Lessons · Nursing · mL per hour from volume and time
mL per hour: the number the pump wants
Pump rate = total volume ÷ time in hours. If the time is in minutes, divide it by 60 first.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
Every bag hung on a pump is this line: a volume, a time, a rate. The order says 1000 mL over 10 hours; the pump asks for mL/h; nothing infuses until a nurse has done the division. The pump beeps at the end because the arithmetic was right, not because it checked it.
How to think about it
Write the volume in millilitres and the time in hours. Divide. If the time was in minutes, turn it into hours first by dividing by 60, or multiply the volume by 60 and divide by the minutes. Round as the problem states, usually to the nearest whole mL/h or tenth.
Worked example
1000 mL over 10 hA litre bag over a day shift plus a bit.
Rate = 1000 / 10 = 100 mL/hVolume over hours. One hundred millilitres an hour.
250 mL over 30 min: 30 / 60 = 0.5 hThe time in hours first.
Rate = 250 / 0.5 = 500 mL/hHalf an hour means twice the volume per hour.
Your turn
500 mL over 4 hours. Write the line.
Rate = 500 / = 125 mL/h
Solve one, graded on the server
The trap
Dividing by the minutes when the pump wants hours. 250 / 30 = 8.3 mL/h, and the antibiotic that was due over half an hour takes thirty hours. Minutes become hours before the division.