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, and ventilation mode adjustments based on patient response.

ARDSnet Table: ventilator_protocol_2008-07

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