Lessons · Nursing · drops per minute
Drops per minute: when there is no pump
gtt/min = mL/h × drop factor (gtt/mL) ÷ 60. The drop factor is printed on the tubing package. Round to a whole drop, because you cannot count half a drop.
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 pump is on another patient, or the power is out, or it is a clinic with gravity tubing. The bag still has to run at the ordered rate, and the only control is the roller clamp and your watch. The drop factor on the package and this one line are the whole method.
How to think about it
Get the rate in mL/h first, from the volume and time if you have to. Read the drop factor off the tubing package: 10, 15, 20 or 60 gtt/mL. Multiply the rate by the drop factor, divide by 60, and round to a whole drop as the rule says. Then count for a full minute.
Worked example
Rate 125 mL/h, tubing 20 gtt/mLThe rate from the order; the drop factor from the package.
125 × 20 / 60 = 41.67 gtt/minMillilitres an hour times drops a millilitre gives drops an hour; over sixty gives drops a minute.
41.67 rounds to 42 gtt/min, the nearest whole dropRounded once, at the end, the way the rule says.
Microdrip 60 gtt/mL at 45 mL/h: 45 × 60 / 60 = 45 gtt/minWith a 60 gtt/mL set the sixties cancel, and drops a minute equals millilitres an hour.
Your turn
Rate 75 mL/h, tubing 15 gtt/mL. Write the line.
gtt/min = 75 × / 60 = 18.75 → 19 gtt/min
Solve one, graded on the server
The trap
Forgetting the 60. 125 × 20 = 2500 drops a minute is a fire hose, and you would notice; 125 × 20 / 6 = 417 looks almost reasonable and is ten times the rate. Hours to minutes, always, and the number should be one you could actually count.