ARDS

Question 1

Explain ARDS:

Answer 1

Lung Damage and inflammaotry mediators trigger increased capillary permeability & so pulmonary oedema, fibrosis and further damage to alveoli.

Oedema -> Lower diffusion
Fibrosis -> Lower diffusion & Compliance
Damage to pneumocytes -> Surfactant Loss -> Low compliance

Its technically a restrictive interstial lung disease

Question 2

What causes ARDS?

Answer 2

Either a direct lung injury or secondary to a systemic illness:

Trauma - Pneumonia - Vasculitis - Gastric Aspiration - Shock - Septicaemia - Pancreatitis - Liver Failure - Haemorrhage - Transfusion - Heroin - Fat Embolism - Burns - Eclampsia

Question 3

What criteria are needed for ARDS?

Answer 3

1) Acute Onset
2) Radiological Evidence
3) No evidence of CHF (PCWP <19mmHg)
4) PaO2/FiO2 <300

Question 4

What are the signs/symptoms of ARDS?

Answer 4

Tachypnoea
Tachycardia
Dyspnoea
Cyanosis
Bilateral Crackles
Peripheral Vasodilation

Question 5

How do we investigate ARDS?

Answer 5

FBC + U&E + LFT + CRP
ABG
CXR -> Bilateral pulmonary infiltrates
Pulm. artery catheter to measure Pulm. Capillary Wedge Pressure (PCWP)

Question 6

How do we manage ARDS?

Answer 6

ITU!!
CPAP or Mech Ventilation while treating cause
Avoid high tidal volumes as they can cause pneumothorax by stretching damaged fibrosed areas of lung

Question 7

How do we determine severity of ARDS?

Answer 7

Combination of symptoms and PaO2/FiO2.
200-300 Mild (still kills 27%)
100-200 Moderate
<100 Severe