Dimensional Analysis Help Needed

Home Health Columnist / Guide · Dec 31, 2012

Moved your post to our Nursing Student Assistance for math help.

livefully · Dec 31, 2012

Hi!

This is my very first post here. I've learned so much from allnurses, glad to be able to answer this question :)

First, the pt is receiving 1.2g 2x a day (q12), so total amount/day is 2.4g.

Next, the vial is not completely labeled, and IRL, i would ask pharmacy to clarify the units. But got now, let's say it is 1.5g/ml.

Every 1ml contains 1.5g, and you need to figure out how many ml to give. So ml goes on top:

1ml/1.5g x 2.4g

The g cancel each other out and you are left with ml on top, so you would give 2.4/1.5 ml = 1.6ml

Hope that helps.

Esme12, ASN, BSN, RN · Dec 31, 2012

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phuretrotr · Jan 1, 2013

mL = 1.2gm* x 1mL x 24hrs** = 28.8mL*** = 1.6mL/day

day = 12hrs x 1.5gm x 1day = 18days

*Cross out the units you do not need by crossing out one on the top for every bottom one. (Bold is what you cross out, italics is what you need.)

**Multiple across the top, then the bottom

***Divide the top (28.8mL) by the bottom (18days) to get your answer.

I did it in this formatting because this is how my school taught us how dimensional analysis was written. However, the further I got in the program, they told us if we have a different way of doing it and it works, we may do it our way.

In your question,

"The patient is to recieve 1.2 gm of medicine q 12 hrs. The vial contains 1.5/ml. How many mg of the medication will the nurse administer to the client each day?"

I'm assuming the 1.5 is mg, and the mg that is bolded is suppose to be mL.

If not, and the question really was asking for mg/day, as sometimes questions try to add un-need information (The vial contains 1.5/mL) into the question to mess you up, then you would lay it out like this...

mg = 1.2gm x 24hrs x 1000mg = 28800mg = 2400mg/day or 2.4gm/day

day = 12hrs x 1day x 1gm**** = 12days

****This really means nothing, but for the sake of alignment when I post this... Helpful tip: know your conversions too... 1000mg = 1gram

I hope I have helped you figure dimensional analysis out.

LPNwannabe123 · Jan 2, 2013

The answer should be mg of med. each day...

The client is to receive 1.2 gm of a med q12h. The vial contains 1.5gm/ml. How many mg of medication will the nurse administer?

Sorry to complicate things, but that's the problem given (confusing)

if it were ml, it would be 1.6

1ml/1.5gms x 1.2 gms/perday x 2doses/perday= 2.4gms/1.5gms.=1.6 grams then to get mg(milligrams) multiply by 1000? making it 1600 mg?

LPNwannabe123 · Jan 2, 2013

Thanks soooo much for the help everyone! :) I'll get it eventially...I revised the problem as it was written per practice by instructor...

Again, thanks a bunch:)

tinks599 · Jan 3, 2013

I had not ever been introduced to dimensional analysis until this past semester in Chemistry...and my instructor was not very...uh...helpful. Despite that, I had to get my head around it and it wasn't easy for me. I went to Target and bought a $4 pre-school kids' white board. It was blank on one side and had lines for learning handwriting on the other side. I bought a set of dry erase markers in a handful of colors. When it came time to balance equations, then really do a LOT of dimensional analysis in each chapter...it just started to work and I could make sense of it. Best $4 I could have ever spent and it fits in my binder. I'll be toting that little gem with me to Microbiology for the same reason. Hope this helps. It fits in my binder. Keep it up. When this all makes sense, you'll nearly feel silly it was so hard...but until you get it is hard then it makes a lot of sense and is easy. You'll get through the hump.

KelRN215, BSN, RN · Jan 3, 2013

The answer should be mg of med. each day...
The client is to receive 1.2 gm of a med q12h. The vial contains 1.5gm/ml. How many mg of medication will the nurse administer?
Sorry to complicate things, but that's the problem given (confusing)
if it were ml, it would be 1.6
1ml/1.5gms x 1.2 gms/perday x 2doses/perday= 2.4gms/1.5gms.=1.6 grams then to get mg(milligrams) multiply by 1000? making it 1600 mg?

If the question is really how many mg of medication the client will receive in a day, the answer is 2400 mg.

The client is receiving 1.2 g q 12 hr which means in a day they are receiving 2 doses. 1.2 g/dose x 2 doses/day = 2.4 g/day. 2.4 g x 1000 mg/g = 2400 mg. The concentration of the medication is irrelevant to the question you posed.

LPNwannabe123 · Jan 3, 2013

Thanks for your confidence:) it is contagious!

LPNwannabe123 · Jan 3, 2013

agree!:)

nurseprnRN, BSN, RN · Jan 5, 2013

The answer should be mg of med. each day...
The client is to receive 1.2 gm of a med q12h. The vial contains 1.5gm/ml. How many mg of medication will the nurse administer?
Sorry to complicate things, but that's the problem given (confusing)
if it were ml, it would be 1.6
1ml/1.5gms x 1.2 gms/perday x 2doses/perday= 2.4gms/1.5gms.=1.6 grams then to get mg(milligrams) multiply by 1000? making it 1600 mg?

No, this is a question that is designed to see if you read carefully. It totally makes NO DIFFERENCE how many mg/ml there are, because that's not what they are asking you.

They have asked: the patient is getting 1.2gm twice a day. Stop right there. How many mg is 1.2 gm? Right, 1200mg.

So. The patient is getting 1200 mg twice a day. How many mg is he getting in a whole day? If you don't multiply two times 1200 for a total of 2400mg, then you have told your faculty that you can't read the question.