Lessons · Nursing · mcg/kg/min to mL/h
mcg/kg/min to mL/h: the long chain, one link at a time
A weight-based drip: the ordered mcg/kg/min times the kilograms gives mcg/min; times 60 gives mcg/h; and dividing by the bag's concentration in mcg/mL gives mL/h. Every figure comes from the order, the weight and the bag label.
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
This is the calculation that puts the most units on one line, and the one where a missing 60 or a missing 1000 turns into a rate that is wildly wrong while looking like a rate. Written as a chain of small conversions, each one checked by its unit, it is four easy lines instead of one hard one.
How to think about it
Write the concentration first: mg in the bag over mL in the bag, then times 1000 for mcg/mL. Then the order times the weight for mcg/min. Then times 60 for mcg/h. Then divide by the concentration for mL/h. Write the unit at the end of every line and check that each one cancels into the next.
Worked example
Ordered 5 mcg/kg/min. Patient 80 kg. Bag: 400 mg in 250 mL.Three things: the order, the weight, the bag.
Concentration = 400 / 250 = 1.6 mg/mL = 1600 mcg/mLMilligrams to micrograms, because the order is in micrograms.
mcg/min = 5 × 80 = 400 mcg/minThe order times the weight.
mcg/h = 400 × 60 = 24000 mcg/hMinutes to hours, because the pump is set per hour.
mL/h = 24000 / 1600 = 15 mL/hMicrograms an hour over micrograms a millilitre leaves millilitres an hour. Fifteen.
Your turn
Ordered 3 mcg/kg/min for a 70 kg patient. Write the micrograms-per-minute line.
3 × 70 = mcg/min
Solve one, graded on the server
The trap
Skipping the 60. Micrograms a minute divided by micrograms a millilitre is millilitres a minute, and the pump is set in millilitres an hour: sixty times more. Write the unit on every line and the missing step shows itself.