Acute Respiratory Distress Syndrome (ARDS)

Question 1

What is Acute Respiratory Distress Syndrome (ARDS)?

Answer 1

ARDS, or acute lung injury, may be caused by direct lung injury or secondary to severe systemic illness.

Lung damage & release of inflam. mediators cause increased capillary permeability and non-cardiogenic pulmonary oedema, often accompanied by multiorgan failure.

Question 2

What are the causes of ARDS?

Answer 2

Pulmonary;

• Pneumonia
• Gastric aspiration
• Inhalation injury
• Vasculitis
• Contusion (bruise)

Other;

• Shock
• Septicaemia
• Haemorrhage
• Multiple transfusions
• DIC
• Pancreatitis
• Acute liver failure
• Trauma
• Head injury
• Malaria
• Fat embolism
• Burns
• Obstetric events
• Drugs/ toxins (aspirin, hroin, paraquat)

Question 3

What are the clinical features of ARDS?

Answer 3

• Ackles! (Bilat. inspir. crackles)
• RR↑ & HR↑
• Dilation (peripheral vasodilation
• Syanosis (cyanosis)

Question 4

What investigations would you perform and what is the diagnostic criteria?

Answer 4

• FBC, U&E, LFT, amylase, clotting, CRP, blood cultures, ABG, CXR (bilateral pulmonary infiltrates)
• Pulmonary artery catheter to measure pumonary capillary wedge pressure (PCWP)

Requires 4 things for diagnosis;

1. Acute onset
2. CXR; bilateral infiltrates (pulmonary oedema)
3. Pulmonary capillary wedge pressure (PCWP) <19mmHg or lack of clinical congestive heart failure
4. Refractory hypoxemia with PaO₂:FiO₂ <200