mcg/kg/min

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Specializes in orthopedics, med/surgery.

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I need the formula for this type of problem. The problem is you have 400mg in 250ml of IV solution and it is infusing at 23ml/hr and the kg is 79.5.

I can't seem to get the units to cancel out correctly or find a problem which has an answer I can look at.

I know you convert the mg to mcg (multiply by 1000) and convert the hour to 60 minutes. Thanks for the help.

I did a search for this but came up empty.

Thanks

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Specializes in Critical Care.

What is it that you want to give to the PT?

I noticed that in the way you stated the question I was missing the desired dose.

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Specializes in OB.

i dont know exactly what you are asking. If you are looking for how many mg per ml, it would be 1.6 (400/250). are you tryingto covert to micrograms? and what is the kg information for??

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What is it that you want to give to the PT?

I noticed that in the way you stated the question I was missing the desired dose.

Exactly! Something is missing.

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Specializes in n/a.

you have four pieces of info

a) 400 mg in 250 ml of iv solution

b) running at 23ml/hr

c) kg is 79.5

d) need mcg/kg/min

therefore

first determine how many milligrams/hour is being delivered by the iv pump. the rate of the iv (ml/hr) is divided by the volume of the iv bag (ml available), then multiply this result by the total amount of medication (mg) in the iv bag.

[color=#663333] rate

ml available

[color=#663333]x dose available

becomes

23ml/hr

250ml

x 400mg

which = 36.8 mg/hr

next, after the milligrams/hour has been determined, use the next formula to convert from milligrams/hour to mcg/kg/min.

[color=#663333] mg

60min

[color=#663333]x 1000 / kg

becomes

36.8mg

60min

x 1000 / 79.5

which = 7.71 mcg/kg/min

hope this helps, also check out this link, it is a database of all kinds of medical calculators and examples of how to do the different problems.

-bettyjo

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Specializes in med/surg, telemetry, IV therapy, mgmt.

there is no missing information. the only formula you need to work these problems is dose desired divided by dose on hand will give you the amount to give. your problem gives you the dose on hand and the amount you are giving and is asking you to compute what the dose desired is. most problems don't do that and in actual practice you're not often going to be doing that kind of calculation--ever. this is the instructor testing your math and rational thinking skill.

the problem that many people have with this is that for the kind of problem where a term is "xmcg/ykg/zminutes" students get hung up on how to perform the intricate arithmetic of that complex fraction especially when it is divided by another fraction which is the dose on hand term that is usually "vmg/wml"! if you don't know how to do that kind of math, don't even attempt it. break it down into smaller increments.

when i show how these problems are worked, it is much easier to do them by dimensional analysis (da) by creating a string of simple fractions that is multiplied together. each fraction in the equation is a relationship (marriage) of factors within the problem that must stay together. this da equation includes all of the necessary conversions and terms and conveniently gets rid of the unwanted labels on the numbers because you set the fractions up so that the labels on the numbers cancel themselves out. the only thing is that you must know what label you want on the number in the numerator and the number of the denominator when you come to the final answer and set up the terms of the equations so they will all cancel out accordingly.

the problem is you have 400mg in 250ml of iv solution and it is infusing at 23ml/hr and the kg is 79.5. to find mcg/kg/minute. . .do this in 2 steps to avoid complex math

dose desired:
that's what you need to find and express as "
x" mcg/"1" kg/"1" min

dose on hand:
400 mg/250 ml

amount to give:
23 ml/hour

ask yourself, how did they get from
"
x
" mcg/"1" kg/"1" min to
23 ml/hour? that's the problem you have to solve.

400 mg/250 ml
(dose on hand) x
23 ml/hour
(infusion rate, or amount to give)
x 1000 mcg/1 mg
(conversion factor)
x 1 hour/60 minutes
(conversion factor) = 613.333 mcg/minute

then, include the patients weight, 613.333mcg/minute/79.5 kg and reduce the denominator to "1" by dividing the 79.5 into the 613.333 to get to "1 kg" which gives you 7.7148 mcg/minute/kg which i would round to 8 mcg/minute/kg and re-write as
8 mcg/kg/minute
(which you can do because the numerical term sitting with the "minute" and the "kg" are both the number "1" and are, therefore, identities)

to verify that this is correct, use that figure to work the problem backwards to get the rate of infusion per hour.

8 mcg/kg
(dose desired)
x 79.5/1 minute
(part of dose desired + patient's weight)
x 1 mg/1000 mcg
(conversion factor)
x 250 ml/400 mg
(dose on hand)
x 60 minutes/1 hour
(conversion factor)
= 23.85 ml/hour
which is close enough to the original figure (we are working with decimals)

fractions are about as easy as the math of these problems can be taken to.

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GO to DosageHelp.com for nursing math, it has everything!

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Specializes in NICU, PICU, PCVICU and peds oncology.

I actually encounter this type of med calculation fairly often with out transplant patients. We do a significant number of deliberate ABO-incompatible hearts and livers in small children and run either ATGAM or rATGAM for the first week or two. The ordered dose will be mg/kg/day and the pharmacy-prepared infusion will have x mg in y mL. One of our safety checks is to ensure that the infusions are running at the correct rate based on the physician order, so we have to do this calculation at the beginning of each shift.

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Thanks. I know I didn't ask the question, but the answer helped. I LOVE dimensional analysis, but if you don't know what you are solving for, you can't even start to set up your question!

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