Nurshing Math Calculations

austin heart, BSN, RN · Jun 11, 2005

If my calculations are correct......

MD/min=60md/1cc x 500cc/200mg x 163.6mcg/1min x 1mg/1000mg =

24.54 md/min

The 163.6mcg/min was fifured by converting 180lbs to kg then multiplying by 2mcg.

Wow, I haven't had to calculate md in along time!

amber1142 · Jun 11, 2005

Hello all...I'm in desperate need of some nursing math help. Here is the math problem....can someone please help in figuring it out. "200 mg of Dopamine HCL in 500 cc of D5W has been ordered for IV infusion at a rate of 2 mcg/kg/min. Your patient weighs 180 lbs. At how many microdrips/min should you infuse the IV using a solution administration set that delivers 60 microdrops/cc?
Any help would be greatly appreciated.
Becky32668

First look at what the actual question is (how many microdrops/minute?) That will be where you begin to set up the equations. Set up your problem starting with what facts you know from what they have told you about microdrops: there are 60 per 1 cc. (note the word "per". Every time you have one number over top of another number that means "per". These are *not* fractions; they are relationships). It looks like this:

60

___

1 cc

Next to each "per unit", you should put another "per unit" with a value that you know (either from what they are telling you in the problem or from a conversion factor in your head). Choose one that matches the bottom unit of measure from "per unit" you have already written down. For example, I have written down 60 drops per 1 cc. So I should choose something with cc's in it for my next "per unit". What I know from the problem is that there are 500 cc's with 200 mg of medication in them. So that is the per unit I write down next to the first one. (Make sure you arrange the next "per unit" so that the matching units are opposite each other.)

Then note that the question says the dosage of medication is given in micrograms so you will have to convert milligrams to micrograms. (That is a conversion factor you should have in your head: 1 mg *per* 1000 mcg). Arrange that "per unit" next to the 500 cc per 200 mg so that the 1 mg part of the 1 mg per 1000 mcg "per unit" is diagonal from from the 200 mg. Now that that per unit is in place we can keep plugging in "per units" one next to the other until you have used up all of the data in the problem. Remember to choose the next per unit based on the unit of measure on the bottom of the previous per unit.

Since the per unit I used last was 1 mg per 1000 mcg I need to look at the data in the problem for something that involves mcg. I see that in the problem they have told me that there is a "per unit" of 2 mcg per 1 kg. So that is my next "per unit." Then I have to put in a something with kg in it (another conversion factor that I know in my head: 1 kg per 2.2 lbs. And then I need to plug in the last bits of information I know: The problem tells me that the person weighs 180 lbs.

60 drops 500 cc 1 mg 2 mcg 1 kg 180 lbs

____ x ______ x _______ x _______ x ______ x _____

1 cc 200 mg 1000 mcg 1 kg 2.2 lbs 1 minute

What you are left with after you multiply all the top numbers (10800000) and multiply the bottom numbers (440000) and then divide the top by the bottom (24.54 or 25) are two units which have nothing to cancel each other out (drops and minutes). That is your answer 25 drops per minute.

austin heart, BSN, RN · Jun 11, 2005

So I was right :)!

Becky32668 · Jun 11, 2005

If my calculations are correct......
MD/min=60md/1cc x 500cc/200mg x 163.6mcg/1min x 1mg/1000mg =
24.54 md/min
The 163.6mcg/min was fifured by converting 180lbs to kg then multiplying by 2mcg.
Wow, I haven't had to calculate md in along time!

Thank you so much for replying, after many hours and much frustration I finally figured it out on my own....seems everyone had their own way of figuring these math problems out, I did come up with the right answer and much dimentional analysis....WHOA!!!! Thanks again...Bek

Becky32668 · Jun 11, 2005

Thank you so much for replying, after many hours and much frustration I finally figured it out on my own....seems everyone had their own way of figuring these math problems out, I did come up with the right answer and much dimentional analysis....WHOA!!!! Thanks again...Bek

Yes, you were right...I did it somewhat different, but still came up with the same answer...I'm not one to read a whole lot...just the facts and tell me how it's done that way and why....I know, that will get me in trouble soon...:)

amber1142 · Jun 11, 2005

Yes, you were right...I did it somewhat different, but still came up with the same answer...I'm not one to read a whole lot...just the facts and tell me how it's done that way and why....I know, that will get me in trouble soon...:)

You're welcome.

coot · Jun 22, 2005

Hello all...I'm in desperate need of some nursing math help. Here is the math problem....can someone please help in figuring it out. "200 mg of Dopamine HCL in 500 cc of D5W has been ordered for IV infusion at a rate of 2 mcg/kg/min. Your patient weighs 180 lbs. At how many microdrips/min should you infuse the IV using a solution administration set that delivers 60 microdrops/cc?
Any help would be greatly appreciated.
Becky32668

search the web under nursing conversions or nursing formulas and conversions i have not had medical math but its coming up in the fall. do u have any advice on nutrition. good luck!!