Base excess

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Base Excess ( BE ), also known as base deviation or base excess or base deficit , is a calculated parameter that is determined on the basis of a blood gas analysis and enables statements to be made about metabolic ( metabolic ) disorders of the acid-base balance ( metabolic acidosis , metabolic alkalosis ) . Put simply, it represents the amounts of acids or bases that are necessary to restore a changed pH value in the body to its normal values. The term and principle were introduced by Astrup and Siggaard-Andersen in 1958 .

The base excess characterizes the deviation from the reference range of the total buffer bases , in the extracellular space as BE (ecf), in the blood as BE (B) or standard base excess (sBE). This is (depending on the laboratory) around 48 mmol / l. The normal values ​​for the BE are, depending on the laboratory, 0 ± 2 mmol / l or ± 3 mmol / l.

In the clinic, the base deviation is suitable for assessing the non-respiratory components in the case of a disturbance in the acid-base balance. In order to be able to make statements about the disturbance of the acid-base balance, the arterial carbon dioxide partial pressure (pCO 2 ) must always be taken into account in addition to the BE . An increased BE can on the one hand indicate metabolic alkalosis (excess of base) and on the other hand, with simultaneously increased pCO 2 , an at least partially compensated respiratory acidosis (CO 2 retention, e.g. in hypoventilation). On the other hand, a decreased BE indicates either metabolic acidosis (loss of base, e.g. in diarrhea), or, with a simultaneous decrease in pCO 2 , an at least partially compensated respiratory alkalosis (increased CO 2 exhalation, e.g. with hyperventilation). The metabolic compensation of a respiratory disturbance of the acid-base balance takes place predominantly via the retention or excretion of bicarbonate via the kidneys, which makes up the largest part of the total buffer bases of the blood.

Furthermore, the BE can be used to estimate the need for NaHCO 3 for symptomatic treatment in metabolic acidosis :

Example: A 75 kg patient with a negative base deviation of −8 mmol / l thus has an approximate deficit of 200 mmol

literature

  • W. Schaffartzik: Base excess - parameters of outstanding clinical importance. In: Anaesthesiologist. Volume 56, Number 5, 2007, pp. 478-481. PMID 17356859 .

Individual evidence

  1. ↑ Chris Nickson: Base Excess vs. Standard Base Excess . In: Life in the fastlane (2012/2013).