[Analysis of acid-base disturbances in the emergency department]

The analysis of acid-base disturbances contributes to the diagnostic work-up of critically ill patients. Most emergency departments are equipped with blood gas point-of-care analyzers that quantify within minutes pH, pCO2, standard bicarbonate, standard base excess, sodium and chloride levels. This article provides a pragmatic stepwise approach to the analysis of acid-base disturbances in the emergency department. Standard base excess is used to assess the adequacy of the secondary (compensatory) response. Calculation of the anion gap based on the actual bicarbonate is used to identify the coexistence of metabolic acidosis and metabolic alkalosis. The delta anion gap allows for the identification of measurement errors, such as falsely elevated lactate and chloride values, which in turn may provide diagnostic clues.