2nd year sudent who needs med. calc. help!!

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I have a crazy instructor who gave us these off the wall med calc. problems on our test. The one goes like this...

You have a pump that's programmed at 50gtts/ml. It's running at 45 gtts/min. How many hours would it take to infuse a 1 liter (1000 ml) bag of solution?

I set mine up how you would to figure out the gtts/min and worked backwards, but i had to play around with it a little to get the answer. My set up looked like this: 1000/x times 50=45

I divided 1000 by 50 and got 20, which would give me 1200min. That didn't work when i put it in for x so I played around with it and got 1100 for x and that worked, i jsut wanted to make sure my concept was right..and the i divided 1100 by 60 and got 18.3 hours...which is what the majority of people got but I just wanted to make sure I did it right..

The other one went like this...

You have an IVPB of Erythromycin 250 ml that needs to infuse in an hour. Your tubing is 60 gtts/ml. How many ml/hr will it run at? what is the gtts/min?

I got 250 for both answers...I just didn't know if I would've done it right for the gtts/min.

Thank you!!!

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1000 ml divided by ((45gtts per min/50 gtts per ml)x60 minutes in an hour)

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Specializes in Sub-Acute/Psychiatric/Detox.

Morte summed it up easily. Dimensional Analysis is much better then the X method, however it is easier at times to see the process you are doing to feel comfortable with it.

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Specializes in being a Credible Source.

To me, #1 is a little easier to see this way:

45 gtt/min x (1 ml/50 gtt) = 0.9 ml/min

1000 ml x (1 min/0.9 ml) = 1111.1 min

1111.1 min x (1 hr/60 min) = 18.5 hr

Problem #2:

Given 250 ml in one hour

250 ml / 1 hr = 250 ml/hr

250 ml/hr x (60 gtt/ml) = 15000 gtt/hr

15000 gtt/hr x (1 hr/60 min) = 250 gtt/min

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Specializes in med/surg, telemetry, IV therapy, mgmt.
You have a pump that's programmed at 50gtts/ml. It's running at 45 gtts/min. How many hours would it take to infuse a 1 liter (1000 ml) bag of solution?

1000 mL
(dose to give) x
50 gtts/mL
(drop factor)
x 1 minute/45 gtts
(infusion rate)
x 1 hour/60 minutes
(conversion factor)
= 18.518518 hours =
18.5 hours
(rounded off)

You have an IVPB of Erythromycin 250 ml that needs to infuse in an hour. Your tubing is 60 gtts/ml. How many ml/hr will it run at? what is the gtts/min?

How many ml/hr will it run at?
The answer is information given in the question itself. It has to run at
250mL/hour
.

Drops per minute will be:

250 mL/1 hour
(dose desired) x
60 gtts/1 mL
(drop factor of tubing)
x 1 hour/60 minutes
(conversion factor)
=
250 gtts/minute

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