Need help on this basic med math problem?

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I have a med math exam tomorrow morning and I cannot figure this problem out:

The patient is to receive Pitocin (oxytocin) at a rate of 8 milliunits per minute. The IV

contains 10 units of Pitocin in 1000 ml Lactated Ringers. How many ml/hr to be set on

the pump to infuse the required dose?

I keep getting the wrong answer because I was never taught units and it's throwing me off.

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I did: 10 units/1000ml = 1min/.008 units but I guess this is not how your supposed to set this up.

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Specializes in NICU, ICU, PICU, Academia.

1 unit = 1000 milliunits (just as 1 gram = 1000 milligrams)

Does that help?

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1 unit = 1000 milliunits (just as 1 gram = 1000 milligrams)

Does that help?

Yes, that helps some. But what about the ml/hr? Can you show me how to set this up? I'm not looking for the answer because I have it, I just don't know how to set it up. I asked my classmates in group meet but they told me the exact same thing you just told me.

So, I just took another shot at the problem and set it up like this=

.008 units/0.17 hr= 1000ml/10 units.

I got 40 as my answer but the right answer is 48....

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Specializes in ICU.

Close, you lost a 0 converting min to hours, should be 0.017 hr. Here's how I would set this up:

(0.008 units/1 min.) x (1000ml/ 10 units) x (60 min./ 1 hr) = 48 ml/hr

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Thank you! I finally get it now. This will be my 2nd week in OB and we have not learned this at all.

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Specializes in Pharmacy, Mathematics, Physics, and Educator.

You are starting with a rate of 8 milliunits/min and you have to change that to mL/h. Start off by writing the given and the units of the answer. This way you can fill in the ratios easier.

8 milliunits/min = mL/h

You will have to change milliunits to mL and min to h. The ratios used to change milliunits to mL are 1000 mL/10 units and 1 unit/1000 milliunits.

The ratio to change min to h is, of course, 60 min/h.

Just line everything up so you cancel out the unwanted units and end up with mL/h.

8 milliunits/min (1000 mL/10 units)(1 unit/1000 milliunits)(60 min/h) = 48 mL/h

Note: all the ratios equal 1, so you are only multiplying by various forms of 1 to change the units of the given into the units of the answer.

Brad Wojcik, PharmD

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Hey there here's what I'd do:

1000ml/10,000 milliunits X 8 milliunits/1 minute X 60 minutes/ 1 hour

Cancel units and multiply straight across to get 48 ml/hr

Love these problems!

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