Acute Respiratory Distress Syndrome Flashcards
What is ARDS?
acute lung inflammation as a result of sepsis, pneumonia, trauma or aspiration.
What can ARDS result in?
shock, either through direct ischaemic damage, or as a result of reperfusion damage.
What are direct causes of ARDS?
trauma, aspiration pneumonia, fat embolism, alveolar haemorrhage
What are indirect causes of ARDS?
sepsis, systemic trauma, shock, stroke, drug overdose (aspirin, heroin), burns, liver failure, pancreatitis, massive blood transfusion, head injury, pregnancy, eclampsia, malaria
What is the pathology of ARDS?
results from local or systemic inflammatory processes. cytokines and other inflammatory mediators recruit macrophages and neutrophils to area. These then release other inflammatory agents, there is a disruption of the boundary between lung tissue and normal capillaries, leading to ‘leaking’ of blood products into air spaces. there is reduced lung compliance and disruption of surfactant leading to collapse of airways.
What can ARDS be difficult to differentiate from?
acute heart failure and infection
How is ARDS differentiated from acute heart failure?
by taking a pulmonary wedge pressure measurement
What are the signs/symptoms of ARDS?
dyspnoea tachycardia tachypnoea bilateral basal crepitations/other abnormal breath sounds chest pain peripheral vasodilation
What must be present to diagnose ARDS?
- Acute onset
- Pulmonary capillary wedge pressure of <19mmHg
- CXR - demonstrating bilateral diffuse infiltrates
- refractory hypoxaemia - PO2:FiO2 <200
What blood investigation would be used to diagnose ARDS?
amylase
FBC
U+E
CRP
What would arterial blood gases be like in ARDS?
- low O2 - often does not respond well to prescribed O2
- pH - can be low initially (due to respiratory acidosis), or may be high in the presence of sepsis, or as result of underlying cause
What would be seen on a chest X-ray in ARDS?
bilateral, widespread infiltrates. may take several hours to appear after onset of symptoms
What is the mortality of ARDS?
50-75%
What is the most important treatment for ARDS?
treat the underlying cause
If ARDS caught early what treatment may be given?
40-60% O2
why might mechanical ventilation be dangerous in ARDS?
high tidal volumes/pressures involved due to poor lung compliance, can lead to pneumothorax
When might mechanical ventilation be considered in ARDS?
if given oxygen and ABG O2 remains <8.2kPa.
What circulatory support may be given for ARDS?
- Give fluids
- consider pulmonary vasodilator to combat high intrapulmonary pressure (e.g. inhaled nitric oxide)
- consider an ionotrope (increase cardiac output without affecting rate) such as dobutamine
