Acute Respiratory Distress Syndrome Flashcards
What is ARDS?
Massive pulmonary oedema that occurs due to increased permeability of alveolar capillaries.
This reduces gas exchange causing breathlessness.
It’s non-cardiogenic pulmonary oedema
Why might ARDS cause alveoli to collapse?
The increased fluid in the alveoli causes the surfactant to spread and this reduces the surfactants role in supporting the alveoli.
What causes ARDS?
Inflammatory mediators that are released with direct lung injury or secondary to a systemic insult
What is the most common cause of ARDS?
Sepsis
What are some causes of ARDS?
Sepsis Trauma Burns DIC Acute pancreatitis Blood transusion Toxic smoke inhalation
What are some pulmonary causes of ARDS?
Pneumonia Gastric aspiration Inhalation injury Burns Vasculitis Near drowning
What are some non-pulmonary causes of ARDS?
Sepsis Acute pancreatitis Trauma Liver injury Head injury Burns Drugs/ toxins
What are the features of ARDS?
Breathlessness Cyanosis Fatigue Confusion Tachypnoea Tachycardia Diffuse crackles Features of shock- cold peripheries and above
(Features depending on cause- e.g. infection, UTI…)
What are some investigations for ARDS?
CXR
What features would suggest dyspnoea due to heart failure?
Raised JVP Peripheral oedema Cardiomegaly S3 heart sound Raised BNP Paroxysmal nocturnal dyspnoea Raised PCWP (Pulmonary capillary wedge pressure) >19mmHg
What criteria are used to diagnose ARDS?
Acute onset
CXR shows bilateral infiltrates
Lack of heart failure- PCWP <19mmHg, normal BNP, ECHO
Ratio of PaO2:FIO2 <200
Last one means there is reduced gas transfer
What is the management for ARDS?
Send to ITU
High flow oxygen
CPAP with high PEEP to prevent alveolar collapsing
Circulatory support- (care with fluids as cause oedema), diuretics
Haemodialysis if signs of renal failure
Treat the cause e.g. broad spectrum ABx if sepsis
What is the PCWP?
Pulmonary capillary wedge pressure
Measured using a Swan- Ganz catheter, it indicates the pressure of the pulmonary vein/ left atrium and is typically raised in heart failure. IT above >19mmHg suggests that there is heart failure.
What blood test can you do if considering heart failure as a cause for oedema?
BNP
What is a raised PCWP?
Above 19mmHg
