MLT GlobeBase excess (BE)
Blood Gases · also called BE, Base deficit, SBE
What it measures
Base excess is the amount of acid or base needed to return blood pH to 7.40 at a pCO₂ of 40 mmHg. It isolates the metabolic component of acid–base disturbance and helps gauge the severity of shock.
Specimen and preparation
- Specimen: Arterial blood in a heparinised (balanced lithium heparin) syringe
- Tube: Other top
- Preparation: Expel air bubbles, cap immediately, mix well and analyse within 30 minutes (ideally 15) at room temperature in a plastic syringe; do not ice plastic syringes, and use a glass syringe on ice only if longer delay is unavoidable. Record FiO₂ and temperature.
Reference range
| Group | Range |
|---|---|
| Arterial | −2 to +2 mmol/L |
Reference ranges differ between laboratories, methods and populations. Always use the range printed on your own lab report.
Causes of high values
- Metabolic alkalosis
- Compensation for chronic respiratory acidosis
- Alkali administration
Causes of low values
- Metabolic acidosis (a negative value is a base deficit)
- Lactic acidosis in shock
- Diabetic ketoacidosis
- Kidney failure
Method
Calculated by the blood gas analyser (standard base excess)
Good to know
A base deficit worse than −6 mmol/L in trauma is associated with significant blood loss and higher mortality.
Related tests
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