In human physiology
, base excess
) refers to the amount of acid
required to return the blood pH
of an individual to the reference interval pH (7.35 - 7.45) with the amount of carbondioxide held at a standard value. The value is usually reported in units of (mEq/L). The normal value is somewhere between -2 to +2. This way you can easily determine wheter an acid/base disturbance is caused by a respiratory, metabolic or mixed metabolic/respiratory problem.
Another definition for base excess is the amount of acid or base that must be added to a litre of blood (ecf) to return the pH to 7.4 at a pCO2 of 40 mmHg.
The term and concept were first introduced by Astrup and Siggaard-Andersen in 1958.
Actual and standard
Actual base excess is the base excess in the blood.
Standard base excess is the value of base excess when the hemoglobin-value is 5g/l. This gives a better view of the base excess of the entire extracellular fluid.