Blood Components and Hemostasis

Blood Components

• Plasma: carries antibodies, nutrients, and waste
• Red Blood Cells (RBCs): carry oxygen to and carbon dioxide from tissues
  • Low oxygen leads to "clubbing" of the fingertips, resembling "Moon Man Fingers"
  • Iron and hemoglobin are crucial for oxygen carrying capacity
  • Hematocrit (HCT) measures the volume of packed red blood cells relative to whole blood
  • Erythropoiesis, the production of RBCs, is triggered by erythropoietin (EPO), a hormone produced by specialized kidney cells
• White Blood Cells (WBCs): involved in inflammatory and immune responses
  • Agranular: lymphocytes (T cells, B cells, NK cells) and monocytes
  • Granular: Basophils, Eosinophils, and Neutrophils (most abundant and first responders)
• Platelets (thrombocytes): produced in the bone marrow and essential for clotting
  • They constrict and plug damaged blood vessels

Hemostasis: Normal Clotting Mechanism

• Coagulation involves vasoconstriction, platelet aggregation to form a plug, and intrinsic/extrinsic clot formation
  • Intrinsic pathway activated by contact with internal vessel tissue
  • Extrinsic pathway activated by contact with damaged external vessel tissue
  • Common pathway: both intrinsic and extrinsic pathways converge on factor X
• Conversion of prothrombin to thrombin leads to insoluble fibrin threads, the final step of clot formation
• Clot dissolution, involving the conversion of plasminogen to plasmin (fibrinolysin), prevents vessel occlusion and tissue damage

Bleeding Disorders

• Thrombocytopenia: decreased platelet count, increasing bleeding risk
  • Monitor stool, urine, and vomit for blood
  • Avoid IVs and injections when possible, applying prolonged pressure if necessary
• Hemophilia: decreased amount or function of clotting factors, impacting secondary hemostasis
  • Hereditary recessive X-linked chromosomal disorder
  • Deficiency in FVIII or FIX
  • Prolonged bleeding after minor or major injuries
  • Bleeding into the brain can lead to stroke or increased intracranial pressure
  • Severity of symptoms depends on the underlying mutation and associated factor activity
  • Prothrombin time is normal, while partial thromboplastin time is prolonged in Hemophilia A and B
  • Confirmation involves specific factor activity and mutation testing of the genes encoding them

Deep Vein Thrombosis (DVT)

• Thrombus formation occurs through coagulation, and DVT symptoms include asymmetrical edema, calf swelling, calf pain, and acute chest pain
• Treatment includes anticoagulants (heparin/warfarin) or prophylaxis (compression, physical activity)
• Virchow's Triad: three factors contributing to DVT
  • Hypercoagulability: increased tendency to clot (e.g., oral contraceptives, inherited disorders, pregnancy)
  • Injury to the vessel wall (e.g., trauma, medication-related)
  • Venous stasis: decreased blood flow or return (e.g., age, immobility)
• Stages:
  • Propagation: clot grows along the vessel
  • Organization: within the vessel layer
  • Recanalization: holes forming in the thrombus
  • Embolism: dislodged thrombus
• DVT becomes a medical emergency when a thrombus dislodges (embolus) and travels to the heart or lungs (pulmonary embolism)

Antiplatelet Medications

• Reduce the formation of the platelet plug by decreasing platelet responsiveness
• Aspirin
  • Indications: MI, CVA
  • MOA: inhibits prostaglandin and thromboxane synthesis, preventing platelet aggregation
  • Contraindications: surgery, invasive procedures, chicken pox/influenza
  • Side effects/Adverse Events: Acute aspirin toxicity with hyperpnea, tinnitus
• Clopidogrel (Plavix)
  • Irreversible inhibitor of the platelet P2Y12 adenosine diphosphate receptor
  • Prevents activation of the glycoprotein IIb/IIIa receptor complex, reducing platelet aggregation
  • Metabolized in the liver to its bioactive form
  • Indications: lowering risk for ischemic events, history of MI, peripheral artery disease, CVA, CAD
  • MOA: antiplatelet
  • Route: PO with loading dose
  • Contraindications: boxed warning for people who poorly metabolize the liver enzyme CYP2C19
  • Side effects/Adverse Events: Bleeding

Anticoagulants

• Heparin
  • Glycosaminoglycans that inactivate clotting factors
  • Subcutaneous for prevention or IV for known issues
  • Monitor aPPT every 6 hours if IV
  • Indications: DVT prevention, blood clot, PE, Cardiac disorders
  • MOA: anticoagulant, blocking the conversion of prothrombin to thrombin and fibrinogen to fibrin
  • Contraindications: active bleed/bleeding disorders, thrombocytopenia

Explore the essential components of blood, including plasma, red blood cells, white blood cells, and platelets. This quiz also delves into the mechanisms of hemostasis and the role they play in clotting. Test your knowledge on how these elements contribute to overall health and immune response.