Proportional Analysis versus Dimensional Analysis - A More Difficult Example

Administer 2000 mL NS intravenous at 115 mL/hr.  The available drip chamber drop factor is 10 gtt/mL.  Calculate the infusion rate in gtt/min


By Proportional Analysis

By Dimensional Analysis

 

Discussion: The proportion analysis technique requires setting up, cross-multiplying, and solving for the unknown variable 3 separate times.  In the end two intermediate results must be set as a ratio to get the final answer.  Intermediate results introduce the risk of inappropriate rounding that may introduce significant error into the final calculation.  With the dimensional analysis technique a single equation is set up and all intermediate results are automatically held in the calculator’s memory to at least 8 decimal places so that a chance for error is eliminated.  Also, a final ratio does not need to be set up, as with the proportion analysis technique.  Instead a single universal approach is used.