Q: I am having a hard time getting my head around dimensional analysis. Do you have a good resource for learning this?
A: Dimensional Analysis (DA) is the preferred way to teach medication calculations, I’ve found. I learned ratios and proportions. DA is similar but tries to standardize the model so that it works for all medication calculations solutions – mg to mg, mcg to mcg, gtts/min, mcg/kg/min, mg/kg, etc.
There are multiple methods of calculating drug dosages, as you know. Research shows that med mistakes are made because the calculation was set up incorrectly leading to mistakes. Dimensional analysis is one method of calculating dosage and calculation problems that is based on a visual conceptual model for setting up an equation in a fraction format based on the info given in the problem.
The aim to cancel out (i.e., get rid of) the units that you are not solving for by canceling out similar units in the numerator and the denominator so that all you have left is the units of measure you are solving for. You do have to have equivalence between the units, of course, so you still have to know your conversion factors.
But the idea of using this model is that the need for formula memorization is decreased and therefore medication calculation is more accurate and results in less errors; it is one method for all medication calculations solutions (Greenfield, Whelan, & Cohn, 2006).
See the post I did on Dimensional Analysis and Medication Calculation for more in-depth info and a couple of practice problems. I will also get a practice worksheet up – check the Members Only page for when that is posted.
Here are some texts that are specifically about Dimensional Analysis:
Calculating Dosages Safely: A Dimensional Analysis Approach
Medical Dosage Calculations: A Dimensional Analysis Approach
Clinical Calculations Made Easy: Solving Problems Using Dimensional Analysis (6th ed.).
Reference:
Greenfield, S., Whelan, B., & Cohn, E. (2006). Use of dimensional analysis to reduce medication errors. Journal of Nursing Education, 45(2), 91-94.
.
