Prescribed 500 mL of 0.45% saline over one hour with a drop factor of 10 gtt/mL. The nurse sets the flow rate at approximately how many drops per minute?

• A. 50 gtt/min
• B. 83 gtt/min
• C. 90 gtt/min
• D. 100 gtt/min

Answer: (B)

The key idea is converting volume per time into drops per minute using the drip factor. The drip factor tells us how many drops make 1 mL, so multiply the mL delivered each minute by the drops per mL.

First, find how many milliliters are given each minute: 500 mL divided by 60 minutes equals about 8.33 mL per minute. With a drop factor of 10 gtt/mL, each milliliter delivers 10 drops, so 8.33 mL/min × 10 gtt/mL ≈ 83.3 drops per minute. Rounding gives about 83 gtt/min.

Thus the flow rate is approximately 83 drops per minute. If you compare to the options, this matches the value around 83 gtt/min.