Whole blood base excess

As in plasma, CO2 equilibration of whole blood depends on the buffer value of nonbicarbonate buffers. Thus CO2 equilibration in whole blood is dependent on hemoglobin concentration and also on pH and oxygenation status. It is possible to derive an approximate equation for whole blood CO2 equilibration and calculation of whole blood base excess as follows ... 

ApH = measured pH - the standard pH of 7.40 AcB (B) the whole blood base excess (i.e., the concentration of titratable base when titrating the blood with strong acid or base to pH = 7.40 at PCO2 IStd] and 37 C)... 

This equation for whole blood base excess (Icnown as the Van Slyke equation ), together with the Henderson-Hasselbalch equation, provides the simplest algorithm for calculation of the various acid-base variables. The buffer... 

However, it is important to remember that the disturbance is assessed from the chemistry of a sample of patient s arterial blood in vitro and not from the biochemistry of the whole patient. For any one patient, the inaccuracy introduced is unknown. To this extent, measures such as the base excess are empirical and the doctor must be aware of these limitations. 

Base excess (BE) This is the amount of strong acid (in mM) which must be added to one litre of oxygenated whole blood, equilibrated with carbon dioxide at a partial pressure of 40 mmHg and at 37°C., in order to bring the pH to 7.4. 

---