Oxalogenesis in parenteral nutrition solution components.

Oxalate has been implicated in the etiology of nephrocalcinosis in premature infants as well as in the formation of insoluble precipitates in total parenteral nutrition (TPN) intravenous tubing. Oxidation of ascorbate to oxalate, especially in the presence of catalysts such as copper and iron, has been implicated in formation of these precipitates. The purpose of this project was to measure oxalate formation in certain TPN components separately and in combination. Neonatal TPN solution components in combination were infused at 5 mL/h under simulated clinical conditions used in a neonatal intensive care unit. Aliquots were assayed at intervals for oxalate by capillary electrophoresis. Oxalate is present in one TPN mixture at concentrations up to 8 ppm. The addition of ascorbate to an aqueous solution of trace metals may promote oxalogenesis.