In a healthy 70 kg adult male, the intracellular fluid volume is:

Appeared in: GMCH - 2016

Explanation

Total body water (TBW) in a healthy adult male is about 60% of the total body weight.
For a 70 kg individual, the TBW is calculated as 70 kg × 0.60 = 42 Litres.
The intracellular fluid (ICF) compartment contains approximately two-thirds of the total body water.
Therefore, the ICF volume is (2/3) × 42 Litres = 28 Litres.
This volume corresponds to 40% of the total body weight (70 kg × 0.40 = 28 L), following the '60-40-20 rule'.

Option A: This value represents the Total Body Water (TBW), which is the sum of both intracellular and extracellular fluids, not just the intracellular component.
Option C: This value represents the Extracellular Fluid (ECF) volume, which is the fluid outside the cells.
Option D: This value is a close approximation of the plasma volume (typically around 3 Litres), which is a sub-compartment of the extracellular fluid.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Calculation of body fluid compartments based on body weight as background academic context rather than a clinical decision trigger.
Understanding fluid distribution is fundamental for managing IV fluid therapy, as different fluids (isotonic, hypotonic, hypertonic) distribute differently across these compartments.
Knowledge of fluid volumes is crucial for calculating drug dosages, as a drug's volume of distribution is related to these specific compartments.
Assessing a patient's hydration status (dehydration or fluid overload) involves understanding shifts between the ICF and ECF compartments.

How to Approach the Question

This is a factual recall and calculation question.
First, recall the standard percentage of total body water (TBW) for a healthy adult male, which is 60% of body weight.
Calculate the TBW for the 70 kg person: 70 kg × 0.60 = 42 Litres.
Next, recall the distribution of TBW. Intracellular fluid (ICF) is two-thirds (2/3) of TBW.
Calculate the ICF volume: 42 Litres × (2/3) = 28 Litres.
Alternatively, use the '60-40-20 rule': 40% of total body weight is ICF. Calculate 70 kg × 0.40 = 28 Litres.

Concept Tested & Keywords

Concept Tested: Calculation of body fluid compartments based on body weight.
Stem keywords: healthy, 70 kg, adult male, intracellular fluid volume
Lead-in keywords: BEST, MOST RELEVANT CLUE
Clinical cues: The question specifies a 'healthy 70 kg adult male', which is the standard reference for these calculations.
Negative lead-in flag: false

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E6 Physiology Guyton 4SAE Part 1 p. 84-86

E6 Medicine Davidson Principles Practice 24e p. 369-371

Practise the full GMCH - 2016

Attempt every question from this paper in a timed mock, then review the full solution for each one.