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

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

Evaluation

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

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

Management

• Transfusions
  • Consider if patient is symptomatic, hemodynamically unstable, hypoxic, or acidotic
  • Most patients with hemoglobin <6 will benefit from transfusion; most patients with hemoglobin >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)

External Links

• DDxOf: Differential Diagnosis of Anemia