99 ASSESSMENT OF CA AND P REQUIREMENTS AND PREVENTION OF OSTEOPENIA IN VLBW INFANTS

Abstract

Severe postnatal bone demineralization has now been recognized to be a common event in the VLBW infant because of calcium (Ca) and phosphorus (P) deficiency. Formula supplemented with Ca and P may not prevent this condition which is due to the wide variation in net calcium absorption. Hypothesis: Intrauterine bone mineral accretion rate will be achieved in VLBW infants postnatally when Ca and P are administered in sufficient quantity to result in a urinary excretion of both elements. Methods: To test this hypothesis we studied 18 periods of 3 weeks in 12 VLBW infants who were fed BM or formula supplemented with Ca-gluconate and Ca-glycerophosphate to produce a urinary excretion of 2-5 mmol/L Ca and P. The increase in bone mineral content (BMC, mg/cm) of the mid humerus measured by photonabsorptiondensitometry was assessed with respect to weight gain. Results: The median increase of BMC was 5.5 mg/cm per 100 g weight gain (range 2.7-9.9). This value is similar to the intrauterine accretion rate (4.6) which we have calculated from the BMC of newborn infants with birthweights between 800 and 4000 g (1). The mineral accretion rate, however was higher than the intrauterine rate in half of the study periods. Conclusion: Measurement of Ca and P in urine is a simple method by which individual requirements of Ca and P supplementation in VLBW may be accessed. Catch up mineralisation was observed in 9 of the babies. (1) Bone mineral content in appropriate and small for gestational infants: a reference for the evaluation of postnatal bone mineralization. Pediat Res 19:1116 (abstr.) (1985).

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