A bag contains 25,000 units of heparin in 500 mL. If the infusion rate is 2,000 units/hour, what is the infusion rate in mL/hour?

A bag contains 25,000 units of heparin in 500 mL. If the infusion rate is 2,000 units/hour, what is the infusion rate in mL/hour?

• A. 20 mL/hr
• B. 40 mL/hr
• C. 50 mL/hr
• D. 60 mL/hr

Answer: (B)

Understand the dose in terms of concentration first. The bag has 25,000 units in 500 mL, so the concentration is 25,000 ÷ 500 = 50 units per mL. To deliver 2,000 units per hour, convert the necessary volume: 2,000 units/hour ÷ 50 units/mL = 40 mL/hour. Check: 40 mL/hour × 50 units/mL = 2,000 units/hour, which matches the prescribed rate.

Understand the dose in terms of concentration first. The bag has 25,000 units in 500 mL, so the concentration is 25,000 ÷ 500 = 50 units per mL. To deliver 2,000 units per hour, convert the necessary volume: 2,000 units/hour ÷ 50 units/mL = 40 mL/hour. Check: 40 mL/hour × 50 units/mL = 2,000 units/hour, which matches the prescribed rate.