Bicarbonate - plasma or serum

Last updated: Thursday, 08, April, 2004

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Item Process
Specimen

5 mL blood in lithium heparin or plain tube.

Method

Spectrophotometry (measures total CO2); derived parameter in blood gas analysis.

Reference Interval
22-32 mmol/L.
ApplicationAcid-base disorders; particularly as initial investigation of metabolic abnormalities and in defining renal tubular acidosis.
Interpretation

Serum bicarbonate is increased in metabolic alkalosis and in compensated respiratory acidosis.

Levels are decreased in metabolic acidosis. An artefactual decrease occurs if the collection tube is only partly filled, or left uncapped, due to loss of CO2.

The terms 'bicarbonate' and 'total carbon dioxide' are often used interchangeably. Although 'bicarbonate' is 1-2 mmol/L lower than total carbon dioxide this difference is not clinically significant.

Reference

Roth KS and Chan JC. Clin Pediatr 2001; 40(10): 533-543.