In a 70 kg adult, plasma volume is approximately

In a 70 kg adult, plasma volume is approximately

• A. 4 L
• B. 28 L
• C. 10 L
• D. 42 L

Answer: (A)

Plasma volume is the liquid portion of blood, and in a typical adult it’s taught as about 4 liters. This value is a practical approximation used in fluid management and pharmacokinetics because exact plasma volume varies with body size, sex, and hydration, but 4 liters provides a convenient ballpark for calculations in a 70 kg adult. For context, total blood volume in this person is roughly 5 liters, so the plasma component is the major part of that. The other numbers are not consistent with what plasma volume is in a healthy adult (they align more with total blood volume, extracellular fluid, or total body water), making 4 liters the most reasonable estimate.

Plasma volume is the liquid portion of blood, and in a typical adult it’s taught as about 4 liters. This value is a practical approximation used in fluid management and pharmacokinetics because exact plasma volume varies with body size, sex, and hydration, but 4 liters provides a convenient ballpark for calculations in a 70 kg adult. For context, total blood volume in this person is roughly 5 liters, so the plasma component is the major part of that. The other numbers are not consistent with what plasma volume is in a healthy adult (they align more with total blood volume, extracellular fluid, or total body water), making 4 liters the most reasonable estimate.