# Help with Pharm Question

I'm pretty good at doing dosage calculations but this question given in class today has stomped me. The teacher got an answer that I can't seem to get. Can anyone do this problem step by step and maybe I can see what i am missing? Also if possible use formula, ration and porportion. or any method other than scientific, I don't use it and don't like it because I think it takes you through unecessary steps and confuses me.

Order: 50 mEq KCL added to 100mL NS at a rate of 10 mEq/hr and 60 gtt/mL. What are the gtt/min?

I have been great at drug calc, but I do problems differently from others; I just use simple logic and not linear algebra like some people do.

If that is correct, I can show you how I did it. It was a question I've never seen before, we dont have that kind of calculations yet, but if I am wrong, Im going to be so embarassed. :chuckle

Specializes in Dialysis.

oooh, good one! Yes, I also got 20 gtt/min.

first i figured that it would be 20ml/hr. (I divided the 50mEq and the 100ml by 10, ending up with 5mEq per 10mL, thus getting 20mL/hr. then i set up the problem:

1hr X 20ml X 60gtt = 1200 = 20gtt/min

___ ____ ____ ____

60min 1hr 1ml 60

Specializes in DOU.

Here's how I would set it up:

gtt/min = 60gtt/ml x 100ml/50mEg x 10 mEq/hr x 1 hr/60min = __________

I get 20 gtt/min

oooh, good one! Yes, I also got 20 gtt/min.

first i figured that it would be 20ml/hr. (I divided the 50mEq and the 100ml by 10, ending up with 5mEq per 10mL, thus getting 20mL/hr. then i set up the problem:

1hr X 20ml X 60gtt = 1200 = 20gtt/min

_____ ____ ____ ____

60min 1hr 1ml 60

That is what I also did (the initial part)

50 mEq / 10 mEq x 1hr = 5 hrs (300 minutes)

Then I did a formula which you use for getting gtt/min.

total volume(mLs) Drops

__________ X ___________ = gtt/min

total Time(mins) 1 milliliter

Dimensional analysis lets you set up the entire problem in one step (dots added for formatting):

100mL...X...10mEq...X...60gtt...X.....1hr ..=..20gtt

50mEq..........1hr...........1mL.........60min.....1min

Notice how each fraction is set up so that all unwanted units cancel each other out and you're left with just the desired units in the answer. You can do this because each 'fraction' is a unity - equal to 1, so it doesn't matter which you put on top and which you put on bottom. This allows you to manipulate them so unwanted units drop out.

thanks everybody this is what i did:

50:100=10:x

50x=1000

x=20

but now that looks like 10 mEq/20 mL which is confusing to me. I am just gonna stop thinking about it this is a made up question by the teacher. all the problems in the book look nothing like this and i can do them with my eyes

thanks everybody this is what i did:

50:100=10:x

50x=1000

x=20

but now that looks like 10 mEq/20 mL which is confusing to me. I am just gonna stop thinking about it this is a made up question by the teacher. all the problems in the book look nothing like this and i can do them with my eyes

No, you're on the right track; the dose is 20mL (which contains 10mEq of KCL), to infuse over 1 hour. This is how it would look using dimensional analysis from this point:

20mL..X..60gtt..X.....1hr......=...20gtt

..1hr........1mL........60min.........1min

Specializes in med/surg, telemetry, IV therapy, mgmt.

order: 50 meq kcl added to 100ml ns at a rate of 10 meq/hr and 60 gtt/ml. what are the gtt/min?

dose desired
: 10 meq/hour

dose on hand
: 50 meq/100 ml

drop factor
: 60 gtts/ml

conversion factor
: 1 hour = 60 minutes

by dimensional analysis, you want the final answer to be gtts/minute.

10 meq/hour
(dose desired)
x 100 ml/50 meq
(dose on hand)
x 60 gtts/ml
(drop factor of iv tubing being used)
x 1 hour/60 minutes
(conversion factor)
=
20 gtts/minute
(infusion rate)

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