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Bleeding Disorders

Hemostasis and Thrombosis. Dependent on three factors:Vascular endotheliumPlateletsCoagulation system. Bleeding Disorders. 1) Increased fragility of vessels2) Platelet defect (deficiency)3) Deranged clotting. Laboratory Tests. 1) Bleeding time2) Platelet count3) Prothrombin time (PT)4) Activ

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Bleeding Disorders

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    1. Bleeding Disorders Richard A. McPherson, M.D. September 12, 2001

    2. Hemostasis and Thrombosis Dependent on three factors: Vascular endothelium Platelets Coagulation system

    3. Bleeding Disorders 1) Increased fragility of vessels 2) Platelet defect (deficiency) 3) Deranged clotting

    4. Laboratory Tests 1) Bleeding time 2) Platelet count 3) Prothrombin time (PT) 4) Activated partial thromboplastin time (APTT, PTT) Factors, fibrinogen, FSP, anticoagulants, platelet function tests (aggregation)

    5. Disseminated Intravascular Coagulation (DIC) Activation of coagulation sequence: thrombi throughout microcirculation Consumption of platelets and coagulation factors to sub-hemostatic levels Activation of fibrinolysis Tissue hypoxia; microinfarcts Hemorrhage from (minor) trauma due to consumption/depletion of clotting factors and fibrinolysis destroying clots

    6. Disseminated Intravascular Coagulation (DIC) Etiologies 1) Release of tissue factor or thromboplastins into circulation 2) Widespread injury to endothelial cells Clinical examples Sepsis Obstetric complications Malignancy Major trauma Treatment: anticoagulate

    7. Thrombocytopenia (Platelets <100 K/mm3) Platelets 20-50K: post traumatic bleeding Platelets <20K: spontaneous bleeding Etiologies Decreased production: bone marrow failure Increased destruction: immunologic (ITP) Increased destruction: nonimmunologic (DIC, TTP) Sequestration (hypersplenism) AIDS: immune complexes, low megakaryocytes

    8. Idiopathic Thrombocytopenic Purpura (ITP) Autoimmune: isolated; or part of SLE; or self-limited in children (post-viral) Antiplatelet Ab against GPIIb/IIIa or Ib Petechiae, easy bruisability, epistaxis, gum bleeding, hemorrhages after minor trauma Intracerebral/subarachnoid hemorrhage Treatment: steroids; splenectomy: >2/3 of patients recover (spleen is source of Ab and site of destruction)

    9. Thrombotic Thrombocytopenic Purpura (TTP) Diagnostic criteria: Fever, thrombocytopenia, microangiopathic hemolytic anemia, neurologic deficit, renal failure Hyaline thrombi in microcirculation: aggregates of platelets coated by fibrin Abnormally large von Willebrand’s antigen Hemolytic Uremic Syndrome Toxin from E. coli 0157:H7 Bloody diarrhea Treatment: total plasma exchange transfusion

    10. Coagulation Factor Disorders Acquired Vitamin K deficiency Parenchymal disease of liver Hereditary deficiencies VIII: hemophilia A IX: hemophilia B VIII and IX sex-linked on X chromosome Other factors

    11. Factor VIII/von Willebrand Factor Complex of 2 proteins: non-covalent bonds 1) VIII procoagulant protein 2) vWF, much larger protein (~99% of complex), series of high molecular weight multimers vWF binds to collagen and to platelet glycoproteins Ib and IIb/IIIa vWF is the “glue” that adheres platelets to subendothelial collagen

    12. Von Willebrand’s Disease Bleeding disorder Spontaneous bleeding from mucous membranes Excess bleeding from wounds; menorrhagia Autosomal dominant: spectrum of mild to severe Most common inherited bleeding disorder Lab tests Normal platelet count; increased bleeding time Prolonged APTT; decreased factor VIII vWF Ag quantitation; platelet aggregation (ristocetin) vWF multimeric analysis (molecular sizes)

    13. Von Willebrand’s Disease vWF multimeric analysis (esoteric procedure) Type I: decreased amount of vWF Type II: loss of high molecular weight multimers Type III: total lack of vWF Treatment: DDAVP Fresh frozen plasma Cryoprecipitate

    14. Factor VIII Deficiency Hemophilia A Most common hereditary disease of serious bleeding Sex-linked (males) ~30% of cases are due to new mutations in VIII Bleeding: Severe <1% VIII Mild 1-5% VIII Moderate 5-75% VIII Antibodies against VIII: After transfusion in hemophilia A De novo in normals

    15. Factor VIII Deficiency Hemophilia A Clinical findings Easy bruising/hemorrhage after trauma, surgery Spontaneous hemorrhages Hemarthroses Labs: Bleeding time normal APTT prolonged; PT normal; VIII low Treatment: VIII concentrates (HIV risk from pools in past) Recombinant VIII

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