Base excess, blood gas

Diagnostic Use

Base excess (also known as base deficit) is a calculated parameter included with blood gas results.

Base excess refers to the amount of base that would need to be added or taken away in order to normalise the pH, assuming that the pCO₂ of the sample was normal. It is an indirect marker of the metabolic component of the acid-base disorder.

Department

Core Biochemistry

Delphic Registration Code

BGS

Synonyms

BE, base deficit

Turnaround Time

60 minutes

Test Code

3505

Specimen Type

• Whole Blood

Specimen Requirements

Tube/Container Type:

Preferred

• Syringe

Preferred Sample Volume (ml)

0.5

No of Samples Required

1

Paediatric Specimen Requirements

Tube/Container Type:

Preferred

• Syringe

Preferred Sample Volume (ml)

0.2

Additional Specimen Information

Patient Specimen - 500uL whole blood in heparinised blood gas syringe
Paediatric Specimen 200 uL whole blood in a 1 mL syringe
Capped syringe sent to lab on ice, within 15 mins.

Aliquot Instructions

Additional Referral/Aliquot Information

Aliquot Instructions - 200 uL whole blood in a 1 mL syringe.
Aliquot Transport to CHL - On ice, sample must be kept anaerobic

Interpretation

A normal base excess is between -3mmol/L and +3mmol/L

In a metabolic acidosis, the base excess will be negative. The lower the base excess, the more severe the metabolic acidosis.

Conversely, a positive base excess is seen in a metabolic alkalosis (i.e. there is an excess of base present in the specimen). Again, the magnitude of the elevation will give an indication as to the severity of the alkalosis.

Base excess will not be influenced by the presence or absence of a coexisting respiratory acid-base disturbance.

Reference Intervals

-3  –  +3 mmol/L

Test Method

Calculated from blood gas parameters

Contact Canterbury Health Laboratories on +64 3 364 0484 or email LabInfo@cdhb.health.nz

Treat as urgent

Contact Information

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