Nephrocalcinosis in premature infants: variability in ultrasound detection.

OBJECTIVE: To measure variability among radiologists in the ultrasound diagnosis of nephrocalcinosis in premature infants. METHODOLOGY: In this prospective multicenter study, renal ultrasounds were performed on 54 very low birth weight infants using a 5.0- and 7.5-MHz transducer, and these ultrasounds were read independently by three radiologists. kappa coefficients were calculated to assess variability in identification of nephrocalcinosis among the radiologists. RESULTS: The kappa coefficient (+/- confidence intervals) using a 5.0-MHz transducer was 0.143 (0.108, 0.178); using the 7.5-MHz transducer, the kappa coefficient was 0.268 (0.243, 0.293). All three radiologists agreed in their identification of nephrocalcinosis on 3 of 54 ultrasounds using a 5.0-MHz transducer; a total of 6 of 54 ultrasounds obtained using a 7.5-MHz transducer were read as positive by all three radiologists. CONCLUSION: There is significant variability among radiologists in the ultrasound identification of nephrocalcinosis in premature infants; a 7.5-MHz ultrasound transducer is associated with less variability in recognizing this lesion.

Can a super oral rehydration solution stimulate intestinal repair in acute viral enteritis?

This study was designed to screen several treatments for their effects on mucosal repair in an established model of piglet rotavirus enteritis. Six ingredients selected to facilitate repair were added to the oral rehydration solution (ORS) and subsequently to the diet: L-glutamine (GLN); rice solids; a soluble fiber (carboxymethylcellulose); nucleotides; polyamines; and fructooligo-saccharides. Rotavirus infection consistently induced a watery diarrhoea lasting 5 to 10 days and produced a jejunal mucosal lesion which was maximal at 3 days, post-inoculation (manifested by a reduction of villus surface area to 30% to 50% of normal). By 7 to 10 day post-inoculation, the villus surface area returned to 50% to 80% of normal. None of the supplemental ingredients added to the ORS had a significant effect in either shortening the clinical illness or in stimulating recovery of the affected mucosa. It is concluded that several types of "Super ORS" are ineffective in enhancing repair in viral enteritis in neonatal colostrum-deprived piglets. These results do not rule out beneficial effects of the additives tested in subjects with more extensive intestinal damage, in those who receive breast milk, or in those with bacterial enteritis.

Effect of different vitamin A intakes on very-low-birth-weight infants.

Formula-fed infants with birth weights < or = 1500 g (n = 61) were stratified by 250-g birth-weight ranges and randomly assigned to receive one of three preterm infant formulas (vitamin A contents of 820 IU, 1640 IU, or 2900 IU/MJ; 1 RE = 3.3 IU vitamin A activity) when subjects tolerated 0.314 MJ.kg-1.d-1. Experimental formula feedings were continued until infants weighed approximately 2 kg or until hospital discharge. Vitamin A status as indicated by serum retinol and retinol-binding protein (RBP) concentrations significantly decreased during experimental formula feeding at the lowest vitamin A intake. All subjects fed the formula providing the lowest vitamin A intake had hyporetinolemia (< 0.70 mumol/L, or < 20 micrograms/dL), which occurred less frequently (P < 0.05) with the intermediate (6 of 20) and the high (6 of 21) vitamin A intakes. Other outcome measures, including increases in weight, length, and head circumference, and ventilatory support and oxygen therapy, were not different among groups. After the end of the experimental formula-feeding period, all infants were fed standard infant formulas with a vitamin A content of 715 IU/MJ. In a subset of 19 of these infants, subsequent vitamin A status was monitored at ages 6-12 mo and was found to be comparable with that of older children and adults, regardless of the vitamin A content of the formula fed during hospitalization.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of phosphorus supply on mineral balance at high calcium intakes in very low birth weight infants.

To evaluate the effect of varying phosphorus intake with constant high calcium intake (430 micrograms/kJ, or 180 mg/100 kcal), we randomly assigned 35 appropriate-for-gestational-age healthy male infants (birth weight, 715-1510 g) on day 21 postnatally to either standard-phosphorus (215 micrograms/kJ, or 90 mg/100 kcal), moderate-phosphorus (254 micrograms/kJ, or 106 mg/100 kcal), or high-phosphorus intake (287 micrograms/kJ, or 120 mg/100 kcal). Three-day mineral balances were determined after 7 d of the study diets. Weight and head circumference gain and intake of energy and vitamin D were not different for all groups. Calcium retentions were sufficient to meet intrauterine accretion in all groups. Phosphorus calculated to be available for soft tissue was significantly higher in the moderate- and high-phosphorus groups, and was sufficient to support soft tissue phosphorus accretion in these two groups. Total absorbed phosphorus and phosphorus tubular reabsorption were each affected by phosphorus intake. We conclude that very low birth weight infants fed high calcium may require greater phosphorus intake than that provided by formulas containing a ratio of calcium to phosphorus of 2:1. We suggest that the optimal mass ratio of calcium to phosphorus for formula for very low birth weight infants is from 1.6:1 to 1.8:1.

Effect of three levels of vitamin D intake in preterm infants receiving high mineral-containing milk.

Very low-birth weight (VLBW) infants fed high-calcium and high-phosphorus (10.74 and 6.93 mmol/MJ; 180 and 90 mg/100 kcal, respectively) infant formulas were randomized to one of three levels of vitamin D intake to approximate 200, 400, and 800 IU/day. Sixty-two infants completed the study (24 to 29 days), with actual mean daily vitamin D intakes of 161, 361, and 766 IU, respectively. Outcomes were not different by group: gains in body weight, length and head circumference, serum calcium, magnesium, phosphorus, alkaline phosphatase, osteocalcin, 25-hydroxyvitamin D, 1,25-dihydroxyvitamin D, and urine calcium:creatinine and magnesium:creatinine ratios. There were no radiographic fractures and/or rickets. A subset of 19 infants was followed between 173 and 380 days to determine descriptively if there was any delayed effect of earlier manipulation of vitamin D intake. They were fed standard infant formulas with a vitamin D content of 400 to 420 IU/L. No significant differences were present among the three groups, and data were combined. Serum 25-hydroxyvitamin D increased (p < 0.05), osteocalcin decreased (p < 0.05), and 1,25-dihydroxyvitamin D decreased (p = 0.06) at follow-up. Thus, for VLBZW infants fed high-calcium and high-phosphorus milk, an average daily vitamin D intake as low as 160 IU maintains normal and stable vitamin D status and normal physical growth, biochemical and hormonal indexes of bone mineral metabolism, and skeletal radiographs versus randomized infants receiving about 400 or 800 IU of vitamin D per day. On follow-up, vitamin D status remained normal for > or = 6 months while infants received < 400 IU of vitamin D per day.

Solubility of calcium salts and carrageenan used in infant formulas did not influence calcium absorption in rats.

Calcium absorption from tricalcium phosphate (TCP) was compared to that from calcium chloride, CaCl2, in the presence and absence of carrageenan in the rat model. There was no difference in percent calcium absorption as indicated by femur uptake of TCP or CaCl2 intrinsically labeled with 45Ca given by gavage (78.4 +/- 9.6 vs. 80.0 +/- 5.9, respectively). Thus, the difference in solubility of the two salts did not influence calcium absorption. When TCP was delivered by gavage in a solution containing 1% carrageenan, calcium absorption was not decreased compared to that of a control without carrageenan. In this model, calcium from TCP in the presence of up to 1% carrageenan is well absorbed.

Bone mineralization in the first year of life in infants fed human milk, cow-milk formula, or soy-based formula.

OBJECTIVE: To test the hypotheses that (1) bone mineral content (BMC) is similar in infants fed soy-based formula (SBF) and human milk (HM) and higher in infants fed cow milk-based formula (CBF) and (2) serum 1,25-dihydroxyvitamin D, an index of mineral sufficiency, is similar in infants fed formula and infants fed HM. DESIGN: Randomized, prospective study of formula-fed group only. SETTING: Recruitment was in a normal newborn nursery. PATIENTS: 72 infants: 10 given HM, 20 given CBF (Similac), 21 given SBF (Isomil), and 21 given SBF (Prosobee). MEASUREMENTS: BMC and 1,25-dihydroxyvitamin D levels at baseline (days 2 through 7 of life) and at 8, 16, 26, and 52 weeks of age. The BMC was similar in all groups at all times; serum 1,25-dihydroxyvitamin D levels were similar in all groups, except that they were elevated at 8, 16, and 26 weeks in those fed Prosobee. CONCLUSIONS: (1) BMC is similar in SBF-, CBF-, and HM-fed infants and (2) compensatory elevation of serum 1,25-dihydroxyvitamin D concentrations may occur in SBF-fed infants.

Bone mineral metabolism in full-term infants fed human milk, cow milk-based, and soy-based formulas.

OBJECTIVE: To study the hypothesis that ingestion of a modified soy-based formula with an improved mineral suspension system may result in bone mineral content similar to that observed in infants fed human milk or cow milk-based formulas. DESIGN: Prospective, self-selected group of infants fed human milk randomized between the two formula-fed groups. SETTING: University-based hospital nursery and follow-up. PARTICIPANTS: Fifty-six normal, healthy, full-term infants, free of major malformations or disorders, including 17 infants fed human milk, 19 infants fed a cow milk-based formula, and 20 infants fed a soy protein formula were followed up to 6 months' postnatal age. The soy-based formula studied was modified to improve the suspendability of the minerals. INTERVENTIONS: Infants were fed human milk or the study formula for the first 4 months, at which time beikost was permitted. Infants fed human milk received vitamin supplementation to provide 400 IU of vitamin D per day. MEASUREMENTS: Anthropometric variables, serum calcium, magnesium, phosphorus, alkaline phosphatase, and parathyroid hormone levels were measured at enrollment, and at 8, 16, and 24 to 26 weeks' postnatal age. Bone mineral content at the distal third radius site was measured with single photon absorptiometry at these times. Growth in the infants did not differ significantly among the groups. There was no significant difference in serum calcium, magnesium, alkaline phosphatase, or parathyroid hormone concentrations among the infants during the study. Serum phosphorus was significantly lower at 8 weeks in the group fed human milk than in that fed the cow milk-based formula. Bone mineral content at 16 and 24 to 26 weeks was higher in the group fed the soy-based formula than in that fed human milk, and bone width was also higher at 16 weeks in the infants fed the soy-based formula. CONCLUSIONS: Improving the suspendability of the mineral system in the soy formula results in bone mineralization in infants fed the soy-based formula similar to that measured in infants fed human milk and cow milk-based formula. We suggest that the suspendability of the minerals used is an important variable in the interpretation of the effect of feedings on the bone mineral status of infants.

Effect of lactose on mineral absorption in preterm infants.

To determine whether a reduction of dietary lactose affects mineral absorption in preterm infants, a controlled, randomized, 72-hour balance study was conducted with very low birth weight infants (birth weights less than 1400 gm) fed Similac Special Care formula with a 50:50 carbohydrate blend of glucose polymers and lactose (n = 8) or a nearly identical formula with 100% carbohydrate as lactose (n = 10). The studies were conducted after at least 3 consecutive days of full oral feeds at a mean age of approximately 23 days. There was no difference between groups in percentage of apparent absorption of calcium, phosphorus, magnesium, zinc, copper, or manganese. Retention of these nutrients was similar to or greater than that which occurs in utero. Calcium absorption was 75% of intake. These results indicate that reducing the lactose content of premature-infant formulas to 50% of the carbohydrate does not impair mineral absorption.

Early neonatal hypocalcemia in extremely preterm infants. High incidence, early onset, and refractoriness to supraphysiologic doses of calcitriol.

Nineteen preterm infants born at or before 32 weeks of gestation were studied to determine the dose of calcitriol that would be effective in the prophylaxis of early neonatal hypocalcemia (serum calcium level, less than 7.0 mg/dL [less than 1.75 mmol/L]). In these infants the course of early neonatal hypocalcemia was not modified by calcitriol administration. Serum 1,25-dihydroxyvitamin D level rose in response to intramuscular administration of calcitriol. The incidence of hypocalcemia in these infants was 37% by 12 hours, 83% by 24 hours, and 89% by 36 hours. Thus, in extremely preterm infants, the incidence of early neonatal hypocalcemia is higher and the onset earlier than in larger preterm infants; furthermore, in these infants the hypocalcemia is refractory even to high doses of calcitriol.