Base excess

Base Excess

Base excess (BE) refers to the difference between the observed and the normal buffer base concentration or, expressed differently, the amount of acid or base required to return the pH to 7.4 in the setting of a normal Paco2.124 The BE is commonly derived from nomograms. Because different models of blood gas analyzers use different methods of calculating the BE, the results may differ among manufacturers.125

Although the name implies an excess of base, a deficit can occur when the observed base concentration is below normal. Some clinicians prefer to use the term base deficit to refer to levels of base that are below normal and to use the term BE for the opposite scenario. Base excess/deficit is another indicator of the metabolic acid–base status. Some centers may measure standard BE or BE of extracellular fluid. The standard BE is calculated differently from BE and was developed as a Paco2-independent index.110

Normal BE values in newborns range from −3 to +1.126 A negative BE, or a base deficit, is observed in the setting of a metabolic acidosis, whereas a positive BE occurs in metabolic alkalosis. The BE is interpreted along with the bicarbonate concentration.