[Mave RN]

We just learned Dimensional Analysis and I found it very helpful. Also, this formula D (order)/ H (what's on hand or supply) X V (vehicle in which the drug will be administered). D/H X V. For example,

order:Orinase 250mg po bid
supply:Orinase 0.25g tablets

As you can see the order for Orinase is 250mg. The pharmacy has supplied you with 0.25g. You must convert the g of the supply into the mg of the order. So, DA is a lot easier to use for this type of problem. The formula is V/H X C (conversion of H)/ C (conversion of D) X D/1. V (vehicle) will be in tablets. So, 1 tab/0.25g X 1g/1000mg (these are the conversions of the supply and the order) X 250mg/1.

I don't know how to put the numbers on top of each other to make it look more simple, but if you put the formulas on paper, they look a lot less confusing than what they look now .

Anyway, so you cross out the grams and the milligrams and you're left with just numbers and the V (vehicle). So, you multiply 1x1x250=250. Then, you do the bottom: multiply 0.25x1000x1=250. Then, divide 250/250 and you get 1 tablet. That is the dosage you will give the pt.

I hope I didn't confuse you, but DA or Dimensional Analysis has really helped me out. I hope I helped out a little bit and didn't make your life a lot more complicated. If you care, PM me so that way I can explain myself a little better. God bless and good luck!!

Mave.

[Daytonite]

Awesome, Mave! You got it! Let me just add one little touch. The bottom line is that you set these equations up so that when you are all done multiplying and cancelling out labels from the numerator and denominator, that the label(s) you are left with are the ones the problem is asking for. Good job, Woman! :hatparty:

[StudentSusan]

Please help. I am a first semester student and my very first test in Holistic was a dosage calculations test. The requirement is you must make a 90 by the 2nd try or your out of the course. I am a nontraditional student and math is not my strongest area. I made a 70 on my first try. In two weeks I have to make a 90. I have a couple of questions that I missed on my first test. I would appreciate any help you are willing to offer.

1. Over the next 4 hours, infuse 500mL D51/2NS w/ 20 mEq KCL. The drop factor is 10 gtts/mL. How many gtts/min will the IV infuse?


2. Ordered: Kantrex 15mg/kg/day given in two equally divided doses.
Supplied: Kantrez 75 mg/2mL. Childs weight: 11 lbs. How many mL will you administer?

[Daytonite]

In setting up and working these problems by dimensional analysis you are creating fractions that are really ratios. Some of these ratios are the equivalent of the number 1 which you might remember from math can always be multiplied by another number to get that same number. In dimensional analysis you are tweaking this ratio to adjust for the labels you are putting with the numbers. When you have fractions with mgs in one of the numerators and mgs in one of the denominators, the mgs label cancels itself out and all you are left with are the numbers. The goal in setting up these equations of ratios is to obtain a final answer with the labels you want on it, such as gtts/min as in the first problem or mL/day in the second problem.

Over the next 4 hours, infuse 500mL D51/2NS w/ 20 mEq KCL. The drop factor is 10 gtts/mL. How many gtts/min will the IV infuse?

500 mL(amount to be given) / 4 hours(over this time) x 1 hr / 60 min (conversion factor of hours to minutes) x 10 gtts / 1 mL (drip factor of tubing) = 20.833 gtts / 1 min = 21 gtts /min (rounded up)

Ordered: Kantrex 15mg/kg/day given in two equally divided doses.
Supplied: Kantrez 75 mg/2mL. Childs weight: 11 lbs. How many mL will you administer?

First of all, to set this up in ratios to do the dimensional analysis you should re-write the ratio of 15mg/1kg/1day, which is a complex fraction, as: 15mg / 1 kg x 1 / 1 day (multiply the top and bottom of the equation by the reciprocal of what is in the denominator which is 1day/1). I am going to use the kg to lb conversion of .454kg = 1lb. This is the equation of fractions (ratios) you need to set up to work this problem:

15 mg / 1 kg x 1 /1 day (amount to be given) x 2 mL / 75 mg (dosage on hand—note how the fraction is set up. This is in order to cancel out the "mg" label.) x 11 lbs /1 (kids weight) x .454 kg /1 lb (lb to kg conversion factor) = 1.9976 mL / day . However, you need to give this daily dose in two equally divided doses, so divide the answer by 2 to get:
1.9976 mL/day / 2 = .9988ml/day = 1 mL (rounded up)

This medication is given IV, so each 1mL dose of the Kantrex 75mg/2mL would be diluted in NS or D5W and administered over 30 or 60 minutes.

[minnielynn]

Hello everyone !! Long time don't post, but i have a question


Ordered 300 cc D5W.45%N/S in 4 hours.
A. How many cc/hr.


I get this one 300cc/4hours = 75cc/hr


B. How many gtt/min if you use 10gtt/ml tubing?

please show me the work on this one. Thanks!!!

[Daytonite]

Ordered 300 cc D5W.45%N/S in 4 hours. How many gtt/min if you use 10gtt/ml tubing? Please show me the work on this one. Thanks!!!

300 cc / 4 hours (desired dosage) x 10 gtt / mL(cc) (drip factor of tubing) x 1 hour / 60 minutes (time conversion factor) = 12.5 gtts/minute, or rounding up, 13 gtts/minute

[Daytonite]

http://www.maagnursing.com/MedCal/index.php - just had to share this one. This is a medication calculation tutorial that is just, as my grandma used to say, the cat's pajamas! You do not have to login or register to do this tutorial! Just click here where it tells you to click here and you are in the program! The left side of the screen has the outline of the course so you always know where you are in the program, or you can skip to a part you particularly want to focus on. There are quizzes at the end of the various sections. This is from the University of San Francisco School of Nursing.

[VickyRN]

Excellent resources:

Intravenous Therapy Questions

Intravenous Therapy Questions - Answer Key Shows mathematical formulas and calculations used to obtain correct answers!

[VickyRN]

Some other excellent dosage tests:

http://connection.lww.com/Products/k...ts/PreTest.doc

http://connection.lww.com/Products/k...s/PostTest.doc

[VickyRN]

Another great resource:

http://www.dalesplace.net/factor.php