Some Observations on the Clinical Approach to Metabolic Acidosis

Abstract

The first step in the clinical approach to patients with metabolic acidosis is to deal with emergencies and to anticipate and prevent dangers associated with therapy. The traditional clinicalanalysisforthepresenceofmetabolicacidosissuffersfrom a number of limitations that at times hinders one’s ability to reach a proper diagnosis. Our aim here is to raise awareness of some of the nuanced difficulties and illustrate why other considerations add value. In patients with metabolic acidosis, analyses based on the anion gap in plasma (Panion gap) 1 or the strong ion difference 2 have major deficiencies. For example, the diagnosis of metabolic acidosis may be missed if one relies solely on pH and the concentration of bicarbonate (HCO3 ) in plasma (PHCO3) without considering changes in the content of HCO3 in the extracellular fluid (ECF) compartment. In addition, the rules of respiratory compensation, which are based solely on the arterial PCO2 rather than the more valuable PCO2 in capillary blood-draining skeletal muscle (as reflected by the venous PCO2), fail to assess the effectiveness of the bulk of the bicarbonate buffer system to remove Hand, hence, whether more H will bind to intracellular proteins in vital organs, such as the brain or the heart. 3