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Another med calculation question

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by Bonny619 Bonny619 (Member)

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I don't know why im having such a hard time with this, all of a sudden.

I'm pretty sure my problem is that I never really learned dimensional analysis.

Here's the question. I don't understand what goes where, but more important, I don't understand WHY they go where they do. Any explanation would be greatly appreciated.

6. Order: A heparin drip is infusing at 20 ml/hr.

Drug Label: Heparin 25,000 units in 500 mL of D5W

At this rate, how many units of heparin per hour are being delivered?

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gemini_star has 2 years experience as a BSN, RN and specializes in Oncology, Medical.

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What's your answer? I got 25 units per hour. I am not quite sure if I am correct.

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BmtTXLVN has 3 years experience and specializes in Geriatric/Psych.

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i believe its 1000 units/hr

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BmtTXLVN has 3 years experience and specializes in Geriatric/Psych.

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25,000 units per 500ml = 50 u/ml x 20 units=1000 units

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gemini_star has 2 years experience as a BSN, RN and specializes in Oncology, Medical.

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You're certainly correct. Geez, I suck. :clown:

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BmtTXLVN has 3 years experience and specializes in Geriatric/Psych.

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we all have those bad days

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Daytonite has 40 years experience as a BSN, RN and specializes in med/surg, telemetry, IV therapy, mgmt.

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a heparin drip is infusing at 20 ml/hr. the label reads heparin 25,000 units in 500 ml of d5w. at this rate, how many units of heparin per hour are being delivered?

you want to end up with units/hour.

25,000 units
/
500 ml
(dose on hand)
x
20 ml
/
1 hour
(dose to give)
=
1,000 units/1 hour
(after canceling out the label, "ml" and performing the math)

another way you can figure this out is to determine how many units you have in each ml of d5w by dividing 25,000units by 500ml to learn that there are 50units of heparin per each ml of solution. if the patient is getting 20ml and hour, that is 20ml x 50 units, or 1000 units of heparin an hour.

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Daytonite,

I need to take drug math this summer. I am going to take it online thru my cc here in Texas. I just want you to know that everytime I have seen a post about Drug math I look at it and study it, and then I look for your explanation. I have just about conquered my DA fear thanks to you. Now I purposely seek out more problems and try to solve them using DA so I will not be surprised when I have to know it cold for our quizzes coming this summer.

Thanks for your explanations. You are one of the few people that can explain math in an internet forum so that I actually understand most of it ! Thanks again!

Laura

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Daytonite has 40 years experience as a BSN, RN and specializes in med/surg, telemetry, IV therapy, mgmt.

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Thank you, Laura. I'm glad if my explanations are helping you. It's very hard to present math problems on this software. I can't show fractions the way I would like. And I can't show how labels are being factored out. It helps to be current in understanding how ratios work and how to do some basic manipulations with fractions. That really is all the math that is involved other than basic adding, subtracting, multiplying and dividing. Good luck with your class. You can always post a question on the forum or PM me if you are stuck on a problem.

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Yep, it was 1000 units/hr.

I'm still gettins stuck on some though. Can you use dimensional analysis on ALL med questions? It just doesnt seem to work on them all. Let me find an example.

4. Order: Ancef 1 gram over 30 minutes. The drip factor is 20gtts/mL

Drug label: Ancef 1 gram in 50 mls of NS.

The nurse would set the pump rate at how many mL/hour?

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Daytonite has 40 years experience as a BSN, RN and specializes in med/surg, telemetry, IV therapy, mgmt.

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ancef 1 gram over 30 minutes. the drip factor is 20gtts/ml. drug label: ancef 1 gram in 50 mls of ns.

the nurse would set the pump rate at how many ml/hour?

this is a simple ratio. you set two ratios (or two fractions), one with an unknown, equal to each other and then cross mutiply to find the variable. you can leave the labels off, but it is important that you make sure that the terms with the same labels occupy the same positions in the ratios (or fraction) on each side of the equation, like this:

50 ml
/
30 minutes
(amount to be given in the time to be given)
=
x
ml
/
60 minutes
(amount to set the pump at per one hour of time)

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