chloride, adjusted for the absolute difference between sodium and chloride

Chloride is arguably the most underestimated quantity in clinical acidbase practice. read more!

Because electroneutrality has to be maintained, reducing the difference between the two main ions in extracellular fluid, Na+ and Cl-, one positive, the other negative, necessarily narrows the space left over for the second most common negative ion species: HCO3-.
As long as PCO2 remains unchanged, the classical Henderson -Hasselbalch- equation tells us that the solution will become more acidotic.

As it is the difference between the two, Na+ and Cl-, that matters and not their absolute values, Cl- gets adjusted for any concomitant changes in Na+ by simple addition and subtraction: Clcorr

(Deriving Clcorr by its change proportional to that of Na+, is preferred when looking for concentrational and dilutional effects.)

consult the glossary for other aspects of acid-base equilibria and the rules and mathematics behind our website:     Glossary