BE

Base excess

Base excess (BE) in the context of an arterial blood gas (ABG) is a calculated value that reflects the amount of excess or deficit of base (bicarbonate) in the blood. It is used to assess the metabolic component of acid-base balance. A normal base excess ranges from -2 to +2 mEq/L.

• Positive base excess (greater than +2 mEq/L) indicates a metabolic alkalosis or compensation for respiratory acidosis, meaning there is excess bicarbonate in the blood.
• Negative base excess (or “base deficit”, less than -2 mEq/L) suggests a metabolic acidosis, indicating a lack of bicarbonate or an accumulation of acids in the blood.

Base excess helps differentiate between respiratory and metabolic causes of acid-base disturbances and is a useful marker in evaluating conditions like shock, kidney disease, and diabetic ketoacidosis.