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#1
02-05-2012
 USMLE Forums Scout Steps History: Not yet Posts: 10 Threads: 6 Thanked 3 Times in 3 Posts Reputation: 13
Mannitol and ECF Volume Calculation

A person was injected 10 g of mannitol (iv). After sufficient time for equilibration, blood is drawn, and the concentration of mannitol in the plasma is found to be 65 mg/ 100ml. urinalysis reveals that 10% of the mannitol had been excreted into the urine during this time period. What is the approximate extracellular fluid volume of this Person?

A) 10 L
B) 14 L
C) 22 L
D) 30 L
E) 42 L
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#2
02-05-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 646 Threads: 52 Thanked 762 Times in 256 Posts Reputation: 773

well mannitol is the same as inulin right??
used to measure ecf

so
if 10% was excreted that means 9 gm is still in the body

and if we use the equation for Vd

then we get Vd=dose/plasma concentration

so Vd ie ECF = (9/65)*100

roughly equals 14

 Tags Pharmacology-, Step-1-Questions

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