Anemia

Background

• Affects 1/3 of the world's population
• Most common causes are uterine and GI bleeding

Severe anemia is defined as a hemoglobin level of 5 to 7 g/dL with symptoms of hypoperfusion including lactic acidosis, base deficit, shock, hemodynamic instability, or coronary ischemia

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

General Anemia Symptoms

• Most patients begin to be symptomatic at ~7gm/dL
• Weakness, fatigue, lethargy, dyspnea on exertion, 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

Acute Anemia

Assess for any signs of bleeding or trauma before considering other causes of chronic anemia.

Algorithm for the Evaluation of Anemia

Chronic 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 normal
  • 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 normal: 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)