Arterial blood gas analysis: selecting the clinically appropriate option for calculating base excess

As part of arterial blood gas analysis, base excess is often reported as a measure of non-respiratory acid-base disturbance. Most blood gas analysers offer the option of calculating either the base excess of the blood sample or the base excess of the extracellular fluid (ECF). We report a case that illustrates that selecting the physiologically appropriate parameter avoids the potential for misinterpretation of acid-base data. We recommend that the base excess of the ECF is the appropriate metabolic blood gas parameter for clinical use.