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Vitamin E measurement in patients receiving intravenous lipid emulsions
D H Henton1, R J Merritt, S Hack
1Division of Digestive Diseases and Nutrition, Children's Hospital of Los Angeles.
Insights
Spectrophotofluorometry overestimates plasma vitamin E in pediatric patients receiving lipid emulsions. High-pressure liquid chromatography is the preferred method for accurate tocopherol status monitoring in intensive care nurseries.
Area of Science:
- Clinical Chemistry
- Pediatric Nutrition
- Analytical Biochemistry
Background:
- Accurate measurement of plasma vitamin E (tocopherol) is crucial for monitoring nutritional status, especially in vulnerable pediatric populations.
- Parenteral nutrition, particularly lipid emulsions, is common in pediatric intensive care but may interfere with vitamin E assays.
- Discrepancies in vitamin E measurements can impact clinical decisions regarding patient care.
Purpose of the Study:
- To compare the accuracy of high-pressure liquid chromatography (HPLC) and spectrophotofluorometry for plasma vitamin E determination.
- To investigate the impact of lipid emulsion administration on vitamin E measurement methods in pediatric patients.
- To identify the most reliable method for assessing tocopherol status in critically ill children.
Main Methods:
- Plasma samples were analyzed from four pediatric groups: those on lipid emulsion, those on parenteral nutrition without lipid emulsion, and surgical controls.
- Vitamin E levels were determined using both high-pressure liquid chromatography (HPLC) and spectrophotofluorometry.
- Comparison of results obtained from the two analytical methods across different patient cohorts.
Main Results:
- Both HPLC and spectrophotofluorometry provided similar vitamin E results in control subjects and patients not receiving lipid emulsions.
- Spectrophotofluorometry yielded significantly higher vitamin E values (200-300% greater) compared to HPLC in patients receiving lipid emulsions.
- The discrepancy is attributed to non-alpha-tocopherol isomers in lipid products interfering with the fluorometric assay.
Conclusions:
- Spectrophotofluorometry is unreliable for measuring plasma vitamin E in pediatric patients receiving lipid emulsions due to interference.
- High-pressure liquid chromatography (HPLC) accurately quantifies alpha-tocopherol, making it the method of choice.
- Routine clinical monitoring of tocopherol status in intensive care nurseries should utilize HPLC over spectrophotofluorometry.
Abstract:
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.
