Analytic calculation of physiological acid-base parameters in plasma

Analytic expressions for plasma total titratablebase, base excess (C_B), strong-ion difference, changein strong-ion difference (SID), change in Van Slyke standardbicarbonate (VSSB), anion gap, and change in anion gap are derivedas a function of pH, total buffer ion concentration, and conditionalmolar equilibrium constants. The behavior of these various parametersunder respiratory and metabolic acid-base disturbances for constant andvariable buffer ion concentrations is considered. For constantnoncarbonate buffer concentrations, SID = C_B = VSSB, whereas these equalities no longer hold under changes innoncarbonate buffer concentration. The equivalence is restored if thereference state is changed to include the new buffer concentrations.