Definition
Actual base excess is the concentration of titratable base when the blood is titrated with a strong base or acid to a plasma pH of 7.40 at a pCO2 of 40 mmHg (5.3 kPa) and 37 °C at the actual oxygen saturation. It is often abbreviated and symbolized as BE. The systematic symbol for actual base excess for arterial blood is cBase(a). The analyzer symbol may be ABE or cBase(B).
What does cBase tell you
“Base excess” is the absolute deviation (in mmol/L) of the buffer base amount from the normal level in blood. “Buffer base” represents the blood’s total buffer capacity, comprising the bicarbonate, hemoglobin, plasma protein, and phosphate buffer systems. The normal buffer base level is 48 ± 2 mmol/L.
Reference ranges
cBase(a) reference range (adult) [25]:
male: -2.7 – (+2.5) mmol/L
female: -3.4 – (+1.4) mmol/L
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Clinical interpretation
A low (negative) BE signifies metabolic acidosis, and a high BE signifies metabolic alkalosis. As for SBC, the principal significance of BE is as part of the analysis of blood acid-base status, i.e., in conjunction with pCO2 and pH. Normally, SBC and BE vary in parallel; however, BE is preferable to SBC in acid-base analysis, being a more exact indicator of “metabolic” buffer capacity (i.e., accounting for variations in buffer systems apart from the bicarbonate buffer).
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