Definition
Anemia is a hematologic condition characterized by a reduction in hemoglobin concentration, hematocrit, or red blood cell (RBC) mass, resulting in impaired oxygen delivery to tissues.
Pathophysiology-Based Classification
1. Decreased Red Blood Cell Production
- Iron deficiency anemia
- Vitamin B12 deficiency anemia (megaloblastic)
- Folate deficiency anemia
- Anemia of chronic disease/inflammation
- Aplastic anemia
- Chronic kidney disease–related anemia (↓ erythropoietin)
2. Increased Red Blood Cell Destruction (Hemolytic Anemia)
- Autoimmune hemolytic anemia
- G6PD deficiency
- Sickle cell disease
- Thalassemia
- Drug-induced hemolysis
3. Blood Loss
- Acute hemorrhage (trauma, surgery)
- Chronic blood loss (gastrointestinal bleeding, menorrhagia)
Classification by Mean Corpuscular Volume (MCV)
| Type | MCV | Common Causes |
|---|---|---|
| Microcytic | < 80 fL | Iron deficiency, thalassemia |
| Normocytic | 80–100 fL | CKD, chronic disease, acute blood loss |
| Macrocytic | > 100 fL | Vitamin B12 deficiency, folate deficiency, alcoholism |
Common Types of Anemia (Clinical & Pharmacotherapy Focus)
Iron Deficiency Anemia
Etiology: Chronic blood loss, malabsorption, inadequate intake
Key Labs: ↓ ferritin, ↓ serum iron, ↑ TIBC
Treatment: Oral or IV iron
Pharmacist Pearls
- Counsel on adherence and GI intolerance
- Separate iron from calcium, PPIs, and antacids
- Consider IV iron if oral therapy fails
Anemia of Chronic Disease (Inflammation)
Etiology: Chronic infection, autoimmune disease, malignancy
Key Labs: Normal/↑ ferritin, ↓ serum iron
Treatment: Treat underlying disease; ESA in selected cases
Pharmacist Pearls
- Iron alone is often ineffective
- Monitor for functional iron deficiency during ESA therapy
Vitamin B12 Deficiency Anemia
Etiology: Pernicious anemia, malabsorption, dietary deficiency
Key Labs: ↑ MCV, ↓ B12 levels
Treatment: IM or high-dose oral vitamin B12
Pharmacist Pearls
- Screen for neurologic symptoms
- Lifelong therapy required in pernicious anemia
Folate Deficiency Anemia
Etiology: Poor nutrition, alcoholism, pregnancy, medications (e.g., methotrexate)
Treatment: Oral folic acid
Pharmacist Pearls
- Exclude vitamin B12 deficiency before supplementation
Hemolytic Anemia
Etiology: Autoimmune, inherited, or drug-induced
Key Labs: ↑ LDH, ↑ indirect bilirubin, ↓ haptoglobin
Treatment: Cause-specific; corticosteroids or immunosuppressants when indicated
Anemia in Chronic Kidney Disease (CKD)
Etiology: Reduced erythropoietin production
Treatment: ESAs + iron supplementation
Pharmacist Pearls
- Ensure adequate iron stores before ESA initiation
- Avoid hemoglobin overcorrection (>11–11.5 g/dL)
Drug-Induced Anemia (High-Yield Table)
| Mechanism | Drugs |
|---|---|
| Bone marrow suppression | Chemotherapy, linezolid, zidovudine |
| Hemolysis | Sulfonamides (G6PD), dapsone |
| Folate antagonism | Methotrexate, trimethoprim |
| Chronic blood loss | NSAIDs, antiplatelets |
Diagnostic Algorithm (Stepwise)
- Confirm anemia with CBC
- Assess MCV (microcytic/normocytic / macrocytic)
- Order reticulocyte count
- Perform iron studies
- Check vitamin B12 and folate
- Evaluate renal and inflammatory markers
- Assess medication history and bleeding risk
CKD-Specific Anemia Management
- Target hemoglobin: 10–11.5 g/dL
- Iron repletion before ESA initiation
- Monitor BP, iron indices, and thrombotic risk
Oncology-Related Anemia
- Common causes: chemotherapy, marrow infiltration, chronic inflammation
- Treatments: transfusion, ESAs (risk–benefit assessment), IV iron
- Monitor for thromboembolic events
ICU & Acute Care Considerations
- Restrictive transfusion strategy (Hb ~7–8 g/dL unless symptomatic)
- Monitor dilutional anemia from IV fluids
- Identify acute hemolysis or bleeding
Patient Counseling Points
- Explain cause-specific therapy
- Emphasize adherence and follow-up labs
- Counsel on dietary sources of iron, B12, and folate