An infusion order calls for 500 mL of 0.9% saline to be delivered over 4 hours using micro drip tubing (60 gtt/mL). What is the required flow rate in drops per minute (rounded to the nearest whole number)?

An infusion order calls for 500 mL of 0.9% saline to be delivered over 4 hours using micro drip tubing (60 gtt/mL). What is the required flow rate in drops per minute (rounded to the nearest whole number)?

• A. 120 gtt/min
• B. 125 gtt/min
• C. 130 gtt/min
• D. 150 gtt/min

Answer: (B)

Flow rate is determined by volume, time, and the drop factor. Start by turning the total volume into an hourly rate: 500 mL over 4 hours equals 125 mL per hour. With micro drip tubing delivering 60 drops per mL, that becomes 125 mL × 60 gtt/mL = 7,500 drops per hour. To get drops per minute, divide by 60 minutes per hour: 7,500 ÷ 60 = 125 drops per minute. You can also use the combined formula: (volume × drop factor) ÷ (time in minutes) = gtt/min, which gives (500 × 60) ÷ 240 = 125. Therefore, the required flow rate is 125 gtt/min.

Flow rate is determined by volume, time, and the drop factor. Start by turning the total volume into an hourly rate: 500 mL over 4 hours equals 125 mL per hour. With micro drip tubing delivering 60 drops per mL, that becomes 125 mL × 60 gtt/mL = 7,500 drops per hour. To get drops per minute, divide by 60 minutes per hour: 7,500 ÷ 60 = 125 drops per minute. You can also use the combined formula: (volume × drop factor) ÷ (time in minutes) = gtt/min, which gives (500 × 60) ÷ 240 = 125. Therefore, the required flow rate is 125 gtt/min.