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5 gr of manitol IV. Plasma concentration of manitol = 30 mg. Calculate EF value

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mannitol AND distribution volume

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mannitol indicator dilution extracellular fluid volume formula dose plasma concentration

Using the indicator-dilution principle:
[ \text{ECF volume}=\frac{\text{amount of mannitol injected}}{\text{plasma concentration}} ]
Assuming the stated plasma concentration is 30 mg/dL:
[ \frac{5\text{ g}}{30\text{ mg/dL}} =\frac{5000\text{ mg}}{30\text{ mg/dL}} =166.7\text{ dL} =16.7\text{ L} ]
Extracellular fluid (ECF) volume = approximately 16.7 L.
If “30 mg” was intended to mean 30 mg/L, the result would instead be 166.7 L, which is not physiologically plausible.

5 gr of manitol IV.40% of 5 gm Plasma concentration of manitol = 30 mg. Calculate EF value

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mannitol AND extracellular fluid

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mannitol volume distribution extracellular fluid indicator dilution amount remaining plasma concentration

Assuming 40% of the 5 g mannitol has been excreted, the amount remaining in the extracellular fluid is:
[ 5\text{ g} - (40% \times 5\text{ g}) = 5 - 2 = 3\text{ g} = 3000\text{ mg} ]
With plasma mannitol concentration = 30 mg/dL:
[ \text{ECF volume}=\frac{3000\text{ mg}}{30\text{ mg/dL}} =100\text{ dL} =10\text{ L} ]
EF/ECF volume = 10 L.

In the dye dilation method interstitial fluid is based measure on ?

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dye dilution AND plasma volume

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dye dilution method Evans blue measures plasma volume interstitial fluid calculation physiology

Interstitial fluid volume is measured indirectly, not by a separate dye.
[ \text{Interstitial fluid volume} = \text{ECF volume} - \text{Plasma volume} ]
  • ECF volume: measured using mannitol, inulin, or sulfate.
  • Plasma volume: measured by dye-dilution using Evans blue dye (it binds albumin and remains within plasma).
So:
[ \boxed{\text{ISF} = \text{Mannitol space} - \text{Evans blue space}} ]
Costanzo Physiology, 7th ed., “Measuring Volumes of Body Fluid Compartments”
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Which of the following base describe Y

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sodium calcium exchanger AND physiology

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Na Ca exchanger 3 sodium 1 calcium membrane transport physiology

Y is the Na⁺-Ca²⁺ exchanger (NCX).
It is a secondary active transport antiporter (counter-transporter):
[ 3Na^+ \text{ enter the cell} \quad \text{while} \quad 1Ca^{2+} \text{ leaves the cell} ]
The energy comes indirectly from the Na⁺ gradient created by the Na⁺/K⁺-ATPase (X). Therefore, Y is not facilitated diffusion and not primary active transport. It is secondary active transport.

Best transport that describe Y

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sodium calcium exchanger AND transport

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sodium calcium exchanger secondary active antiport physiology

Y is best described as a secondary active antiporter (counter-transport).
It is the Na⁺/Ca²⁺ exchanger:
[ 3Na^+ \text{ move into the cell} \quad \leftrightarrow \quad 1Ca^{2+} \text{ moves out} ]
  • Na⁺ moves down its electrochemical gradient.
  • This energy drives Ca²⁺ out against its gradient.
  • It does not directly use ATP.
Katzung’s Basic and Clinical Pharmacology, 16th ed., “Activity of the Sodium-Calcium Exchanger.”
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