclusions: Different assays, and even different reagents within an assay group, display variable effects by therapeutic concentrations of rivaroxaban.

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Background and Purpose-Patients treated with oral anticoagulants (ACs) have an increased risk of intracerebral hemorrhage (ICH), which is more often fatal than spontaneous ICH. Options to reverse the AC effect include intravenous administration of vitamin K, plasma, and coagulation factor concentrate. However, the optimal management of AC-related ICH has not been determined in any randomized trial. In this study, the present management of AC-related ICH was surveyed, and determinants of survival were assessed. Methods-We retrospectively reviewed the medical records of all AC-related ICHs at 10 Swedish hospitals during a 4-year period, 1993 to 1996. Survival status after the ICH was determined from the Swedish National population register. Results-We identified 151 patients with AC-related ICH. Death rates were 53.6% at 30 days, 63.6% at 6 months, and 77.5% at follow-up (mean 3.5 years). The case fatality ratio at 30 days was 96% among patients unconscious on admission (nϭ27), 80% among patients who became unconscious before active treatment was started (nϭ15), 55% among patients in whom no special action was taken except withdrawal of AC treatment (nϭ42), and 28% among patients given active anti-coumarin treatment while they were still conscious (nϭ64). The case fatality ratio at 30 days was 11% in the group treated with plasma (nϭ18), 30% in the group treated with vitamin K (nϭ23), and 39% in the group treated with coagulation factor concentrate (nϭ23). Within the first 24 to 48 hours after admission, 47% of the patients deteriorated. Choice of therapy to reverse the AC effect differed substantially between the hospitals (PϽ0.0001), as did the time interval from symptom onset to start of treatment. Multiple logistic regression analysis showed only 2 factors (intraventricular extension of bleeding and ICH volume) that were independently related to case fatality at both 30 days and 6 months. The results were similar when the analysis was restricted to patients who were conscious on admission. Conclusions-In AC-related ICH, a progressive neurological deterioration during the first 24 to 48 hours after admission is frequent, and the mortality is high. Choice of therapy to reverse the AC effect differed considerably between the hospitals. There was no evidence that any treatment strategy was superior to the others. A randomized controlled trial is needed to determine the best choice of treatment.

Particulate air pollution is known to increase cardiovascular morbidity and mortality. Proposed mechanisms underlying this increase include effects on inflammation, coagulation factors, and oxidative stress, which could increase the risk of coronary events and atherosclerosis. The aim of this study was to examine whether short-term exposure to wood smoke affects markers of inflammation, blood hemostasis, and lipid peroxidation in healthy humans. Thirteen subjects were exposed to wood smoke and clean air in a chamber during two 4-h sessions, 1 wk apart. The mass concentrations of fine particles at wood smoke exposure were 240-280 mug/m3, and number concentrations were 95,000-180,000/cm3. About half of the particles were ultrafine (< 100 nm). Blood and urine samples were taken before and after the experiment. Exposure to wood smoke increased the levels of serum amyloid A, a cardiovascular risk factor, as well as factor VIII in plasma and the factor VIII/von Willebrand factor ratio, indicating a slight effect on the balance of coagulation factors. Moreover, there was an increased urinary excretion of free 8-iso-prostaglandin2alpha, a major F2-isoprostane, though this was based on nine subjects only, indicating a temporary increase in free radical-mediated lipid peroxidation. Thus, wood-smoke particles at levels that can be found in smoky indoor environments seem to affect inflammation, coagulation, and possibly lipid peroxidation. These factors may be involved in the mechanisms whereby particulate air pollution affects cardiovascular morbidity and mortality. The exposure setup could be used to establish which particle characteristics are critical for the effects.

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