A question on dosage calculations

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i am not going into the nursing program till january 2007. however, i would like to familarize myself with dosage calculations. my question is, do you use dimensional analysis when having to do a conversion? i hope this doesn't sound stupid. i just want to get a better understanding of this.

cheryl

rn 2008

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

You can use dimensional analysis or you can simply multiply or divide the appropriate number in the problem by what you know to be the equivalent conversion. Whatever floats your boat. As long as you understand what you are doing and why you are doing it.

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Specializes in Too many to list.

Some of us (math challenged folks) find dimensional analysis to be real helpful as we don't have to do much actual analysis, just set up the problem to give you the units you need for the answer. I HATE MATH.

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i agree with indigo girl dimensional analysis is helpful. Oh ..and I HATE MATH TOO. Dont worry you will find out what works out better 4 u.

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I get math but still believe DA is the way to go..

just take your (desired dose/dose on hand) x (X / Quantity or Volume)

write that out like a normal multiplying fractions equation and cross multiply to solve for x

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Specializes in Ante-Intra-Postpartum, Post Gyne.

I am the worst at math in here...I do not even know what DA is!:idea:

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

DA is just an abbreviation of Dimensional Analysis.

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I prefer ratio porportion for everything!!!! Ratio porportion can take you all the way. IMO ;)

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what does ratio proportion involve?

I am the worst at maths and have been that way since grade 3. :idea: :o

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

Ratios are nothing more than fractions. Setting up ratio problems pretty much evolves around setting up a fraction where the numerator is the medication dose you want (or are ordered) to give and the denominator is the medication dose you have on hand. It only works when you don't have to make conversions from the apothecary system to the metric system. The only problem with this is that you need to understand that when you reduce that resulting fraction down, and you do have to reduce it down, you need to understand that your answer is now about the number of pills or the amount of liquid you are going to give.

The reason dimensional analysis (also called factor label method) is favored is because all of that is built into the equation you are setting up. Your goal is to set up an equation of conversion factors that are in the form of fractions multiplied together with the very specific purpose of factoring out (or, cancelling out) the labels that are attached to the numbers. There isn't much thinking on this. Where one fraction has as, an example, a number with the label "inches" in it's numerator there needs to be another fraction somewhere in the equation that has a number with the label "inches" in it's denominator so that the label "inches" will cancel, or factor out, leaving you with the labels you actually want at the very end of the calculation. The thing is that you might need the "inches" to get from "feet" to "meters" in the final answer. I actually feel that dimensional analysis is better used with IV drip rate problems. When it comes to figuring out how many tablets of something or how many mL of a solution you need to draw into a syringe from a vial, it is much quicker to do the old ratio math. When you start working with some of those complex cardiac and blood pressure medications you may well want to know the dimensional analysis method to get those drip rates and infusion rates correct.

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Thanks again DaytoNite

I will do some practice ;)

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