dosage calculation

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I'm an RN student and have a math test coming up in 2 days. I would like to refer back to a question that was posted back in 2009 for practice purposes.

A mother in delivery is to recieve 4 mu of pitocin per min. The bag of LR contains 1000ml with 20 units of pitocin. How many ml/hr will you infuse the medication at?

The answer was 12, but could someone explain how they arrived at that answer using the proportion method?

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1000ml/20 = 50 50/4= 12.5ml/hr, my school would have rounded to 13 though?

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Specializes in Pedi.

20 units = 20,000 milliunits.

20,000 milliunits/1,000 mL = 20 milliunits/mL.

The patient is to receive 4 mu/min x 60 min/hr = 240 mu/hr. 240 mu/hr x 1 mL/20 mu = 12 mL/hr.

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Specializes in CNA.

I think I use dimensional analysis, but I found that if I do it the cross canceling way, it'll never fail me..and it hasn't yet:

First....I converted so we all have the same units, mu. There is 20,000 mu in 20 units. I am sure you can ifgure out how I got that.

Then at the top of my page I put ml/hr and circle it, as that is what I want to know.

I set up the problem so I can cancel out everything so all that is left is ml and hr.

4mu/min X 1000mL/20000mu X 60min/1hr = 12

If you write this down it's much easier. 4 mu corsses out with 20000mu. the minutes also cross out since there is one in the denominitor and 60 minutes in the numerator. All that is NOT crossed out is mL in the numerator, which we want, and hr in the denominator, which we also want. So you know you set it up right if that's all you have left and everything else crosses out, evenly.

Then does do the math straight across..and you get twelve even.

=]

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1000ml/20 = 50 50/4= 12.5ml/hr, my school would have rounded to 13 though?

No, because you don't divide units into cc to get units per cc. Exactly backwards.

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I got 12 mL per hr. I use that method as well

....

order is 4 milli units per minute

have 20,000 milliunits per 1000 mL

20,000mu 4mu

-------- x ------- = 0.2 milliunits per minute x 60 min = 12 milliunits per hour

1000mL Xmin

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Can you email me I have a question about test [email protected]

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