pathophysiology of congestion and oedema Flashcards
down what gradient does water (and all fluid in the body) flow?
pressure
what does Darcy’s law state and what does it mean phyiologically?
Q= change in pressure/resisitance
any changes in pressure or resistance of the cardiovascular system will result in a change in blood flow
what is congestion?
relative excess of blood in vessels of tissues or organ
does congestion involve active hyperaemia?
no
give an example of local acute congestion?
deep venous thrombosis
give an example of local chronic congestion?
hepatic cirrhosis
give an example of generalised acute congestion?
congestive cardiac failure
describe the pathophysiology of DVT causing infarction and ischaemia?
1.bloood backs up in the veins, venules and capillaries
2. decreased outflow of blood
3, local, acute congestion
4. decrease in pressure gradient
5. decrease in flow as a result of this
6. no O2 supply so ischaemia and infarction
what does hepatic cirrhosis result from?
serious liver damage from hepatitis B virus or alcohol
what is the pathophysiology of hepatic cirrhosis?
1, serious liver damage
- regenerating liver forms nodules of hepatocytes with intervening fibrosis
- this alters hepatic blood flow
- so causes congestion in portal vein and branches.
- increased portal venous pressure
- and there is an increase in collateral circulation
what are some consequences of portal-system hypertension?
blood is shunted to areas causing features like oesophageal varices and caput medisae
what is dangerous about oesophageal varices?
they only have a thin lining over them so can easily be ruptured, causing haemorrhage
what is congestive cardiac failure?
the heart is unable to clear blood from the right and left ventricles (the heart is an ineffective pump)
what is the pathophysiology of congestive cardiac disease?
- decrease in cardiac output
- decrease in renal glomerular filtration rate
- this causes the activation of the renin-angiotensin-aldosterone system
- this causes sodium and water retention
- therefore there is an increase in the amount of fluid in the body
- there is a fluid overload in the veins
what is the pathophysiology of pulmonary oedema caused by left ventricular failure?
- increase in left atrial pressure
- passive retrograde flwo to pulmonary veins, capillaries and arteries
- increase in vascular pressure
- increase in pulmonary blood volume
- increased hydrostatic pressure leads to increased filtration
what are the signs of central venous congestion?
increased JVP, hepatomegaly, peripheral oedema
what causes central venous congestion?
right heart failure-blood damns back to systemic circulation
what is the appearance of hepatic central venous congestion?
nutmeg appearance, red/brown and pale spotty appearance macroscopically
what is the route of fluid from the microcirculation?
capillaries-interstitium-capillaries and lymphatics
what are three components that affect net flux and filtration? and disturbance of any of these causes what?
- hydrostatic pressure
- oncotic pressure
- permeability characteristics and area of endothelium
causes oedema
what is oedema?
accumulation of abnormal amounts of fluid in the extravascular compartment
what are effusions and give some examples?
fluid collections in body cavities.
pleural, pericardial and joint effusions, ascites
what is transudate oedema caused by?
alterations in the haemodynamic forces which act across the capillary wall
what can cause transudate oedema?
- heart failure, fluid overload
- hypoproteinaemia
- lots of water and electrolytes
- low specific gravity
what are the causes of exudate oedema?
- inflammation
- tumour
- allergy
- higher protein/albumin content of cells
- high specific gravity
what is the pathophysiology of pulmonary oedema caused in the lungs?
- perivascular and interstitial transudate
- progressive oedematous widening of alveolar septa
- accumulation of oedema fluid in alveolar spaces
what is the pathophysiology of peripheral oedema from right heart failure?
- right heart failure
- blood retained in systemic veins
- increase in pressure in capillaries
- increase in filtration
- peripheral oedema
what kinds if oedema does congestive cardiac failure cause?
pulmonary oedema
peripheral oedema
what is the kind of oedema caused lymphatic system blockage?
lymphoedema
what are the common causes of lymphoedema?
- fibrosis from radiotherapy
- compression of lymphatic vessels eg. by tumour
- invasion of tumour into lymphatics
what is the pathophysiology of oedema in abnormal renal function?
- increased Na and water retention
- increased intravasclular fluid volume
- secondary increase in hydrostatic pressure
- oedema
give an example of a cause of primary abnormal renal function causing oedema?
hypertension causing acute tubular damage
give an example of a cause of secondary abnormal renal function causing oedema?
heart failure causing reduces renal blood flow
what is the pathophysiology of low protein oedema?
- decreased protein content of blood
- decreased oncotic pressure
- increased filtration
what are three causes low protein oedema?
nephrotic syndrome -leaky glomerular so lose protein
hepatic cirrhosis-liver can’t synthesise enough protein
malnutrition-insufficient intake of protein
what is the pathophysiology of permeability oedema?
- damage to endothelial lining
- increase in membrane pores
- water leaks out
- proteins and large molecules also leak out
what are some causes of permeability oedema?
burns acute inflammation (eg. pneumonia)
