Very low birth weight infants have little storage of hepatic retinol and are, therefore, highly dependent upon an exogenous supply. The recent association between low serum retinol level and bronchopulmonary dysplasia and the persistently low serum levels of retinol during total parenteral nutrition prompted a prospective study to evaluate serial changes in serum retinol levels during 1 month of total parenteral nutrition (retinol dose 455 µg/d) and again during 1 month of total enteral feeding (retinol dose 200 to 300 µg/d) in the same infants. Infants were divided into two groups. Group 1 consisted of infants weighing less than 1,000 g (n = 24) and group 2 consisted of infants weighing 1,000 to 1,500 g (n = 17). Although initial mean levels of retinol were similar in both groups (14.8 ± 0.9 and 13.5 ± 0.7 µg/dL), there was wide variation between infants. In group 1 infants, there was a significant (P < .01) decline in retinol level by the second week of life (to 9.2 ± 1 µg/dL), which persisted during total parenteral nutrition, but increased to 13.4 ± 2 after 1 week of enthral feeding. This level was maintained throughout enteral feeding. In group 2 infants, there was no significant change in serum retinol level throughout the study. During total parenteral nutrition, several infants had retinol levels below 10 µg/dL, a level associated with signs of retinol deficiency in older children. Because losses of retinol are known to occur in smaller volume total parenteral nutrition solutions, it was speculated that losses of retinol in our patients were due to retinol losses in the total parenteral nutrition delivery system. Because lipid might prevent these losses, in vitro studies were done to compare retinol losses in total parenteral nutrition v the usual daily dose of Intralipid. Results indicated 80% loss of retinol in total parenteral nutrition compared to only 10% loss in Intralipid. Lipid stability, as monitored by light microscopy and laser light scatter, indicated no changes in the stability of the lipid particles with the addition of the vitamin.

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