Neurological condition in 18-month-old children perinatally exposed to polychlorinated biphenyls and dioxins

The neurological optimality of 418 Dutch children was evaluated at the age of 18 months, in order to determine whether prenatal and breast milk mediated exposure to polychlorinated biphenyls (PCBs) and dioxins affected neurological development. Half of the infants were breast-fed, the other half were formula-fed. PCB concentrations in cord and maternal plasma were used as a measure of prenatal exposure to PCBs. To measure postnatal exposure, PCB and dioxin congeners were determined in human milk and in formula milk. After adjusting for covariates, transplacental PCB exposure was negatively related to the neurological condition at 18 months. Although greater amounts of PCBs and dioxins are transferred via nursing than via placental passage, an effect of lactational exposure to PCBs and dioxins could not be detected. We even found a beneficial effect of breast-feeding on the fluency of movements. We conclude that transplacental PCB passage has a small negative effect on the neurological condition in 18-month-old toddlers.

Effect of dietary triacylglycerol fatty acid positional distribution on plasma lipid classes and their fatty acid composition in preterm infants

Seven premature infants were each fed, for 1 wk in a crossover design. The beta formula contained triacylglycerols resembling the stereoisomeric structure of human milk fat (25.4% by wt 16:0, 76.1% of which is at the sn-2 position), whereas in the alpha formula 87.3% of total 16:0 (25.7% by wt was at the sn-1,3 positions. Plasma lipids and their fatty acid compositions were determined at the end of each 1 wk study period. Infants fed with the beta formula had higher percentages of palmitic acid in plasma sterol esters, triacylglycerols, and free fatty acids, and lower linoleic acid in triacylglycerols than with the alpha formula. Premature infants fed formulas with triacylglycerols 16:0 predominantly in the sn-2 rather than the sn-1,3 positions had alterations in their plasma fatty acids consistent with enhanced absorption of 16:0 from the sn-2 compared with the sn-1,3 positions.

Immunologic effects of background prenatal and postnatal exposure to dioxins and polychlorinated biphenyls in Dutch infants

Immunologic effects of pre- and postnatal polychlorinated biphenyl (PCB)/dioxin exposure in Dutch infants from birth to 18 mo of age are explored. The total study group consisted of 207 healthy mother-infant pairs, of which 105 infants were breast-fed and 102 children were bottle-fed. Prenatal PCB exposure was estimated by the PCB sum (PCB congeners 118, 138, 153, and 180) in maternal blood and the total toxic equivalent (TEQ) level in human milk (17 dioxin and 8 dioxin-like PCB congeners). Postnatal PCB/dioxin exposure was calculated as a product of the total TEQ level in human milk multiplied by the weeks of breast-feeding. The number of periods with rhinitis, bronchitis, tonsillitis, and otitis during the first 18 mo of life was used as an estimate of the health status of the infants. Humoral immunity was measured at 18 mo of age by detecting antibody levels to mumps, measles, and rubella. White blood cell counts (monocytes, granulocytes, and lymphocytes) and immunologic marker analyses CD4+ T-lymphocytes, CD8+ T-lymphocytes, activated T-lymphocytes (HLA-DR+CD3+), as well as T cell receptor (TcR) alpha beta+, TcR gamma delta+, CD4+CD45RA+ and CD4+CD45RO+ T-lymphocytes, B-lymphocytes (CD19+ and/or CD20+) and NK cells (CD16+ and/or CD56+/CD3-) in cord blood and venous blood at 3 and 18 mo of age were assessed in a subgroup of 55 infants. There was no relationship between pre- and postnatal PCB/dioxin exposure and upper or lower respiratory tract symptoms or humoral antibody production.(ABSTRACT TRUNCATED AT 250 WORDS)

Immediate commencement of amino acid supplementation in preterm infants: effect on serum amino acid concentrations and protein kinetics on the first day of life

To determine whether the general reluctance to begin amino acid administration to preterm infants from birth onward might lead to loss of lean body mass and impairment of growth, we measured amino acid levels and protein kinetics in 18 preterm infants. Nine infants received amino acids (1.15 +/- 0.06 gm.kg-1.day-1) and glucose (6.05 +/- 1.58 gm.kg-1.day-1), whereas the other nine infants received only glucose (6.48 +/- 1.30 gm.kg-1.day-1) from birth onward. Protein kinetics on the first postnatal day were measured with a stable isotope dilution technique with [1-13C]leucine as a tracer. No statistically significant differences were noted in blood pH, base excess, urea concentration, or glucose levels. Both total amino acid concentration and total essential amino acid concentration were significantly lower and were below the reference range in the nonsupplemented group. Plasma amino acid levels of five essential amino acids (methionine, cystine, isoleucine, leucine, arginine) were below the reference range in the nonsupplemented group, whereas only cystine was below the reference range in the supplemented group. Nitrogen retention was improved significantly by the administration of amino acids (-110 +/- 44 mg nitrogen per kilogram per day in the glucose-only group vs +10 +/- 127 mg nitrogen per kilogram per day in the group given glucose and amino acids; p = 0.001); leucine oxidation was not significantly increased in the supplemented group (41 +/- 13 mumol.kg-1.hr-1 vs 46 +/- 16 mumol.kg-1.hr-1). Leucine balance also improved significantly (-41 +/- 13 mumol.kg-1.hr-1 vs -8 +/- 16 mumol.kg-1.hr-1; p = 0.01) because of a combination of an increased amount of leucine being used for protein synthesis and a lower amount of leucine coming from protein breakdown. Plasma cystine concentration, the only amino acid below the reference range in the supplemented group, was highly predictive for protein synthesis in that group. We conclude that the administration of amino acids to preterm infants from birth onward seems safe and prevents the loss of protein mass.

The click-evoked oto-acoustic emission, c-EOAE, in preterm-born infants in the post conceptional age range between 30 and 68 weeks

Click-evoked otoacoustic emissions (cEOAEs) were repeatedly recorded in an operational sample of 144 very low birth weight (VLBW) infants. A subgroup of 22 was composed of all those babies in which at least 4 recordings were successfully done. The mean birth weight of this group was 1040 g, and the mean duration of assisted ventilation was 17 days. The OAE-recordings were done in the post conceptional age (PCA) range between 30 and 68 weeks. In relation to ear function screening it was shown that the EOAE was present in 95% of the ears at least once at any age, while it was present in all recordings in only 34%. From a longitudinal analysis of the recordings per infant it appeared that: (1) the OAE recorded was already present in one infant at the PCA of 29.4 weeks; (2) in most infants the level of the OAE varies strongly between recordings; (3) in each infant the OAE-level shows an increase with age, on average this growth amounts to 10 dB between the PCAs of 31 and 42 weeks; (4) there is no clearcut difference in the growth of high- and low-frequency components of the EOAE.

Feeding premature newborn infants palmitic acid in amounts and stereoisomeric position similar to that of human milk: effects on fat and mineral balance

The effect of the structure of human milk triglycerides on intestinal fat absorption remains controversial. Twelve infants were each fed, for 1 wk in a crossover design, two formulas that differed only in triglyceride configuration. The "beta" formula contained triglycerides similar to those in human milk (26% palmitic acid, esterified predominantly to the sn-2 position) whereas in the "alpha" formula, which contained triglycerides similar to those in formulas currently marketed, palmitate was mainly at the sn-1,3 positions. Fatty acid, fat, and mineral balances were measured at the end of each 1-wk period. Myristic, palmitic, and stearic acids were absorbed better from the beta formula, but total fat excretion was not reduced. During the feeding of beta formula fecal calcium excretion was lower, urinary calcium higher, and urinary phosphate lower. A formula containing triglycerides similar to those in human milk has significant effects on fatty acid intestinal absorption and improves mineral balance in comparison with a conventional formula.

Perinatal exposure to polychlorinated biphenyls and dioxins and its effect on neonatal neurological development

Polychlorinated biphenyls (PCBs) and dioxins (polychlorinated dibenzo-p-dioxins (PCDDs), and dibenzofurans (PCDFs)) are widespread environmental contaminants which are neurotoxic in animals. Perinatal exposure to PCBs, PCDDs, and PCDFs occurs prenatally via the placenta and postnatally via breast milk. To investigate whether such an exposure affects the neonatal neurological condition, the neurological optimality of 418 Dutch newborns was evaluated with the Prechtl neurological examination. Half of the infants were breast-fed, the other half were formula-fed, representing a relatively high against a relatively low postnatally exposed group, respectively. As an index of prenatal exposure, four non-planar PCBs in cord and maternal plasma were used. These PCB levels were not related to neurological function. As measures of combined pre- and early neonatal exposure, 17 dioxin congeners, three planar, and 23 non-planar PCB congeners were determined in human milk in the second week after delivery. Higher levels of PCBs, PCDDs, and PCDFs in breast milk were related to reduced neonatal neurological optimality. Higher levels of planar PCBs in breast milk were associated with a higher incidence of hypotonia. This study confirms previous reports about the neurotoxic effects of these compounds on the developing brain of newborn infants.

Quantification of carbohydrate oxidation by respiratory gas exchange and isotopic tracers

Estimates of glucose oxidation measured by indirect respiratory calorimetry and by [U-13C]glucose tracer were compared as a function of respiratory exchange ratio (RER) in 14 studies performed on 9 healthy adult subjects. RER was varied between 0.7 and 1.04, either by fasting or by infusing glucose. 13C enrichment of plasma glucose and expired CO2 were measured by mass spectrometry. The two methods gave similar results when the nonprotein respiratory quotient (NPRQ) was between 0.76 and 0.90. Glucose oxidation by the tracer method was quantified to be higher than that by respiratory calorimetry when NPRQ was < 0.76; it was lower than the respiratory calorimetry estimate when NPRQ was > 0.90. The discrepancy between the two methods at low RER may represent the contribution of gluconeogenesis, whereas, at high RER, the discrepancy may be the consequence of lipogenesis. We conclude that respiratory calorimetry and [13C]glucose tracer give comparable results only in a narrow range of RER. These data are important when the disposal of glucose is compared using these techniques in different metabolic states with varying respiratory quotients.

Nutrition in the neonate

Good nutrition is of great importance for all living individuals, especially for the rapidly growing newborn infant. Nutrition is needed not only for the maintenance of physiologic functions but also for growth. Despite extensive research in this field, numerous questions remain regarding the nutrition of the term as well as the preterm infant. It should be stressed that the requirements of term infants are different from those of preterm infants, and a further distinction has to be made between very low birth weight and extremely low birth weight infants. In this review, the following issues are addressed: breastfeeding versus formula feeding, the role of polyunsaturated fatty acids, nutrition of the infant with bronchopulmonary dysplasia, and parenteral nutrition.

Whole-body protein turnover in preterm appropriate for gestational age and small for gestational age infants: comparison of [15N]glycine and [1-(13)C]leucine administered simultaneously

Measurements of whole-body protein turnover in preterm infants have been made using different stable isotope methods. Large variation in results has been found, which could be due to different clinical conditions and/or the use of different tracers. We studied 14 appropriate for gestational age and nine small for gestational age orally fed preterm infants using [15N]glycine and [1-(13)C]leucine simultaneously, which allowed us to make a comparison of commonly used methods to calculate whole-body protein turnover. Whole-body protein turnover was calculated from 15N enrichment in urinary ammonia and urea after [15N]-glycine administration and from the 13C enrichment in expired CO2 after administration of [1-(13)C]leucine. Enrichment of alpha-ketoisocaproic acid after [1-(13)C]leucine constant infusion was measured as a direct parameter of whole-body protein turnover. Group means for whole-body protein turnover using [15N]glycine or [1-(13)C]leucine ranged from 10 to 14 g.kg-1.d-1, except when using the end product method that assumes a correlation between leucine oxidation and total nitrogen excretion. We found very low 15N enrichment of urinary urea in the majority of small for gestational age infants. These infants also had a lower nitrogen excretion in urine and oxidized less leucine. Nitrogen balance was higher in small for gestational age infants (416 +/- 25 mg.kg-1.d-1) compared with appropriate for gestational age infants (374 +/- 41 mg.kg-1.d-1, p = 0.003). [15N]Glycine does not seem to exchange its label with the body nitrogen pool to a significant degree and is therefore not always suitable as a carrier for 15N in protein turnover studies in premature infants.

Substrate utilization during the first weeks of life

It is assumed that substrate utilization changes markedly around birth, from mainly glucose utilization before, to glucose/fat utilization after birth. We studied substrate oxidation and turnover in preterm infants on the first day and during the first weeks of life. We found that only part of the glucose that is infused on the first day of life is oxidized, while glucose is also converted into fat at the same time. Almost half of the energy expenditure is provided by fat oxidation on day 7 and 28 of life. Fat oxidation is dependent on the type of fat oxidized; the rate of oxidation of medium chain triglycerides (MCT) is higher than that of long chain fatty acids. MCT can replace glucose as an energy source. Proteins contribute only to a small extent (approximately 7%) to the energy expenditure at all ages.

Effects of polychlorinated biphenyls (PCBs) and dioxins on growth and development

Polychlorinated biphenyls (PCBs) and dioxins are potentially toxic compounds which occur widely in the environment. Their effects on the growth and development of infants at the levels currently found in highly industrialised western countries is not well known. This Dutch multicenter study, combining animal and human studies, tries to answer this question. Animal studies showed that PCB 169, given once during pregnancy at a dose of 1.8 g kg-1 bodyweight, has an effect on developmental parameters, dopamine regulation and fertility. Effects on thyroid hormones were also found in animals, probably due to both a competitive binding of PCB metabolites to the thyroxine binding protein and increased glucuronidation. Perhaps to compensate for this, an increased diodase activity in the brain was found. Human studies involved 400 mother-infant pairs, half of them being breast-fed, the other half were fed a formula devoid of PCBs and dioxins. PCB levels were measured in serum and dioxin and PCB levels in breastmilk. Levels were found to be as high as previously found in highly industrialised countries. Growth and development were carefully documented, but no data are as yet available. In pregnant women, a significant negative correlation was found between some dioxin and PCB congeners in milk and plasma thyroid hormones, while newborn infants showed higher thyroid stimulating hormone (TSH) at higher levels of dioxin exposure. In summary, data from this combined multicenter study involving animals and humans increases our insight into the potentially negative effects of PCBs and dioxins on growth and development.

Effects of prenatal exposure to betamethasone and indomethacin on the glomerular filtration rate in the preterm infant

The effects of gestational age (GA), body weight, and prenatal exposure to betamethasone and indomethacin on the glomerular filtration rate (GFR) on d 3 of life in preterm infants were studied. GFR measurements were performed in 147 preterm infants with a GA between 23.4 and 37.0 wk by means of the continuous inulin infusion technique. Mean GFR values increased significantly with GA (r = 0.60, p < 0.001) and with body weight (r = 0.44, p < 0.001). Multivariate analysis indicated that GA was the most important determinant for this increase. Prenatal exposure to indomethacin resulted in significantly lower GFR values (-0.15 +/- 0.03 mL/min, p < 0.001) at d 3 after birth. Prenatal administration of betamethasone and indomethacin significantly (p < 0.001) increased the GFR in comparison with exposure to indomethacin alone to levels not different than those seen in patients who were not prenatally exposed to betamethasone or indomethacin. GFR measurements were repeated in 40 preterm infants on d 10 after birth. During this 7-d period, a significant increase in GFR values (0.17 +/- 0.03 mL/min, p < 0.001) was detected. This postnatal increase in GFR values was independent of GA and was not influenced by prenatal exposure to betamethasone or indomethacin. We conclude that prenatal exposure to betamethasone or indomethacin exerts significant effects on the renal function of preterm infants in the first days of life.

Dioxin and PCB levels in blood and human milk in relation to living areas in The Netherlands

Dioxins and polychlorinated biphenyls (PCBs) are ubiquitous toxic compounds in the environment. Negative influences of these compounds on the health status of human beings have been described. Especially susceptible might be the fetus, which is exposed in utero, and the newborn breast-fed infant, since both are exposed to relatively high levels of dioxins and PCBs during a critical period of organ growth and development. We investigated PCB levels in 406 maternal plasma samples as well as PCB and dioxin levels in 172 human milk samples with relation to living area of women living for at least five years in the western industrialized part of the Netherlands or the northern more rural part. The western part was further subdivided into one urban and two highly industrialized areas. After correction for covariates, we found significantly higher levels of PCB 118 in maternal plasma as well as significantly higher levels of the dioxin-TEQ and of ten individual dioxin and PCB congener levels in human milk in the western more industrialized areas of the Netherlands compared to the northern more rural part. We did not find significant differences in planar, mono-ortho or di-ortho PCB-TEQ levels in human milk between all different areas. We conclude that significantly higher levels of a number of dioxin and PCB congeners are found in women living in industrialized areas compared to women living in rural areas in the Netherlands.

Effects of dioxins and polychlorinated biphenyls on thyroid hormone status of pregnant women and their infants

Dioxins [polychlorinated dibenzo-p-dioxins (PCDD), dibenzofurans (PCDF)] and polychlorinated biphenyls (PCB) are potentially hazardous compounds. Animal studies have demonstrated that PCDD, PCDF, and PCB can alter thyroid hormone homeostasis. We investigated thyroid hormone levels in 105 mother-infant pairs. To estimate maternal and infant exposure, four nonplanar PCB congeners were measured in maternal plasma during the last month of pregnancy and in umbilical cord plasma. Seventeen PCDD and PCDF congeners, three planar PCB congeners, and 23 nonplanar PCB congeners were measured in human milk. Higher PCDD, PCDF, and PCB levels in human milk, expressed as toxic equivalents, correlated significantly with lower plasma levels of maternal total triiodothyronine and total thyroxine, and with higher plasma-levels of TSH in the infants in the 2nd wk and 3rd mo after birth. Infants exposed to higher toxic equivalents levels had also lower plasma free thyroxine and total thyroxine levels in the 2nd wk after birth. We conclude that elevated levels of dioxins and PCB can alter the human thyroid hormone status.

Conversion of octanoic acid into long-chain saturated fatty acids in premature infants fed a formula containing medium-chain triglycerides

A large number of very-low-birth weight infants are fed formulas containing medium-chain triglycerides (MCT) to enhance fat and calcium absorption. Studies are available on the intestinal absorption of MCT, which is nearly complete, but uncertainties exist on the metabolic fate of octanoic acid, the major component of MCT. Oxidation accounts for approximately 50% of the dietary intake, and losses as dicarboxylic acids in the urine are negligible. Since storage in adipose tissue is limited, conversion into long-chain fatty acids (LCFA) is likely to be an important route. To study the nonoxidative metabolism of MCT, six preterm infants fed a standard premature formula containing 38 weight% (wt%) MCT (54 mol% medium-chain fatty acids (MCFA), of which 35 mol% is octanoic acid) were studied at 4 weeks of age, when on full oral intake and receiving on average 130 kcal/kg/d. The study consisted of an oral primed constant-rate infusion of [13C]-octanoate and the measurement of the 13C enrichment of individual fatty acids in plasma triglycerides (TG) by a highly sensitive on-line combustion method using gas chromatography-isotope ratio mass spectrometry (GC-IRMS). We observed a significant incorporation of the dietary [13C]-octanoic acid in plasma TG (10.0% +/- 4.5% of the enrichment of the diet). A noticeable incorporation of the label was detected in myristic and palmitic acids (4.6% +/- 2.5% and 7.8% +/- 4.1% of the octanoic enrichment of the diet). The absolute amount of the fatty acids was studied with conventional GC, and the plasma TG fatty acid profile differed markedly from the diet.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino acid solutions for premature neonates during the first week of life: the role of N-acetyl-L-cysteine and N-acetyl-L-tyrosine

Tyrosine and cyst(e)ine are amino acids that are thought to be essential for preterm neonates. These amino acids have low stability (cyst(e)ine) or low solubility (tyrosine) and are therefore usually present only in small amounts in amino acid solutions. Acetylation improves the stability and solubility of amino acids, facilitating a higher concentration in the solution. We compared three commercially available amino acid solutions, Aminovenös-N-päd 10%, Vaminolact 6.5%, and Primène 10%, administered to 20 low-birth-weight neonates on total parenteral nutrition from postnatal day 2 onward. Aminovenös-N-päd 10% contains acetylated tyrosine and acetylated cysteine; the other solutions do not contain acetylated amino acids and differ in the amount of tyrosine and cysteine added. On postnatal day 7, plasma amino acids were measured together with urinary excretion of amino acids and the total nitrogen excretion; 38% of the intake of N-acetyl-L-tyrosine and 53% of the intake of N-acetyl-L-cysteine were excreted in urine. Plasma levels of N-acetyl-L-tyrosine (331 +/- 74 mumol/L) and N-acetyl-L-cysteine (18 +/- 29 mumol/L) were higher than those of tyrosine (105 +/- 108 mumol/L) and cystine (11 +/- 9 mumol/L), respectively. Plasma tyrosine levels in the groups receiving small amounts of tyrosine remained just below the reference range. We show a linear correlation of plasma cystine with the intake of cysteine (r = .75, p = 0.01), but not with N-acetyl-L-cysteine. The estimated intake of cysteine should be 500 mumol.kg-1.d-1 in order to obtain levels comparable with those shown in normal term, breast-fed neonates. Nitrogen retention did not differ among the three groups (247 to 273 mg.kg-1.d-1).(ABSTRACT TRUNCATED AT 250 WORDS)

Minor neurological dysfunction and quality of movement in relation to neonatal cerebral damage and subsequent development

Minor neurological dysfunction (MND) and quality of movement were studied in relation to neonatal cerebral damage and developmental assessments at 3 1/2 years of age in 66 very low-birthweight children without obvious disability. MND was found in 19 children and was significantly related to the quality of movement. The results demonstrate that MND is associated with neonatal cerebral damage at preschool-age, but that the assessment of quality of movement is associated with more complex sensory motor tasks and simultaneous processing. At preschool-age, quality of movement might therefore be a better marker of later learning problems than traditional signs of minor neurological dysfunction.

The vitamin K controversy

Discussion about the efficacy and safety of vitamin K prophylaxis has recently restarted. In this review, new developments in diagnosis of vitamin K deficiency (including vitamin K plasma levels and protein induced by vitamin K absence [PIVKA]-II detection) and therapy of early, classic, and late hemorrhagic disease of the newborn are highlighted. Special attention is brought to the efficacy of preventing early and late hemorrhagic disease. The recently described association between intramuscular vitamin K administration and cancer is debated. The very high plasma levels, the intramuscular injection itself, or the adjuvants in the solution might all be responsible. These factors are all absent in oral administration. Therefore, we recommend repeated oral administration for preventing classic and late hemorrhagic disease of the newborn. Additionally, we recommend maternal supplementation of vitamin K for preventing early hemorrhagic disease of the newborn, especially when the mother is using medications that interfere with vitamin K metabolism.

Metabolic consequences of increasing energy intake by adding lipid to parenteral nutrition in full-term infants

The effect on energy metabolism and fuel utilization of increasing energy intake by adding intravenous lipid to a glucose and amino acid regimen was examined. Twenty fullterm, appropriate-for-gestational-age, intravenously fed neonates were entered into one of two groups: total energy intake was 261 kJ.kg-1 x d-1 (62 kcal.kg-1 x d-1) in group 1 and 355 kJ.kg-1 x d-1 (85 kcal.kg-1 x d-1) in group 2. Both groups received 2.8 g protein.kg-1 x d-1 and 14 g glucose.kg-1 x d-1. Group 2 received an additional 2 g lipid.kg-1 x d-1. Metabolic rate, respiratory gas exchange, and nonprotein substrate oxidation were similar in both groups. The addition of energy as lipid enhanced nitrogen retention (230 vs 306 mg.kg-1 x d-1; P < 0.02) and utilization (52.8% vs 66.5%; P < 0.03). Our data suggest that nitrogen utilization is improved in parenterally fed neonates by adding fat and increasing energy intake without change in metabolic rate, carbon dioxide production, oxygen consumption, and nonprotein substrate utilization. Energy expenditure does not necessarily increase with increasing energy intake independently of diet composition.

Effect of dexamethasone on protein metabolism in infants with bronchopulmonary dysplasia

Corticosteroids result in protein wasting in human adults and rats. To determine to what extent this therapy affects protein metabolism in preterm infants, we studied 10 very low birth weight infants before a gradually tapered dexamethasone regimen was started and at day 4 of treatment (dexamethasone dosage 0.35 +/- 0.09 mg.kg-1.day-1), and seven infants at day 19 of treatment (dexamethasone dosage, 0.10 +/- 0.01 mg.kg-1.day-1). Protein breakdown and turnover rates were increased at day 4 of treatment but not any more at day 19 of treatment. Protein synthesis rate was not significantly affected during dexamethasone therapy. Weight gain was severely diminished during the first week of treatment but not during the next 2 weeks. We conclude that nitrogen balance during high dosages of dexamethasone is significantly lower because of an increase in proteolysis and not because of a suppression of synthesis.

Effects of biological and social factors on the cognitive development of very low birth weight children

OBJECTIVE

To investigate the effects of biological and social factors on the cognitive development of very low birth weight children, a longitudinal follow-up study was conducted from birth to 3.6 years of age.

METHODOLOGY

The study group consisted of a cohort of 79 surviving high-risk, very low birth weight infants. Neonatal cerebral ultrasonographic findings and a neurological score were used as indicators of biological risk. A sociodemographic risk score and the Home Observation for Measurement of the Environment inventory were used as indicators of social risk. Cognitive development was assessed at ages 1 and 2 years by the Mental scale of the Bayley Scales of Infant Development and at age 3.6 years by the Kaufman Assessment Battery for Children.

RESULTS

The mean mental index at 1 year of age was 96 (SD 19), at 2 years of age 86 (SD 26), and at 3.6 years of age for intelligence 87 (SD 13) and for achievement 86 (SD 14). In a stepwise multiple regression analysis of biological as well as social factors, the neurological score alone was the best predictor for cognitive development at 1 year of age, explaining 46% of the variance. From 2 years of age onward, the best predictors for cognitive development were the neurological score together with the home environment, explaining 46% of the variance for the Mental Developmental Index at age 2, 34% for intelligence, and 56% for achievement at age 3.6.

CONCLUSIONS

Children at high biological risk were able to catch up on their cognitive delay in a highly stimulating home environment. Children at low as well as high biological risk in a less stimulating home environment showed a decline in cognitive development. For these children, early intervention programs might be important in the prevention of cognitive disabilities.

Ambient light, ophthalmic artery blood flow velocities and retinopathy of prematurity

Exposure to bright light was recently proposed as a possible risk factor for the development of retinopathy of prematurity. A semi-longitudinal Doppler ultrasound study was conducted of ophthalmic artery flow velocities at normal and increased ambient light in 22 preterm infants, at post-menstrual ages from 28 to 37 weeks. The aim of this study was to obtain relationships between ophthalmic artery blood flow velocities at various post-menstrual ages and lighting conditions and the occurrence of retinopathy of prematurity. A gradual increase in average blood flow velocities was seen between 28 and 37 weeks. A stepwise increase in flow velocity was seen in all cases when ambient light was increased from moderate to intense. Five of the 22 infants developed retinopathy. No association could be established between ophthalmic artery flow velocities or light-induced changes in flow velocity and the occurrence of retinopathy.

Glucose kinetics and glucoregulatory hormone levels in ventilated preterm infants on the first day of life

Glucose production and oxidation were measured in ventilated preterm appropriate-for-gestational-age and small-for-gestational-age infants on the first day of life. Using a new technique of NaH13CO3 infusion followed by a [U-13C]glucose infusion, we measured glucose oxidation rates without measuring the CO2 production rate. Infants were studied at 18 +/- 4 h (mean +/- 1 SD) of life and received parenterally administered glucose only (4.2 +/- 0.5 mg.kg-1 x min-1). In 13 of 16 patients, the glucose production rate exceeded 1.0 mg.kg-1 x min-1. Infants born from mothers who had been receiving steroids antenatally had higher glucose production rates (2.3 +/- 1.1 mg.kg-1 x min-1) compared with infants from mothers who had not (1.1 +/- 0.8 mg.kg-1 x min-1, p = 0.036). The glucose oxidized (2.9 +/- 1.0 mg.kg-1 x min-1) was lower than the amount of glucose infused (p = 0.005) and was not different for appropriate-for-gestational-age and small-for-gestational-age infants. Plasma levels of glucose, insulin, glucagon, and total IGF-I were not correlated with glucose metabolism on the first day of life. Total IGF-II levels were negatively correlated with the rate of glucose appearance. We conclude that preterm infants on the first day of life receiving a glucose infusion of 4.2 mg.kg-1 x min-1 continue to produce glucose. The glucose oxidation rate is lower than the glucose infusion rate and the contribution of glucose oxidation to the total energy expenditure is limited.

Visual functions in relation with neonatal cerebral ultrasound, neurology and cognitive development in very-low-birthweight children

In order to determine the relationship between visual functions and neonatal cerebral ultrasound, neurological examinations and cognitive development, a prospective longitudinal study was conducted in 69 high-risk very-low-birthweight children. Visual development was studied at 1 and 2.6 years of corrected age by assessment of visual acuity, binocular visual fields, optokinetic nystagmus and strabismus. Visual impairments were found in 33% at age 1 and in 28% at age 2.6. Visual impairments were related to intraparenchymal damage, as detected by neonatal cerebral ultrasound, as well as to abnormal neurological examinations and lower mean developmental indices. A stepwise multiple regression analysis with neonatal cerebral ultrasound as the dependent variable and visual functions at ages 1 and 2.6 and neurological examinations at ages 1 and 2 as independent variables, however, demonstrated that standardized neurological examinations were better markers of neonatal cerebral damage than visual functions. In cognitive development at ages 1 and 2, the neurological examination at age 1 was the most important variable. In cognitive development at age 3.6, visual functions at age 2.6 were more important. Early visual impairments might thus influence later cognitive development. The effectiveness of appropriate early intervention strategies to stimulate visual and cognitive development in infants with less severe visual impairments should be subject to further study.

Early assessment and neurodevelopmental outcome in very low-birth-weight infants: implications for pediatric practice

To determine which assessments are useful, at what age, in order to identify handicaps in very low-birth-weight infants, neonatal cerebral ultrasound findings, neurological examinations and the mental scale of the Bayley Infant Scales of Development at 1 and 2 years of age were examined in relation to neurodevelopmental outcome at 3.6 years of age in a cohort of 79 high-risk very low-birth-weight infants. At 3.6 years of age, a minor handicap was found in 9 (11%) and a major handicap in 4 (5%) children. Cerebral palsy was found in 9 (11%) children at 3.6 years of age and could only be diagnosed reliably at 2 years of age. For short-term follow-up, as feedback to the neonatologist, the positive predictive value of intraparenchymal damage, as detected by neonatal cerebral ultrasound, was greater than the positive predictive value of a definitely abnormal neurological examination at 1 year of age. Visual handicaps (n = 4, 5%) and severe hearing deficits (n = 1, 1%) were all detected in the first year of life. A mental handicap was found in 7 (9%) children. It was impossible to predict mental handicaps for the individual child. Only 35% of the children with a mental delay at 2 years of age had a mental handicap at 3.6 years of age, whereas 35% had a normal cognitive outcome. Pediatricians therefore should be cautious in the interpretation of developmental test results in infancy. Long-term follow-up is essential for the child and its parents.

Behaviour problems of very low-birthweight children

Parent and clinician reports of behaviour problems among very low-birthweight (VLBW) children at 3 1/2 years of age were studied in relation to indicators of neonatal cerebral damage, cognition and social factors. VLBW children had more depressed behaviour and more internalizing problems by parent report, and also scored significantly more often within the clinical range on total problem scores, than children in the comparison group. Neither neonatal cerebral ultrasound nor neurological examinations were directly associated with behavioural outcome. Cerebral damage was related to cognitive development. Cognition directly influenced behaviour problems according to clinician report, while the home environment did so according to parent report. The authors suggest that depressed behaviour of preschool VLBW children might be associated with parental reactions to the birth of a VLBW child, and that their attention problems might be linked indirectly to brain damage via cognitive impairments.

Glucose metabolism in a term infant with transient hyperinsulinism and high carbohydrate intake

Transient hyperinsulinaemia is a well-known cause of hypoglycaemia in newborn infants. The hypoglycaemia may be caused by a decreased glucose production and/or an increased glucose uptake. Whether the increased uptake is caused by increased glucose oxidation or increased non-oxidative disposal is not known. The aim of this study was to investigate the fate of the large amount of glucose infused in a term infant who developed hypoglycaemia due to transient hyperinsulinaemia shortly after birth and was treated with high glucose infusions. On day 6 an indirect calorimetry study was performed, together with a glucose turnover study. Carbohydrate intake was 13.6 mg/kg per minute (19.6 g/kg per day). Both studies were repeated on day 11, when carbohydrate intake was normalised to 7.8 mg/kg per minute (11.2 g/kg per day). Glucose oxidation was 28% higher and non-oxidative glucose disposal was 257% higher on day 6 as compared to day 11. Our results indicate that hypoglycaemia during hyperinsulinism is the result of increased non-oxidative disposal of glucose and not increased glucose oxidation. The results indicate a remarkable capacity of the newborn for lipogenesis during high carbohydrate intake.

Hearing and language in preschool very low birthweight children

To get more insight into preschool language and hearing in high-risk very low birthweight (VLBW) children, we conducted a prospective study in a cohort of 79 children. The prevalence of language impairment and hearing loss at age 3-4 years, their relationship to each other as well as to perinatal conditions, neurodevelopmental outcome and the home environment are described. Mild hearing loss was found in 26%, moderate hearing loss in 13% and severe hearing loss in 3% of the children. None of the children was deaf. Abnormal tympanometry was found in 57% of the children. Hearing loss at age 4 years was related to a less optimal neonatal condition and was not related to the obstetrical condition or to neonatal cerebral ultrasound findings. Language impairment was found in 21% of the children at age 3.6 years. Receptive and expressive language was not related to perinatal conditions. There was no relation between the language assessments and the audiological assessments. Cognition and the home environment of the child were the only independent variables in the prediction of language in preschool VLBW children.

Decreased glucose oxidation in preterm infants fed a formula containing medium-chain triglycerides

Several formulas for preterm infants contain medium-chain triglycerides (MCT) to enhance fat absorption. Although fat absorption with MCT was slightly higher in several studies in preterm infants, a beneficial effect on growth has only been reported in one publication. We hypothesized that when part of the fat blend of preterm formula is substituted by MCT oil, this might lead to a different metabolic pattern in which, due to the preferential oxidation of MCT, an increase in lipogenesis from glucose could lead to an increase in metabolic rate. To study the impact of MCT on glucose metabolism, 18 preterm infants were randomized to receive either an MCT or an LCT formula containing 38- and 6%-by-weight medium-chain fatty acids, respectively, in their fat blend. At 4 wk of age, the metabolic rate, substrate utilization, glucose kinetics, and oxidation were measured by indirect respiratory calorimetry in combination with a constant-rate oral infusion of [U-13C]glucose. The "true" rate of appearance of glucose (Ra "true") was measured from the dilution of the uniformly labeled (m + 6) species of infused tracer, whereas "apparent" rate of appearance of glucose (Ra "apparent") was measured from the dilution of infused tracer C (carbon). The latter was measured by an on-line combustion method using a gas chromatograph-isotope ratio mass spectrometer. At a carbohydrate intake of 8.4 mg.kg-1.min-1, total utilization of carbohydrate was equal in both groups at 7.6 mg.kg-1.min-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Neonatal cerebral ultrasound, neonatal neurology and perinatal conditions as predictors of neurodevelopmental outcome in very low birthweight infants

To determine the assessments before discharge from the intensive care unit, that will predict outcome most accurately, a prospective longitudinal study in a cohort of 79 high risk VLBW children was conducted from birth to 3.6 years of age. Birthweight, gestational age, obstetrical and neonatal optimality, neonatal neurological examinations and neonatal cerebral ultrasound were studied in relation to outcome. The best predictor for outcome was a simple cerebral ultrasound classification according to the presence or absence of ventriculomegaly and intraparenchymal damage of any cause. Infants with normal neonatal cerebral scans or abnormal scans without ventriculomegaly almost invariably had a normal neurological outcome. In infants with cerebral lesions with ventriculomegaly the incidence of normal neurological outcome decreased to less than 50%. Intraparenchymal damage was associated with cerebral palsy as well as other (mental and sensori) handicaps in over 85% of the cases. Neonatal neurological examinations at preterm age had additional value in predicting neurological outcome especially in the group with ventriculomegaly. Neither birthweight, nor gestational age, obstetrical or neonatal optimality were independent variables in the prediction of outcome in high risk VLBW children at 3.6 years of age.

Comparison of two preterm formulas with or without addition of medium-chain triglycerides (MCTs). I: Effects on nitrogen and fat balance and body composition changes

Medium-chain triglycerides (MCTs) are included in the fat blend of several preterm formulas because of their complete absorption and rapid oxidation. The effects of two different fat blend compositions on nitrogen and fat balances and macronutrient oxidation were investigated in 28 healthy very-low-birth weight infants at 4 weeks of age. A preterm formula with a traditional corn oil/MCT blend containing 38% MCTs (MCT group) was compared to a new fat blend, designed to resemble human milk more, containing 6% MCTs (LCT group). There were no differences in nitrogen absorption or in excretion. Median nitrogen retention was 74% (MCT) vs. 71% (LCT) of intake. Fat absorption was higher (p less than 0.05) in the MCT group (88%) vs. 79% in the LCT group (median values). MCTs did not stimulate fat oxidation as measured by indirect calorimetry, so fat deposition was also higher on the MCT formula. As weight gain was not different between groups, the percentage of weight gain consisting of fat accretion was significantly (p less than 0.005) higher with the MCT formula (24% vs. 21%). On the other hand, there was no increase in percent protein accretion (both 15% of weight gain). We conclude that the existence of a slightly lower fat absorption in the healthy growing neonate fed a LCT formula compared with a MCT formula does not impair growth or nitrogen retention, but merely induces a slight decrease in the high relative fat accretion encountered in the preterm neonate.

Comparison of two preterm formulas with or without addition of medium-chain triglycerides (MCTs). II: Effects on mineral balance

Medium-chain triglycerides (MCTs) are included in the fat blend of several preterm formulas because of their complete absorption and rapid oxidation. The effects of two different fat blend compositions on calcium (Ca), phosphorus (P), and magnesium (Mg) balances and plasma levels and on plasma levels of parathyroid hormone (PTH), alkaline phosphatase (AP), and 1,25-dihydroxyvitamin D [1,25-(OH)2D] were investigated in 28 healthy very-low-birth weight infants at 4 weeks of age. A preterm formula with a traditional corn oil/MCT blend containing 38% MCTs (MCT group) was compared to a new fat blend, designed to resemble human milk more, containing 6% MCTs (LCT group). There was a higher absorption of Ca in the MCT group (73% vs. 60%. p less than 0.005), and an equal absorption of P (both 92%). The excretion of Ca correlated with the excretion of fat (p less than 0.00005). The LCT group showed a higher median PTH level (MCT: 2.1 pmol/L, LCT: 4.7 pmol/L, p less than 0.01) and a higher urinary P excretion (p less than 0.001). Mg absorption was also lower with LCT, but retention of Mg exceeded intrauterine values in both groups. Mineral plasma levels were in the normal range in both groups. AP was not different between groups and in the upper part of the reference range, whereas 1,25-(OH)2D levels were above the normal range and also not different between groups. We conclude that with the LCT formula, Ca absorption is slightly lower than with the MCT formula, whereas P absorption is unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of early amino acid administration during total parenteral nutrition on protein metabolism in pre-term infants

1. We investigated the effects of starting amino acid administration on post-natal day 2 on protein turnover and nitrogen balance in appropriate-for-gestational-age, very-low-birth-weight infants. Eighteen infants were divided into two groups. Group A received from day 2 onwards an amino acid solution, whereas group B started on this solution after day 4. Both groups were exclusively parenterally fed, 200 kJ day-1 kg-1 on post-natal days 3 and 4. Group A (birth weight 1.5 +/- 0.3 kg) received 4.6 g of glucose, 1.9 g of fat and 2.3 g of amino acids day-1 kg-1 body weight. Group B (birth weight 1.4 +/- 0.2 kg) received 7.0 g of glucose and 1.9 g of fat day-1 kg-1 body weight. 2. At post-natal day 3, a primed constant infusion of 3 mg of [15N]glycine day-1 kg-1 was given. Protein flux, protein synthesis and protein breakdown were calculated from the 15N enrichment in urinary ammonia. In five out of nine infants in group B no plateau of 15N enrichment in urinary urea could be detected, whereas in group A two out of nine infants did not reach a plateau. For this reason we did not use the end product urea for our calculations. 3. The administration of the amino acids resulted in a higher protein flux (6.9 +/- 1.5 g day-1 kg-1 versus 5.2 +/- 0.9 g day-1 kg-1) and a higher protein synthesis rate (6.0 +/- 1.4 g day-1 kg-1 versus 4.6 +/- 0.8 g day-1 kg-1) in group A.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of heparin in arterial catheters on the coagulation in preterm infants

The coagulation of 16 healthy preterm infants (control infants) was compared with 15 ventilated preterm infants (study infants) receiving 0.5 ml/hr of a solution containing 5 IU/ml heparin intra-arterially in order to keep a radial artery catheter patent. A venous sample was obtained in both groups, in the study group a sample from the arterial catheter was also taken. Both the heparin dependent (APTT, thrombin time) and the heparin independent coagulation factors (AT-III, Clotting Factors I, II, V and VII) were not different between the venous samples of both groups. The arterial samples showed a significantly elevated APTT and thrombin time compared with venous samples, especially when the heparin level in the sample was higher than 0.1 IU/ml. These elevations are due to heparin in the sample from the arterial line as the venous sample in the same patient did not show any heparin effect. The heparin non-dependent factors were not different between venous and arterial samples. We conclude that a solution containing 5 IU/ml heparin given at a rate of 0.5 ml/hr does not influence coagulation in preterm infants. Determination of heparin independent coagulation factors can be done in both venous samples and samples taken from the arterial catheter, in these arterial samples the heparin dependent factors can be influenced by the heparin present in the catheters.