Q - plasma/interstitial

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Q - plasma/interstitial

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3 Posts

Norcal
Forum Newbie

Topics: 1
Posts: 3

10/12/04 - 08:22 AM

It may be a stupid one but I'm kinda confused. I have learned from Costanzo phys book that plasma = 1/4 of the ECF and interstitail fluid = 3/4 of the ECF.
Dr Goljan brought up this question :
How many liters of isotonic saline you need to infuse into patient to increase his plasma volume by 1 L. Answer according to him is : 3L.

Well in my opinion is 4L cause its 1/4 of the ECF.
Just wonder how you guys would answer if you'd happened to get this question on the real exam.

mdwannabe
Forum Guru

Topics: 37
Posts: 1,133

10/12/04 - 12:40 PM

in actuality the realtionship is 10.5L to 3L so it is not straight forward 1/4 to 3/4. It is more like 2/3 to 1/3 ... at least it sems that way to me. So 3 l is correct replacement for 1L gain in intravascular volume.

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mjl1717
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Topics: 958
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10/12/04 - 02:31 PM

Just piggybacking on mdwannabe's thought and to make this clear. I also found that some books use 3/4 and 1/4 and others use 2/3 and 1/3 for interstitial fluid / plasma respectively. I prefer 2/3 and 1/3.
Using the markers mannose, inulin or sucrose for ECF and Evans blue or albumin(RISA) for plasma. I like 2/3 and because the I for ICF or interstitial is always 2/3. Thats how I remember it.
Also as I remember the total fluid should be near 42 L.

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