Dosage calculation help?

Published

I've pretty much got the hang of doing all of the calculations with the exception of the ones like this

mcg/kg/min

Order: 3mcg/kg/min patient weighs 87.4 kg

Supply: 50mg in 250mL

I don't know if there are different ways of doing this, but I use the ratio and proportion method

but, I can't get to that point (I've tried solving the problem and inserting it into this equation 50mg: 250mL :: "my super wrong answer"mg : xmL

The answer never comes out right.

For whatever reason, I'm having the most trouble with these.

Help? Please?

If someone could work it out all the way I would really appreciate it!

Up Vote Up Vote ×

Did you do the conversion between mcg and mg?

Up Vote Up Vote ×

Yes I did.

it was 0.003 I believe

My answer kept ending up to be something like .00036639 after I added it to the equation and solved for x

the answer is supposed to be 79mL/hr

Up Vote Up Vote ×

Edit. She got it right.

Up Vote Up Vote ×

You have to multiply 3mcg times the kilo wt.

87.4 X 3mcg =262.2 mcg You would then convert to mg so .262 mg

I do the Dimensional analysis. I haven't started class yet, but have been practicing. Here is how I did it

ml/hr = 250ml/50mg X .262mg/min X 60min/1 hr.

So the top is 250 X .262 X 60 then divided by the bottom number 50.

My answer is 78.6 and round to 79 mL/hr. It is hard to follow when typed out but write it out on paper and you will see the mg and the min. cross each other out so you are left with ml/hr.

I used to do the ratio/prop. method and I read on here to try the Dimensional analysis method and you can't go wrong as you have to end with the correct symbols. It is so true. I would get the right answers on basic calculations with ratio but then like the above I would be stuck. Hope this helps.

Up Vote Up Vote ×

I use ratio/proportion too. Here's the problem worked out with that method. Hope it helps!

Order: 3mcg/kg/min patient weighs 87.4 kg

Supply: 50mg in 250mL

You need to do a couple of steps before setting up your ratio...

First, work with the units you have:

3 mcg x 87.4 kg = 262.2 mcg/min

Next, convert to mg/min:

262.2 mcg = 0.2622 mg/min

Since your final answer is in ml/hr, convert from ml/min to ml/hr:

0.2622mg x 60min = 15.732 mg/hr

Now you're ready to set up your ratio:

50 mg : 250 ml = 15.732 mg : x

50x = 3933

x = 78.66 ml, which rounds to 79 ml

Up Vote Up Vote ×
Specializes in Surgery.

I do it all as one long problem just so I can look at it and know if I'm leaving anything out:

Rx = 3 mcg/kg/min

S = 50 mg/250 mL

C = mL/hour

W = 87.4 kg

250 mL

50 mg

x

1 mg

1000 mcg

x

3 mcg

1kg/min

x

60 min

1 hour

x

87.4 kg

=

78.66 mL/hour or 79 mL/hour

I had to type it like this to get it to post correctly.

Up Vote Up Vote ×

I'm so glad someone else is asking this question. I was looking for help with the same thing. Can anyone give suggestions for a good book to practice dosage calculations? Something extremely easy to understand and breaks down each and every step? I am trying to get the hang of the math while i'm in my nursing assessment class. I start in Jan and i don't want to wait till the last minute. Thanks in advance!!:nurse:

Up Vote Up Vote ×

I bought the "Dosage Calculations" book by Pickar and did it from front to back before the first day of school. It really helped alot!

Up Vote Up Vote ×

Thank you, I'm going to look for that at Barnes and Nobles tonight..

Up Vote Up Vote ×
+ Join the Discussion