Haemostasis & Bleeding Disorders Lecture Notes PDF

HAEMOSTASIS & BLEEDING DISORDERS Ola Saed El-fetiany Lecturer at Medical Physiology Department, Faculty Of Medicine, Alexandria University  Haemostasis ▪Hemostasis means prevention of blood loss or stoppage of bleeding. ▪Haemostasis is the process of forming clots in the walls of...

HAEMOSTASIS & BLEEDING DISORDERS Ola Saed El-fetiany Lecturer at Medical Physiology Department, Faculty Of Medicine, Alexandria University  Haemostasis ▪Hemostasis means prevention of blood loss or stoppage of bleeding. ▪Haemostasis is the process of forming clots in the walls of damaged blood vessels and preventing blood loss, while maintaining blood in a fluid state within the vascular system. 2 PLATELETS (THROMBOCYTES)  Shape: small, non- nucleated oval cells. Site of formation: bone marrow. Normal count: 150,000- 450,000 cell/ cmm. Life span: 8 days.  Hemostasis Prevention of blood loss or stoppage of bleeding. 1. Vascular spasm. 2. Formation of platelet plug. 3. Formation of blood clot.  Platelet plug formation Mechanism: 1. Platelet adherence 2. Platelet activation 3. Platelet aggregation 8  If there is a large hole, a blood clot is required The clot begins to develop a few seconds after the vascular injury.  The intrinsic pathway Activated when blood comes into contact with a rough surface (contact activation). The extrinsic pathway Activated when blood comes in contact with material from damaged tissues (tissue factor activation). The ultimate step in clot formation is the conversion of fibrinogen → fibrin. Blood coagulation (clotting): This is the process by which the blood clot is formed and involves 3 main steps: Formation of prothrombin activators. Conversion of prothrombin into thrombin by prothrombin activators. Conversion of fibrinogen into fibrin threads by thrombin. CAUSES OF BLEEDING DISORDERS Thrombocytopenia: Decreased platelet count Characterized by spontaneous skin purpura & hemorrhage & prolonged bleeding after trauma. Causes of thrombocytopenia: 1-Failure of platelets production BM failure: cytotoxic drug, radiotherapy, aplastic anemia. 2-Increased consumption of platelets *Immune autoimmune, drug-induced, *Disseminated intravascular coagulation (DIC) *Idiopathic thrombocytopenia purpura (ITP) HAEMOPHILIA Haemophilia : group of inherited blood disorders in which there is a life-long defect in clotting.  Haemophilia Inheritance Two chromosomes determine the sex of an individual, X and Y. Female XX Male XY Haemophilia A is inherited as an X- linked recessive trait. It occurs in males and in homozygous females (which is only possible in the daughters of a haemophilic male and a carrier or haemophiliac female However, mild haemophilia A is known to occur in heterozygous females due to X- inactivation, Approximately 30% of patients have no family history; their disease is presumably caused by new mutations.  Carrier Mother (one normal gene and one defective gene) Each daughter has 50:50 chance being a carrier Each son has 50:50 chance of having haemophilia.  Father with Haemophilia Daughter of haemophiliac will inherit his X and be carrier. Sons of a haemophiliac will not be affected as they inherit fathers Y chromosome which does not carry gene. Haemarthrosis in severe haemophilia  BLOOD TRANSFUSION Blood transfusions are a relatively common medical procedure, and while typically safe, there are multiple complications that practitioners need to be able to recognize and treat. Blood is typically stored in components. Fresh whole blood has always been thought of as the standard for transfusion; however, medical advancement has allowed the efficient use of the different components, such as packed red blood cells (PRBCs), individual factor concentrates, fresh frozen plasma (FFP), platelet concentrates  Indications of blood transfusion: Loss of large amount of blood as in hemorrhage Severe anemia Severe leucopenia (decreased WBCs) Thrombocytopenic purpura (decreased platelets) Hemophilia.  COMPLICATIONS OF blood transfusion 1. Febrile reaction 2. Transfusion-associated circulatory overload 3. Allergic reaction 4. Infection :hepatitis c infection 5. Human immunodeficiency virus infection 6. Fatal hemolysis: It results from ABO incompatibility, ANTICOAGULANTS In vitro anticoagulants (outside the body): Smooth siliconized containers. Oxalate compounds: they precipitate calcium, which is essential for blood clotting. Citrate compounds: they cause non ionization of calcium. Heparin. In vivo anticoagulants (inside the body): 1. Heparin: animal origin mast cells and basophils it prevents the action of thrombin I.V and S.C. 2. Coumarin compounds: plant origin block the effect of vit. K which is important for blood clotting. orally Eg. dicumarol and warfarin.