1000 mL of D5NS with 20,000 units of heparin is infusing at 20 mL/hour. The IV set delivers 60 gtt per mL. How many units of heparin are delivered per hour?

• A. 200 units/h
• B. 400 units/h
• C. 600 units/h
• D. 800 units/h

Answer: (B)

Understand that the amount of drug delivered per hour comes from the concentration in the IV solution and the infusion rate. The heparin solution has 20,000 units in 1,000 mL, so the concentration is 20 units per mL. At 20 mL infused each hour, the patient receives 20 units/mL × 20 mL/hour = 400 units per hour. The drip factor (60 gtt/mL) isn’t needed for this calculation since we’re asked for units per hour, not drops per minute. Therefore, the delivery is 400 units per hour.