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HEMOSTASIS

HEMOSTASIS. Vessel injury. Dr. Taj. Thrombogenic. Antithrombogenic. (Favors fluid blood). ( Favors clotting ). OBJECTIVES. At the end of the lecture you should be able to describe….. What is hemostasis What are the steps of hemostasis The 2 pathways of coagulation

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HEMOSTASIS

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  1. HEMOSTASIS Vessel injury Dr. Taj Thrombogenic Antithrombogenic (Favors fluid blood) (Favorsclotting)

  2. OBJECTIVES • At the end of the lecture you should be able to describe….. • What is hemostasis • What are the steps of hemostasis • The 2 pathways of coagulation • The role of platelets in hemostasis • Bleeding & clothing disorders

  3. HEMOSTASIS From an injured blood vessel is the • Prevention of blood loss Or • Stoppage of bleeding Or • Arrest of bleeding from a broken blood vessel

  4. STEPS OF HEMOSTASIS • Vascular Spasm • Formation of platelet plug • Blood Coagulation • Clot Retraction

  5. VASCULAR SPASM(Vascular Constriction) • Factors • Nervous reflexes • Local myogenic spasm • Local humoral factor • For smaller vessels • Platelets  Thrombokanc A2 • Importance • Censhing injuries  Intense spasm  No lethal loss of blood

  6. FORMATION OF PLATELET PLUG • Importance of platelet plug  small vascular damage

  7. BLOOD COAGULATION Formation Of Clot • Blood clotting is the transformation of blood from a liquid into a solid gel form • Pathways • Intrinsic • Extrinsic • Initiated by: Activator substances from traumatized vascular wall, plts & blood proteins • Begins to develop in • 15-20 sec  Minor trauma • 1-2 min.  Severe trauma

  8. physical events of Clotting process

  9. PLATELETS Formed by fragmentation from megakaryoctyes

  10. PLATELETS SHAPE: MINUTE ROUND OR OVAL DISCS SIZE: 1-4 um IN DIAMETER HALF LIFE: 8-12 DAYS COUNT: 150,000 – 300,000/ microlitrer • Contractile, adhesive, cell fragments. • Store coagulation factors & enzymes • Surface Binding sites for fibrinogen • Surface Glycoprotein Antigens-HPA1.

  11. FUNCTIONAL CHARACTERISTICS: • ACTIN AND MYOSIN MOLECULES • THROMBESTHENIN • ENDOPLASMIC RETICULUM AND GOLGI APPARATUS • MITOCHONDRIA • ENZYME SYSTEMS FOR SYNTHESIS OF PROSTAGLANDINS • FIBRIN STABILIZING FACTOR • GROWTH FACTOR

  12. MECHANISM • Formation of Prothrombin activator complex • Conversion of prothrombin into thrombin • Conversion of fibrinogen into fibrin

  13. INITIATION OF COAGULATIONFormation Of Prothrombin Activator Complex • 2 Ways • By Extrinsic pathway  trauma to vascular wall and surrounding tissues • By Intrinsic pathway  trauma to the blood •  Is the rate - limiting factor

  14. CONVERISON OF PRTHROMBIN TO THROMBIN By Prothrombin Activator Complex • Prothrombin • Plasma protein (Alpha2 globulin) • Mol. Wt. - 68,700 • Plasma conc. - 15 mg/dl • Unstable protein • Synthesized by liver • Vitamin-K is required for synthesis

  15. CONVERSION OF FIBRINOGEN TO FIBRIN Formation Of Clot • Fibrinogen • Mol. Wt. – 340,000 • Plasma conc. – 100 – 700 mg/dl • Synthesized in liver

  16. ACTION OF THROMBIN ON FIBRONOGEN TO FORM FIBRIN

  17. BLOOD CLOT • A meshwork of fibrin fibres running in all directions and entrapping blood cells, platelets and plasma

  18. CLOT RETRACTION • When clot contracts, it expresses most of the fluid from the clot within 20-60 min.  Serum • SERUM CANNOT CLOT • ROLE OF PLTS IN CLOT FORMATION • VICIOUS CIRCLE OF CLOT FORMATION

  19. Clotting Factors

  20. EXTRINSIC MECHNANISM FOR INITIATING CLOTTING

  21. INTRINSIC MECHNANISM FOR INITIATING CLOTTING

  22. ROLE OF THROMBIN IN HEMOSTASIS

  23. ROLE OF CALCIUM IONS IN CLOTTING • No Ca++ No Clotting • Blood samples are prevented from clotting by adding: • Citrate ions  Deionization of Ca++ • Oxalate ions  ppt the Ca++

  24. LYSIS OF BLOOD CLOTS PLASMIN Plasminogen / Profibrinolysin T-PA Plasmin or Fibrinolysin Lysis of clot

  25. INTRAVASCULAR ANTICOAGULANTS • Endothelial Surface Factors • Smoothness of Endothelium • Glycocalyx Layers • Thrombomodulin Protein • Antithrombin action of Fibrin and Antithrombin III • 85-90 % Thrombin binds with Fibrin • 10-15 % Thrombin binds with Antithrombin III

  26. INTRAVASCULAR ANTICOAGULANTS • Heparin • - vely charged conjugated polysaccharide • Increase the effectiveness of Antithrombin III • Produced by • Mast cells • Basophil cells • Most widely used anticoagulant clinically e.g. in stroke • Alpha2 – Macrogobulin • Acts as a binding agent for several coagulation factors

  27. BLEEDING & CLOTTING DISORDERS • Liver diseases & Vitamin-K deficiency • Hemophilia • Thrombocytopenia

  28. BLEEDING DISORDERS • Liver diseases & Vitamin-K deficiency • e.g. Hepatitis, Cirrhosis • Decreased formation of clotting factors • Icnreased clotting time • Vitamin K dependent factors • Prothrombin, Factor VII, IX, X

  29. HEMOPHILIA • HEMOPHILIA A • Classic Hemophilia • 85 % cases • Def. Of factor VIII • HEMOPHILIA B • 15 % cases • Def. Of factor IX

  30. THROMBOCYTOPENIA • PLT count upto 50,000 ul • Less than 10,000 ------ Fatal • ETIOLOGY • Decreased production • Aplastic anemia • Leukemia • Drugs • Infections (HIV, Measles)

  31. HEMOPHILIA • Genetic disorders • Transmitted by female chromosome as recessive trait • Occurs exclusively in male Females are carriers • Types • Hemophilia A • Hemophilia B

  32. HEMOPHILIA • Clinical Features • Easy bruising, massive bleeding after trauma or operation, hemorrhages in joints • Factor VIII • Small Comp.  Hemophilia A • Large Comp.  Von-Willebrand’s disease • Rx • Injection of factor VIII (Hemophilia A) • Injection of factor IX (Hemophilia B)

  33. THROMBOCYTOPENIA • Increased destruction • ITP • Drugs • Infections • Clinical Features • Easy brusability • Epistaxis • Gum bleeding • Hemorrhage after minor trauma • Petechiae/Ecchumosis

  34. THROMBOCYTOPENIA • Diagnosis • PLT decreased • B.T increased • Rx • Rx of the underlying cause • PLT concentrates • Fresh whole blood transfusion • Splenectomy

  35. THANK YOU

  36. ANTI COAGULANTS FOR CLINICAL USE • Heparin ---------- Subcutaneous or intramuscular • Warfarin --------- Oral

  37. THROMOEMBOLIC CONDITIONS • Thrombus • Abnormal clot that develops in a blood vessel • Embolus • Freely flowing clots • Emboli from Lf heart or large arteries ------------ • Emboli from Rt heart or venous system ---------- • Etiology • Roughened Endothelia surface • Sluggish flow of blood • Rx • Use of genetically engineered t-PA • Use of streptokinase

  38. Prolonged Immobilization Propping the knees with underlying pillows Intravascular clot Grows up and down Clot disengages Venous blood Massive pulmonary embolism FEMORAL THROMBOSIS & MASSIVE PULMONARY EMBOLISM

  39. DISSEMINATED INTRAVASCULAR COAGULATION • Results from • Presence of large amounts of traumatized or dying tissue in the body • Releases tissue thromboplastin • Clots are small and numerous • Seen in Septicemic shock

  40. BLEEDING DISORDERS • Vitamin-K • Fat soluble vitamin • Required by liver for formation 4 clotting factors • Sources • Diet • Sythesized in the intestinal tract by bacteria • Deficiency • Malabsorption syndromes • Biliary obstruction • Broad spectrum antibiotics • Dietary def (in Neonates) • Rx.: Treat the underlying cause Vit K injections

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