[Lissa1046]

I am a student currently taking Anatomy and Physiology I to hopefully get accepted into nursing school. Bad news, is the teacher just assumes we know how to do converting and preparing solutions. When we ask her, then she decides to show us. Most teachers would at least explain how it is done before letting the class do the labs on their own. But anyway...Here is an example, we were supposed to prepare 50ml of 4.0% w/v glucose. After racking our brains we came up with 4g of glucose needed to prepare the solution. But my question is...is there a way that nurses figure this out that can be easier? Is there a set formula to use? It just doesn't make sense to me. Can anyone help before I loose my mind?

[michw2]

Melissa Is that all they gave you for that problem?

[suzanne4]

A 4% solution is 4 grams per 100cc, therefore you would need 2 grams for to make 50 cc.

Same as if you are calculating calories of a bag of IV fluid, perhaps this will be easier to understand.

And percentage is based on that amount in 100cc, so a 5% glucose solution would have 5 grams per 100 cc or 50 grams per 1000cc. 4 calories per gram of carbs, so each 1000 cc bag will have 200 calories. Just remember to base whatever the percentage is on that amount in 100 grams, so you have to multiply to get the amount in 1000cc or divide for less than 100cc.

I promise that it will get easier....................Good luck

[chris_at_lucas_RN]

When I read the OP, I thought, wow, why are we doing dosage calcs in A&P? Then I realized it was a matter of terminology--understanding molar, molal, percent weight, etc. (Boy, it's been a long time!)

Look at the definitions for the various terms describing concentrations (which is what this really is, not dosage calcs--but that's ok, dosage calcs are coming!), and you will see exactly how to construct one. A good way to learn those are to make up questions of your own and try them out. The differences are rather subtle but important.

What you are describing is the kind of test question you will see in nursing school: one which, in order to get the right answer, you have to know some other stuff.

Good post! Thanks! Haven't thought of that stuff in quite a while...

[Lissa1046]

Originally Posted by suzanne4

A 4% solution is 4 grams per 100cc, therefore you would need 2 grams for to make 50 cc.

Same as if you are calculating calories of a bag of IV fluid, perhaps this will be easier to understand.

And percentage is based on that amount in 100cc, so a 5% glucose solution would have 5 grams per 100 cc or 50 grams per 1000cc. 4 calories per gram of carbs, so each 1000 cc bag will have 200 calories. Just remember to base whatever the percentage is on that amount in 100 grams, so you have to multiply to get the amount in 1000cc or divide for less than 100cc.

I promise that it will get easier....................Good luck

So, let me clarify...does the 5% solution mean automatically that I would need 5 grams of glucose per 100cc (which is the same as 1mL)? Or did I miss something...?

[Lissa1046]

Originally Posted by chris_at_lucas

When I read the OP, I thought, wow, why are we doing dosage calcs in A&P? Then I realized it was a matter of terminology--understanding molar, molal, percent weight, etc. (Boy, it's been a long time!)

Look at the definitions for the various terms describing concentrations (which is what this really is, not dosage calcs--but that's ok, dosage calcs are coming!), and you will see exactly how to construct one. A good way to learn those are to make up questions of your own and try them out. The differences are rather subtle but important.

What you are describing is the kind of test question you will see in nursing school: one which, in order to get the right answer, you have to know some other stuff.

Good post! Thanks! Haven't thought of that stuff in quite a while...

Thank you for the correction, I should have posted this under concentrations! A&P is whipping my butt! LOL. I went for some tutoring yesterday...but I am hoping the light bulb will go off soon. I think the biggest 2 problems are the teacher not explaining how we are supposed to figure out our lab problems, and the class being only 8 weeks long! Time to go cram, thank you all for your help! I am sure I will be posting again soon.

[suzanne4]

Originally Posted by Lissa1046

So, let me clarify...does the 5% solution mean automatically that I would need 5 grams of glucose per 100cc (which is the same as 1mL)? Or did I miss something...?

Yes! What ever the percentage, you need that amount in 100 cc or mls, so for making 1000 cc you would need 50 grams of glucose.

[Lissa1046]

Originally Posted by suzanne4

Yes! What ever the percentage, you need that amount in 100 cc or mls, so for making 1000 cc you would need 50 grams of glucose.

WOW! I get it now. Thank you so much! I think the lightbulb went off