What drip factor was used in the infusion calculation for the 3% hypertonic saline example?

• A. 10 gtt/mL
• B. 15 gtt/mL
• C. 20 gtt/mL
• D. 60 gtt/mL

Answer: (A)

Drip factor is the IV tubing’s calibration: it tells you how many drops make up 1 milliliter of fluid. Infusion rate in drops per minute is calculated using volume to be infused times the drip factor, divided by the time in minutes (drops/min = mL × gtt/mL ÷ minutes). In the 3% hypertonic saline example, the tubing used delivers 1 mL in 10 drops, so the drip factor is 10 gtt/mL and that value is the one applied in the calculation. Using any other drip factor would change the resulting drop rate for the same volume and time; for instance, a microdrip set (60 gtt/mL) would yield many more drops per minute for the same infusion. Example: infusing 50 mL over 30 minutes with a 10 gtt/mL set gives 50 × 10 ÷ 30 ≈ 16.7 gtt/min.