Medication Math for the Nursing Student

When you're doing applied math numbers have units of measure, or "dimensions," attached to them. There are lots of formulas out there, but here's the big idea: when you plug values into a formula and pay close attention to what happens to the units as the formula is simplified, you'll see that all the units cancel out except those units that end up in your answer. This always happens if the formula is correct and you plug in the appropriate factors.

So what someone figured out is that you don't need formulas at all. For every problem you can just take the factors associated with it and arrange them so all the units you don't want cancel out. You're then left with only the units you do want (the ones in your answer). This process is fairly trivial, and with only slight attention to detail, you always get the right answer, bing-bang-boom, every time.

The technique has been taught to students of applied science for longer than I have been able to determine and for the sole reason that students using it make fewer mistakes. You pay attention to the units of measure and if they're not canceling out right, you know that you're doing something wrong and that your answer is guaranteed to be wrong.

As nurses doing calculations, error is not an option. Passing med-math class may require getting only 80% of test problems right, but coming up with the right answer only four out of five times isn't good enough when real patients are at risk. While mistakes can still be made using any technique, dimensional analysis does the best job of minimizing them. The only fault lies in the name. Perhaps the Math-Weenie-No-Brainer technique would be more appropriate. At any rate, give dimensional analysis a try. At the end of a 12-hour shift, when you're tired, things are crazy, and you have to do a med-math calculation, you'll be glad you did.

Eric Lee, RN

Haven't read this, but there is a book now (Dimensional Analysis for Meds). If the publisher were to send me a copy, I'd be willing to review it.

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