Congestion and oedema Flashcards
darcys law
flow = change in pressure over resistance
congestion
relative excess of blood in vessels of tissue or organ. passive process, secondary phenomenon, can be acute or chronic
examples of congestion
DVT, hepatic cirrhosis, congestive cardiac failure, hepatic central venous congestion
hepatic cirrhosis
results from liver damage, regenerating liver forms nodules of hepatocytes with intervening fibrosis, loss of normal architecture portal blood flow blocked, collateral circulation, local chronic congestion- haemorrhage risk
collateral circulation
shunts, various sites anastomose with the systemic circulation. main street blocked so use side streets and alleys
congestive cardiac failure
heart unable to clear blood, right and left ventricles, decreased CO, decreased GFR which causes activation of renin angiotensin alderosterone system, increase sodium and water retention, increase fluid in body, increase fluid in veins. heart cannot clear blood, back pressure, blood damned back.
normal microcirculation
driven by hydrostatic pressure, balanced by osmotic pressures and endothelial permeability, filtration from capillary beds to interstitium to capillaries and lymphatics
oedema
accumulation of fluid in extravascular compartment, ECF and body cavities
peripheral oedema
increased interstitial fluid in tissues
effusions
fluid collection in body cavities eg pleural, pericardial, joint, abdominal cavity- ascites
oedema transudate
not much protein or albumin, few cells, lots of water and elctrolytes, low specific gravity, alterations in haemodynamic forces that act across capillary wall
oedema exudate
as a result of inflammatory due to increase vascular permeability, something else going on eg tumour inflammation allergy, higher protein content, water and electrolytes, high specific gravity
pulmonary oedema due to left ventricular failure
increased left arterial pressure, increased pulmonary vascular pressure, increased pulmonary blood volume, increased pressure, increased filtration and pulmonary oedema
pulmonary oedema in lungs
perivascular and interstitial transudate, progressive oedematous widening of alveolar septa, accumulation of oedema fluid in alveolar spaces
peripheral oedema
right heart failure, cannot empty right ventricle in systole so blood retained in systemic veins which leads to increased pressure in capillaries increased filtration and then peripheral oedema,
congestive cardiac failure and oedema
right and left ventricles both fail, pulmonary oedema and peripheral oedema at the same time, all about hydrostatic pressure
lymphatic blockage
lymphatic obstruction leads to hydrostatic pressure upset, lymphatic drainage is required for normal flow, if blocked then lymphedema eg breast cancer may require radiotherapy to axilla which leads to fibrosis which leads to decreased outflow which leads to oedema of upper limb
oedema in abnormal renal function
abnormal renal function results in sodium chloride and water retention. this is secondary in heart failure which reduces renal blood flow, and can be primary if acute tubular damage eg hypotension, decreased renal function is due to lack of salt and water, lack of intravascular fluid volume, leads to secondary increase in capillary pressure and then oedema
low protein oedema occurs when (examples)
nephrotic syndrome, hepatic cirrhosis, malnutrition
how does low protein cause oedema
low protein causes low capillary oncotic pressure, leads to increased filtration
permeability oedema
damage to endothelial lining leads to increase pores in membrane which leads to osmotic force moving towards zero and proteins and larger molecules can leak out not just water
permeability oedema examples
acute inflammation such as pneumonia, burns
