Need help on this basic med math problem?

Nursing Students General Students

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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.

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

Specializes in NICU, ICU, PICU, Academia.

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

Does that help?

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....

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

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

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

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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