Which formula is used to calculate milliliters per hour when a fluid is to be infused over a set time?

Which formula is used to calculate milliliters per hour when a fluid is to be infused over a set time?

• A. Volume ÷ Time
• B. Time ÷ Volume
• C. Dose ÷ Concentration
• D. Volume × Time

Answer: (A)

Infusion rate is a measure of how fast a fluid is delivered, expressed as milliliters per hour. When you know the total volume to be infused and the total time over which it should be given, you compute ml per hour by dividing the volume by the time: ml ÷ hours. For example, 500 mL over 4 hours equals 125 mL per hour. Using time divided by volume would give hours per milliliter, which isn’t a rate. Dose divided by concentration gives the volume needed for a drug dose, not the infusion rate. Volume multiplied by time yields milliliter-hours, not a rate. So the correct formula is volume divided by time.

Infusion rate is a measure of how fast a fluid is delivered, expressed as milliliters per hour. When you know the total volume to be infused and the total time over which it should be given, you compute ml per hour by dividing the volume by the time: ml ÷ hours. For example, 500 mL over 4 hours equals 125 mL per hour. Using time divided by volume would give hours per milliliter, which isn’t a rate. Dose divided by concentration gives the volume needed for a drug dose, not the infusion rate. Volume multiplied by time yields milliliter-hours, not a rate. So the correct formula is volume divided by time.