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Acute Respiratory Distress Syndrome (ARDS)

Judd Heideman

Background

  • A syndrome of diffuse inflammation and injury of the alveoli and capillary endothelium leading to fluid and protein accumulation in the interstitium and alveoli, pulmonary edema, and hypoxemic respiratory failure; 30-50% mortality rate
  • Triggers:
  • Pulmonary
    • Pneumonia (viral and bacterial) • Lung contusion
    • Direct inhalation injury • Aspiration
    • Primary graft dysfunction of pulmonary transplant
  • Extra-pulmonary
    • Sepsis (most common cause) • HSCT
    • Trauma • Burns
    • Massive blood transfusions/TRALI • Pancreatitis
    • Drugs (amiodarone, chemotherapy, cocaine, opioids)

Evaluation

  • Diagnosis: Berlin Criteria
  • New or worsening respiratory symptoms beginning within one week of diagnosis
  • New bilateral opacities present on chest radiograph or CT chest
    • Not explained by effusions, collapse of lobe/lung, or nodules
  • Absence of left heart failure or volume overload
  • Severity: based on PaO2/FiO2 ratio with a PEEP ≥ 5 cm H2O
  • PaO2 = arterial partial pressure of O2 (requires ABG)
  • FiO2 = fraction of inspired oxygen (expressed as a decimal between 0.21 and 1.0)
PaO2/FiO2 ratio PEEP
Mild 201-300 ≥5
Moderate 101-200 ≥5
Severe \<100 ≥5

Management

  • Frequently requires intubation; non-invasive ventilation not a great treatment
  • Low tidal volume (Vt) ventilation mortality benefit
  • Goal Vt = 4-8 mL/kg of predicted body weight (obese patients don’t have bigger lungs)
  • Plateau pressure goal: ≤30 cm H2O
  • Oxygenation goal: PaO2 55-80 or SpO2 88-95%
  • pH goal: ≥7.20, “permissive hypercapnia”
  • Treat the underlying cause (see “Triggers” above)
Last update: 2022-06-02 13:28:55