The Nursing Math Thread  page 6
A member pm'd me the following question highlighted below. We created this thread for you guys to talk about math, solve math problems, and post math websites that you have found helpful. I was... Read More

Aug 8, '08Occupation: An LPN. Now... to get that license number and work!! Specialty: LTC ; Joined: Aug '08; Posts: 33; Likes: 3Quote from TweetyThanx for asking that! I had asked as general ?? for some pointers! But WOW!!! What a plethera of info that came!! I bookmarked this one for future use!! Thanx again!!A member pm'd me the following question highlighted below. We created this thread for you guys to talk about math, solve math problems, and post math websites that you have found helpful.
I was wondering, is there a sticky or a special site that can be coordinated for "math sufferers". Perhaps, beginning calculations or shall i say the basics..simple to complex...step by step on how to calculate. I'm a visual learner, numbers and I don't work well. I am trying, but I've got a block! 
Aug 11, '08Joined: Mar '08; Posts: 1,866; Likes: 1,357I have a basic question. Our school posted 20 drug dosage questions, but won't post the answers. (They say if they did, no one would do the work!! whatever!!!)
Here is the question:
The order is to administer Kefzol 500 mg IVPB q6h for 4 days. Kefzol 225mg per 2ml is available. How many mL of Kefzol would you add to the IVPB per dose?
ANSWER:
When you work it out, you get 2.22222 mL. MY QUESTION do you round off to 2mL or 2.2 mL??
I say you round off to 2 mL but a few other students have stated it should be 2.2 mL? who is correct??
One more question for clarification:
If your giving a drub by IV PUSH, you would round off to the nearest tenth? i.e. 1.44 as ur answer would be rounded off to 1.4 (not just 1)
Thanks 
Aug 11, '08Occupation: Student, wife, and Mom of 3, and that is plenty! From: US ; Joined: May '07; Posts: 900; Likes: 298Yes, round off to the nearest tenth for meds given from a syringe. The syringes are marked to give tenth of a ml doses.

Aug 11, '08Specialty: med/surg, telemetry, IV therapy, mgmt ; Joined: May '05; Posts: 15,027; Likes: 8,983Quote from flames9beth66335 is correct in telling you that when you are giving liquid doses involving syringes you consider that the syringes are marked to an accuracy of 1/10 of a ml, or cc, so your answers should reflect that.i have a basic question. our school posted 20 drug dosage questions, but won't post the answers. (they say if they did, no one would do the work!! whatever!!!)
here is the question:
the order is to administer kefzol 500 mg ivpb q6h for 4 days. kefzol 225mg per 2ml is available. how many ml of kefzol would you add to the ivpb per dose?
answer:
when you work it out, you get 2.22222 ml. my question do you round off to 2ml or 2.2 ml??
i say you round off to 2 ml but a few other students have stated it should be 2.2 ml? who is correct??
one more question for clarification:
if your giving a drub by iv push, you would round off to the nearest tenth? i.e. 1.44 as ur answer would be rounded off to 1.4 (not just 1)
thanks
however, your answer to the first problem is incorrect. it is a good idea on tests to write your work down and double check it. use all the time you are given up to the last minuteespecially if the outcome is important to your school career! or a patient's safety!
the order is to administer kefzol 500 mg ivpb q6h for 4 days. kefzol 225mg per 2ml is available. how many ml of kefzol would you add to the ivpb per dose?
dose desired: 500 mg
dose on hand: 225 mg/2 ml
500 mg (dose desired)/225 mg (dose on hand) x 2 ml (amount the dose on hand comes in) = 4.444 ml, rounds to 4.4 ml 
Aug 11, '08Joined: Mar '08; Posts: 1,866; Likes: 1,357OOPSS!!! Question should have been225 mh PER 1ml (not 2) should double check my typing, sorry!!
I thought with IV PiggyBack, was the small bag, hung above the main bag, which is prepared by the pharmacy, so you as the RN can not add to it????
So this gives you 2.2222 ml and should be rounded to 2.2 ml. Ok I'm cool with that, but referencing my books, Henke and Calculations made easy, they both round it to 2 ml (vice 2.2 ml) I'm not stating your incorrect daytonite, I have always respected your replies. Just weird that one finds these conflicting answers,lol Thanks, I truly appreciate your time. 
Aug 11, '08Specialty: med/surg, telemetry, IV therapy, mgmt ; Joined: May '05; Posts: 15,027; Likes: 8,983Quote from flames9you are correct. the iv piggyback is the small bag of 50cc or 100cc of ns or d5w that is hung above the main iv infusion. when drugs are added to them it is often done by the pharmacy, but in some facilities during the nighttime or in an emergency the nurse may end up having to mix the piggyback. i've worked in several places where we were not allowed to give anything by iv push. instead we had to mix the drug in a piggyback and drip it. that could only be done by us nurses on the unit. the pharmacy wasn't going to bother mixing every prn dose of iv valium for us when a patient needed it.oopss!!! question should have been225 mh per 1ml (not 2) should double check my typing, sorry!!
i thought with iv piggyback, was the small bag, hung above the main bag, which is prepared by the pharmacy, so you as the rn can not add to it????
so this gives you 2.2222 ml and should be rounded to 2.2 ml. ok i'm cool with that, but referencing my books, henke and calculations made easy, they both round it to 2 ml (vice 2.2 ml) i'm not stating your incorrect daytonite, i have always respected your replies. just weird that one finds these conflicting answers,lol thanks, i truly appreciate your time.
the rounding to 2 instead of 2.2 is a mathematics thing and has to do with scientific notation. if the numbers going into the calculations are whole integers then the results are supposed to be expressed as whole integers. a scientist would only express the answer as 2.2 if one of the numbers going into the calculation was, let's say, 225.0 mg. it's just one of those quirky things that people who have taken chemistry or physics know when it comes to doing the math connected with them. for your tests you might want to clarify with your instructors what they will accept as correct answers when it comes to rounding them off. 
Aug 11, '08Joined: Mar '08; Posts: 1,866; Likes: 1,357Thanks again daytonite. On our exams it states to round off to 2 decimal places WHEN NECESSARY,lol And thats where the confusion lays with this problem.I know with a syringe when to round off, but with this IV Piggy Back it leads to confusion, at least for my tiny male brain!!
I guess since I have never completed any "hands on" filling of these bags, it does not help! SO I assume (yes bad to do,lol) one would use a syringe to draw up your 2.2 ml of the drug and add it to the bag! Damn new nurses,lol I hope your feeling well daytonite. Cheers 
Aug 11, '08Specialty: med/surg, telemetry, IV therapy, mgmt ; Joined: May '05; Posts: 15,027; Likes: 8,983I'm feeling quite well since my chemo has been over for several months. However, I am having surgery again next week. It will slow my typing down a bit is all. Pull a piggyback bag the next time you are in lab or clinicals and look at it and a couple of syringes so you can make some correlations here.

Aug 11, '08Occupation: Student, wife, and Mom of 3, and that is plenty! From: US ; Joined: May '07; Posts: 900; Likes: 298Quote from flames9When you are doing drip factors you will do this...you can't give part of a drop!:chuckleOn our exams it states to round off to 2 decimal places WHEN NECESSARY,lol And thats where the confusion lays with this problem.

Aug 11, '08Specialty: med/surg, telemetry, IV therapy, mgmt ; Joined: May '05; Posts: 15,027; Likes: 8,983Quote from beth66335I wouldn't.When you are doing drip factors you will do this...you can't give part of a drop!:chuckle

Aug 11, '08Joined: Mar '08; Posts: 1,866; Likes: 1,357I'm pretty sure daytonite could do a 0.34 of a drip if she really wanted too!! You hear those Cuck Norris Fables, such as "His tears cures cancer, but her never cries" or" chuck norris can sneeze with his eyes open" Well Daytonite can with her eyes closed an squeeze out a .34 of a drop!! lol She is that good!!! We students owe her a lot!! I bow down!!!

Aug 15, '08Joined: Aug '08; Posts: 51; Likes: 47This formula helps with simple calculations. Say 25 mg of a drug is ordered and on hand is a vial containing 50mg/2ml. How many mL do you give.
Set it up like this
50mg x 25mg = 50 x= 50 x=1 mL
2 mL xml 50 50
Keep mg across from one another on the top, and mL across from one another on the bottom. Then do simple cross multiplying, divide by the number next to x and this will give you your mL.
To calculate gtts/min, you have to know your drop factor which is either 20 gtt/min (standard) or 60gtts/min for a microdrip. Here is the fromula i use
total volume (ml) x drop factor/ 1 min = gtt/min
minutes (*not hrs)
so lets say. 250ml x 20gtt/1min= 5000= 83.3=83 gtts/min
60 min 60
Hope this helps.Last edit by nrsgnerd on Aug 15, '08 
Aug 17, '08Joined: Aug '08; Posts: 6; Likes: 2The math is one of my weak areas, as well...I found the following websites helpful. And you can even start reviewing from basic algebra and work your way forward...there arre also quizzes to test yourself...
www.accd.edu/SAC/NURSING/math/default.html
www.alysion.org/dimensionalanalysis.htm
Hope they are helpful!!