Metabolic acidosis during parenteral nutrition: Pathophysiological mechanisms.

Total parenteral nutrition (TPN) is associated with metabolic complications including metabolic acidosis (MA), one of the main disorders of acid-base balance. The main causes involved in the appearance of MA during TPN administration are the metabolism of cationic amino acids and amino acids containing sulfuric acid (exogenous addition), the titratable acidity of the infused parenteral solution, the addition of acidificant agents (hydrochloric acid, acetic acid), thiamine deficiency, disruption of carbohydrate and lipid metabolic pathways and D-fructose administration. Moreover, hypophosphatemia that appears during TPN therapy contributes significantly to the maintenance of MA. This review describes in a comprehensive way the pathophysiological mechanisms involved in the appearance of MA induced by intravenous administration of TPN products most commonly used in critically ill-patients.