Episode 195: ARDS

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Apr 1, 2024

Exploring the diagnostic criteria and severity levels of ARDS, differentiation from cardiogenic pulmonary edema, pathophysiology phases, etiology, and comprehensive management strategies including fluid management, steroids, oxygenation techniques, and mechanical ventilation goals. Advanced strategies discussed are salvage ventilation modes, prone positioning, inhaled pulmonary vasodilators, and VV ECMO for unresponsive cases.

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ANECDOTE

Classic Night Shift ARDS Case

A 70-year-old with ILD and sick contacts presented febrile and hypoxic, saturating 65% on room air, illustrating classic ARDS presentation.
This case highlights how preexisting lung disease and infection can precipitate rapid decompensation.

INSIGHT

Berlin Criteria And Severity

ARDS is defined as non-cardiogenic pulmonary edema using the Berlin criteria within seven days and bilateral infiltrates.
Severity hinges on PaO2/FiO2 with mild 200–300, moderate 100–200, and severe <100 mmHg.

INSIGHT

High Incidence And Mortality

ARDS is common in ventilated ICU patients, occurring in up to a quarter of them.
Mortality is high, often 35–45%, usually driven by multi-organ failure.

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We review Acute Respiratory Distress Syndrome

Hosts:
Sadakat Chowdhury, MD
Brian Gilberti, MD

Download Leave a Comment 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