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25 Cards in this Set
- Front
- Back
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What are the contact activation factors and how are they related?
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FXII/HMWK/PK. HMWK can activate prekallikrein which can then activate FXII leading to the intrinsic pathway cascade.
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How are HMWK and PK important in inflammation?
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After PK is activated, kallikrein can activate HMWK to form bradykinin (which is important for inflammation) and pro-urokinase to form urokinase (which is important for fibrinolysis).
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Does someone with a long PTT have a bleeding problem?
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Not necessarily. Deficiencies in Factor XII, HMWK and prekallikrein will prolong the PTT but do not necessarily signify a bleeding problem.
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What factors promote the conversion of plasminogen to plasmin?
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Certain contact factorsn (Xia, XIIa, Kallikrein) & urokinase--intrinsic; as well as tPA--extrinsic
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What factors try to inhibit factors that promote the conversion of plasminogen to plasmin?
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Plasminogen activator inhibitor 1 & 2 (PAI 1 & 2), alpha 2- antiplasmin, and alpha 2-macroglobulin; PAI 1 and alpha 2-antiplamsin are most important
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What newly discovered protein works to inhibit fibrinolysis?
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thrombin activatable fibrinolysis inhibitor
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What two roles does thrombin serve to produce insoluble fibrin?
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Thrombin first clips amino termini of the A and B domains of fibrinogen which leads to a reversal in polarity of the protein and an aggregate soluble fibrin complex. Once thrombin activates factor XIIIa, cross linking occurs between the aggregated proteins to produce an insoluble fibrin clot.
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How does plasmin affect insoluble fibrin?
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It clips between the E and D domains of fibrin to form fibrin degradation products (FDPs).
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Which immunoassay is used to triage patients suspected of having a vein thrombosis or pulmonary embolus due to plasmin induced breakdown of fibrin?
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D-dimer assay.
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What does Virchow's triad address?
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Virchow's triad addresses factors involved with hemostasis which include: 1. Changes in blood coagulability 2. Changes in the vessel wall (i.e. fragility), and 3. Changes in blood flow (i.e. anemia)
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What is the most important factor in determining whether someone has a bleeding disorder?
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The clinical history
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What are some important factors in determining the history of someone with a bleeding disorder?
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Anatomic location, duration and severity (transfusion needed), drug history, surgery, pregnancy, dental procedures, menstrual history, dietary history, occupational history, family history (X-linked)
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What are some things that can affect a long PT or PTT?
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1. Artifact--clotted sample, short draw, high hematocrit 2. Acquired factor deficiencies--viatamin K, liver disease, Coumadin 3. Iatrogenic inhibitors--heparin, direct thrombin 4. Natural inhibitors--lupus anticoagulant, factor specific factors 5. Congenital factor deficiencies (most rare)
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How do mixing studies help determine the etiology of bleeding disorders?
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1. A correction indicates a factor deficiency 2. An immediately observable lack of correction indicates lupus anticoagulant, and 3. A delayed observable lack of correction indicates a factor inhibitor
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What factors are associated with the different hemophilias?
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Hemophilia A--fVIII (The Royal Disease); Hemophilia B--fIX; Hemophilia C (fXI); X-linked, almost always males
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When women test for a factor VIII deficiency, what should be suspected?
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von Willebrand disease is more likely as factor VIII ciruclates bound to vWf
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How can hemophilia be treated?
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Replacement therapies include fVIII/IX concentrates or recombinant fVIII/IX. Temporary therapies include cyroprecipitate and DDAVP for fVIII and fresh frozen plasma for Hemophilia B (fIX). Antifibrinolytic agents can be used. Bethesda assay can be used to check for immune reaction to therapy. Immunosuppression can be used for patients with high anti-factor antibodies.
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What is the most common bleeding disorder?
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von Willebrand factor disease
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How are the multimers for vWf transported to the endothelial surface?
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Via Weibel-Palade bodies
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What causes of bleeding are related to vWf?
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1. Defective primary hemostasis due to an inability of platelets to adhere to the endothelium; especially mucocutaneous bleeding. 2. Defective secondary bleeding due to low fVIII transport; soft tissue bleeding like with hemophilia
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How is vWf classified?
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Type 1 < Type 2 < Type 3 in severity. Commonality is inverse to severity.
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How can vWf be diagnosed using laboratory tests?
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1. prolonged PTT 2. prolonged PFA-100 3. Normal platelet count 4. Ristocetin dependent and independent functionality tests 5. vWf antigen analysis 6. Abnormal vWF multimer pattern test
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How is vWf disease treated?
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cryoprecipitate, fresh frozen plasma, fVIII concentrate, DDAVP (causes release of vWF from endothelium), estrogens or oral contraceptives
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What are some diseases associated with decreased survival due to thrombocytopenia?
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immune thrombocytopenic purpura, microangiopathic hemolytic anemia (including thrombotic thrombocytopenic purpura & hemolytic uremic syndrome, look for schistocytes), disseminated intravasuclar coagulation (caused by TF release, and consummption of coag factors, TT, PT, and PTT prolonged)
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What are some systemic causes of thrombocytopenia?
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1. Decreased production due to leukemia/lymphoma, nutritional deficiency, etc. 2. Splenic sequestration can lead to 80 to 90% of platelets remaining in the spleen
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