The laboratory control of anticoagulant thromboprophylaxis during the early postpartum period after cesarean delivery.

INTRODUCTION: The incidence of venous thromboembolism (VTE) after cesarean section is up to 0.6%, and the widespread use of cesarean section draws attention to this group. The dosage and duration of low-molecular-weight heparin (LMWH) prophylaxis after delivery is estimated by anamnestic risk-scales; however, the predictive potency for an individual patient's risk can be low. Laboratory hemostasis assays are expected to solve this problem. The aim of this study was to estimate the potency of tests to reflect the coagulation state of patients receiving LMWH in the early postpartum period. MATERIALS AND METHODS: We conducted an observational study on 97 women undergoing cesarean section. Standard coagulation tests (Fg, APTT, prothrombin, D-dimer), an anti-Xa assay, rotation thromboelastometry and thrombodynamics/thrombodynamics-4D were performed. Coagulation assay parameters were compared in groups formed in the presence or absence of LMWH to estimate the laboratory assays' sensitivity to anticoagulation. RESULTS: Coagulation assays revealed hypercoagulation after delivery and a tendency toward normalization of coagulation during early postpartum. The thromboprophylaxis results revealed a higher percentage of coagulation parameters within the normal range in the LMWH group. CONCLUSION: This research is potentially beneficial for the application of thrombodynamics and thrombodynamics-4D in monitoring coagulation among patients with high VTE risk who receive thromboprophylaxis with heparin.

Hemostasis and thrombosis beyond biochemistry: roles of geometry, flow and diffusion.

An important trend in the modern concept of blood coagulation is the growing agreement that, in order to understand regulation of coagulation in vivo and disorders of its function, it is essential to take into account its spatial heterogeneity, diffusion, and flow. In a way, this suggests that the idea of the "coagulation cascade" itself becomes increasingly misleading because there is no such place in an organism where reactions of this cascade really co-exist: activation, propagation and termination of coagulation are regulated by different subsets of chemical reactions that have different spatial localization and depend on cofactors expressed by different cell types in different tissues, so that only diffusion and flow can link these distinct "compartments" together into the one functional system. Here we review the last two decades of evidence obtained from in vitro, in vivo and computational systems biology approaches. When combined, the data comprise into an adequately comprehensive picture of the spatial regulation and organization of blood coagulation. In addition to the basic insights into the regulatory mechanisms, these approaches provided interesting results in the fields of coagulation diagnostics and other applications. Finally, the remaining unresolved and conflicting issues in the spatiotemporal regulation of coagulation are discussed.

Effect of pre-analytical conditions on the thrombodynamics assay.

INTRODUCTION: Standardization of pre-analytical conditions is the obligatory step for all potential diagnostic tests. Spatial clot growth (Thrombodynamics) is a new global hemostasis assay that considers spatial organization of coagulation. The principal parameter is rate of fibrin clot growth from the tissue-factor coated surface. In this work we studied the pre-analytical variables of Thrombodynamics assay that include conditions of blood collection, sample preparation and storage. MATERIALS AND METHODS: Blood of apparently healthy volunteers was used. Eight types of citrate blood collection tubes were tested, centrifugation conditions for plasma preparation were evaluated and impact of plasma freezing/thawing was tested. RESULTS: Among the blood collection tubes tested, BD Vacutainer glass tubes showed a significantly higher clot growth rate compared to plastic tubes. There was no difference between 3.2% and 3.8% of sodium citrate. For plasma preparation, a single 15 min centrifugation at 1,600 g shows significantly increased clot growth rate compared to plasma obtained by two sequential centrifugations (15 min 1 600 g, 5min 10,000 g). There was no significant difference between 1,600 g and 2,100 g if the second centrifugation was performed. For the second centrifugation there was no difference between 20 min at 1 600 g and 5 min at 10,000g. Frozen-thawed plasma showed increased clot growth rate compared to fresh plasma. CONCLUSION: The data represent the necessary steps for the standardization of Thrombodynamics assay and for the formulation of the operating guide.

The kinetochore-bound Ska1 complex tracks depolymerizing microtubules and binds to curved protofilaments.

To ensure equal chromosome segregation during mitosis, the macromolecular kinetochore must remain attached to depolymerizing microtubules, which drive chromosome movements. How kinetochores associate with depolymerizing microtubules, which undergo dramatic structural changes forming curved protofilaments, has yet to be defined in vertebrates. Here, we demonstrate that the conserved kinetochore-localized Ska1 complex tracks with depolymerizing microtubule ends and associates with both the microtubule lattice and curved protofilaments. In contrast, the Ndc80 complex, a central player in the kinetochore-microtubule interface, binds only to the straight microtubule lattice and lacks tracking activity. We demonstrate that the Ska1 complex imparts its tracking capability to the Ndc80 complex. Finally, we present a structure of the Ska1 microtubule-binding domain that reveals its interaction with microtubules and its regulation by Aurora B. This work defines an integrated kinetochore-microtubule interface formed by the Ska1 and Ndc80 complexes that associates with depolymerizing microtubules, potentially by interacting with curved microtubule protofilaments.