Oedema Flashcards
List the 4 causes of oedema
Raised capillary pressure (Pc)
Reduced plasma osmotic pressure (πc)
Lymphatic insufficiency
Increases capillary permeability
Define oedema
Accumulation of fluid in the in the interstitial space
Does an increase or decrease in net filtration pressure (NFP) lead to oedema
An increase in NFP supports oedema
Give causes for a raised capillary pressure (Pc)
Arteriolar dilation (thus more blood flow)
Raised venous pressure (causes a back pressure)
List causes of raised venous pressure
Left ventricular failure (pulmonary oedema)
Right ventricular failure (systemic oedema)
Prolonged standing
Why does reduced plasma osmotic pressure cause oedema?
Plasma osmotic pressure (πc) decrease --> less reabsorption of interstitial fluid into capillary --> More oedema
The πc decrease can occur due to decreased plasma protein
What causes reduced plasma osmotic pressure (πc)?
- Malnutrition
- Protein malabsorption
- Excessive excretion
- Hepatic failure
Why does lymphatic insufficiency cause oedema?
The lymphatics aren’t taking away excess fluid
What can cause lymphatic insufficiency?
Lymph node damage
Filariasis
What can cause increased capillary permeability?
Inflammation
Protein leakage due to histamine
How is pulmonary oedema caused?
Left ventricular failure --> back pressure in pulmonary veins --> pulmonary capillary pressure (πc) increases --> net filtration pressure (NFP) increases --> Oedema
How does low vascular resistance in the pulmonary circulation reduce the chance of pulmonary oedema?
Low vascular resistance --> capillary pressure (πc) is low --> Net filtration pressure is low --> Less oedema
What adaptations help avoid pulmonary oedema?
- low pulmonary vascular resistance
- efficient lymphatics
