Estimating the net effect of unmeasured ions in human extracellular fluid using a new mathematical model. Part II: Practical issues.

Building on the theoretical considerations developed in Part I of this two-part series, a population range was established for a new extracellular fluid acid-base parameter using Monte Carlo simulation. This new parameter the unmeasured ion excess, had a normal range of +/- 2.50 mEq/l which was slightly narrower than the normal range for the standard base excess at +/- 3.20 mmol/l. In both cases, most of this variation occurred as a result of the estimation of the bicarbonate concentration. Finally, several short clinical vignettes were explored to highlight the differences between the unmeasured ion excess and the standard base excess.