Pathophysiology Chapter 22: Disorders of Hemostasis Quiz

Disorders of Hemostasis

• Hemostasis: the stoppage of blood flow to prevent blood loss and hemorrhage
• Two main categories of disorders:
  • Inappropriate formation of clots (thrombosis)
  • Failure to clot in response to an appropriate stimulus (bleeding)

Mechanisms of Hemostasis

• Three stages:
  1. Vascular constriction
  2. Formation of the platelet plug
  3. Blood coagulation

States of Hemostasis

• Vascular constriction:
  • Vessel spasm constricts the vessel and reduces blood flow
  • Leads to a transient event that usually lasts minutes or hours
• Formation of the platelet plug:
  • Small breaks in the vessel wall are sealed with a platelet plug
  • Platelet plug formation involves activation, adhesion, and aggregation of platelets
  • Change from smooth disks to spiny spheres
  • Platelet adhesion requires the protein molecule Von Willebrand factor
• Blood coagulation:
  • Clotting factors are synthesized in the liver using Vitamin K
  • Coagulation process results from the intrinsic and extrinsic pathways
  • Intrinsic pathway: slow process (clotting in 1-6 minutes)
  • Extrinsic pathway: fast process (clotting in 15 seconds)

Clot Retraction and Clot Dissolution

• Clot retraction:
  • Normally occurs over 20-60 minutes after clot formation
  • Clot joins the edges of the broken blood vessel
  • Requires a large number of platelets
• Clot dissolution:
  • Fibrinolysis: the process by which a blood clot is dissolved
  • Plasmin digests fibrin strands of the clot
  • Naturally occurring plasminogen activators: tissue-type plasminogen activator

Hypercoagulability

• An exaggerated form of hemostasis
• Predisposes to thrombosis and blood vessel occlusion
• Two forms of hypercoagulable states:
  • Conditions that create increased platelet function
  • Conditions that cause accelerated activity of the coagulation system

Conditions Associated with Hypercoagulability

• Increased platelet function:
  • Atherosclerosis
  • Diabetes
  • Smoking
  • Elevated lipid and cholesterol levels
  • Increased platelet levels
• Accelerated activity of the coagulation system:
  • Pregnancy
  • Use of oral contraceptives
  • Postsurgical state
  • Immobility
  • Congestive heart failure
  • Malignant disease

Thrombocytosis

• Primary thrombocytosis:
  • Myeloproliferative (bone marrow) disorder
  • Abnormalities in thrombopoietin receptor and platelet binding
• Secondary thrombosis:
  • Leads to increased platelet production
  • Disease state that stimulates thrombopoietin production

Bleeding Associated with Platelet Disorders

• Thrombocytopenia:
  • Reduction in platelet number
  • Decrease in the number of circulating platelets to less than 150,000
  • Characterized by petechiae and purpura
  • Results from:
    • Decrease in platelet production
    • Increased sequestration of platelets in the spleen
    • Decreased platelet survival

Disorders of the Red Blood Cells

• Function of the Red Blood Cells:
  • Transportation of oxygen to the tissues
  • Hemoglobin binds to carbon dioxide and carries it from the tissues to the lungs
• Red Blood Cell Destruction:
  • The RBC has a life span of 90-120 days
  • Broken down in the spleen
  • The degradation products (iron and amino acids) are recycled

Laboratory Tests for Red Blood Cells

• Red blood cell count (RBC)
• Hemoglobin (grams per 100 mL of blood)
• Hematocrit
• Percentage of reticulocytes (normally approximately 1%)

Transfusion Therapy

• Whole Blood
• Packed Red Blood Cells (PRBC)
• Platelets
• Cryoprecipitate
• Plasma

Anemia

• Anemia: an abnormally low number of circulating red blood cells or level of hemoglobin or both
• Results in diminished oxygen-carrying capacity
• Primary causes of anemia:
  1. Excessive loss of red cells from bleeding
  2. Destruction (hemolysis) of RBCs
  3. Defective RBC production
  4. Inadequate RBC production due to bone marrow failure
• Clinical manifestations:
  • Fatigue, weakness, dyspnea
  • Headache, faintness
  • Pallor of skin, mucous membranes, conjunctiva, nail beds
  • Tachycardia, low cardiac output, palpitations, ventricular hypertrophy

Acute Blood Loss Anemia

• Clinical and red cell changes depend on the rate of hemorrhage and whether bleeding loss is internal or external
• Causes circulatory collapse
• Up to 50% RBC mass may be lost without signs or symptoms
• RBC may also fall related to hemodilution

Chronic Blood Loss Anemia

• Chronic anemia leads to iron deficiency anemia
• Asymptomatic until Hgb is less than 8 d/dL
• GI bleeding, menstrual disorders
• RBCs produced have too little Hgb
• Is small and pale

Hemolytic Anemia

• Characterized by:
  • Premature destruction of RBCs
  • Shortened life-span
  • Increased bone marrow activity causes increased release of reticulocytes
  • Increase in erythropoiesis
• Is normocytic and normochromic

Sickle Cell Disease

• Abnormal substitution of an amino acid in the hemoglobin molecules
• Inherited disorder in which abnormal hemoglobin leads to chronic hemolytic anemia, pain, organ failure
• Recessive disorder:
  • Sickle cell trait
  • Sickle cell disease
• Clinical manifestations:
  • Factors associated with sickling/vessel occlusion
  • Acute pain
  • Jaundice
  • Vaso-occlusive crisis
  • Sluggish blood flow causes chronic damage
  • Acute chest syndrome

Iron Deficiency Anemia

• Etiology:
  • Dietary deficiency
  • Loss of iron through bleeding
  • Iron is a component of heme
  • Deficiency leads to decreased hemoglobin synthesis
  • Impaired oxygen delivery
• Is microcytic and hypochromic
• Clinical manifestations:
  • Related to impaired oxygen transport and lack of hemoglobin
  • Pica
  • Spoon-shaped deformity of fingernails
  • Glossitis
  • Angular cheilitis
  • Dysphagia

Megaloblastic Anemia

• Caused by impaired DNA synthesis that results in enlarged red blood cells
• MCV > 100 fL
• Impaired maturation and division
• Develops slowly
• Megaloblastic anemia:
  • Comes from Vitamin B12 deficiency and folic acid deficiency
  • Vitamin B12 is essential for DNA synthesis and nuclear maturation
  • Predisposes to myelin breakdown
  • Causes neurologic symptoms
  • Risk factors: proton pump inhibitors, GI disease, gastrectomy, or gastric bypass