Edema Pathophysiology Flashcards
Revised starling equation for determining transendothelial solvent filtration per second ( Jv):
Jv= LpS([Pc- Pi]- sigma[Pip- Pig])
Jv = transendothelial solvent filtration per second
[Pc- Pi]- sigma[Pip- Pig] = Net driving force
Pc = capillary hydrostatic pressure
Pi= interstitial hydrostatic pressure
Pi p= plasma protein oncotic pressure
Pi g= subglycocalyx oncotic pressure
Lp= hydrolic conductivity of the membrane
S= surface area of filtration
Sigma= stavermanns reflection co-efficient
Steverman’s reflection co-efficient?
It is denoted by the Greek letter sigma.
It is a unit less constant that is specific to the permeability of a membrane to a given solute.
When sigma is close to 1 the plasma membrane is less permeable to large molecules such as albumin and other solvents, while permeable to water and other small molecules to eflux into the extravascular space.
Stavermanns reflection co-efficient of glomerular capillaries?
It is close to 1 and therefore under normal conditions no protein cross to the glomerular filtrate
What is the steverman’s reflection co-efficient of hepatic sinusoids ?
It is Zero. Therefore they are fully permeable to transluminal diffusion of proteins.
Why does more fluid exit the capillary than re-enters it ?
The net driving force ([Pc-Pi]- sigma[Pic- Pig] outward from the capillary is +9mmHg and the venular end it is -8 mmHg. Therefore, more fluid exit the capillary than re-enters it.
What is the Jv of glomerular capillaries?
125ml/ min or 180 Litters/ day. The total transendothelial solvent filtration rate of glomerulus is also called GFR.
The Jv of the capillaries of the body except the kidneys are ?
5ml/min or 8 litters per day.
What are the implications of the revised starling equation?
1) intravascular volume comprises RBC volume, plasma volume, and glycocalyx volume
2) ultrafiltrate is produced due to filtration across glycocalyx and no Venous reabsorption occurs at the Venous end.
3) Lymph forms the major route for return of the fluid into circulation.
What should be the key considerations when deciding the IV fluid type, rate and amount?
The pathophysiology of the condition and protecting the integrity of the endothelial glycocalyx.
What are the 5 Rs of IV fluid administration( NICE guidelines)?
Resuscitation
Routine maintenance
Replacement
Redistribution
Reassessment
What are crystalloids ?
These are solutions of inorganic ions and small organic molecules in water and are divided into iso, hypo, or hypertonic solutions.
What is cytotoxic edema or cell edema?
It is also known as cell edema or oncosis. It is a condition in which unchecked influx of sodium and other cations into neurons and astrocytes due to the failure of energy dependent mechanisms of extrusion causes influx of water resulting in osmotic expansion of the cell manifesting as cytotoxic cell edema.
What are the causes of extracellular matrix or interstitial edema?
1) Aberrant change in starling Forces acting across the microvascular walls.
2) damage to the endothelial glycocalyx which can alter endothelial membrane hydrolic conductivity and stavermanns reflection co-efficient for plasma proteins.
3) obstructions and alterations in lymphatic drainage system.
Why is edema detrimental to tissue function?
The excess accumulation of fluid in the extracellular matrix significantly increases the diffusion distance for oxygen and other nutrients, which may compromise cellular metabolism.
The increase in diffusion distance also impairs the removal of potentially toxic byproducts of cellular metabolism.
How does edemogenic stress affect the homeostasis of tissues in anatomically minimally expandable spaces?
The tissues such as brain, kidneys, and skeletal muscles in volar and anterior tibial compartments have very little anatomical space for expansion. Therefore, a small increase in transcapillary fluid filtration increase interstitial hydrostatic pressure significantly. Which in turn will reduce the vascular transmural pressure gradient and thereby reduce nutrient tissue perfusion.
