A dog weighing 20 kg requires maintenance fluids. Using a standard maintenance rate of 50 mL/kg/day, calculate the hourly rate.

• A. 33.3 mL/hour
• B. 41.7 mL/hour
• C. 50.0 mL/hour
• D. 66.7 mL/hour

Answer: (B)

Maintenance fluids are expressed as mL per kg per day. To get an hourly rate, multiply the animal’s weight by the daily rate to get the total mL for the day, then divide by 24 hours.

For a 20 kg dog at 50 mL/kg/day: 20 × 50 = 1000 mL per day. 1000 mL/day ÷ 24 hours ≈ 41.7 mL/hour.

So, the hourly maintenance rate is about 41.7 mL/hour. Other rates would imply different daily totals (e.g., 33.3 mL/hour equals 800 mL/day, which is 40 mL/kg/day; 50.0 mL/hour equals 1200 mL/day, which is 60 mL/kg/day).