1. Parenteral amino acid solutions undergo photo-oxidation, which may be an important factor in total parenteral nutrition-associated hepatic dysfunction. Light-exposed parenteral solutions containing amino acids, in addition to vitamins and trace minerals, generate free radicals, which, in turn, may contribute to this type of injury. This study examined the characteristics of H2O2 production in a parenteral amino acid solution modelled on a commercially available paediatric parenteral amino acid solution.

2. The solution was exposed to light in the presence of riboflavin-5′-monophosphate (riboflavin), and peroxide formation in the presence and absence of catalase (H2O2 formation) was assayed using potassium iodide/molybdate.

3. Peak H2O2 production occurred at a light intensity of 8 μW cm−2 nm−1 in the 425–475 nm waveband and was linear to 2 h of light exposure. H2O2 production reached 500 μmol/l at 24 h.

4. H2O2 was directly related to a riboflavin concentration of up to 20 μmol/l and was maximal at 30 μmol/l.

5. H2O2 production was greatest in the amino acid/riboflavin solution at a pH of between 5 and 6.

6. Under the conditions of light exposure intensity, light exposure time, riboflavin concentration and pH found during the administration of parenteral nutrition in neonatal intensive care units, net H2O2 production occurs in solutions modelled on a paediatric parenteral amino acid preparation.

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