To assess the effect of irradiation on total parenteral nutrition solutions with reference to reactive oxidant production and decline in antioxidant potential and the effect that these solutions have on critically ill patients.
Laboratory investigation utilizing irradiated and non- irradiated, commercially available, total parenteral nutrition (TPN) solutions.Interventions: Measurements of vitamin E and malondialdehyde (MDA) levels. The PBN (α- phenyl-n-test-butylnitrone) spin trap was utilized to measure the presence of free radicals and TEMPOL (2,2,6,6-tetramethyl-4-hydroxy-piperidine-oxyl) was utilized to assess antioxidant capacity. Irradiated TPN was administered to 12 patients and plasma and urinary isoprostanes were measured.
Irradiation reduced Vitamin E levels significantly (p<0.0025). MDA products were present in both samples, but were increased significantly (p<0.0001) in irradiated samples as were free radicals measured by PBN spin trapping. The irradiated sample had a higher scavenging capacity of TEMPOL free radical which was not initially expected. This was confirmed to be due to depletion of nutrient antioxidants in irradiated samples.Urinary isoprostanes increased by 4.24 units (95% confidence interval: 0.03 to 8.21) 2 hours after administration of irradiated TPN. (p<0.014).
Lipid hydroperoxides are formed in TPN bags and this is increased by irradiation. This is associated with a significant reduction in Vitamin E. In addition urinary isoprostanes were increased significantly in those that received irradiated TPN. This is relevant in that oxidant stress influences outcome and is associated with development of multiple organ dysfunction. TPN is therefore potentially pro-inflammatory because it is depleted in antioxidants and preformed lipid hydroperoxides are present in the solution.
Total parenteral nutrition whether irradiated or not, may be pro-inflammatory. Enteral nutrition is preferred, however if not possible, consideration should be given to the co-adminisrtation of additional antioxidant vitamins.
Guy Richards, None.