Lesson 19: Sickle Cell Anemia

Sickle Cell Anemia

Overview

  • Inherited disorder affecting erythrocytes.
  • Key characteristic: Amino acid substitution (valine for glutamic acid) on beta globulin chain.

Effects on RBC Function

  • Deoxygenation of HgbS leads to sickling, altering RBC geometry.
  • Sickled cells clump, causing microvascular obstruction in vital organs and joints.
  • Lifespan of sickled cells: 12-17 days vs. normal RBC lifespan: 120 days.

Crisis Triggers

  • Factors that can trigger sickle-cell crisis (avoid during perioperative period):
    • Pain
    • Hypothermia
    • Hypoxemia
    • Acidosis
    • Dehydration

Complications of Sickle Cell Disease

  • Vaso-Occlusive Crisis:

    • Most common manifestation.
    • Results in impaired tissue perfusion and ischemic injury.
    • Treatment: Analgesics and hydration; Hydroxyurea can reduce incidence/severity.

  • Acute Chest Syndrome:

    • Significant source of mortality (1-20%).
    • Mechanics: Thrombosis, embolism, infection; more common in children.
    • Diagnosis: New lung infiltrates on CXR + chest pain/cough/dyspnea/wheezing.

  • Sequestration Crisis:

    • Rapid removal of RBCs by spleen leads to anemia and hemodynamic instability.

  • Aplastic Crisis:

    • Short RBC lifespan; viral infections (e.g., parvovirus B19) lead to bone marrow suppression and anemia.

  • Pneumococcal Disease:

    • Highest risk in children.
    • Prophylaxis: Vaccination and daily penicillin until age five.

Additional Complications

  • Asthma prevalence: 50% of patients.
  • Pulmonary hypertension prevalence: 10% of patients.