Sickle-Cell Anemia

  1. General information (see Figure 5.2 below)
    1. Most common inherited disorder in US African American population; sickle cell trait found in 10% of African Americans
    2. Autosomal recessive inheritance pattern
    3. Individuals who are homozygous for the sickle cell gene have the disease (more than 80% of their hemoglobin is abnormal [HgbS]).
    4. Those who are heterozygous for the gene have sickle cell trait (normal hemoglobin predominates, may have 25%-50% HgbS). Although sickle cell trait is not a disease, carriers may exhibit symptoms under periods of severe anoxia or dehydration.
    5. In this disease, the structure of hemoglobin is changed; the sixth rung of the beta chain changes glutamine for valine.
    6. HgbS (abnormal Hgb), which has reduced oxygen-carrying capacity, replaces all or part of the hemoglobin in the RBCs.
    7. When oxygen is released, the shape of the RBCs changes from round and pliable to crescent shaped, rigid, and inflexible.
    8. Local hypoxia and continued sickling lead to plugging of vessels.
    9. Sickled RBCs live for 6-20 days instead of 120, causing hemolytic anemia.
    10. Usually no symptoms prior to age 6 months; presence of increased level of fetal hemoglobin tends to inhibit sickling.
    11. Death often occurs in early adulthood due to occlusion or infection.
    12. Sickle cell crisis
      1. Vaso-occlusive (thrombocytic) crisis: most common type
        1. crescent-shaped RBCs clump together; agglutination causes blockage of small blood vessels.
        2. blockage causes the blood viscosity to increase, producing sludging and resulting in further hypoxia and increased sickling.
      2. Splenic sequestration: often seen in toddler/preschooler
        1. sickled cells block outflow tract resulting in sudden and massive collection of sickled cells in spleen.
        2. blockage leads to hypovolemia and severe decrease in hemoglobin and blood pressure, leading to shock.
  2. Medical management: sickle cell crisis
    1. Drug therapy
      1. Urea: interferes with hydrophobic bonds of the HgbS molecules
      2. Analgesics/narcotics to control pain
      3. Antibiotics to control infection
    2. Exchange transfusions
    3. Hydration: oral and IV
    4. Bed rest
    5. Surgery: splenectomy
  3. Assessment findings
    1. First sign in infancy may be "colic" due to abdominal pain (abdominal infarct)
    2. Infants may have dactylitis (hand-foot syndrome): symmetrical painful soft tissue swelling of hands and feet in absence of trauma (aseptic, self-limiting)
    3. Splenomegaly: initially due to hemolysis and phagocytosis; later due to fibrosis from repeated infarct to spleen
    4. Weak bones or spinal defects due to hyperplasia of marrow and osteoporosis
    5. Frequent infections, especially with H. influenzae and D. pneumoniae
    6. Leg ulcers, especially in adolescents, due to blockage of blood supply to skin of legs
    7. Delayed growth and development, especially delay in sexual development
    8. CVA/infarct in the CNS
    9. Renal failure: difficulty concentrating urine due to infarcts; enuresis
    10. Heart failure due to hemosiderosis
    11. Priapism: may result in impotence
    12. Pain wherever vaso-occlusive crisis occurs
    13. Development of collateral circulation
    14. Diagnostic tests
      1. Hgb indicates anemia, usually 6-9 g/dl
      2. Sickling tests
        1. sickle cell test: deoxygenation of a drop of blood on a slide with a cover slip; takes several hours for results to be read; false negatives for the trait possible.
        2. Sickledex: a drop of blood from a finger stick is mixed with a solution; mixture turns cloudy in presence of HgbS; results available within a few minutes; false negatives in anemia clients or young infants possible.
      3. Hgb electrophoresis: diagnostic for the disease and the trait; provides accurate, fast results.
  4. Nursing interventions: sickle cell crisis
    1. Keep child well hydrated and oxygenated.
    2. Avoid tight clothing that could impair circulation.
    3. Keep wounds clean and dry.
    4. Provide bed rest to decrease energy expenditure and oxygen use.
    5. Correct metabolic acidosis.
    6. Administer medications as ordered.
      1. Analgesics: acetaminophen, meperidine, morphine (avoid aspirin as it enhances acidosis, which promotes sickling)
      2. Avoid anticoagulants (sludging is not due to clotting)
      3. Antibiotics
    7. Administer blood transfusions as ordered.
    8. Keep arms and legs from becoming cold.
    9. Decrease emotional stress.
    10. Provide good skin care, especially to legs.
    11. Test siblings for presence of sickle cell trait/disease.
    12. Provide client teaching and discharge planning concerning
      1. Pre-op teaching for splenectomy if needed
      2. Genetic counseling
      3. Need to avoid activities that interfere with oxygenation, such as mountain climbing, flying in unpressurized planes