Episode 195: ARDS
We review Acute Respiratory Distress Syndrome
Hosts:
Sadakat Chowdhury, MD
Brian Gilberti, MD
https://media.blubrry.com/coreem/content.blubrry.com/coreem/ARDS.mp3
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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,