Conflicting reports exist regarding the relative tocopherol isomer content of Intralipid ranging from 99% as alpha-tocopherol to as much as 90% as gamma-tocopherol. Our direct assay of Intralipid as well as plasma levels measured in premature infants receiving Intralipid confirm the existence of a low alpha, high gamma-tocopherol content and imply the need for alpha-tocopherol supplementation in patients receiving Intralipid, particularly the relatively tocopherol-deficient premature infant. Furthermore, the observation of abnormal erythrocyte hemolysis test values despite "normal" total tocopherol plasma concentrations may be explained by high plasma levels of non-alpha, biologically less active isomers. The quantitation of tocopherol isomers helps explain this discrepancy and suggests the need for future studies of vitamin E status to employ measurements of tocopherol isomers in reporting results.
This study was designed to reevaluate the kinetics of vitamin A losses in the plastic intravenous infusion system used clinically in premature infants and to attempt to establish an improved method of delivery that would avoid significant and unpredictable losses. The losses of retinol, retinyl acetate, and retinyl palmitate were assessed in the presence of various concentrations of the emulsifier Tween 20. For a period of more than 24 h and at a concentration of 0.0085% Tween 20, retinol and retinyl acetate were delivered at 17.4 and 33.9% of the originally intended dose, respectively, while retinyl palmitate was at 100%. At 1% Tween 20, retinyl acetate was completely delivered but even at 2% Tween 20 only 51% of the retinol was delivered. The data suggest that predictable infusions of vitamin A may be attained by using retinyl palmitate rather than retinol in multivitamin preparations.
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