Acute Respiratory Distress syndrome (ARDS)
- May be caused by either direct lung injury or occur secondary to severe systemic illness
- Lung damage and release of inflammatory mediators causes increased capillary permeability and pulmonary oedema often accompanied by multiorgan failure
Causes
- Pulmonary
- Pneumonia
- Aspiration
- Inhalation
- Injury
- Vasculitis
- Contusion
- Pneumonia
- Other
- Shock
- Septicaemia
- Haemorrhage
- Multiple transfusions
- Pancreatitis
- DKA
- Acute liver failure
- Head injury
- Malaria
- Fat embolism
- Burns
- Obstetric events - pregnancy, eclampsia, amniotic fluid embolus
- Drugs/toxins – aspirin, heroin, paraquat
- Shock
Clinical features
- Cyanosis
- Tachypnoea
- Tachycardia
- Peripheral vasodilation
- Bilateral fine inspiratory crackles
Investigations
- FBC, U&Es, LFT, amylase, clotting
- Blood cultures
- ABG
- CXR
- Pulmonary artery catheter to measure pulmonary capillary wedge pressure
Diagnostic criteria
- Acute onset
- CXR – bilateral pulmonary infiltrate
- Pulmonary capillary wedge pressure <19mmHg or lack of clinical CCF
- Refractory hypoaemia
- Reduced total thoracic compliance <30ml/cm H2O
Management
- Respiratory support
- CPAP with 40-60% O2
- Mechanical ventilation – low tidal volume, low pressure approach
- CPAP with 40-60% O2
- Circulatory support
- Monitor central pressures using Swan-Gantz
- Give ionotropes (e.g. dobutamine), vasodilators and blood transfusion
- Consider treating pulmonary hypertension with nitric oxide
- Haemofiltration maybe needed for renal failure
- Monitor central pressures using Swan-Gantz
- Sepsis
- Broad spectrum antibiotics – avoid nephrotoxic ones
- Broad spectrum antibiotics – avoid nephrotoxic ones
- Nutritional support
Prognosis
- Overall mortality 50-75%
- Depends on disease and the number of organs >3 organs involved for >1wk is invariably fatal