Vitamin E measurement in patients receiving intravenous lipid emulsions.

Two methods for the determination of plasma vitamin E--high-pressure liquid chromatography and spectrophotofluorometry--were compared on samples from four groups of pediatric patients: children and infants receiving lipid emulsion as part of their parenteral nutrition regimen, neonates receiving parenteral nutrition who were not receiving lipid emulsion at the time of blood sampling, and short admission surgery control subjects. In control subjects and patients not receiving lipid emulsions, both methods yielded similar results for vitamin E as alpha-tocopherol. In contrast, in patients receiving lipid emulsion, the fluorometric method yielded values ranging from 200% to 300% greater than did high-pressure liquid chromatography. The source of the discrepancy is most probably the presence of naturally occurring non-alpha-tocopherol isomers in the lipid products, which add to the fluorescent measurement but are resolved by high-pressure liquid chromatography. This study confirms clinically that fluorescent measurement of vitamin E is no longer the method of choice for monitoring tocopherol status in intensive care nurseries.

Vitamin A sorption to polyvinyl and polyolefin intravenous tubing.

The loss of vitamin A to plastic infusion tubing from a total parenteral nutrition solution was studied using an in vitro infusion system and HPLC quantification of vitamin A. Polyolefin tubing was compared to polyvinyl chloride at varied vitamin A concentration, infusion temperature, and flow rate. Significantly enhanced recovery of vitamin A was found with the polyolefin tubing compared to that of the polyvinyl chloride under all conditions tested. After 24 hours under the varied conditions of the study, vitamin A availability ranged from 47 to 87% with polyolefin and 19 to 74% with polyvinyl chloride. These differences may be expected to result in significantly greater vitamin A delivery from polyolefin compared to polyvinyl chloride tubing to patients treated in neonatal intensive care units.

A subacute rabbit model for hepatobiliary dysfunction during total parenteral nutrition.

Total parenteral nutrition (TPN) in children is associated with the complicating syndromes of cholestasis and cholelithiasis. The causes of these syndromes are not completely clear. Gastrointestinal hypomotility associated with enteral fasting may be involved in the pathogenesis of both syndromes. We compared weanling rabbits maintained solely on TPN with chow pair-fed and free-fed controls over a 10-day period. Gastrointestinal transit time, assessed with a solid marker technique, was significantly greater in the TPN-treated animals. No difference in intestinal or biliary bacterial flora was demonstrated by aerobic or anaerobic cultures. Gallbladder bile contained a higher percentage of lithocholic acid, unconjugated bilirubin, and total calcium in the TPN-treated animals. Markers of hepatic dysfunction were elevated in the serum of the TPN-treated animals. Mild steatosis and edema were the only histologic differences in the livers of the TPN-treated animals. We conclude that gastrointestinal hypomotility associated with enteral fasting plays a role in the pathophysiologic changes leading to TPN-associated hepatobiliary dysfunction. This dysfunction may be mediated by an increase in the absolute and relative concentrations of lithocholic acid in the bile of TPN-treated animals.

The use of fecal alkaline phosphatase as an indicator of intestinal damage.

Fecal alkaline phosphatase excretion was evaluated as a marker for intestinal damage in rats. Animals received either intraperitoneal bleomycin or saline. Controls were pair-fed with animals in the bleomycin group throughout the study. Both groups demonstrated similar patterns of fecal alkaline phosphatase excretion. There was, however, marked daily variability of fecal enzymatic activity. Fecal alkaline phosphatase excretion was largely composed of intestinal alkaline phosphatase, which was characterized by enzymatic inhibition with L-phenylalanine. Dietary intake as well as daily fecal output and protein excretion were reduced immediately following bleomycin injections and gradually increased to baseline values by 7 days. It appeared that both the direct toxic effects of bleomycin and dietary intake influenced fecal alkaline phosphatase excretion. Routine clinical application of this assay may be limited because of the number of factors which may affect its excretion.