Math calculations test next week, HELP ME!

noele1213 · Jan 3, 2006

I'm not trying to be sarcastic here at all, please believe that, but I'm a little nervous reading your post. Do instructors teach you this or expect you to learn it yourself? I hope they indeed do spend a great deal of time with med calculations as I would think it's critical to nursing.

Megs7617 · Jan 3, 2006

Hi everyone! I have just finished my first semester in Foundations of Nursing and begin next week in Adults 1 (Med-surg1). In order for us to start clinicals we have to pass this math calculations test the first day of class and I am a human wreck trying to figure out some of these problems. If anyone is interested, can you please help me figure them out?
1. Acyclovir 400mg in 100ml of D5W is ordered to infuse over 0.25 hours. The IV tubing delivers 10gtt/ml. The rate of the infusion will be how many gtts/min?
2. A Heparin drip is ordered: 500ml DW with 50,000 unit of Heparin to infuse at 1100units/hour. How many ml/hr will the pt receive?
*p.s. can you explain to me the procedures for figuring out units?
3. 500ml of D5W with 0.5G Theophylline is ordered to infuse at 50ml/hr. How many mg will the pt received per hour?
Thank you so much for your patience, this will really help.

ok, we have only just begun learning IV calculations but I am going to take a try at number one. Im not sure about the second and third questions.

1. 100ml divided by 15 minutes times 10 = 66.6 = 67 gtt/min

truern · Jan 3, 2006

1. acyclovir 400mg in 100ml of d5w is ordered to infuse over 0.25 hours. the iv tubing delivers 10gtt/ml. the rate of the infusion will be how many gtts/min?
100 ml x 10 gtt/15 min = 67 gtts/min in this case, the 400 mg acyclovir is a distractor. drip rates are figured amount to infuse times drip factor of the tubing divided by the time to infuse in minutes.
2. a heparin drip is ordered: 500ml dw with 50,000 unit of heparin to infuse at 1100units/hour. how many ml/hr will the pt receive?
*p.s. can you explain to me the procedures for figuring out units?
if there are 50,000 units in 500 ml dw, then there are 100 units in 1 ml (make it simple) to infuse 1100 units in an hour, you'd need to infuse 11 ml per hour. (1100/100 = 11)
3. 500ml of d5w with 0.5g theophylline is ordered to infuse at 50ml/hr. how many mg will the pt received per hour?
first convert 0.5 grams to milligrams: 500 mg. 500 mg per 500 ml is the same as 1 mg per 1 ml. so if you're infusing 50 ml/hr, they're getting 50 mg per hour. i set it up as 1 mg/1 ml:x mg/50 ml..cross multiply to get 1x = 50

somebody correct me if i'm wrong...it's been a long break :lol2:

Daytonite, BSN, RN · Jan 3, 2006

ack! truesn beat me to the posting. i was off line typing out how to work out the problems for you. i'll go one better however and give you three websites to check out. the first will explain how to set these problems up and the second has lots of practice problems with the answers. however, they don't give the step-by-step solutions. i strongly suggest that you set aside of block of 3 or 4 hours and hunker down to figure out how to work these problems, or you will never learn them. once you think you've "got it" try changing the problems around so you have to find ml/hr rather than gtts/min until you have this nailed down. another way to turn a problem around is to be told you want to give xxmg of a drug at xxml an hour. you have a 500ml bag of solution. how many mg must you add so the bag lasts 8 hours? math requires that you work problem after problem or you will never truly understand what you are doing. i was taught this basic formula that works for tablets and liquids: dose desired divided by dose on hand times the amount you have available. problems should be set up as ratios with labels on the numbers so the labels cancel each other out until you get the label you want on the final answer. the other thing i was taught as a short cut years ago when working with drip factors of tubings when we had to regulate drip rates and did not use pumps. figure out the amount in ml you want to give per hour and then divide by 3 (for a 20gtts/min tubing), 4 (for a 15gtts/min tubing), 6 (for a 10gtts/min tubing) or 60 (for a 60gtts/min tubing). it cuts two ratios down into one ratio very quickly when working these problems.

now, here are the answers:

1. 67 gtts/min

the equation is:

[1 hour divided by 60 minutes] multiplied by [100ml (amount desired) divided by .25 hour] multiplied by [10gtts divided by 1ml] = 66.6666gtts/min or 67gtts/min

2. 11ml/hour

the equation is:

[1100 units(dose desired) divided 1 hour] quantity multiplied by [500ml (amount) divided by 50,000 units (dose on hand)] = 11ml/hr

3. 50mg/hour

convert .5g to 500 mg before working problem

then equation is:

[50ml divided (amount desired) by 1 hour] multiplied by [500mg divided by 500ml (amount on hand)] = 11ml/hour

these problems are set up so that the labels attached to the numbers cancel out to give you the final labels that you want on the final answer as the problem asks you for.

here are the web sites:

http://www.indstate.edu/mary/tutorial.htm

http://go.dbcc.edu/hhps/nursing/nur_1201_nur_1260c_nur1213.html - a wonderful site with practice problems of iv calculations. answers are provided, but not the step-by-step solutions. just click on the links provided.

http://www.dalesplace.net/introduc.htm dales place math help for nursing math. knock yourself out on this site.

truern · Jan 3, 2006

Thanks, Daytonite...you always have such GREAT sites :)

To the OP: once you get into clinicals and actually start USING the math, it will make more sense. I found it helps me to visualize the medication in the problem....to actually think about what I'm supposed to give and how it's supplied..well, you get the picture:p

Good luck on your exam!! Let us know how it goes.

rn2bn07, BSN, RN · Jan 4, 2006

Thanks for all who have responded to this thread. I love this site, it has helped me so much. I know some of them may have been easy to some people but I had forgot to mention that I had pharmacology two years ago, before I even started the Program, so my mind was blank at a lot these problems. But with your help I am back in the light of things and I will let you know how it went after I take the test. Good luck to you all, Thanks again

rn2bn07, BSN, RN · Jan 15, 2006

Hey, thanks to you all who replied, I received 20 out of 20 right! I was so excited I passed and appreciate everyone who helped, Thanks

Daytonite, BSN, RN · Jan 15, 2006

Yahoo! You see, working at this stuff does pay off. Math is really not as hard as people want to think it is. It's one of the myths that has stuck around for ages that needs to be broken. Congratulations!

:balloons: :balloons: :balloons: :balloons:

sydylo · Jan 18, 2006

Hello. I have a math calculation, also, and am just a little confused. I love math, and I am good at the conversions, but there is a question on the handout that I just don't get.

Child 5 lbs, you are ordered to give 10 mg/kg of Tylenol. You have infant drops available in a concentration of 80 mg/0.8 ml dropper. How much do you give?

I have the weight conversion down, 2.3 kg. I am just not sure what to do there.

The other question is an infant weighs 32 lbs and needs Tylenol for pain relief, 15 mg/kg. The concentration available is 160 mg/5 ml.

I know once it clicks I will be good, I am just not understanding the reasoning right now. Any help would be greatly appreciated. Thanks!

hrtprncss · Jan 18, 2006

Hello. I have a math calculation, also, and am just a little confused. I love math, and I am good at the conversions, but there is a question on the handout that I just don't get.
Child 5 lbs, you are ordered to give 10 mg/kg of Tylenol. You have infant drops available in a concentration of 80 mg/0.8 ml dropper. How much do you give?
I have the weight conversion down, 2.3 kg. I am just not sure what to do there.
The other question is an infant weighs 32 lbs and needs Tylenol for pain relief, 15 mg/kg. The concentration available is 160 mg/5 ml.
I know once it clicks I will be good, I am just not understanding the reasoning right now. Any help would be greatly appreciated. Thanks!

After converting to kg, u need to dimensional analysis twice

first, if 10mg is given for every kg, then first solve for how many mg given for 2.3 kg...

second, once u have the dosage for the weight, u have to do dimensional analysis again to get how many cc it is for that given Xmg. if you know you have 80 mg per 0.8 cc then you'd be able to get the final answer...

same thing with the next question...it's two steps

Achoo!, LPN · Jan 18, 2006

Child 5 lbs, you are ordered to give 10 mg/kg of Tylenol. You have infant drops available in a concentration of 80 mg/0.8 ml dropper. How much do you give?

I have the weight conversion down, 2.3 kg. I am just not sure what to do there.

The other question is an infant weighs 32 lbs and needs Tylenol for pain relief, 15 mg/kg. The concentration available is 160 mg/5 ml.

2.3 kg x 10 mg= 20 mg

80 mg 20

______ _____

0.8 ml X ml

0.8 x 20 divided by 80 = 0.04 ml.

This is what I have been self teaching myself. I think that is correct. I just started. use the same formula for the other problem.

Tracy