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Tags: Critical Care, Pulmonary

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