Hello! I am a nursiing student getting ready for a med matH test and doing practice questions.

I am having trouble with a med math question, that I feel should be easy, but it is getting me stuck. Do I use the 200 to calculate, or the 1000?

Order: 45% Isocal tube feeding, 200ml to run at 42 ml/hr

Available: Isocal 1000mL can

How many mL will the nurse use to make the above order?

mL Isocal__________ mL water__________

Thank you in advance!

13 Answers

This is the way I learned it:

Want 45% strength, which means 55% will be water (45% strength means 45% formula, 55% water).

There are 2 different ways to do it:

0.45 x 200 mL = 90 mL

200 mL – 90 mL = 110 mL

Discard 110 mL of Isocal and replace it with 110 mL of water.

This gives you 90 mL (45%) Isocal and 110 mL (55% water).

OR

200/0.45 = 444.444

444 – 200 = 244

Add 244 mL of water to the 200 mL Isocal can.

This gives you a total of 444 mL (244 mL + 200 mL = 444 mL) of which 244 mL (55%) is water and 200 mL (45%) is Isocal.

Specializes in Psych.
Correct. Just trying to figure out if the 1000 can is there just to throw me, and i should calculate from the 200 in the order,

Basically since it says you have 1000 mL you will pour out 90 and mix with 110 for the total of 200 like you had posted.

Correct. Just trying to figure out if the 1000 can is there just to throw me, and i should calculate from the 200 in the order,

You calculate from the 200 in the order.

Basically since it says you have 1000 mL you will pour out 90 and mix with 110 for the total of 200 like you had posted.

The way I learned it, you would pour out 100 mL of Isocal and replace that with 110 mL of water. That gives you 90 mL (45%) of Isocal and 110 mL (55%) of water - which is what you want 45% strength, which means need to dilute with 55% water.

Not sure I understand the question.

"200ml to run at 42 ml/hr"

I don't understand what calculation you need to do.

Give 200 ml.

Give it at 42 ml/hr.

It should take about 4 hrs, 45 minutes.

Maybe I am missing something here. I am an ER nurse, and don't get orders like this, but.....

Sorry i updated it. I am a student doing med math practice questions, and it is a dilution questions. How much of each formula and water

Specializes in Pedi.

So you're trying to dilute the formula to 45% strength? That's an odd strength (in pediatrics, we usually do 1/2 strength or 3/4 strength) but 45% of 200 = ? That's your formula amount. The difference between that and 200 is the amount of water you need.

I'm still not understanding the question. You need to mix Isocal with water, with 45% of the mixture isocal and 55% water, for a total of 200 ml?

ha, well these are not necessarily real life situation questions. That is what I thought too, 90 ml water and 110 water.

Correct. Just trying to figure out if the 1000 can is there just to throw me, and i should calculate from the 200 in the order,

Specializes in Pedi.
Correct. Just trying to figure out if the 1000 can is there just to throw me, and i should calculate from the 200 in the order,

That's just the full volume of the can. Isocal is a powder formula that needs to be mixed prior to administration.

In this question, isocal is a liquid. It's in milliliters.

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