rida
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73 year old man with congestive heart failure visits his physician complaining of labored breathing and swelling in his lower extremities. Edema in the lower extremities becomes worse after prolonged standing. Which of the following sets of changes is present in the lower extremities of this man compared to normal?
Lymph flow/Microvascular hydrostatic pressure/Interstitial fluid oncotic
A) increaseed/no change/decreased
B) Decreased/decreased/decreased
C) Increased/decreased/increased
D) increased/increased/decreased
E) All increased
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| mdwannabe
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Lymph flow increases...but not enough to clear edema
Micro HP..increases due to back due to pump failure
But ISF oncotic pressure should not change, since permiability is preserved, proteins won't leak out, edema is due to disballance b/w HP and oncotic pressure in microvasculature,
But I don't see such set here.
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| mani
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yea, agree
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| rida
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The answer given was D, can anyone explain????
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| Idiopathic
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oncotic pressure decreases in CHF due to liver congestion and dysfunction, i believe. Less albumin is produces, or rather, a lower concentration of circulating albumin, causing more of a mismatch in hydrostatic/oncotic pressure. Sound close?
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| mani
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fluid coming out of vessels will literally "wash away" the intersrtitial proteins ----> dec interstitial oncotic pressure. i m sure about it. idiopathic do u agree?
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| mdwannabe
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If the book says so...it is possible, but then any edema for any reason would set off an unbreaking cycle, where the ISF would continually suck the fluid out of capilaries all the time, once the HP would for some reason increase to cause initial edema.
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| mani
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i m sorry u are mixing up few things.just recall strlings forces. when increased lymph flow will decrease intesrtial oncotic pressure, ,it will actually decrease the filtertation pressure. isnt it? if i m not clear plz let me know. o ll explain in full deetail
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| mdwannabe
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Sure...Sratling law will definetely work...But the ISF oncotic pressure should be in opposition of Intravesicular oncotic pressure, when comapring both the Intravesicular wins. But when considering Intravesicular Hydrostatic pressure it is the greates out the four, hence it will push some fluid out of vascular space, to interstitium. This pressure will be opposed by IS HP, which will decrease the amount of fluid exiting vessels, but not stop complitely. So so residual fluid will alway exit form vascular space to interstitium, but will be cleared by lymphatic chanells, that have very particular structure, having their external wall attached to interstitial matrix, so when matrix expands due to water influx due to reasons above, tha channels expand with it and accomodate eflux of water.
And now...back to my previous response...
It is CRAP... coz once ISF oncotic pressure decreases...less pull will occur...not more...as my answer suggested. So it will contribute to decrease the amount of fluid exitting intravascular space.
But the question remains as to the exact mechanism of Oncotic pressure decrease. The suggested "wash out" seems feasible...but I don't know for sure.
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| mani
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decrease in ISF oncotic pressure is for 2 reasons:
1. increased filtered fluid will decrease the conc of isterstial protiens.
2. incresed filtered fluid will increase lymph flow that will take with it the interstitial prot
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| mdwannabe
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accepted :-)
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