congestion and oedema Flashcards
what is the equation for blood flow?
Q = delta P/R
what is congestion?
Relative excess of blood in vessels of tissue or organ
Passive process, secondary phenomenon
Not like acute inflammation - active hyperaemia
give examples of localised acute/ chronic and generalised acute congestion:
Local acute congestion - Deep vein thrombosis
Local chronic congestion - Hepatic cirrhosis
Generalised acute congestion - Congestive cardiac failure
describe the cause of deep vein thrombosis
Blood backs up in veins, venules, capillaries
decreased outflow of blood - local acute congestion
low-pressure gradient
low flow across the system (Flow = delta P/R)
hence -> low change in P
-> decreased flow
No O2-> ischaemia and infarction
describe the pathophysiology of hepatic cirrhosis:
Results from serious liver damage eg HBV, alcohol
Regenerating liver forms nodules of hepatocytes with intervening fibrosis
Loss of normal architecture
- altered hepatic blood flow
Portal blood flow blocked
- congestion in the portal vein and branches
- increased portal venous pressure
- collateral circulation
->several sites anastomose with systemic circulation
Local chronic congestion - haemorrhage risk
describe the pathophysiology of congestive cardiac failure
low Cardiac Output (CO)
low Renal Glomerular Filtration Rate (GFR)*
activation of the renin-angiotensin-aldosterone system
high Na and H2O retention*
high amount of fluid in the body
high Fluid (overload) in veins (Treatment: diuretics)
what is oedema?
Accumulation of fluid in the intercellular tissue compartment (extracellular fluid) and body cavities
how is transudate oedema caused?
Alterations in the haemodynamic forces which act across the capillary wall
Cardiac failure, fluid overload
Not much protein/albumin (few cells)
Lots of H2O & electrolytes
Low specific gravity
how is exudate oedema caused?
Part of the inflammatory process due to increased vascular permeability
Tumour, inflammation, allergy
Higher protein/albumin content (cells)
H2O & electrolytes
High specific gravity
describe how left ventricular failure caused pulmonary failure:
high left atrial pressure
-> Passive backward flow to pulmonary veins, capillaries and arteries
high pulmonary vascular pressure
high pulmonary blood volume
high capillary hydrostatic pressure
-> High filtration and pulmonary oedema
In lungs
-> perivascular and interstitial transudate
-> Progressive oedematous widening of alveolar septa
-> Accumulation of oedema fluid in alveolar spaces
describe how right ventricular failure leads to peripheral oedema
cannot empty RV in systole
Blood retained in systemic veins
-> High pressure in capillaries
-> high filtration
-> peripheral oedema
also, secondary portal venous congestion via the liver
describe how congestive heart failure leads to both peripheral and pulmonary oedema:
The right and left ventricles both fail
Pulmonary oedema and peripheral oedema occur at the same time
describe the pathophysiology of lymphatic blockage:
Lymphatic Obstruction – hydrostatic pressure upset
Lymphatic drainage is required for normal flow
If the lymphatic system is blocked -> lymphoedema
describe the pathophysiology of oedema in abnormal renal function:
Abnormal renal function results in Salt (NaCl) and H2O retention
Secondary in heart failure - reduced renal blood flow
Primary: acute tubular damage eg hypotension
renal function is the result of both
- high salt and H2O
- high intravascular fluid volume
- secondary high capillary hydrostatic pressure
- oedema
describe the pathophysiology of low protein oedema:
Oncotic Pressure - transudate
capillary oncotic pressure requires normal protein levels
Hypoalbuminaemia
-> low capillary oncotic pressure -> high filtration
