Estimating the net effect of unmeasured ions in human extracellular fluid using a new mathematical model. Part I: Theoretical considerations.

A theoretical framework for the formulation of a derived variable to be used for the prediction of the net effect of unmeasured charged species present in human extracellular fluid was explored. This new variable was based on contemporary strong ion and classical buffer base theories and tested against the standard base excess using simulation. It proved to be more accurate in predicting the existence of unmeasured charged species in the extracellular fluid when disturbances of either strong ions, weak acids or both were present.