Episode 195: ARDS

We review Acute Respiratory Distress Syndrome

Sadakat Chowdhury, MD
Brian Gilberti, MD

April 1st, 2024 Download Leave a Comment Tags: ,

Show Notes

  • Definition of ARDS:
    • Non-cardiogenic pulmonary edema characterized by acute respiratory failure.
    • Berlin criteria for diagnosis include acute onset within 7 days, bilateral pulmonary infiltrates on imaging, not fully explained by cardiac failure or fluid overload, and impaired oxygenation with PaO2/FiO2 ratio <300 mmHg, even with positive end-expiratory pressure (PEEP) >5 cm H2O.
  • Severity based on oxygenation (Berlin criteria):
    • Mild: PaO2/FiO2 200-300 mmHg
    • Moderate: PaO2/FiO2 100-200 mmHg
    • Severe: PaO2/FiO2 <100 mmHg
  • Epidemiology:
    • Occurs in up to 23% of mechanically ventilated patients.
    • Mortality rate of 30-40%, primarily due to multiorgan failure.
  • Differentiation from Cardiogenic Pulmonary Edema:
    • Chest CT shows diffuse edema and pleural effusion in cardiogenic edema; patchy edema, dense consolidation in ARDS.
    • Ultrasound may show diffuse B lines in cardiogenic edema; patchy B lines and normal A lines in ARDS.
  • Pathophysiology:
    • Exudative phase: Immune-mediated alveolar damage, pulmonary edema, cytokine release.
    • Proliferative phase: Reabsorption of edema fluid.
    • Fibrotic phase: Potential for prolonged ventilation.
  • Etiology:
    • Direct lung injury (pneumonia, toxins, aspiration, trauma, drowning) and indirect causes (sepsis, pancreatitis, transfusion reactions, certain drugs).
  • Diagnostics:
    • Comprehensive workup including imaging (chest X-ray, CT), laboratory tests (complete blood count, basic metabolic panel, blood gases), and specialized tests depending on suspected etiology.
  • Management Strategies:
    • Steroids: Beneficial in certain etiologies of ARDS, with specifics on dosing and duration.
    • Fluid Management: Conservative fluid strategy, diuresis guided by patient condition.
    • Ventilation: Non-invasive ventilation (NIV) preferred in specific cases; mechanical ventilation strategies to ensure lung-protective ventilation.
    • Proning: Used in severe ARDS to improve oxygenation.
    • Inhaled Vasodilators: Used for refractory hypoxemia and specific complications like right heart failure.
    • Extracorporeal Membrane Oxygenation (ECMO): Considered for severe ARDS as salvage therapy.
    • Supportive Care: Includes monitoring and management of complications, nutrition, and physical therapy.
  • Ventilation Specifics:
    • Tidal volume and pressure settings aim for lung-protective strategies to prevent ventilator-induced lung injury.
    • Permissive hypercapnia, plateau pressure, PEEP, and ventilation mode adjustments based on patient response.
    • ARDSnet Table: ventilator_protocol_2008-07

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