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Published byKerry Dickerson Modified over 9 years ago
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HEMOSTASis Nada Mohamed Ahmed , MD, MT (ASCP)i
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Contents Normal hemostasis Primary hemostasis disorders
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Haima + Stasis Prevent blood loss
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Maintains blood flow Prevents bleeding
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HEMOSTASIS Definition - Heme = blood - stasis = to halt
It is the process of forming clots in the wall of damaged blood vessels & preventing blood loss while maintaining blood in a fluid state with in the vascular system. Spontaneous arrest of bleeding by physiological process.
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Formation of Platelet Plug Formation of blood clot
Stages of Hemostasis Vascular Constriction Formation of Platelet Plug Formation of blood clot Fibrinolysis
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stages of primary hemostasis
Platelet Adhesion Platelet Activation Platelet Aggregation
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platelet adhesion
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Platelet activation : platelet release action
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Platelet aggregation
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Secondary hemostasis “Cascade of reactions” by Macfarlane, R.G.,1967
It states that ‘inactive’ enzymes are activated, and the ‘activated’ enzymes in turn activates other inactive enzymes until final step is reached.
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Clotting Factors Factor I Fibrinogen Factor II Prothrombin Factor III
Thromboplastin Factor IV Calcium Factor V Labile factor, or proaccelerin Factor VI Non – existent Factor VII Stable factor or proconvertin Factor VIII Antihaemophilic factor / globulin A Factor IX Christmas factor or Antihaemophilic factor B Factor X Stuart – Prower factor Factor XI Plasma thromboplastin antecedent or Antihaemophilic factor C Factor XII Hageman factor or Contact factor Factor XIII Fibrin stabilizing factor or Laki – Lorand factor
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Intrinsic Pathway
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Conversion of Prothrombin to Thrombin & Fibrin Polymerization
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Extrinsic Pathway
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why blood does not clot in circulation ?
Endothelial surface factor -smoothness -layer of glycocalyx -Negatively charged Velocity of circulation Natural anticoagulants Activation of Fibrinolytic system Liver removes activated clotting factors
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FIBINOLYSIS
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Haemostatic (Bleeding) Disorders
Disease conditions characterized by excessive bleeding tendency due to defect in the haemostatic system, caused by: Vascular defects Platelet defects Coagulation defects Excessive fibrinolysis
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Acquired Platelet Disorders Congenital Thrombocytopenia
(low platelet count) Thrombocytopathy (Abnormal Platelet function) Decreased production. Excessive destruction. Sequestration in the spleen. Acquired Drugs: Asprin Uremia Myeloproliferative disorders Multiple myeloma SLE Congenital Glanzman’s disease Bernard Soluier’s Storage granules defect
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Thrombocytopenia caused by decreased platelet production
Congenital: Thrombocytopenia Aplastic anemia Acquired: States of Bone Marrow Failure: Aplastic Anemia Viral Infections Nutritional Deficiencies Chemotherapy & Radiation Therapy Infiltration of Abnormal Cells Leukemia. ,Metastatic Cancer.
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Thrombocytopenia Excessive platelet destruction: Causes are :
.1- Drug induced thrombocytopenias. 2-Post-Transfusion (within 5 to 14 days) 2-Autoimmune Hemolytic Anemia/thrombocytopenia.
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Thrombocytopathies (Abnormal Platelet Function) Inherited Qualitative Platelet Disorders may be due to abnormalities of platelet membrane glycoproteins, - Glanzmann Thrombastenia, abnormal GPIIb/IIIa – Bernard-Soulier Syndrome, abnormal GPIb, GPIX and GPV 2. platelet granules, These may occur due to absence of granules in platelets, storage pool disorder (characterized by disturbed platelet aggregation to collagen.
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Acquired Disorders of Platelet Function (Cont…)
Drugs: Best example is ASPIRIN which is the MOST COMMON cause of acquired platelet function disorder. Aspirin irreversibly affect the cyclo-oxygenase enzyme. The effect last 4-7 days and it takes about 10 days before the platelets are replaced. Presents as elevated bleeding time but purpura is unusual.
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Diagnosis Platelet count Bleeding time Specific Tests
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Platelet Count 50,000 - 100,000 Mild Thrombocytopenia
NORMAL , ,000 CELLS/MM3 < 100, Thrombocytopenia 50, ,000 Mild Thrombocytopenia < 50, Sever Thrombocytopenia
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Provides assessment of platelet count and function
Bleeding Time Provides assessment of platelet count and function Normal value 2-8 minutes
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Specific Tests Tests for specific Platelet Functions.
Platelet aggregation test. Test for platelet secretion. Clot retraction test.
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Clot Retraction Release of fibrin stabilizing factor
Contractile protein of platelets
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