NCLEX-RNPharmacological and Parenteral TherapiesMedium
A provider orders 1,000 mL of 0.9% normal saline to infuse over 8 hours using tubing with a drop factor of 15 gtt/mL. The IV pump is unavailable, so the nurse must set the infusion by gravity. How many drops per minute should the nurse set?
- A63 gtt/min
- B21 gtt/min
- C42 gtt/min
- D31 gtt/min
Show answer & explanationAnswer & explanation
Correct answer: D. 31 gtt/min
First find the hourly rate: 1,000 mL ÷ 8 hr = 125 mL/hr. Then convert to gtt/min: (125 mL/hr × 15 gtt/mL) ÷ 60 min/hr = 1,875 ÷ 60 = 31.25, rounded to 31 gtt/min.
Why the other options are wrong
- A. This rate is far too fast and would not match the 8-hour infusion order.
- B. This would result from an incorrect drop factor calculation.
- C. This rate would infuse the fluid too quickly, faster than ordered.
IV Drip Rate Calculation
Gravity IV flow rate (gtt/min) = (Volume in mL x Drop factor in gtt/mL) / Time in minutes.
- Convert total infusion time to minutes or use hourly rate x drop factor / 60
- Always round drops per minute to the nearest whole number
- Drop factor varies by tubing: macrodrip 10-20 gtt/mL, microdrip 60 gtt/mL
Memory trick: 'Volume times drop factor, divide by the minutes'