Enhanced-calorie formulas: considerations and options.

The long-term developmental impact of nutrition on the preterm newborn has recently been shown to be of even greater importance than previously recognized. Very immature or ill infants are challenged by the need for a high caloric intake, but are unable to tolerate large fluid volumes. These patients may require enhanced-calorie formulas to achieve the desired growth goals. Formula enhancement has traditionally been performed by uniquely developed recipes of base formula concentration with the addition of powdered formula or single components such as medium-chain triglycerides oil, protein, or polycose. These mixtures have been largely unstudied for bioavailability, long-term outcomes, and tolerance. Deviation from recommended protein, fat, carbohydrate, mineral, and vitamin delivery limits may impair growth or lead to undesirable side effects. The practitioner must have an understanding of when and how to use an enhanced formula and the important monitoring and assessment needs of the patient receiving enhanced-calorie formula.

Incidence and physiologic characteristics of hypothermia in the very low birth weight infant.

PURPOSE: To determine the incidence of and physiologic characteristics associated with hypothermia in a very low birth weight (VLBW) population. METHODS: Retrospective through medical record review. Records were reviewed from most current dating backward. A total of 199 consecutive records were reviewed to achieve a sample of 100 VLBW infants meeting inclusion criteria from a 40-bed neonatal intensive care unit (NICU) in an urban tertiary care center in the midwest. PROCEDURE: Admission serum glucose content, blood bicarbonate, oxygen concentration, and temperature were recorded from the medical record and examined for differences. RESULTS: Forty-five percent of the sample was hypothermic on admission. Hypothermic infants were significantly more likely to be academic (p = 0.0001) than normothermic infants. No significant differences were found between the groups for glucose values or oxygen requirements. CONCLUSIONS: Hypothermia continues to be an important issue in neonatal care affecting almost half of VLBW infants. Interventions need to be used to reduce hypothermia and acidemia in VLBW infants.

Neonatal nutritional requirements and formula composition: a review.

Adequate neonatal nutrition is essential for appropriate growth and avoidance of complications associated with deficiencies. Neonatal nutritional requirements vary with metabolic states, degree of prematurity, and diseases affecting the gastrointestinal, pulmonary, and cardiac systems. Differences exist between formula brands for protein, fat, and carbohydrate sources. Differences also exist between formulas designed for preterm and full-term infants, as well as infants with special nutritional needs. Optimal nutrition should be a consistent goal for each infant, whether in a healthy newborn nursery, intensive-care unit, or home care setting. Nurses must be aware of the possibilities available to address the special needs of infants.

Long-term subcutaneous terbutaline tocolysis: report of possible neonatal toxicity.

Terbutaline is a beta-sympathomimetic agent that has gained wide use in obstetrics as a tocolytic agent. In addition to inhibiting uterine contractions, terbutaline can cause other clinically significant beta-mediated effects. Terbutaline readily crosses the placenta, and both fetal and neonatal toxicity have been reported. We report possible cardiovascular toxicity secondary to long-term prenatal terbutaline exposure involving three preterm infants of a quadruplet pregnancy. The infants developed cardiovascular decompensation with bradycardia, metabolic acidosis, poor tissue perfusion, and decreased urine output. The infants' conditions were resistant to all routine interventions but responded well to dobutamine infusion. We theorize that long-term prenatal beta-mimetic exposure led to downregulation of fetal beta-receptors. This resulted in impaired myocardial function, increased peripheral vascular resistance, and poor cardiac output. We suggest that neonates with a history of prenatal exposure to terbutaline should be observed closely after birth for any evidence of cardiovascular deterioration.

A case-control study of hypocalcemia in high-risk neonates: racial, but no seasonal differences.

A role for vitamin D in the defense against falling serum calcium (Ca) concentrations following cord clamping has been suggested. Since race and season are known to affect vitamin D status, we theorized that black race and birth in winter are additional risk factors for neonatal hypocalcemia (NHC). We retrospectively studied 13,462 infants born at University Hospital (Cincinnati, OH) between January 1, 1984 and December 31, 1987. Serum Ca was measured at 24 hours of age routinely in infants with low birth weight (less than 2500 g), preterm delivery (less than 2500 g), preterm delivery (less than 37 weeks), neonatal asphyxia, and diabetic mothers. After exclusion of infants of diabetic mothers (to remove maternal diabetes as a major confounder) and infants with major congenital anomalies, 714 infants remained. In multiple regression analysis, low serum Ca values were significantly associated with low gestational age (p less than 0.01), low Apgar score (p less than 0.01), and white race (p less than 0.01) (R2 = 0.457). Season or month of birth was not significant. In pair-matched analysis controlling for factors other than season, season of birth did not affect serum Ca. In pair-matched analysis controlling for factors other than race, white race was once again a risk factor for hypocalcemia. Thus, low gestational age, low Apgar score, and white race, but not black race and delivery in winter, are risk factors for NHC. We speculate that in our climate and with the prevailing diet in pregnancy, vitamin D deficiency does not appear to play a role in NHC.(ABSTRACT TRUNCATED AT 250 WORDS)

A role for magnesium in neonatal parathyroid gland function?

Little is known of the factors regulating parathyroid function in the neonatal period. Twenty-seven term infants born after uncomplicated pregnancies, labors, and deliveries were studied to test the hypothesis that in normal newborns the amplitude of parathyroid hormone (PTH) response to decreasing serum ionized calcium (iCa) correlates with serum magnesium (Mg) concentrations. Serum iCa (ion selective electrode, Radiometer ICA 1), PTH (1-84 intact molecules, radioimmunoassay) and Mg (atomic absorption) were measured at birth (cord blood) and 24 hours of age. Repeated measures analysis of covariance showed decreasing serum iCa (p less than 0.01) and increasing serum Mg (p less than 0.01) and PTH (p less than 0.01) over time. The change in PTH over the first 24 hours was directly correlated with cord blood (r = 0.38, p less than 0.05) and 24-hr Mg concentrations (r = 0.53, p less than 0.01). We conclude that the ability of the parathyroid gland to respond to decreasing serum iCa after birth is directly related to Mg status. We speculate that neonatal hypomagnesemia may lead to a blunted PTH secretory response, thus contributing to early neonatal hypocalcemia.

Postnatal surge in serum calcitonin concentrations: no contribution to neonatal hypocalcemia in infants of diabetic mothers.

It has been suggested that hypercalcitoninemia may contribute to neonatal hypocalcemia in infants of diabetic mothers (IDM). Because the role of calcitonin (CT) in Ca metabolism in humans is questionable, we hypothesized that serum CT peaks similarly after birth in IDM and controls and that serum Ca concentrations do not correlate with serum CT. Forty-seven term IDM (White classes B-RT) were compared with 31 controls. Controls were born after normal pregnancies, labors, and deliveries. Blood samples (cord and 24 h) were analyzed for Ca, Mg, parathyroid hormone (PTH), and CT. Repeated measures analysis showed increasing serum Mg, PTH, and CT, and decreasing Ca over time. The incidence of hypocalcemia was significantly higher in the diabetic group (p less than 0.01) and the incidence of hypomagnesemia was borderline significantly higher (p less than 0.06). There were no differences in cord or 24-h serum concentrations of CT between groups. In multiple regression analysis, serum Ca and PTH were correlated (p less than 0.02, R2 = 0.33), but not serum Ca and CT; the increase in serum PTH in relation to serum Ca at the nadir (24 h) correlated directly with serum Mg concentrations (R2 = 0.31, p less than 0.05). Thus, serum CT increases after birth irrespective of the rate of decrease of serum Ca in both IDM and controls; high CT concentrations observed after birth (as compared with adult norms) do not seem to play a role in the pathogenesis of neonatal hypocalcemia in IDM; and responsiveness of parathyroid gland at birth is adversely affected by hypomagnesemia, which supports the theory of functional hypoparathyroidism in Mg deficiency.

Spectrum and natural history of congenital hyperparathyroidism secondary to maternal hypocalcemia.

Fourteen cases of congenital hyperparathyroidism secondary to maternal hypocalcemia have been reported. We report two additional cases that highlight the wide spectrum of the disease. We extensively studied the parathyroid function of these infants to test the hypothesis that the biochemical hyperparathyroidism found in these infants would be transient in nature, since the presumed etiology (maternal and subsequent fetal hypocalcemia) should disappear soon after birth with establishment of enteral feedings. Infant 1 was born to a mother with idiopathic hypoparathyroidism with poor compliance to therapy and documented hypocalcemia in pregnancy. Severe congenital demineralization and intrauterine fractures with clinical and radiologic bowing of the long bones were obvious. Bone mineral content and bone mineral content/bone width ratio, measured by photon absorptiometry, were both markedly below normal. Infant 2 was born to a mother with postsurgical hypoparathyroidism with excellent compliance. The mother was normocalcemic. The infant was clinically and radiologically asymptomatic. The bone mineral content was just at the lower limit of normal, but bone mineral content/bone width ratio was below the normal limits. Biochemical features include elevation of cord serum parathyroid hormone (1-84, radioimmunoassay) in both cases, coexisting with serum calcium, phosphorus concentrations within normal limits. Serum parathyroid hormone fell to within normal ranges by 9 days of age in both infants. With no treatment, bone mineral content at 1 month of age was normal in both infants.

Postnatal changes in serum osteocalcin and parathyroid hormone concentrations.

Cord clamping at birth leads to interruption of calcium (Ca) supply to the fetus. After birth, neonatal parathyroid hormone (PTH) secretion appears stimulated by hypocalcemia, with serum PTH increasing after birth and peaking at 24 hours of age. This rise in PTH presumably leads to bone resorption and Ca release. We theorize that bone formation may also be affected and that a serum marker of bone formation, serum osteocalcin (OC) concentrations, will decrease postnatally. OC is synthesized by osteoblasts and its serum concentrations are believed to reflect bone formation. We measured serum ionized Ca (iCa), PTH, and OC in cord blood and at 2 and 24 hours in 26 neonates born after uncomplicated pregnancies, labors, and deliveries. Serum iCa (mg/dl) decreased from 5.79 +/- 0.06 (cord, means +/- SEM) to 5.31 +/- 0.05 (2 hr), then to 4.89 +/- 0.05 (24 hr) (p less than 0.05). Serum PTH (microliter Eq/ml) increased from 35.9 +/- 4.3 (cord) to 41.7 +/- 4.0 (2 hr) (p = 0.1), and to 50.3 +/- 4.6 (24 hr) (p less than 0.01). Serum OC (ng/ml) decreased from 55.1 +/- 10.6 (cord), to 12.4 +/- 4.3 (2 hr) (p less than 0.01), then remained stable at 12.7 +/- 1.9 (24 hr). The change (cord minus 24 hr) in OC correlated inversely with the change in PTH over the first 24 hours of age (r = -0.42. p = 0.03). Therefore, there is a sudden decrease in an index of bone formation (i.e., serum OC) in the first 24 hours of life in which rising serum PTH may have had an impact.(ABSTRACT TRUNCATED AT 250 WORDS)

Serum ionized calcium concentrations in normal neonates.

Adult serum ionized calcium (iCa) concentrations are higher when using the newer, highly sensitive, ion-selective electrodes compared with older electrodes. Currently used neonatal normative ranges were established using older electrodes and not under standardized conditions or age. Thirty term infants, carefully screened to exclude confounding factors that could affect serum iCa concentration, were studied at birth and 2 and 24 hours of age for serum iCa concentrations. Mean concentrations declined from 1.45 mmol/L (5.82 mg/dL) at birth to 1.33 mmol/L (5.34 mg/dL) at 2 hours to 1.23 mmol/L (4.92 mg/dL) at 24 hours. The 95% confidence limits at 24 hours ranged from 1.10 to 1.36 mmol/L (4.40 to 5.44 mg/dL). Using newer ion-selective electrodes, normal neonatal ranges for iCa concentrations during the first 24 hours of age are higher than published references.