Anemia

Background

• Anemia is a condition of decreased hemoglobin (Hb) concentration compared to age-matched and gender-matched controls.
  • Males: Hb < 13 g/dL
  • Non-Pregnant Females: Hb < 12 g/dL
  • Pregnant-Females: Hb < 11g/dL
  • Children: Hb < <11-12 g/dL (depends on age)
• Affects 1/3 of the world's population
• Most common causes are uterine and GI bleeding

Pathophysiology

4 mechanisms:

• Loss of RBCs by hemorrhage (e.g. GI bleed, trauma)
• Increased destruction (SCD, hemolytic anemia)
• Impaired production (iron deficiency, folate deficiency, B12 deficiency, aplastic anemia/myelodysplastic syndrome)
• 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

• CBC for evaluation, look at MCV
  • Microcytic: Iron Levels, Reticulocyte Count, Ferritin, TIBC
  • Macrocytic: Folate Level, B12 Level, Reticulocyte Count

Microcytic Anemia (<81 fL)

• RDW high → evaluate Ferritin, which is a measurement of iron storage
  • 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 normal 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
  • Using a restrictive transfusion strategy (transfusing <6-8) has found to be beneficial, as liberal transfusion strategy (transfusing <10) not showing any benefit and has shown harm
    • GI bleeds using restrictive transfusion strategy saw a decreased mortality and rebleed rate
  • Always draw labs necessary for diagnosis prior to transfusing
  • 1 unit PRBCs should raise the Hgb by 1gm/dL
• Iron-deficiency anemia
  • PO: Ferrous sulfate 325mg (65mg elemental iron) with Vitamin C (to aid in absorption)
  • IV: Ferrous Sucrose 300mg in 250mL NS over 2hrs

Disposition

Depends on underlying cause of anemia

Admission

• Evidence or potential for ongoing blood loss
• Signs of end-organ dysfunction (altered mental status, cardiac ischemia, etc.)

Discharge

• Most stable patients can be discharged w/ outpatient follow-up if they are asymptomatic or only mildly symptomatic following an incidental finding of anemia.

See Also

• Transfusions
• Myelophthisic Anemia
• Microangiopathic Hemolytic Anemia (MAHA)

External Links

• DDxOf: Differential Diagnosis of Anemia
• emDOCS - Anemia in the ED Setting: Pearls and Pitfalls