Anemia Study Notes

Anemia

Introduction to Anemia

  • Definition: Anemia is a clinical condition characterized by a decreased red blood cell (RBC) mass, reflected in lowered hemoglobin (Hb) and hematocrit (Hct) levels that are expected for the age and sex of the individual.
    • Special considerations: Presence of pregnancy, the state of hydration of the individual, and the altitude must be accounted for.
  • Alternative Definition: Anemia is characterized by a decrease in RBC count, Hb level, or packed cell volume (PCV), which may arise from:
    • Decreased production of RBCs
    • Increased destruction of RBCs
    • Excess blood loss
  • Causes of Anemia: Genetic disorders, nutritional problems, infections, drugs, and toxins.

Physiological Implications of Anemia

  • A reduction in RBC indices leads to decreased oxygen-carrying capacity of the blood.

Assessment of Anemia

  • Indicators: RBC count, PCV, Hb level, and other RBC indices are used to evaluate anemia.

Hemoglobin (Hb) Cut-off Points for Anemia

  • Men (>15 yrs): Hb level < 13.0 g/dL (Normal range: 130-180 g/L)
  • Women (>15 yrs): Hb level < 12.0 g/dL (Normal range: 120-160 g/L)
  • Children (6 months - 5 years): Hb levels < 11 g/dL
  • Children (6-14 years): Hb levels < 12 g/dL

Influence of Altitude on Hemoglobin Levels

  • General Hint: Higher Hb values may be seen in individuals living at altitudes above sea level.
  • Example: Comparing Mr. G at sea level and at 3500 meters above sea level.
    • Question: At which altitude is Mr. G’s Hb level expected to be higher?

Packed Cell Volume (PCV)

  • Values:
    • Males: 40-52% (0.40–0.52 in SI unit)
    • Females: 37-47%
    • N/B: PCV is not a reliable indicator for anemia as it can show high values in dehydration or fluid infusion.
    • Children: PCV cut-off for anemia: 30–33%

Hematocrit (Hct) Values by Demographic

  • Children (6–59 months): Hct = 0.33
  • Non-pregnant women (15–49 yrs): Hct = 0.34
  • Pregnant women: Hct = 0.36
  • Men (>15 years): Hct = 0.39

Types of Anemia

Clinical Presentation

  • Acute: Usually caused by acute bleeding or hemolysis.
  • Chronic: Associated with prolonged physiological conditions such as pregnancy.

Pathogenic Classification

  1. Hypo-regenerative Anemia

    • Bone marrow fails to respond adequately to increased erythropoietin resulting from low Hb levels.
    • May be due to inadequate nutrient supply for erythropoiesis or infiltration of bone marrow.
    • Typical Reticulocyte Count: < 50×10^9/L

  2. Regenerative Anemia

    • Bone marrow responds appropriately to low RBC mass by increasing erythrocyte production.
    • Characterized by an increased reticulocyte count in response to bleeding or hemolysis.
    • Typical Reticulocyte Count: > 100×10^9/L
    • Normal reticulocyte count: 0.5-1.5% (50-100×10^9/L)

Morphological Classification

  • Based on size and color of RBCs.
    • Normocytic Anemia: MCV of 80-90 fL, normal color; reduced RBC count.
    • Examples: Hemorrhagic anemia, autoimmune hemolytic anemia, hemoglobinopathies, anemia of chronic disease.
    • Macrocytic Anemia: MCV > 100 fL; normal color; reduced RBC count.
    • Examples: Megaloblastic anemia due to B12 or folate deficiency.
    • Microcytic Anemia: MCV < 80 fL; reduced color.
    • Examples: Iron deficiency anemia, thalassemia, anemia of chronic diseases.

Hematological Indices Calculation Formulas

  • MCV = Hct × 10/RBC
  • MCH = Hb × 10/RBC
  • MCHC = Hb × 10/Hct
  • RBC × 3 = Hb
  • Hb × 3 = Hct
  • Hb = Hct/3

Etiological Classification

  1. Hemorrhagic Anemia: Caused by excessive blood loss; can be acute or chronic.

    • Acute Hemorrhagic Anemia: Sudden loss of ≥15% of total blood volume. Plasma replacement occurs within 24 hours; RBC replacement takes 4-6 weeks.
    • Chronic Hemorrhagic Anemia: Long-term blood loss due to conditions like peptic ulcer, hookworm infestation, menorrhagia, and bleeding hemorrhoids.

  2. Hemolytic Anemia: Distinction between acquired (extrinsic) and inherited (intrinsic) forms.

    • Acquired: Normal RBCs are hemolyzed by external factors (e.g., antibodies, chemicals).
    • Inherited: Defective RBCs are shortened in lifespan. Examples: Sickle cell disorders, thalassemia.

Hemolytic Disease of the Newborn (HDN)

  • A classical case of hemolytic anemia characterized by maternal antibodies destroying fetal RBCs via transplacental transmission.
  • Isoimmunization occurs; maternal IgG antibodies cross the placenta, leading to fetal RBC destruction.
    • Outcome: Fetal reticulocytosis and severe anemia indicated by increased umbilical artery lactate levels.

Nutritional Anemia

  • Results from deficiency of nutrients essential for RBC production.
    • Key nutrients: Iron, proteins, vitamins C, B12, and B9.
  • Iron Deficiency Anemia: Most common type; characterized by decreased iron availability for hemoglobin synthesis.
  • Symptoms: Brittle nails (koilonychias), brittle hair, atrophy of lingual papilla.

Other Types of Nutritional Anemia

  1. Protein Deficiency Anemia: Resulting from deficiency of proteins required for hemoglobin production; typically macrocytic and hypochromic.
  2. Pernicious Anemia: B12 deficiency due to autoimmune destruction of gastric parietal cells; presents with large, immature RBCs.
  3. Megaloblastic Anemia: Caused by folate deficiency; characterized by immature megaloblastic RBCs.

Aplastic Anemia

  • Associated with the disorder of red bone marrow, leading to reduced RBC production and replacement by fatty tissue.
  • Causes include bacterial toxins, radiation exposure, and viral infections (HIV, hepatitis).

Anemia of Chronic Diseases

  • Due to disturbance in iron metabolism; associated with chronic infections, inflammation, or malignancy.
  • Recognized as the second most common type following iron deficiency anemia.

Severity Classification of Anemia (WHO)

  • Mild:

    • 6–11 months: 100-109 g/L
    • 5–11 years: 110-114 g/L
    • 12–14 years: 110-119 g/L
    • ≥15 years (non-pregnant women): 110-119 g/L
    • ≥15 years (pregnant women): 100-109 g/L
    • ≥15 years (men): 110-129 g/L

  • Moderate:

    • 6–11 months: 70-99 g/L
    • 5–11 years: 80-109 g/L
    • 12–14 years: 80-109 g/L
    • ≥15 years (non-pregnant women): 80-109 g/L
    • ≥15 years (pregnant women): 70-99 g/L
    • ≥15 years (men): 80-109 g/L

  • Severe:

    • 6–11 months: < 70 g/L
    • 5–11 years: < 80 g/L
    • 12–14 years: < 80 g/L
    • ≥15 years (non-pregnant women): < 80 g/L
    • ≥15 years (pregnant women): < 70 g/L
    • ≥15 years (men): < 80 g/L

Physiological Anemia

Anemia in Pregnancy

  • From the 4th week of gestation, total blood volume increases by 35-45% above non-pregnant levels, with plasma volume rising by 40-45%.
  • Results in modest reduction of hematocrit; peak hemodilution occurs at 24-26 weeks.

Physiologic Anemia of Infancy

  • Following delivery, neonatal Hb and Hct begin to drop, reaching a nadir at 6-8 weeks. Normal Hb values at that time are 9-11 g/dL.
  • This phenomenon is typically a normal development unless associated with RBC diseases or infections.

Adaptive Mechanisms of the Body to Anemia

  • Anemia significantly reduces oxygen delivery to tissues, determined by blood oxygen content and cardiac output.
  • Normal compensation mechanisms: increased oxygen extraction by tissues, especially those such as kidney, skeletal muscle, and skin.
  • Inadequate compensation can trigger increased erythropoietin production.

Clinical Effects of Anemia

  • Cardiac Output: Increased cardiac output leads to more hemoglobin exposure in peripheral tissues; typically results in tachycardia.
  • Signs and Symptoms:
    • Reproductive System: Menstrual irregularities such as oligomenorrhea and amenorrhea.
    • Renal System: Dysfunctional renal function leading to albuminuria.
    • Respiratory System: Tachypnea, difficulty breathing (dyspnea).
    • Neuromuscular Effects: Headache, lack of concentration, irritability.
    • Gastrointestinal Symptoms: Anorexia, vomiting, abdominal discomfort, constipation.
    • Skin/Mucous Membrane Symptoms: Pallor in skin/mucous membranes, brittleness of nails.

Management of Anemia

  • Requires comprehensive patient assessment including history and evaluation of:
    • Etiology and severity of anemia.
    • Treatment options including pharmacological and non-pharmacological approaches.
  • Possible treatment may involve blood transfusions (whole blood or specific blood products).

Assignment

  • Discuss mountain sickness.

Conclusion

  • Thank you!