A patient with severe hypernatremia (serum Na+ 175 mEq/L, normal body weight 70 kg) has a total body water of 40 L. Using the Adrogue-Madias approach, what is the approximate approximate intracellular fluid volume?
- A 18 L
- B 22 L
- C 27 L ✓
- D 30 L
Correct answer: C. 27 L
Explanation
Total body water equals 40 L. Extracellular fluid normally comprises roughly one-third of TBW, so ECF is approximately 13 L. Intracellular fluid equals TBW minus ECF, giving 27 L. Although hypernatremia shifts water from ICF to ECF acutely, the question asks the compartmental volume based on the normal fractional distribution applied to the stated TBW of 40 L. TBW is about 57 percent of body weight in this case, consistent with volume depletion, but the ICF fraction remains two-thirds of TBW.
Reference: Ganong's Review of Medical Physiology, 26th ed.
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