Lessons · Nursing · how long an infusion takes
How long the bag will take
Time = volume ÷ rate. With the rate in mL/h the answer is in hours; the decimal part times 60 is the minutes.
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
The bag went up at 0800 at 100 mL/h and the family asks when it will be done, and so does the pharmacy for the next one. Volume over rate gives hours; the fraction of an hour becomes minutes; the clock does the rest.
How to think about it
Divide the volume by the rate. Keep the decimal. The whole number is hours; multiply what is after the decimal by 60 for the minutes. Add that to the start time on the 24-hour clock, carrying over at 60 minutes.
Worked example
1000 mL at 100 mL/hA litre, at a hundred an hour.
Time = 1000 / 100 = 10 hVolume over rate. Ten hours.
500 mL at 150 mL/h: 500 / 150 = 3.33 hA decimal. The .33 is a third of an hour, not 33 minutes.
0.33 h × 60 = 20 min, so 3 h 20 min; started 0800, finishes 1120The fraction into minutes, then onto the clock.
Your turn
750 mL at 125 mL/h. Write the line.
Time = 750 / = 6 h
Solve one, graded on the server
The trap
Reading 3.33 h as 3 hours 33 minutes. The .33 is a third of an hour, twenty minutes. The decimal part is multiplied by sixty, every time.