Circulatory Disturbances I Flashcards
What is oedema?
Abnormal accumulation of fluid within interstitial fluid
What are the two types of oedema fluid?
- Non-inflammatory oedema (low protein/cell - transudate)
- Inflammatory oedema (protein/cell rich - exudate)
What are the 4 pathogeneses of oedema?
- Increased intravascular hydrostatic pressure
- Decereased plasma osmotic pressure - loss or lack of albumin
- Increased capillary peremeability - usually inflammatory in origin
- Decreased lymphatic drainage - (inflammation/compression)
How does increased intravascualr hydrostatic pressure result in oedema?
- Increased intravascular hydrostatic pressure as a result of increased blood volume in the microvasculature
- Can be localised or systemic/general
- Systemic caused by right (ascites portal venous system) or left-sided heart failure (pulmonary oedema - pulmonary venous system)
How does decreased osmotic pressure result in oedema?
Decrease in plasma proteins (albumin) = increased fluid filtration and decreased absorption ultimatley resulting in generalised oedema
What is the cause of Hypoalbuminaemia (decreased albumin)?
Decreased synthesis of albumin by the liver or increased loss of albumin from the circulation
Decreased hepatic production caused by protein malnutrition/malabsorption or severe liver disease
Excessive loss from circulaiton is caused by multiple factors - Protein losing enteropathy, protein losing nephropathy, severe haemorrhage/blood loss, plasma exudation associated with severe burns
How does increased vascular permeability cause oedema?
- Inflammatory or immunilogial stimuli causing vasodilation and increased microvascular permeability
- Endothelial cell contraction and widening interendothelial gaps
- Increased permeability means proteins escape into the iunterstitial fluid and the osmotic pressure increases
- Fluid is then drawn from the plasma into the interstital fluid
- resulting in oedema and dilution of the inflammatory agent
How does decreased lymphatic drainage cause oedema?
Decreases the removal of fluid that normally accumulates in the interstitium causing oedema (usually localised)
What causes (7) decreased lymphatic drainage?
- Lymphatic vessel compression
- Lymphatic vessel constricition
- Internal bloackage
- Congenital malformation - aplasia or hypoplasia
- Surgical removal of lymph nodes
- Lymphangitis
- Intestinal lymphangiectasia
What are the morphological characteristics and clinical consequences of oedema and effusions?
Grossly - clear to slightly yellow gelatinious fluid
Microscopically - pale eosinophilic homognous fluid
Clinical significance:
- Location dependent
- Minimal clinical impact subcutaneously etc.
- Serious organ dysfunction if in a confined space e.g. brain
Physiologic and Pathologic
What is Hyperaemia?
An active process in which arterial dilation causes increased blood flow with increased inflow and normal or decreased outflow
Can be physiologic (Occurs during increased oxygen demand, dissipation of heat, digestion of food) or pathologic (occuring during early vascular resposne to an inflammatory stimulus)
What is congestion?
A passive process in whcih there is decreased outflow of blood from a tissue with normal inflow
This can be local or generalised and acute or chronic
What causes local congestion?
Obstruction/compression of venous outflof caused by neoplastic or inflammatory masses, displacement of organs or fibrosis resulting from healed injury
What causes generalised congestion?
Decreased paasage of blood through the heart or lungs due to heart failure (right or left sided)
What is shock?
Characterised by circulatory dyshomeostasis due to decreased cardiac output or decreased effective circulating blood volume +/- increased peripheral vascular resistance
