Congestion and oedema Flashcards
What is Darcy’s law
Flow = pressure gradient / resistance
What is congestion
Relative excess of blood in vessels of tissue or organ
Clinical example of local acute congestion
Deep vein thrombosis
Clinical example of local chronic congestion
hepatic cirrhosis
Clinical example of generalised acute congestion
congestive cardiac failure
Why does DVT cause congestion
Thrombus blocks veins causing blood to back up into veins, venules and capillaries
Reduced outflow of blood, reduced pressure gradient so reduced flow
What does hepatic cirrhosis result from
Serious liver damage - eg hepatitis or alcohol
How does hepatic cirrhosis cause congestion
Liver tries to regenerate and forms nodules of hepatocytes with fibrosis between
Loss of normal architecture means altered hepatic blood flow, portal vein blocked so congestion
What is local chronic congestion at risk of
haemorrhage
Congestive cardiac failure pathophysiology
Heart unable to clear blood either because of ischaemia or valve disease
Reduced cardiac output means reduced glomerular filtration rate and activation of renin-angiotensin-aldosterone system, increasing amount of fluid
Effect of congestive cardiac failure on lungs
Pulmonary oedema
Effect of congestive cardiac failure on liver
Central venous congestion
Clinical signs of congestive cardiac failure
Crepitations in lungs Tachycardia Raised JVP Hepatomegaly Peripheral oedema
What is ‘nutmeg’ liver
Due to hepatic central venous congestion
Pericentral hepatocytes are red (stasis of poorly oxygenated blood)
Periportal hepatocytes are pale
What three things ultimately effect movement of fluid through capillary beds
Hydrostatic pressure from heart
Osmotic pressure to balance
Endothelial permeability and area
Which side of capillaries has high capillary hydrostatic and lower capillary oncotic pressure (filtration)
Arterial
Which side does reabsorption occur
Venous
Which equation shows the balance of normal components of microcirculation
Starling’s equation
What is oedema
Accumulation of abnormal amounts of fluid in the extravascular compartment
What is oedema called when it is:
a) increased interstitial fluid in tissues
b) fluid collections in body cavities
a) peripheral oedema
b) effusions
Differences between transudate and exudate oedema
Transudate - alterations in haemodynamic forces, cardiac failure, not much protein, lots of water and electrolytes, low specific gravity
Exudates - part of inflammatory process, tumour inflammation allergy, higher protein content, high specific gravity
When does pitting oedema occur
Left and right heart failure (congestive cardiac failure)
What happens if the lymphatic system is blocked
Lymphoedema
