An IV infusion of 1 liter over 11 hours is to be delivered. What should the flow rate be in milliliters per hour?

• A. 91 mL/h
• B. 90 mL/h
• C. 95 mL/h
• D. 92 mL/h

Answer: (A)

Flow rate equals the total volume to be infused divided by the total time. Here, 1 liter is 1000 mL, to be delivered over 11 hours. 1000 ÷ 11 = 90.909... mL/hour. Round to the nearest whole mL/hour, giving 91 mL/hour. If you used 90 mL/hour, you’d infuse 990 mL in 11 hours (under by 10 mL); at 92 mL/hour, you’d infuse 1012 mL (over by 12 mL). So 91 mL/hour is the correct rate.