A unit of packed red blood cells is 250 mL. The remaining half unit is to be infused over 1 hour using a set that delivers 20 drops per mL. What is the required drip rate in drops per minute?

A unit of packed red blood cells is 250 mL. The remaining half unit is to be infused over 1 hour using a set that delivers 20 drops per mL. What is the required drip rate in drops per minute?

• A. 42 gtt/min
• B. 31 gtt/min
• C. 50 gtt/min
• D. 36 gtt/min

Answer: (A)

The main idea is to convert the amount to be infused into drops and then divide by the infusion time. Half a unit of packed red blood cells is 125 mL. With a drop factor of 20 drops per mL, the total drops to infuse are 125 × 20 = 2500 drops. The infusion time is 1 hour, which is 60 minutes. So the drip rate is 2500 drops ÷ 60 minutes ≈ 41.7 drops per minute, rounds to 42 gtt/min. This matches the given rate.

The main idea is to convert the amount to be infused into drops and then divide by the infusion time. Half a unit of packed red blood cells is 125 mL. With a drop factor of 20 drops per mL, the total drops to infuse are 125 × 20 = 2500 drops. The infusion time is 1 hour, which is 60 minutes. So the drip rate is 2500 drops ÷ 60 minutes ≈ 41.7 drops per minute, rounds to 42 gtt/min. This matches the given rate.