Question

The body fluid compartments of a patient were measured, which showed the following values:

Na - 10
K - 140
Cl - 15

Name the fluid compartment.

• A. Interstitial fluid
• B. ECF
• C. ICF
• D. Total body fluid

Hint:

Recall which compartment has high potassium and low sodium as its dominant electrolytes.

Answer 1

The Correct Option is C

Step 1: Recall the electrolyte composition of body fluid compartments.
The two major fluid compartments differ dramatically in their electrolyte profile:
- ECF (Extracellular Fluid): High sodium (~140 mEq/L), low potassium (~4-5 mEq/L), high chloride (~103 mEq/L). Sodium is the principal ECF cation.
- ICF (Intracellular Fluid): Low sodium (~10-12 mEq/L), high potassium (~140-150 mEq/L), low chloride (~4 mEq/L). Potassium is the principal ICF cation.

Step 2: Match the given values.
The given values are:
- Na = 10 mEq/L (low) -- consistent with ICF
- K = 140 mEq/L (high) -- consistent with ICF
- Cl = 15 mEq/L (low) -- consistent with ICF

Step 3: Conclusion.
The electrolyte profile shows low Na, high K, and low Cl -- this pattern is characteristic of Intracellular Fluid (ICF). The Na-K ATPase pump actively maintains this gradient by pumping 3 Na⁺ out and 2 K⁺ into the cell per cycle.