Acute Chest Syndrome

Aka: Acute Chest Syndrome

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II. Epidemiology

  1. Most common cause of death in Sickle Cell Anemia
  2. Most common in children (ages 2 to 4 years old)
  3. Less common in adults, but much more severe with higher mortality when it occurs

III. Precautions

  1. Acute Chest Syndrome is the leading cause of death in Sickle Cell Anemia
  2. Early diagnosis and treatment is critical to survival

IV. Pathophysiology

  1. Precipitating factors (see below) reduce oxygen tension in small lung vessels
  2. Deoxygenated Hemoglobin S polymerizes
  3. Localized vaso-Occlusion cascades into worsening sickling and obstruction
  4. Vascular endothelium undergoes injury, leading to Platelet aggregation and thrombosis

V. Risk Factors: Precipitating

  1. Children
    1. Young age (<4 years old)
    2. Comorbid Asthma
    3. Acute respiratory infection (Bronchitis, Pneumonia)
      1. Viruses
      2. Mycoplasma pneumonia (most common Bacterial cause)
  2. Adults
    1. Sickle Cell Crisis (precedes Acute Chest Syndrome by 24 to 72 hours)
    2. Pulmonary Infarction or direct vaso-occlusive disease
    3. Acute fatty embolism or necrotic Bone Marrow embolism
    4. Acute respiratory infection (Bronchitis, Pneumonia)
      1. Chlamydia pneumoniae (most common)
      2. Legionella
      3. Mycoplasma pneumonia

VI. Symptoms

  1. Acute onset cough
  2. Acute Chest Pain
  3. Wheezing
  4. Dyspnea
  5. Fever

VII. Signs

  1. Presents as Pneumonia with comorbid Sickle Cell Anemia
    1. However has much higher mortality than Pneumonia
    2. Always assume Acute Chest Syndrome first in those with Sickle Cell Anemia
  2. Fever (children; adults are typically afebrile)
  3. Tachypnea and other signs respiratory distress
  4. Hypoxia

VIII. Differential Diagnosis

  1. Pneumonia
  2. Acute Coronary Syndrome
  3. Asthma Exacerbation
  4. Pulmonary Embolism and Pulmonary Infarction
  5. Symptomatic severe Anemia
  6. Splenic Sequestration (under age 4 years old)
  7. Fat embolism
  8. Pulmonary parenchyma with Sickle Cell Crisis

IX. Labs

  1. Complete Blood Count
  2. Reticulocyte Count
  3. Serum chemistry panel
  4. Blood Culture
  5. Sputum Culture
  6. Serum Protein Electrophoresis
    1. Hemoglobin-S before and after transfusion

X. Imaging

  1. Chest XRay (or Chest CT)
    1. Indicated in all febrile Sickle Cell Anemia patients without obvious infection source
    2. New lung infiltrate suggestive of Pneumonia
    3. Children often have right middle lobe involvement
    4. Adults typically have multi-lobar involvement

XI. Diagnosis: Requires Chest XRay infiltrate AND one of 4 criteria

  1. Chest Pain
  2. Fever >101.3F (38.5 C)
  3. Respiratory symptoms
  4. Hypoxemia

XII. Diagnosis: Red Flag findings associated with higher mortality

  1. White Blood Cell Count doubles over baseline
  2. Platelet Count >200,000
  3. Hemoglobin decreases more than 1 g/dl from baseline
  4. Multilobar infiltrates

XIII. Monitoring

  1. Continuous Pulse Oximetry for Hypoxemia
    1. Arterial Blood Gas indicated for drop in oximetry

XIV. . Other targets of monitoring

    1. Bronchospasm
    2. Acute Anemia

XV. Management

  1. Admit to Intensive Care Unit
    1. Admit all patients with suspected ACS (even if relatively well appearing)
    2. However, may consider discharge if normal Vital Signs and Chest XRay, mild cough and controlled pain
  2. Consult with hematology
  3. Oxygen to keep Oxygen Saturation >90-92% (PaO2 > 60 mmHg)
    1. Use only if patient is hypoxemic
    2. Avoid hyperoxygenation due to marrow suppression and worse outcomes
  4. Incentive Spirometry
    1. Frequently while awake (at least every 2 hours)
    2. Encourage patients to perform 10-15 times during commercial breaks
  5. Broad spectrum Antibiotics (one third of cases are due to infection)
    1. Acute Chest Syndrome is clinically indistinguishable from Bacterial Pneumonia
    2. Includes coverage for atypical respiratory Bacteria
    3. Sickle Cell Anemia patients are higher risk for Mycoplasma pneumonia and Chlamydia Pneumonia
    4. Example protocol: Ceftriaxone and Azithromycin (typical Pneumonia coverage)
    5. Consider Vancomycin for recent hospitalization and concern for healthcare acquired Pneumonia
  6. Opioid Analgesics
    1. See Sickle Cell Crisis for pain management
  7. Intravenous Fluids
    1. Start with crystalloid (NS or LR) at 1 to 1.5x maintenance and adjust based on urinary output
    2. May start with crystalloid bolus of 10-20 cc/kg for 1-2 Liters (however avoid Fluid Overload and reasses)
  8. Reactive airway disease management if present
    1. Consider Bronchodilators (e.g. Albuterol)
    2. BIPAP or CPAP may be used for increased respiratory distress
  9. Mechanical Ventilation risk factors
    1. Platelet Count <200,000
    2. Multilobular involvement
    3. Coronary Artery Disease
  10. Exchange Transfusion
    1. Goal: Decrease sickled Hemoglobin to <30% in Acute Chest Syndrome
    2. Blood should be cross-matched, Leukocyte depleted, and irradiated
    3. Consider Consultation with a Sickle Cell Disease specialist
    4. Indications
      1. Oxygen Saturation <90% despite Supplemental Oxygen or A-a Gradient >30
      2. Increasing respiratory distress (Tachypnea, Hypoxia, increased work of breathing)
      3. Progressive Pulmonary Infiltrates (esp. multilobular)
      4. Decreasing Hemoglobin despite simple transfusion (or Hemoglobin >9 g/dl)
    5. Standard Blood Transfusion may be used as alternative if exchange transfusion not available
      1. Indicated for Hemoglobin more than 1 g/dl below baseline
      2. However increased risk of Cerebrovascular Accident due to increased blood viscosity
      3. Transfuse one unit at a time and observe for 6 hours before transfusing additional units
      4. Indications to transfuse 2 units initially
        1. Hemoglobin <8 mg/dl
        2. Rapid decompensation
    6. Bedside exchange transfusion may also be done manually
      1. Exchange 70 cc/kg for a single volume exchange
      2. Withdraw in 50 cc volumes from one arm, and infuse into the other arm
    7. Adverse effects
      1. Typical risks (blood-borne infection, acute Transfusion Reaction, volume overload)
      2. Hyperviscosity Syndrome (e.g. CVA)
      3. Delayed hemolytic reaction (at days 3-14)
      4. Transfusion associated lung injury (TRALI)
        1. Presents within 6 hours of transfusion with Pulmonary Edema, Hypotension, Dyspnea

XVI. Prevention

  1. Incentive Spirometry when hospitalized for Sickle Cell Crisis (VOC)
  2. Hydroxyurea reduces Acute Chest Syndrome Incidence by 50% (and sickle cell mortality 40%)

XVII. Complications

  1. Pulmonary fibrosis

XVIII. Prognosis

  1. Child: 3% mortality rate, overall less severe presentation than in adults over age 20 years
  2. Adult: 9 to 12% mortality rate (esp. Respiratory Failure)

XIX. References

  1. Glassberg and Weingart in Majoewsky (2012) EM: Rap 12(9): 2-3
  2. Welsh and Welsh (2016) Crit Dec Emerg Med 30(11): 15-23
  3. Lowe and Wang (2018) Crit Dec Emerg Med 32(11): 17-25
  4. Jones (2024) Am Fam Physician 110(1): 58-64 [PubMed]
  5. Vichinsky (2000) N Engl J Med 342:1855-65 [PubMed]
  6. Yawn (2015) Am Fam Physician 92(12): 1069-76 [PubMed]

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