Anemia

Background

• Affects 1/3 of the world's population
• Most common causes are uterine and GI bleeding
• Pathophysiology
  • 4 mechanisms:
    1. Loss of RBCs by hemorrhage (e.g. GI bleed)
    2. Increased destruction (SCD, hemolytic anemia)
    3. Impaired production (iron/folate/B12 deficiency, aplastic/myelodysplastic anemia)
    4. Dilutional (rapid IVF infusion)

Clinical Features

• Most pts begin to be symptomatic at ~7gm/dL
• Weakness, fatigue, lethargy, DOE, palpitations
• Skin, nail bed, mucosal pallor
• Widened pulse pressure
• Jaundice, hepatosplenomegaly (hemolysis)
• Peripheral neuropathy (B12 deficiency)

Differential Diagnosis

Anemia

RBC Loss

• Hemorrhage

RBC consumption (Destruction/hemolytic)

• Hereditary
• Acquired
• Microangiopathic Hemolytic Anemia (MAHA)
• Autoimmune hemolytic anemia

Impaired Production (Hypochromic/microcytic)

• Iron deficiency
• Anemia of chronic disease
• Thalassemia
• Sideroblastic anemia

Aplastic/myelodysplastic (normocytic)

• Marrow failure
• Chemicals (e.g. ETOH)
• Radiation
• Infection (HIV, parvo)

Megaloblastic (macrocytic)

• Vitamin B12/folate deficiency
• Drugs (chemo)
• HIV

Diagnosis

Algorithm for the Evaluation of Anemia

• Microcytic Anemia (<81 fL)
  • RDW high
    • Ferritin low: Iron deficiency anemia
    • Ferritin normal: Anemia chronic disease or sideroblastic anemia (e.g. lead poisoning)
  • RDW normal
    • RBC count low: Anemia chronic disease, hypothyroidism, Vitamin C deficiency
    • RBC count nl or high: Thalassemia

• Normocytic Anemia ((81-100 fL)
  • Retic count nl
    • RDW normal: Anemia chronic disease, anemia of renal insufficiency
    • RDW high: Iron, Vit B12, or folate deficiency
  • Retic count high
    • Coombs Positive: Autoimmune cause
    • Coombs negative: G6PD, SCD, spherocytosis, microangiopathic hemolysis

• Macrocytic Anemia (MCV>100 fL)
  • RDW high: Vit B12 or folate deficiency
  • RDW nl: ETOH abuse, liver disease, hypothyroidism, drug induced, myelodysplasia

Treatment

• Transfusions
  • Consider if pt is symptomatic, hemodynamically unstable, hypoxic, or acidotic
  • Most pts w/ Hb <6 will benefit from transfusion; most pts w/ Hb >10 will not
  • Always draw labs necessary for diagnosis prior to transfusing
  • 1 unit PRBCs should raise the Hgb by 1gm/dL

See Also

• Transfusions
• Myelophthistic anemia
• Microangiopathic Hemolytic Anemia (MAHA)