A 54-Kg woman is admitted to your emergency department suffering from convulsions after running a
marathon. The patient is hyponatremic (low plasma Na+). You learn from her companion that she weighed
50 Kg before the race. To assess her body fluid composition, you inject 100 mg of inulin. After an
equilibration period, a blood sample is drawn which has an inulin concentration of 7.2 mg/L. You
catheterize her bladder and drain off 500 mL of urine, which is found to contain a total of 10 mg of inulin.
The woman is severely overhydrated because her:
*A. extracellular volume is 12.5 L.
B. extracellular volume is 13.2 L.
C. total body water is 12.5 L.
D. total body water is 13.2 L.
I get B, but the answer is really A - but why?
marathon. The patient is hyponatremic (low plasma Na+). You learn from her companion that she weighed
50 Kg before the race. To assess her body fluid composition, you inject 100 mg of inulin. After an
equilibration period, a blood sample is drawn which has an inulin concentration of 7.2 mg/L. You
catheterize her bladder and drain off 500 mL of urine, which is found to contain a total of 10 mg of inulin.
The woman is severely overhydrated because her:
*A. extracellular volume is 12.5 L.
B. extracellular volume is 13.2 L.
C. total body water is 12.5 L.
D. total body water is 13.2 L.
I get B, but the answer is really A - but why?