How should I evaluate and manage a patient with severe anemia?

Evaluation and Management of Severe Anemia

For severe anemia (hemoglobin <7-8 g/dL), immediately transfuse packed red blood cells while simultaneously initiating diagnostic workup—do not delay transfusion to complete investigations. 1

Immediate Management

Transfusion Decision

• Transfuse 2-3 units of packed red blood cells immediately for hemoglobin <7.4 g/dL to achieve a target of 7-9 g/dL. 1
• Each unit increases hemoglobin by approximately 1 g/dL. 1
• For patients with cardiovascular disease, hemodynamic instability, or active symptoms (chest pain, dyspnea, altered mental status), target a higher threshold of >8 g/dL. 1
• Monitor vital signs continuously during transfusion to detect reactions (fever, hypotension, respiratory distress). 1
• Recheck hemoglobin 1 hour post-transfusion to confirm adequate response, then daily until stable. 1

Critical Monitoring

• Implement continuous cardiac monitoring during the acute phase, particularly in elderly patients or those with known cardiac disease. 1
• Assess for signs of volume overload during transfusion (dyspnea, crackles, elevated jugular venous pressure). 2

Concurrent Diagnostic Workup

While transfusion proceeds, immediately obtain the following laboratory tests without delaying treatment: 1

Initial Laboratory Panel

• Complete blood count with differential and reticulocyte count to assess bone marrow response and classify anemia type. 1, 3
• Peripheral blood smear to identify red cell morphology (schistocytes suggest hemolysis, macrocytes suggest B12/folate deficiency, microcytes suggest iron deficiency). 3
• Iron studies: serum ferritin, transferrin saturation (TSAT), total iron binding capacity. 2, 4
• Vitamin B12 and folate levels to identify nutritional deficiencies. 2, 4
• Serum creatinine and estimated glomerular filtration rate (eGFR) to evaluate for chronic kidney disease. 2, 4
• Lactate dehydrogenase (LDH), haptoglobin, indirect bilirubin, and direct antiglobulin test (Coombs) if hemolysis is suspected. 5

Additional Testing Based on Clinical Context

• Stool guaiac or fecal immunochemical test if gastrointestinal bleeding is suspected. 4
• Hemoglobin electrophoresis if thalassemia or hemoglobinopathy is suspected (family history, ethnicity, microcytosis). 3
• Bone marrow aspiration and biopsy if pancytopenia, unexplained anemia, or concern for malignancy/myelodysplasia exists. 2, 3

Treatment of Underlying Cause

Iron Deficiency Anemia

• For confirmed iron deficiency (low ferritin <30 ng/mL, low TSAT <20%), initiate intravenous iron for moderate-to-severe anemia requiring rapid correction. 4, 6
• Oral iron (40-60 mg elemental iron daily in divided doses) is appropriate only for mild anemia when time permits (>6-8 weeks). 4
• Intravenous iron is more effective than oral iron for moderate-to-severe deficiency and avoids gastrointestinal side effects. 6
• Investigate the source of iron loss: refer to gastroenterology if gastrointestinal bleeding is suspected to rule out malignancy. 4

Vitamin B12 or Folate Deficiency

• Administer vitamin B12 supplementation (1000 mcg intramuscularly daily for 1 week, then weekly) if deficiency is confirmed. 4
• Provide folate supplementation (1-5 mg daily orally) if folate deficiency is identified. 4

Chronic Kidney Disease

• Refer to nephrology for management if eGFR <30 mL/min/1.73m² and anemia is present. 4
• Consider erythropoiesis-stimulating agents (ESAs) with concurrent intravenous iron only after stabilization and in consultation with nephrology. 1, 7
• Do not use ESAs for acute management—their onset of action is too slow (weeks) for severe anemia. 1

Hemolytic Anemia

• If hemolysis is confirmed (elevated LDH, low haptoglobin, elevated indirect bilirubin, positive Coombs test), obtain immediate hematology consultation. 5
• Avoid platelet transfusion if thrombotic thrombocytopenic purpura (TTP) is suspected until hematology evaluates. 5

Common Pitfalls to Avoid

• Do not delay transfusion while awaiting complete diagnostic workup—treatment and diagnosis must proceed simultaneously. 1
• Do not rely solely on hemoglobin threshold; assess symptoms (dyspnea, chest pain, syncope), comorbidities (coronary artery disease, heart failure), and rate of decline. 1
• Do not use ESAs as primary therapy for acute severe anemia—they are inappropriate for immediate correction. 1, 7
• Do not transfuse liberally in hemodynamically stable patients with iron deficiency—transfusions should be used rarely regardless of hemoglobin level. 6
• Do not overlook coexisting causes of anemia (gastrointestinal bleeding, hemolysis, renal disease, nutritional deficiency) that require specific treatment. 2

Post-Stabilization Management

Iron Supplementation

• Initiate iron supplementation if deficiency is identified, as most patients with chronic anemia require supplemental iron. 1
• Continue intravenous or oral iron until iron stores are repleted (ferritin >100 ng/mL, TSAT >20%). 4

Follow-Up Monitoring

• Recheck hemoglobin weekly until stable, then monthly to assess response to treatment. 1
• Repeat iron studies, B12, and folate levels after 4-6 weeks of supplementation to confirm repletion. 4
• Arrange outpatient hematology follow-up if the cause remains unclear or if bone marrow disorder is suspected. 2, 3