Acute Respiratory Distress Syndrome

Acute Respiratory Distress Syndrome (ARDS)

Acute,diffuse,inflammatory lung injury associated with variety of etiologies.

 

Clinical diagnosis (Berlin definition)

All of the following criteria should be present

 1. Respiratory Distress within 7 days.

 2. Bilateral lung opacities on chest xray or CT.

 3. Respiratory failure not explained by heart failure or volume overload.

 4. PaO2/FiO2 < 300

 

Severity of ARDS (based on PaO2/FiO2)

  • Mild : > 200 <= 300

  • Mod : > 100 <= 200

  • Sev : <= 100

Note – if ABG is not available then in place of PaO2/FiO2 , SaO2/FiO2 can also be taken with value 315.

 

Etiology

  • Direct – Pneumonia, Aspiration, Inhalational lung injury, Chest trauma, Near drowning

  • Indirect – Sepsis, Shock, Trauma, Cardiopulmonary bypass, TRALI, Burns, Increased ICT.

 

Pathophysiology

Fluids accumulation in the lungs not explained by heart failure ( noncardiogenic pulmonary edema). Triggering event is cytokine mediated endothelial leak followed by migration of inflammatory cells.

 

Complications

  • Lung – pulmonary embolism, barotrauma, VAP

  • GI – ulcer , bacterial translocation, bleeding

  • Neuro – Hypoxic brain injury

  • Cardiac – arrhythmia, myocardial dysfunction

  • Renal – AKI

  • Others – malnutrition, pneumothorax, electrolyte imbalance, atelectasis, multiorgan dysfunction, DVT,etc

 

Management

  • Usually supportive. If etiology found then treating etiology like sepsis with antibiotics.

  • Mechanical ventilation- Low tidal volume

  • Usually no role of corticosteroids.

  • others

  • Sedation

  • Muscle relaxant

  • Fluid management

  • Nutrition

  • Prone ventilation

  • Extracorporeal membrane oxygenation (ECMO)

 

Prognosis

Poor with mortality more than 40%