Test Code CO2 Carbon Dioxide

Important Note

Every effort should be made to fill vacuum tubes completely when collecting blood because a decrease of up to 3 mEql/L can be observed with partially filled tubes.

Additional Codes

Cerner	NextGen
Carbon Dioxide	Carbon Dioxide
CO2

Alternate Name(s)

CO2

Bicarbonate

Bicarb Level

HCO3-

Useful For

The carbonic acid–bicarbonate buffer system is one of the important buffer systems that maintains the pH of the blood. Total CO2 (i.e., bicarbonate plus dissolved CO2) measurements are used together with other clinical and laboratory information (arterial pH and pCO2) for the evaluation of acid-base disorders. Total CO2 is generally increased in respiratory acidosis, metabolic alkalosis, and excessive alkali intake. CO2 is decreased in compensated respiratory alkalosis, metabolic acidosis, and in renal disorders where H+ ions cannot be excreted.

Methodology

Enzymatic Endpoint (reflectance spectrophotometry)

Patient Preparation

None

Collection Instructions

Standard phlebotomy practices.

Specimens should remain tightly capped.

Every effort should be made to fill vacuum tubes completely when collecting blood.

Specimen Requirements

Container

Specimen Type	Tube
Lithium Heparin Plasma
PST	or or
Serum	or
SST	or or

Stability

Storage	Temperature	Stability
Room Temperature, tightly capped	18-28°C	≤ 24 hours If serum or plasma is separated within 4 hours.
Refrigerated, tightly capped	2-8°C	≤ 3days If serum or plasma is separated within 4 hours.
Frozen, tightly capped	≤-18 °C	≤ 1 month If serum or plasma is separated within 4 hours.

Rejection Criteria

Gross Hemolysis

Result Reporting and Reference Values

Reported in mmol/L.

Age	Low	High	Critical Low	Critical High
0-17Y	18	27	11	40
18-150Y	21	31	11	40

Reflex Testing