Hematology

Spleen

Largest Lymphoid Organ:
- Functions as the primary site for filtering blood.
- Initiates an immune response to blood-borne antigens.
Blood Cleansing:
- Employs phagocytes to cleanse the blood.
Erythrocyte Management:
- Destroys old erythrocytes (red blood cells).
Blood Reservoir:
- Stores approximately 200-300 mL of blood.
Cellular Components:
- Contains macrophages for phagocytosis.
- Houses B and T lymphocytes.

Spleen Removal

Consequences:
  - Leukocytosis: High levels of circulating lymphocytes post-surgery.
  - Reduced Iron: Decreased iron levels in circulation.
  - Diminished Immune Response: Particularly IgM response impacted.
  - Circulating Old Cells: Old, damaged cells remain in circulation longer.

Lymph Nodes

Function:
- Filters lymph as it travels through the lymphatic system.
System Integration:
- Integral part of both the hematologic and immune systems.
Lymphocyte Interaction:
- Initial encounter point for lymphocytes and antigens.
Macrophage Presence:
- Macrophages reside within lymph nodes to assist in filtration.

Erythropoiesis Requirements

Nutritional Needs:
  - Requires proteins and vitamins:
    - Cobalamin (Vitamin B12)
    - Folate (Vitamin B9)
    - Pyridoxine (Vitamin B6)
    - Vitamin E
    - Riboflavin (Vitamin B2)
    - Niacin (Vitamin B3)
    - Iron
    - Ascorbic Acid (Vitamin C)
Consequences of Nutritional Deficiencies:
- Lack of proper nutrients may lead to various types of anemia.

Iron Cycle

Iron's Role:
- Integral component of hemoglobin (HGB).
- Majority bound to heme.
Iron Loss:
- Approximately 1 mg of iron lost daily through different bodily processes (menses, urine, sweat).
Daily Iron Requirement:
- A need for 25 mg/day for effective erythropoiesis, but only 1-2 mg obtained from diet.
Storage of Iron:
- Stored at various sites: spleen (as ferritin or hemosiderin), macrophages, liver (in hepatocytes), erythrocytes, GI- intestinal cells.
Absorption and Transport:
- Iron is absorbed in the jejunum and transported to the bone marrow for hemoglobin synthesis.
Iron Transport:
  - Transported by transferrin to the bone marrow.
  - Ferritin: Major intracellular iron storage protein.
  - Apoferritin: Ferritin without attached iron.
  - Majority of iron sourced from recycling of iron from degraded RBCs:
    - RBCs broke down into heme and iron, released into bloodstream, binds to apotransferrin, then becomes transferrin.
    - Unused iron stored as ferritin or hemosiderin in liver until required by bone marrow.

Anemias

Definition:
- Involves too few erythrocytes or decreased quality or quantity of hemoglobin.
- Can arise from impaired erythrocyte production, acute/chronic blood loss, increased erythrocyte destruction, or combinations of these factors.
Classification:
  - By size (terminology ending in -cytic):
    - Macrocytic
    - Microcytic
    - Normocytic
  - By hemoglobin content (terminology ending in -chromic):
    - Normochromic
    - Hypochromic

Pathophysiology Manifestations

Oxygen Carrying Capacity:
  - Reduced capacity leads to tissue hypoxia.
  - Compensatory mechanisms activate:
    - Fluid shifts into blood vessels increasing volume but decrease blood viscosity, resulting in faster flow and turbulence.
    - Leads to cardiac dilation and potential heart valve insufficiency if untreated.
Hypoxemia Effects:
- Dilation of arterioles, venules, capillaries increases blood flow and venous return, boosting stroke volume and heart rate, risking heart failure.
Respiratory Response:
- Increased rate and depth of respiration for greater oxygen availability, resulting in symptoms such as Shortness of Breath (SOB), tachycardia, dizziness, fatigue.

Common Manifestations

Skin:
- Pallor or jaundice (due to RBC breakdown).
Other Symptoms:
  - Impaired healing, thinning and early graying of hair.
  - Vitamin B12 deficiency potentially leads to nervous system disorders.
  - Abdominal pain, nausea, vomiting, anorexia, and weakness.

Acute vs Chronic Blood Loss

Acute Blood Loss:
- Results in loss of intravascular volume (e.g., trauma).
- Within 24 hours (non-severe loss), plasma is replaced by water and electrolytes from interstitial spaces.
Chronic Blood Loss:
  - Occult (generally slow, e.g., bleeding ulcers, neoplasms).
  - Produces fewer manifestations compared to acute loss.
  - Large losses necessitate replacement with saline, dextran, albumin, or blood/PRBCs.

Megaloblastic (Macrocytic) Anemias

Characteristics:
- Large stem cells (megaloblasts) result in larger (macrocytic) erythrocytes.
Causes:
  - Deficiencies in Vitamin B12, folate; pernicious anemia.
  - Results in defective RBCs that die prematurely, leading to fewer erythrocytes in circulation.
  - DNA synthesis and cell division blockage occurs.

Pernicious Anemia

Definition:
- A form of macrocytic anemia caused by vitamin B12 deficiency primarily due to the lack of intrinsic factor from gastric cells.
Associated Disorders:
- Autoimmune thyroiditis, autoimmune gastritis, Type 1 Diabetes Mellitus (T1DM), gastrectomy/gastric atrophy.
Role of Vitamin B12:
- Essential for DNA synthesis; results in decreased numbers of RBCs, WBCs, and platelets.

Manifestations of Pernicious Anemia

Early Symptoms:
- Mood swings, infections, gastrointestinal disturbances, cardiac or kidney ailments.
Classic Symptoms:
  - Neurological manifestations such as:
    - Extreme weakness, fatigue.
    - Abnormal reflexes.
    - Paresthesias of feet and fingers.
    - Paranoid delusions, dementia, hallucinations.
    - Gait disturbances, appetite loss, abdominal pain, weight loss.
    - Smooth, beefy red sore tongue; possible yellowing of skin due to jaundice.
  - Neurological Impact:
  - Can cause nerve demyelination leading to irreversible symptoms such as loss of position sense and vibration, ataxia, and spasticity.

Treatment of Pernicious Anemia

Vitamin B12 Replacement:
- Weekly injections until deficiency corrected, then monthly for life.
- Oral B12 in high doses can also be effective.

Folate (Folic Acid) Deficiency Anemia

Characteristics:
- Macrocytic anemia requiring folate for DNA and RNA synthesis.
- More prevalent than vitamin B12 deficiency.
Associated Conditions:
  - Seen in malnourished clients, alcoholics, individuals with Crohn's disease or ulcerative colitis (UC).
  - Improvement noted due to fortified foods and dietary supplements.
  - Results in decreased RBC, WBC, and platelets.

Specific Manifestations of Folate Deficiency Anemia

Oral Symptoms:
- Cheilosis (scales and fistulas of the mouth).
- Stomatitis (inflammation of the mouth), painful ulcerations, burning mouth syndrome.
Systemic Symptoms:
- Diarrhea, dysphagia, flatulence, blunted affect, depression, sleep deprivation, memory loss, irritability.
- Often presents with potential thiamine deficiency leading to neurologic manifestations.
Treatment:
- Oral folate until deficiency corrected followed by a diet rich in folate.
- Symptoms typically resolve within 2 weeks of folate administration.

Iron Deficiency Anemia (IDA)

Classification:
- Microcytic-hypochromic anemia, characterized by abnormally small erythrocytes with reduced amounts of hemoglobin.
Lab Findings:
- Decreased MCV, MCH, MCHC, and ferritin levels.
Prevalence:
- Most common form of anemia worldwide.
- High-risk groups include toddlers, adolescent girls (due to poor diet), and women of childbearing age.
Causes:
- Dietary deficiency, impaired iron absorption (e.g., sprue, decreased fat absorption), chronic renal failure (CRF), increased requirements, chronic blood loss, chronic diarrhea, medications causing GI bleeding, heavy menstrual bleeding, or occult bleeding disorders; helminth infections, H. pylori infection, and heavy metal exposure.

Pathophysiology of IDA

Development Stages:
  1. Stage 1: Decreased bone marrow stores of iron.
  2. Stage 2: Diminished iron transport to bone marrow leading to iron deficiency erythropoiesis.
  3. Stage 3: Entry of small hemoglobin-deficient cells into circulation, presenting with manifestations.
Progression:
- Slowly develops over time.

Manifestations of IDA

Early Symptoms:
- Fatigue, weakness, shortness of breath (SOB), pale earlobes, palms, or conjunctiva, PICA (craving for non-nutritive substances).
Later Symptoms:
- Koilonychias (spoon-shaped nails), brittle and thin nails with coarse ridges, cheilosis, glossitis, stomatitis, painful ulcerations of the oral cavity, dysphagia, gastritis, neuromuscular changes (headache, irritability, tingling, numbness, vasomotor disturbances), and splenomegaly.
Impact on Children:
- May result in cognitive impairment.

Treatment of IDA

Diagnostic Tests:
- Lab tests measuring ferritin, transferrin saturation levels, and overall iron levels.
- Identify the underlying cause of IDA.
Iron Supplementation:
- Iron replacement therapy and a diet high in iron are essential.
- Improvement typically occurs within 2 months, demonstrated by improved hematocrit (HCT) or ferritin levels.

Laboratory Findings in Anemia

Serum Ferritin:
- Indicates amount of stored iron.
- Normal ranges: 12-263 ng/mL in young women; 20-250 in males; generally lower in older females.
Total Iron Binding Capacity (TIBC):
- Measures available transferrin: Normal ranges 250-350 mcg/dL.
Hematocrit (HCT):
- Percentage of RBCs in whole blood.
- Normal ranges: 34-46% in females; 36-53% in males.
Hemoglobin (HGB):
- Normal levels: 12-16 g/dL.
RBC Count:
- Normal ranges: 3.71-5.31 x 10^6 cells/µL.
Mean Corpuscular Volume (MCV):
- Average size of circulating RBCs; normal range: 78-102 fL.
Reticulocyte Count:
- Level of erythropoietin activity in bone marrow; normal range: 0.8-2.5%.
Mean Corpuscular Hemoglobin Concentration (MCHC):
- Average amount of hemoglobin per volume of RBCs; normal range: 32-36 g/dL.
Red Cell Distribution Width (RDW):
- Variation in size of circulating RBCs; normal range: 38-48.

Anemia of Chronic Disease (ACD)

Characteristics:
  - Decreased erythropoiesis and impaired iron utilization in clients with chronic conditions or chronic inflammation.
  - Develops within 1-2 months following the onset of disease.
  - Initially normocytic and normochromic; can progress to resemble iron deficiency anemia (hypochromic and microcytic) if untreated.
  - Commonly observed in hospitalized patients.

Pathophysiology of ACD

Cytokine Involvement:
- Chronic inflammation or infection induces macrophages and lymphocytes to release cytokines, notably reducing RBC production.
Iron Dynamics:
- Circulating iron drops as it converts to storage form (ferritin), decreasing erythropoiesis alongside a deficient production of erythropoietin by the kidneys.

Treatment of ACD

Hypotonic Iron Levels:
- Typically depicted by low iron levels, low or normal TIBC, and normal or high ferritin.
Interventions:
  - Erythropoietin treatment for chronic renal failure (CF) may be ineffective in various other conditions.
  - Trying to alleviate underlying conditions may assist.
  - Consider blood transfusions, keeping in mind the risks of stroke, hypertension, and mortality.

Aplastic Anemia

Definition:
- A condition marked by bone marrow aplasia, leading to a significant reduction of mature cells.
Pancytopenia:
- Characterized by the presence of anemia, leukopenia, and thrombocytopenia.

Manifestations

General Symptoms:
- Weakness, fatigue, pallor, dyspnea, fever/chills (from leukopenia), bacterial infections, petechiae, nosebleeds, alongside both cardiac and respiratory manifestations.

Treatment

Intervention Strategies:
- Address underlying disorders, consider allogenic bone marrow transplants, and blood transfusions.

Hemolytic Anemia

Characteristics:
- Resulting from the premature destruction of erythrocytes, leading to increased destruction > production.

Clinical Manifestations

Symptoms:
- Splenomegaly, jaundice, aplastic anemia, potential for deformation of bones, pathologic fractures, pallor, fatigue, SOB, tachycardia.
Causes:
- May stem from autoimmune destruction among other causes.

Treatment

Therapeutic Approaches:
- Utilization of steroids, immunosuppressive medications, and possibly splenectomy.

Polycythemia Vera (PV)

Definition:
- A slow-growing blood cancer classified as a stem cell disorder leading to excessive RBC production.
Associated Blood Components:
- Often accompanied by elevated white blood cells (WBCs) and platelets.
Genetic Component:
- Associated with a mutation in the Janus kinase 2 gene (JAK2 gene) that confirms diagnosis by causing increased erythropoietin receptor activation.
Risk Factors:
- Congestive heart failure (CHF), chronic obstructive pulmonary disease (COPD), sleep apnea, living at high altitudes, and smoking.

Manifestations of PV

Symptoms:
- Weakness, dizziness, abdominal pain, joint pain, headaches, and intense itching that worsens with exposure to water or heat.
- Additional symptoms include a ruddy complexion, elevated blood pressure, drowsiness, delirium, and spleen enlargement.
Complications:
- Risks include stroke, pulmonary embolism (PE), myocardial infarction (MI), leukemia, and kidney dysfunction.

Treatment of PV

Therapeutic Approaches:
  - Reduction of red cell proliferation (e.g., hydroxyurea causing myelosuppression) alongside blood volume reduction (phlebotomy).
  - Use of medications such as aspirin, dipyridamole, or interferon-alpha to manage symptoms.
  - With effective management, average survival is noted at 10-15 years.

Sickle Cell Anemia (SCA)

Definition:
- A genetic defect affecting hemoglobin synthesis, which leads to the production of abnormal hemoglobin known as sickle hemoglobin S (Hb S).
Prevalence:
- Most predominantly observed in individuals of sub-Saharan African ancestry, particularly among African Americans in the US.

Pathophysiology of SCA

Sickling Effects:
- Under hypoxic conditions or dehydration, RBCs elongate and sickle, increasing blood viscosity and slowing circulation.
- Sickled cells become hemolyzed in the spleen, causing anemia due to pooling of blood and resultant infarction of splenic vessels.
Risk Factors for Hypoxia:
- Includes acute illness, temperature fluctuations, high altitude exposure, and stress.
- Results in decreased RBCs and elevated serum bilirubin levels.

Clinical Manifestations of SCA

Symptoms:
- Hemolytic anemia characterized by pallor, fatigue, jaundice, and irritability along with vascular obstruction due to thrombosis.
Crisis Types:
  - Four crisis types include the following:
    1. Vaso-occlusive Crisis:
       - Characterized by extremely painful sickling causing obstruction, leading to potential strokes or end-stage renal disease.
    2. Sequestration Crisis:
       - Occurs primarily in children under five, characterized by pooling of blood in the spleen and liver.
    3. Aplastic Crisis:
       - Reduced erythropoiesis with premature RBC death usually following viral infections.
    4. Hyperhemolytic Crisis:
       - Related to certain medications or infections, although not instances are rare.

Treatment of SCA

Management Strategies:
- Focuses on preventing the consequences of anemia, avoiding triggers for crises, ensuring adequate hydration and oxygen levels, infection prevention, pain management, and potentially hydrea treatments to reduce crises.
- Transfusion therapy may also be necessary for severe anemia cases.

Compensatory Mechanisms for Anemia

Responses to Restore Tissue Oxygenation:
  - Increased Heart Rate (Tachycardia) - to enhance cardiac output.
  - Increased Respiratory Rate (RR) - to improve oxygen intake.
  - Increased Blood Flow to Vital Organs.
  - Increased Erythropoietin Activity.

Platelets

Production Mechanism:
  - Derived from megakaryocytes.
  - Platelets (thrombocytes) predominantly reside in the spleen.
  - Thrombopoietin: Hormone that stimulates platelet production in bone marrow.
Lifespan:
- Platelets have a lifespan of about 10 days before sequestering and destruction occur in the spleen.
Thrombocytopenia Definition:
- Defined as platelet counts falling below 100,000/mm³, leading to prolonged bleeding times.
- Spontaneous bleeding can occur if counts drop below 20,000/mm³.

Hemostasis and Platelets

Clot Formation Process:
  - Occurs at the site of vascular injury, facilitated by:
    - Epithelial cells
    - Platelets
    - Clotting factors
Vascular Response:
  - In the event of injury, vasoconstriction occurs in arterioles to limit blood loss.
  - Damaged endothelial cells release von Willebrand factor, which facilitates platelet aggregation and plug formation.
  - Platelet aggregation leads to formation of a more permanent plug.

Inflammatory Response

Chemo mediators:
- Triggered inflammatory processes involve prostaglandins and histamine, activating platelets.
Coagulation System Activation:
- Results from activated platelets and damaged endothelium, leading to a fibrin clot formation to prevent further blood loss.
- Subsequent processes include repair, fibrinolysis, and eventual dissolution of the clot.
Thromboxane A2 (TXA2):
- Produced by platelets; induces vasoconstriction and promotes platelet aggregation.

Purpuric Disorders

Description:
- Presentation of red or purple spots on the skin, resulting from bleeding vasculature.
Cause:
- Can occur due to deficiency of normal platelets leading to leakage through small capillary tears.

Thrombocytopenia

Thresholds:
- Platelet count under 150,000 units/µL of blood indicates thrombocytopenia.
- Counts below 20,000 units/µL can result in spontaneous bleeding.
Manifestations:
- Symptoms may include petechiae, ecchymosis, purpura, and frank bleeding from mucous membranes.
Causes:
- Results from decreased platelet production or increased consumption.
- Common disorders include Immune Thrombocytopenic Purpura (ITP) and Heparin-Induced Thrombocytopenia (HIT).

Immune Thrombocytopenic Purpura (ITP)

Acute Form:
- Typically occurs in children; often related to infections or drugs and usually remits within 1-2 months.
Chronic Form:
- Characterized by autoantibodies (IgG class) binding to specific platelets, leading to their removal by macrophages in the spleen.
Prevalence:
- Chronic ITP commonly affects adults, tends to worsen progressively.

Manifestations of Chronic ITP

Symptoms Progression:
- Initially minor bleeding issues (petechiae, purpura) that may escalate to major bleeding from mucosal areas (e.g., hematuria, menorrhagia, epistaxis).
Associated Symptoms:
- May also present fever, weight loss, and headache, oscillating between remissions and exacerbations.

Treatments for Chronic ITP

Options:
  - 1. Glucocorticoids:
       - Aim to suppress immune response and reduce platelet destruction in the spleen.
  - 2. Intravenous Immunoglobulin (IVIG):
       - Administered to prevent major bleeding incidents.
  - 3. Splenectomy:
       - Surgical removal of the spleen may be performed to mitigate destruction of platelets.
  - 4. Immunosuppressive therapies:
       - Such as azathioprine or cyclophosphamide are utilized in chronic cases.

Thrombotic Thrombocytopenic Purpura (TTP)

Explanation:
  - Also known as Moschcowitz disease, this multisystem disorder results from platelet aggregation causing occlusions in arterioles and capillaries of the microcirculation.
  - Organ ischemia results from excessive platelet consumption.
  - Commonly associated with a defect in the enzyme ADAMTS13.

Thrombocythemia

Classification:
- Platelet counts exceeding 450,000/µL of blood.
Essential Thrombocythemia:
- Due to chronic, myeloproliferative neoplasm from a bone marrow defect.
Secondary Thrombocythemia:
- Can occur post-splenectomy; includes platelets that would typically be stored in the spleen, circulating instead.
Manifestations:
- Symptoms may present as arterial or venous thrombosis, leading to microvasculature issues or signs of color change and sensations in extremities.

Common Symptoms of Thrombocythemia

Vascular Symptoms:
- Often manifested as warm, red hands/feet, painful burning sensations, headaches, paresthesias, and dizziness, with potential for bleeding complications.

Altered Platelet Function

Causes:
  - Multiple factors affecting platelet functionality, including:
    - Aspirin (ASA) and NSAIDS.
    - Chronic Renal Failure (CRF).
    - Liver disease.
    - Cardiopulmonary bypass surgeries.
    - Severe deficiencies in iron or folate.
    - Autoimmune diseases.

Clotting System (Cascade)

Pathways:
  - Intrinsic Pathway:
    - Activated by Hageman factor (Factor XII) upon vascular injury exposure.
  - Extrinsic Pathway:
    - Initiated by activation of tissue thromboplastin when epithelial cells are damaged; interacts with Factor VII.
Common Pathway:
- Both pathways converge into a common pathway eventually activating Factor X leading to clot formation.
- There exist interactions, where components in one pathway can activate members of another.

Intrinsic Pathway

Activation Trigger:
- Initiated by Hageman factor (Factor XII) upon exposure to vessel injury.

Extrinsic Pathway

Initiation:
- Triggered by Tissue Thromboplastin upon damage to epithelial cells, interacting with Factor VII.

Clot Formation

Mechanism:
  - Prothrombin Activation:
    - Prothrombin combined with Factors X and V leads to conversion of prothrombin to thrombin.
  - Thrombin's Role:
    - Converts fibrinogen into fibrin which polymerizes to form a clot.

Clot Inhibitors

Inhibitory Factors:
  - Thrombin Inhibitors:
    - Antithrombin III binding with heparin.
  - Tissue Factor Pathway Inhibitor (TFPI):
    - Inhibits Factor Xa during the prothrombin process, preventing activation of additional clotting factors.
  - Protein C + Protein S:
    - Degrade Factors Va and VIIIa.
  - Thrombomodulin:
    - Thrombin-binding protein that regulates coagulation.
Implications of Deficiencies:
- Absence of these inhibitors may lead to hypercoagulation and heightened clot formation.

Clot Lysis

Mechanism:
  - Managed by the fibrinolytic system.
  - Involves:
    - Tissue plasminogen activator (t-PA)
    - Urokinase-like plasminogen activator (u-PA)
    - Plasmin Enzyme:
      - Converts clots into fibrin degradation products (FDPs); D-Dimer is used for detection of DVT or PE.

Coagulation Disorders

Definition:
- Result from defects or deficiencies in one or more clotting factors, leading to impaired hemostasis and consumptive thrombohemorrhagic disorders.

Vasculitis

Description:
- Inflammation of blood vessels which can damage vessel integrity leading to activation of platelets and coagulation cascade.
- Severe cases can initialize clotting issues in vessels.

Vitamin K Deficiency

Importance of Vitamin K:
- Necessary for the synthesis and regulation of prothrombin and other clotting factors.
- Major dietary sources include green leafy vegetables.
Causes:
- Seen in parenteral nutrition alongside antibiotics damaging normal gut flora or conditions such as bulimia.
Treatment:
- Administering parenteral vitamin K which corrects deficiency within 8-12 hours.

Liver Disease and Coagulation

Impact on Clotting:
- Leads to defects in the clotting system causing deficiencies of factors IX, plasminogen, and thrombopoietin especially.
Treatment:
- Fresh frozen plasma is used to supply necessary clotting factors.

Disseminated Intravascular Coagulation (DIC)

Definition:
- Characterized by widespread clotting in medium or small blood vessels throughout the body, potentially leading to ischemia and necrosis.
Complications:
- Can result in multiorgan system failure, often seen in sepsis (most commonly), metastatic cancer, acute leukemia, and trauma patients.
Features:
  - Exhibits both bleeding and clotting problems due to consumption of clotting factors and platelets, resulting in serious hemorrhagic events.
  - Breakdown of fibrin produces fibrin split products (FSP), also called fibrin degradation products (FDP).
  - D-Dimer: Molecule from plasmin breakdown, is specific for DIC; ELISA tests can indicate thrombin activity markers.

DIC Manifestations and Treatment

Symptoms:
- Oozing from IV sites, surgical wounds, and extensive purpura/petechiae/hematomas.
- Frequently bleeding from three unrelated sites can also suggest DIC.
Treatment Approach:
- Primary focus on eliminating the underlying condition, replacing clotting factors, and consideration of IV Heparin infusion (though this remains controversial).
- Maintenance of organ function is crucial for patient outcomes.