Definition
Standard bicarbonate (cHCO3-(P,st)) is the concentration of hydrogen carbonate in plasma from blood which has been equilibrated with a gas mixture with pCO2 = 40 mmHg (5.3 kPa) and pCO2 = 100 mmHg (13.3 kPa) at 37 °C. The systematic symbol for arterial blood is cHCO3-(aP,st). The analyzer symbol may be SBC or cHCO3-(P,st).
What does cHCO3-(aP,st) tell you
The “standard” bicarbonate concentration is the bicarbonate concentration that would be measured in a blood sample, if the sample were fully oxygenated and further equilibrated to a pCO2 tension of 40 mmHg (5.3 kPa). Thus, “standardizing” measurementconditions eliminates any respiratory influence on the bicarbonate concentration. In these circumstances, a low bicarbonate concentration signifies metabolic acidosis, a high bicarbonate concentration signifies metabolic alkalosis.
Reference ranges
cHCO3-(aP,st) reference range (adult) [24]:
male: 22.5-26.9 mmol/L
female: 21.8-26.2 mmol/L
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Clinical interpretation
As described above, the SBC is principally important in the analysis of the acid-base status (i.e., in conjunction with pCO2 and pH).
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