A physician orders 2500 mL of NS to infuse at 150 mL per hour. The drop factor is 15 gtt/mL. How long will the IV run?

A physician orders 2500 mL of NS to infuse at 150 mL per hour. The drop factor is 15 gtt/mL. How long will the IV run?

• A. 16 Hours 36 Minutes
• B. 16 Hours 40 Minutes
• C. 17 Hours
• D. 15 Hours 45 Minutes

Answer: (B)

When you know the total volume to infuse and the rate, timing is volume divided by rate. Here, 2500 mL is to be infused at 150 mL per hour. 2500 ÷ 150 equals 16.666... hours, which is 16 hours plus 0.666... of an hour. 0.666... × 60 minutes equals 40 minutes. So the IV will run for 16 hours and 40 minutes. The drop factor (15 gtt/mL) isn’t needed to determine duration, but it would be used to convert the flow to drops per minute if that calculation were asked: 150 × 15 ÷ 60 = 37.5 gtt/min.

When you know the total volume to infuse and the rate, timing is volume divided by rate. Here, 2500 mL is to be infused at 150 mL per hour. 2500 ÷ 150 equals 16.666... hours, which is 16 hours plus 0.666... of an hour. 0.666... × 60 minutes equals 40 minutes. So the IV will run for 16 hours and 40 minutes. The drop factor (15 gtt/mL) isn’t needed to determine duration, but it would be used to convert the flow to drops per minute if that calculation were asked: 150 × 15 ÷ 60 = 37.5 gtt/min.