In this body fluid model, what is the intravascular space volume?

• A. 2 L
• B. 4 L
• C. 6 L
• D. 8 L

Answer: (B)

Intravascular space is the fluid inside blood vessels—the plasma portion of blood. In many body-fluid models used for nutrition support, this compartment is defined as about 4 liters. This value is a practical rounding that aligns with the typical plasma volume estimated for an average adult and is used to simplify calculations of how fluids distribute between compartments. While the exact plasma volume can vary (often around 3 L in a standard 70-kg person), the model in this question adopts 4 L for the intravascular space, and that is why the correct choice is 4 L.