Used in assessing acid-base status
Base excess is defined as the amount of strong acid that must be added to each liter of fully oxygenated blood to return the pH to 7.40 at a temperature of 37°C and a pCO2 of 40 mmHg (5.3 kPa), while a base deficit (ie. a negative base excess) is defined by the amount of strong base that must be added.
The formula for base deficit is as follows:
Base excess = 0.02786 X pCO2 X 10^(pH - 6.1) + 13.77 X pH - 124.58