Trauma, GI hemorrhage (may be occult) are common causes; less common are genitourinary sources (menorrhagia, gross hematuria), internal bleeding such as intraperitoneal from spleen or organ rupture, retroperitoneal, iliopsoas hemorrhage (e.g., in hip fractures). Acute bleeding is associated with manifestations of hypovolemia, reticulocytosis, macrocytosis; chronic bleeding is associated with iron deficiency, hypochromia, microcytosis.
Causes are listed in Table 63-3 Classification of Hemolytic Anemiasa .
- Intracellular RBC abnormalities: most are inherited enzyme defects [glucose-6-phosphate dehydrogenase (G6PD) deficiency > pyruvate kinase deficiency], hemoglobinopathies, sickle cell anemia and variants, thalassemia, unstable hemoglobin variants.
- G6PD deficiency: leads to episodes of hemolysis precipitated by ingestion of drugs that induce oxidant stress on RBCs. These include antimalarials (chloroquine), sulfonamides, analgesics (phenacetin), and other miscellaneous drugs (Table 63-4 Drugs That Carry Risk of Clinical Hemolysis in Persons with G6PD Deficiency).
- Sickle cell anemia: characterized by a single-amino-acid change in β globin (valine for glutamic acid in the 6th residue) that produces a molecule of decreased solubility, especially in the absence of O2. Although anemia and chronic hemolysis are present, the major disease manifestations relate to vasoocclusion from misshapen sickled RBCs. Infarcts in lung, bone, spleen, retina, brain, and other organs lead to symptoms and dysfunction (Fig. 63-2. Pathophysiology of Sickle Cell Crisis).
- Membrane abnormalities (rare):spur cell anemia (cirrhosis, anorexia nervosa), paroxysmal nocturnal hemoglobinuria, hereditary spherocytosis (increased RBC osmotic fragility, spherocytes), hereditary elliptocytosis (causes mild hemolytic anemia).
- Immunohemolytic anemia (positive Coombs' test, spherocytes): Two types: (a) warm antibody (usually IgG): idiopathic, lymphoma, chronic lymphocytic leukemia, systemic lupus erythematosus, drugs (e.g., methyldopa, penicillins, quinine, quinidine, isoniazid, sulfonamides); and (b) cold antibody-cold agglutinin disease (IgM) due to Mycoplasma infection, infectious mononucleosis, lymphoma, idiopathic; paroxysmal cold hemoglobinuria (IgG) due to syphilis, viral infections.
- Mechanical trauma (macro- and microangiopathic hemolytic anemias; schistocytes): prosthetic heart valves, vasculitis, malignant hypertension, eclampsia, renal graft rejection, giant hemangioma, scleroderma, thrombotic thrombocytopenic purpura, hemolytic-uremic syndrome, disseminated intravascular coagulation, march hemoglobinuria (e.g., marathon runners, bongo drummers).
- Direct toxic effect: infections (e.g., malaria, Clostridium perfringens toxin, toxoplasmosis).
- Hypersplenism (pancytopenia may be present).
Elevated RI, polychromasia and nucleated RBCs on smear; also spherocytes, elliptocytes, schistocytes, or target, spur, or sickle cells may be present depending on disorder; elevated unconjugated serum bilirubin and LDH, elevated plasma hemoglobin, low or absent haptoglobin; urine hemosiderin present in intravascular but not extravascular hemolysis, Coombs' test (immunohemolytic anemias), osmotic fragility test (hereditary spherocytosis), hemoglobin electrophoresis (sickle cell anemia, thalassemia), G6PD assay (best performed after resolution of hemolytic episode to prevent false-negative result).
| TREATMENT | ||
AnemiaGENERAL APPROACHESThe acuteness and severity of the anemia determine whether transfusion therapy with packed RBCs is indicated. Rapid occurrence of severe anemia (e.g., after acute GI hemorrhage resulting in Hct<25%, following volume repletion) or development of angina or other symptoms is an indication for transfusion. Hct should increase 3-4% (Hb by 10 g/L [1 g/dL]) with each unit of packed RBCs, assuming no ongoing losses. Chronic anemia (e.g., vitamin B12 deficiency), even when severe, may not require transfusion therapy if the pt is compensated and specific therapy (e.g., vitamin B12) is instituted. SPECIFIC DISORDERS
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