Seminars in thrombosis and hemostasis
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Hereditary fibrinogen abnormalities comprise two classes of plasma fibrinogen defects: Type I, afibrinogenemia or hypofibrinogenemia, which has absent or low plasma fibrinogen antigen levels (quantitative fibrinogen deficiencies), and Type II, dysfibrinogenemia or hypodysfibrinogenemia, which shows normal or reduced antigen levels associated with disproportionately low functional activity (qualitative fibrinogen deficiencies). In afibrinogenemia and hypofibrinogenemia, most mutations of the FGA, FGB, or FGG fibrinogen encoding genes are null mutations. In some cases, missense or late truncating nonsense mutations allow synthesis of the corresponding fibrinogen chain but intracellular fibrinogen assembly and/or secretion are impaired. ⋯ Determination of the molecular defects is important because it gives the possibility to confirm the diagnosis, to elaborate a diagnostic strategy, to distinguish in some cases that the patient is at risk of thrombosis rather than bleeding, and to enable prenatal diagnosis. However, genotype-phenotype correlations are not easy to establish. Replacement therapy is effective in treating bleeding episodes, but because the pharmacokinetics of fibrinogen after replacement therapy is highly variable among patients, it is important to adjust the treatment individually.
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Activation of coagulation frequently occurs in severe infection and sepsis and may contribute to the development of thrombosis. Coagulation abnormalities in sepsis range from a small decrease in platelet count and subclinical prolongation of global clotting times to fulminant disseminated intravascular coagulation (DIC), characterized by simultaneous widespread microvascular thrombosis and profuse bleeding from various sites. ⋯ Hypothetically, patients with thrombophilia may suffer from more severe coagulopathy in case of severe infection or sepsis, which may result in a more serious clinical course and an unfavorable outcome. On the basis of the knowledge of the pathogenesis of thrombosis in severe inflammation and sepsis, strategies aimed at the inhibition of coagulation activation have been developed and have been found favorable in experimental and clinical studies.
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No standard exists for venous thromboembolism (VTE) prophylaxis after traumatic brain injury (TBI). Caregivers agree that there is an early time point after injury in which the chances of spontaneous injury progression are high and the risks of prophylactic anticoagulation are excessive, and that these injuries eventually stabilize to the point that anticoagulation may be safely started. Translating this consensus into an application that can inform bedside decision making has not occurred. ⋯ Although interest in this field has increased of late, many studies are limited by the simple dichotomization of TBI patients as having the presence or absence of intracranial blood. Although methodologically easier, this approach does not account for the heterogeneity of TBI and, consequently, the spectrum of time to stabilization. To address this, our group has created an algorithm which stratifies patients by risk for spontaneous progression and tailors a unique VTE prophylaxis regimen to each arm.
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Semin. Thromb. Hemost. · Jun 2013
ReviewClotting activation and hyperfibrinolysis in cirrhosis: implication for bleeding and thrombosis.
Hyperfibrinolysis may be detected in patients with cirrhosis, particularly in case of severe liver failure. Hyperfibrinolysis is usually associated with prolonged global tests of clotting activation, which are then dependent on impaired synthesis of clotting factors by liver cells. The term "coagulopathy" has therefore been coined to indicate the existence of hyperfibrinolysis and blood hypocoagulation in cirrhosis, and, for a long time, these changes have been believed to facilitate bleeding. ⋯ The support of these findings by more recent data allows a redefinition of the overall clotting picture, in particular hyperfibrinolysis, in cirrhosis. Thus, this review analyzes prevalence and clinical impact of hyperfibrinolysis in cirrhosis, focusing in particular on whether it is primary or secondary to clotting activation. Furthermore, we focused such changes in the context of more recent data showing an association between cirrhosis and thrombosis.
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Sepsis, defined as infection-induced systemic inflammatory response syndrome, invariably leads to hemostatic abnormalities ranging from insignificant coagulopathy to disseminated intravascular coagulation (DIC). The inflammation-induced activation of coagulation, the downregulation of physiologic anticoagulant pathways, and impairment of fibrinolysis play a pivotal role in the pathogenesis of microvascular fibrin thrombosis and multiple organ dysfunction syndrome (MODS) in DIC associated with sepsis. The balance between tissue plasminogen activator and plasminogen activator inhibitor-1 mainly regulates fibrinolytic activity. ⋯ Evidence indicates that physical entrapment of bacteria by fibrin at the site of infection may limit their capacity to disseminate into nearby tissues, organs, and systemic circulation. Under this circumstance, impairment of fibrinolysis has protective role in the host defense. Given the protective and pathologic potential of fibrinolysis during sepsis, therapeutics that control DIC as a systemic syndrome, while maintaining the host defense at the infectious foci, are required for the protection against both the development of MODS and for the host defense mechanisms.