A unit of packed red cells (350 mL) is to be infused over 3 hours using an IV set delivering 15 drops per mL. What is the required drip rate in drops per minute?

A unit of packed red cells (350 mL) is to be infused over 3 hours using an IV set delivering 15 drops per mL. What is the required drip rate in drops per minute?

• A. 29 gtt/min
• B. 28 gtt/min
• C. 31 gtt/min
• D. 32 gtt/min

Answer: (A)

To figure the drip rate, multiply the total volume to be infused by the IV set’s drop factor to get the total number of drops, then divide by the infusion time in minutes. Here, 350 mL to be infused with a drop factor of 15 drops per mL gives 350 × 15 = 5,250 drops total. The infusion time is 3 hours, which is 180 minutes. So the rate is 5,250 drops ÷ 180 minutes ≈ 29.17 drops per minute. Since you can only deliver whole drops, round to 29 drops per minute. The required drip rate is 29 gtt/min.

To figure the drip rate, multiply the total volume to be infused by the IV set’s drop factor to get the total number of drops, then divide by the infusion time in minutes. Here, 350 mL to be infused with a drop factor of 15 drops per mL gives 350 × 15 = 5,250 drops total. The infusion time is 3 hours, which is 180 minutes. So the rate is 5,250 drops ÷ 180 minutes ≈ 29.17 drops per minute. Since you can only deliver whole drops, round to 29 drops per minute. The required drip rate is 29 gtt/min.