Edema question???????

9livesRN, BSN, RN · Sep 15, 2010

Hypervolemia will lead edema by increasing the venous hydrostitic preassure"

how confusing!

break down:

hypervolemia will lead to edema since the osmolarity of the blood will be less then in the tissues, hence water will move out of the blood (vascular) into the interstitial area (tissues) causing edema.

it it all moves because of osmosis

Richard_Head · Sep 19, 2010

Hypervolemia does not cause edema. A change in the balance of net pressures between the tissue and the vascular system causes edema. Hypervolemia can contribute by increasing intravascular hydrostatic pressure (which favors fluid deposition into tissues) while not affecting intravascular oncotic pressure (which favors retention of vascular volume) resulting in a increased pressure gradient and net fluid movement into the interstitial space. If the hypervolemia was caused by iv administration of albumin instead of crystalloid, edema would be less likely to result because intravascular hydrostatic and oncotic pressure will have increased. In the case of CHF edema forms beacuse the heart is unable to keep up with venous return and venous capillary hydrostatic pressure increases thereby decreasing the arterial to venous pressure gradient. Edema in renal patients occurs due to a similiar mechanism, except actual fluid retention occurs and will eventually exceed compensatory increases in CO. Renal patients also typically have decreased serum oncotic pressure which also favors formation of edema. FYI if you bolus a liter of LR nearly 80% will leave the intravascular space by the time the bolus is complete (the % is less with subsequent boluses). With 5% albumin bolus only 25% of the volume administered will leave the vascular space initially. Osmosis has little to do with the fomation of edema in most clinical scenarios (except renal failure)...profound electrolyte derangement would have to exist (usually with other more important symptoms presenting first) for it be of significance.