# med. calculations - page 2

Hello i am a new R.N. in NICU, I transfered from our Special Care Unit and am having a hard time with the med calculations of figuring some of our medications in NICU ex, heparin flushes for UAC/UVC... Read More

1. ---40cc of 1/4 NS:

30cc of Sterile Water
10cc of Normal Saline

---20cc of 1/4 NS:

15cc of Sterile Water
5cc of Normal Saline

This gives you 1/4 (or 25%) of Normal Saline mixed with 3/4 (or 75%) of Sterile Water.

If you needed only 20cc of 1/4 Normal Saline, you would adjust this. You would then draw up 5cc (5cc being 1/4 of your total desired solution) of Normal Saline and 15cc (the other 3/4) of Sterile Water.

Now, when you add your Heparin, you need to figure out how concentrated you need it (i.e., do you need 1:1, 1/2:1, etc.) 1:1 means one unit of Heparin for every cc of solution you have. In the 40cc situation, you have 40cc of solution and so would need 40U of Heparin. In the 20cc situation, you would only need 20U of Heparin- you need less because there is less total solution.

If you needed 20cc of total flush, in a 1:1 concentration, you would only add 20U of Heparin. If you needed 20cc of 1/2:1 concentration, you would add 10U of Heparin (because 10 is 1/2 of 20), etc. etc.

Now, there is one more thing to consider. Let's say you had 40cc of 1/4 NS mixed up. Then you add 40U of Heparin, which comes in 10U/cc. You would need to add 4cc total of Heparin to get 40U. But if you just add this in, you will actually have 44cc of total solution, and it will be more dilute than you actually want it (it is a small amount of dilution, but in the NICU, small is all it takes to be less effective). Technically, this gives you a 0.9:1 concentration; ask your unit if this is acceptable or not (on mine it is not). In order to account for the volume of Heparin, you must subtract an equal amount of fluid. For example, in this case, you would mix your starting solution of 1/4 NS. Of the 40cc you mixed, you would draw up and waste 4cc of this in the sink. You now have 36cc of 1/4 NS. You would then add your 4cc (total of 40U) to the solution, bringing it back up to 40 and completing your Heparin flush.

Does this make sense?

Edited to add: In our unit, the MD will write an order specifying which solution to use during flushes of the line, and whether or not using the infusing IV solution is acceptable for also flushing the line, depending on the baby's electrolyte levels, additives in the bag, etc.
Last edit by NICU_Nurse on Mar 20, '03
2. Couldn't have said it better myself!

Heather
3. tHAT WAS GREAT EXPLAINING I AM GONNA TRY TO PRINT IT OFF! tHANK YOU SOOOO MUCH rACQUEL
www.rmartinez8@marykay.com
4. The physician orders Zosyn 3.375gm IV q 8 hours. You havea vial of Zosyn 4.5 . You need to add 5ml of sterile water for each gram of zosyn to reconstitute the powder. How much sterile water would you add to the vial of zosyn to reconstitute? How much of the reconstituted zosyn would you add to 50ml of NS?
5. Quote from maline1954
the physician orders zosyn 3.375gm iv q 8 hours. you havea vial of zosyn 4.5 . you need to add 5ml of sterile water for each gram of zosyn to reconstitute the powder. how much sterile water would you add to the vial of zosyn to reconstitute? how much of the reconstituted zosyn would you add to 50ml of ns?
this was also posted in the nursing student assistance forum and was answered there: http://allnurses.com/forums/f205/new...on-266749.html

do a straight ratio equivalency to determine the answer to the first question. . .how much sterile water would you add to the vial of zosyn to reconstitute?
5 ml/1 gram = x ml/4.5 grams, cross multiply and solve for x

x = 22.5, this answer means you will add 22.5 ml of sterile water to the vial of zosyn to reconstitute the powder.

how much of the reconstituted zosyn would you add to 50ml of ns?
assume that the reconsituted vial contains 22.5 mls of solution with 4.5 gramsm of the zosyn in it since you were given no other information.
dose desired: 3.375 grams

dose on hand: 4.5 grams/22.5 ml

3.375 grams (dose desired)/4.5 grams (dose on hand) x 22.5 ml (amount of solution the zosyn is in) = 16.875 ml (dose to give), rounded to 16.9ml (most syringes aren't marked for .9 mls), or 17ml
6. I need help with this med problem, and thanks so much for the help i received with my other problem. Tx again.....I did try this problem , just need to kno if I'm correct.........A new order for Vancomycin 1250 mg IV is received. A 1 gram vial of Vancomycin is reconstituted with 20 ml of water. What is the total volume of Vancomycin that you would add to a 250 ml bag of NSS?

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