North American Veterinary Licensing Examination (NAVLE) Practice Test

How many milliliters of packed red blood cells are needed for a 6-kg cat to raise its PCV from 15% to 25%?

1. 15 ml

2. 120 ml

3. 60 ml

4. 30 ml

The correct answer is: 60 ml

To determine the amount of packed red blood cells needed to raise the packed cell volume (PCV) in a cat, specific calculations involving the cat's weight and the desired change in PCV must be performed. First, consider the concept that each unit of packed red blood cells typically raises the PCV by a predictable amount. For a 6-kg cat, the starting PCV is 15%, and the goal is to reach 25%, which means an increase of 10%. To estimate the volume of blood needed, the formula often used is: **Volume of PRBC (mL) = Weight (kg) × 10 mL/kg × (Desired PCV - Initial PCV) / Average PCV of PRBC** Here: - Weight of the cat = 6 kg - Desired increase in PCV = 10% (from 15% to 25%) - Average PCV of the packed red blood cells (approximately 70% to 80%) can typically be considered as about 70% for the sake of calculation. Now, plugging in the numbers based on the weight: - Volume of PRBC needed = 6 kg × 10 mL/kg × (25% -