Effect of preeclampsia in the mother on the leucine metabolism in the newborn infant.

The leucine turnover in newborn infants is influenced by factors such as nutritional state and corticosteroid treatment. Little is known about maternal factors influencing the leucine turnover in the newborn. In order to approach the effect of preeclampsia in the mother on neonatal protein turnover, we studied the leucine turnover in preterm infants soon after birth and again after 7 days. Ten infants from preeclamptic mothers (birth weight 1,280 +/- 240 g, gestational age 31 +/- 2 weeks) and 15 control patients (birth weight 1,320 +/- 210 g, gestational age 30 +/- 2 weeks) were enrolled. The leucine turnover was measured using a primed constant 5-hour intravenous infusion of [1-(13)C]leucine within the first 24 h after delivery and again on day 7 of life. The turnover (leucine flux; micromol.kg(-1).h(-1)) was calculated from the enrichment in alpha-ketoisocaproic acid in plasma. The leucine turnover on day 1 was 300 +/- 65 in the preeclampsia group and 358 +/- 70 in the controls (ANOVA, p < 0.05). The values on day 7 were 474 +/- 73 in the preeclampsia group and 485 +/- 80 in the control group (n.s.). To conclude, the leucine turnover on day 1 is lower in infants of preeclamptic mothers as compared with controls. This difference has disappeared on day 7 of life after receiving the same protein and energy intake.     

Acute effects of intravenous glutamine supplementation on protein metabolism in very low birth weight infants: a stable isotope study.

Although very low birth weight infants are subjected to severe stress and glutamine is now considered a conditionally essential amino acid that may attenuate stress-induced protein wasting in adults, current amino acid solutions designed for neonatal parenteral nutrition do not contain glutamine. To determine whether a short-term supplementation with i.v. glutamine would affect protein metabolism in very low birth weight infants, 13 preterm neonates (gestational age, 28-30 wk; birth weight, 820-1610 g) receiving parenteral nutrition supplying 1.5 g x kg(-1) x d(-1) amino acids and approximately 60 nonprotein kcal x kg(-1) x d(-1) were randomized to receive an i.v. supplement made of either 1) natural L-glutamine (0.5 g x kg(-1) x d(-1); glutamine group), or 2) an isonitrogenous glutamine-free amino acid mixture (control group), for 24 h starting on the third day of life. On the fourth day of life, they received a 2-h infusion of NaH(13)CO(3) to assess the recovery of (13)C in breath, immediately followed by a 3-h L-[1-(13)C]leucine infusion. Plasma ammonia did not differ between the groups. Glutamine supplementation was associated with 1) higher plasma glutamine (629 +/- 94 versus 503 +/- 83 microM, mean +/- SD; p < 0.05, one-tailed unpaired t test), 2) lower rates of leucine release from protein breakdown (-16%, p < 0.05) and leucine oxidation (-35%, p < 0.05), 3) a lower rate of nonoxidative leucine disposal, an index of protein synthesis (-20%, p < 0.05), and 4) no change in protein balance (nonoxidative leucine disposal - leucine release from protein breakdown, NS). We conclude that although parenteral glutamine failed to enhance rates of protein synthesis, glutamine may have an acute protein-sparing effect, as it suppressed leucine oxidation and protein breakdown, in parenterally fed very low birth weight infants.     

Effects of antenatal steroids on protein metabolism in preterm infants on the first day of life

OBJECTIVE: To analyze, in an existing cohort of infants, whether antenatal administered corticosteroids influence protein metabolism in preterm infants on the first day of life. Study design Three groups of infants were studied. The mothers of 25 infants had received 2 or more doses of corticosteroids, the mothers of 5 had received 1 dose, and there was no antenatal steroid exposure for 8 infants. Within a few hours after birth, a double-tracer leucine infusion was started by intravenous and intragastric routes and continued for 5 hours while the infants received only intravenous glucose. RESULTS: The plasma alpha-keto-isocaproic acid (KIC) enrichment (mol percent excess, MPE) from the intravenous tracer was not different between infants who reveived no antenatal steroids (8.58+/-1.64), 1 dose (7.60+/-0.78), and 2 or more doses (7.61+/-1.29). From the intragastric tracer, the plasma KIC enrichment from the intragastric tracer was different among the 3 groups, 7.62+/-2.35 for 0 doses, 5.78+/-0.85 for 1 dose, and 5.53+/-1.58 for 2 or more doses of antenatal steroids.Plasma KIC enrichment from the intravenous tracer was significantly higher than from the intragastric tracer in infants who received antenatal steroids, whereas there was no difference in infants who had not received antenatal steroids. Plasma leucine enrichment showed the same results. CONCLUSIONS: Antenatal corticosteroid administration to the fetus has no effect on whole-body leucine metabolism on the first day of life. However, it is associated with an increase in splanchnic leucine uptake at birth.     

Metabolism of methionine in the newborn infant: response to the parenteral and enteral administration of nutrients

The rates of transmethylation and transsulfuration of methionine were quantified using [1-(13)C]methionine and [C2H3]methionine tracers in newborn infants born at term gestation and in prematurely born low birth weight infants. Whole body rate of protein breakdown was also measured using [2H5]phenylalanine. The response to enteral formula feeding and parenteral nutrition was examined in full term and prematurely born babies, respectively. The relative rates of appearance of methionine and phenylalanine were comparable to the amino acid composition of mixed body proteins. Rates of transmethylation were high, both in full term infants (fast 32 +/- 14 micromol kg(-1) x h(-1); fed 21.7 +/- 3.2) and in preterm infants (57.2 +/- 14.8). Significant flux through the transsulfuration pathway was evident (full term: fast 6.0 +/- 4.4, fed 4.1 +/- 2.1; preterm: 24.9 +/- 9.9 micromol kg(-1) x h(-1)). Transsulfuration of methionine is evident in the human newborn in the immediate neonatal period, suggesting that cysteine may not be considered a "conditionally" essential amino acid for the neonate. The high rate of transmethylation may reflect the high methylation demand, whereas high rates of transsulfuration in premature babies may be related to high demands for glutathione and to the amounts of methionine in parenteral amino acid mixtures.     

Parenteral fat emulsions based on olive and soybean oils: a randomized clinical trial in preterm infants

OBJECTIVE: To evaluate in premature infants a new parenteral lipid emulsion based on olive and soybean oils (ratio 4:1), with less polyunsaturated fatty acids (PUFA) and more alpha-tocopherol than standard soybean oil emulsion. STUDY DESIGN: Premature infants (gestational age, 28-<37 weeks) were randomized to receive one of the two emulsions within the first 72 hours of life. The triglyceride dose was increased to 2 g/kg/day within 3 days. Plasma phospholipid fatty acids, alpha-tocopherol/lipid ratio, and urinary malondialdehyde (MDA) excretion were determined at baseline and after 7 days. RESULTS: Of 45 recruited infants, 33 completed the study per protocol (15 soybean oil, 18 olive oil emulsion). At study end, groups did not differ in plasma phospholipid arachidonic acid, total n-6 and n-3 metabolites, but the olive oil group showed higher values of the PUFA intermediates C18:3n-6 (0.19% +/- 0.01% vs. 0.13% +/- 0.02%, P < 0.05) and C20:3n-6 (2.92% +/- 0.12% vs. 2.21% +/- 0.17%, P = 0.005). The plasma alpha-tocopherol/total lipd ratio was higher in the olive oil group (2.45 +/- 0.27 micromol/mmol vs. 1.90 +/- 0.08 micromol/mmol, P = 0.001), whereas urinary MDA excretion did not differ. CONCLUSION: The lower PUFA supply with the olive/soybean oil emulsion appears to enhance linoleic acid conversion. The reduced PUFA content, combined with a higher antioxidant intake in the olive oil group, results in an improved vitamin E status. The olive oil-based emulsion is a valuable alternative for parenteral feeding of preterm infants who are often exposed to oxidative stress, while their antioxidative defense is weak.     

Leucine kinetics during simultaneously administered insulin and dexamethasone in preterm infants with severe lung disease

The objective of this study was to determine whether insulin administration would prevent the well-documented catabolic effect of dexamethasone given to preterm infants with chronic lung disease. We studied leucine metabolism in 11 very-low-birth-weight infants before dexamethasone treatment and on d 2, 4, and 7 thereafter. During the first 4 d of dexamethasone, insulin was administered i.v. at a dose of 0.5 (n = 7) or 1.0 (n = 5) IU/kg/d. Leucine turnover was not significantly different between d 0 (337 +/- 41.3 micromol leucine/kg/h), d 2 (288 +/- 27.2 micromol leucine/kg/h), d 4 (302 +/- 22.1 micromol leucine/kg/h), and d 7 (321 +/- 21.2 micromol leucine/kg/h), and neither was leucine breakdown (272 +/- 21.9 micromol leucine/kg/h on d 0, 225 +/- 21.5 micromol leucine/kg/h on d 2, 231 +/- 21 micromol leucine/kg/h on d 4, and 242 +/- 17.6 micromol leucine/kg/h on d 7). Weight gain rates were significantly lower during the first week of dexamethasone treatment compared with the week before treatment or the second and third week. We conclude that during insulin and corticosteroid administration in very-low-birth-weight infants, no changes were observed in leucine kinetics in contrast to previous studies. The decrease in weight gain was not reversed.     

Whole body protein turnover measured with 13C-leucine and energy expenditure in preterm infants

Our study was undertaken in preterm infants to examine the relationship of whole body protein kinetics with protein intake and energy expenditure. Leucine kinetics were determined in seven low birth wt preterm infants fed human milk or human milk enriched with protein (2.5 to 4.3 g protein/kg.d). The infants received a short (4-h) constant infusion of L-[1-13C]leucine and leucine turnover and oxidation were calculated from 13C-plasma leucine and expired 13CO2 enrichments measured by mass spectrometry. Energy expenditure was measured by indirect calorimetry. Nonoxidative leucine disposal (an estimate of protein synthesis) and leucine derived from protein (an estimate of protein breakdown) were, respectively, 2.98 +/- 0.82 and 2.06 +/- 0.74 mumol/kg.min. Whole body protein turnover and deposition, derived from leucine kinetics, were 8.22 +/- 2.31 and 2.17 +/- 0.50 g/kg.d, whereas energy expenditure was 56.3 kcal/kg.day. Protein turnover was correlated with protein intake but not with protein deposition. Energy expenditure was correlated with protein turnover, synthesis, and breakdown but not with protein deposition. These data are in agreement with the fact that protein deposition depends upon protein intake, but they also suggest that an elevated protein deposition is not necessarily the result of a rapid protein turnover or associated with an elevated energy expenditure.     

早产儿胃肠外营养相关性胆汁淤积综合征的危险因素研究

目的：研究早产儿胃肠外营养相关性胆汁淤积综合征（PNAC）的危险因素。方法：回顾性分析2000年1月至2011年10月静脉营养应用超过14 d的244例早产儿的临床资料,通过病例对照研究调查PNAC发生的危险因素。结果：单因素分析发现,PNAC组（n=23）与非PNAC组（n=221）相比,胃肠外营养（PN）总应用时间更长、氨基酸累计用量及脂肪乳累计用量更大、氨基酸每日最高用量及脂肪乳每日最高用量更高、PN应用第14天时的静脉热卡更多、出生体重更小、贫血及新生儿感染发生率更多（P<0.05）。氨基酸累计用量超过PNAC组氨基酸累计用量的非PNAC组早产儿,脂肪乳累计用量大,PN总应用时间长,机械通气使用情况高, 胎龄更小。脂肪乳累计用量超过PNAC组脂肪乳累计用量的非PNAC组早产儿,胎龄更小。PN总应用时间超过PNAC组PN总应用时间的非PNAC组早产儿,胎龄更小。结论：PN总应用时间、氨基酸累计用量、氨基酸每日最高用量、脂肪乳累计用量、脂肪乳每日最高用量、PN应用14天时的静脉热卡、低体重、新生儿感染及贫血为PNAC的危险因素,其他危险因素需进一步探究。     

A modified vitamin regimen for vitamin B2, A, and E administration in very-low-birth-weight infants

INTRODUCTION: Very-low-birth-weight (VLBW; birth weight, <1,500 g) infants receive preterm infant formulas and parenteral multivitamin preparations that provide more riboflavin (vitamin B2) than does human milk and more than that recommended by the American Society of Clinical Nutrition. VLBW infants who are not breast-fed may have plasma riboflavin concentrations up to 50 times higher than those in cord blood. The authors examined a vitamin regimen designed to reduce daily riboflavin intake, with the hypothesis that this new regimen would result in lower plasma riboflavin concentrations while maintaining lipid-soluble vitamin levels. METHODS: Preterm infants with birth weight < or =1,000 g received either standard preterm infant nutrition providing 0.42 to 0.75 mg riboflavin/kg/day (standard group), or a modified regimen providing 0.19 to 0.35 mg/kg/day (modified group). The modified group parenteral vitamin infusion was premixed in Intralipid. Enteral feedings were selected to meet daily riboflavin administration guidelines. Plasma riboflavin, vitamin A, and vitamin E concentrations were measured weekly by high-performance liquid chromatography. Data were analyzed with the independent t test, chi, and analysis of variance. RESULTS: The 36 infants (17 standard group, 19 modified group) had birth weight and gestational age of 779 +/- 29 g and 25.5 +/- 0.3 weeks (mean +/- SEM) with no differences between groups. Modified group infants received 38% less riboflavin (0.281 +/- 0.009 mg/kg/day), 35% more vitamin A (318.3 +/- 11.4 microg/kg/day), and 14% more vitamin E (3.17 +/- 0.14 mg/kg/day) than standard group infants. Plasma riboflavin rose from baseline in both groups but was 37% lower in the modified group during the first postnatal month (133.3 +/- 9.9 ng/mL). Riboflavin intake and plasma riboflavin concentrations were directly correlated. Plasma vitamin A (0.222 +/- 0.022 microg/mL) and vitamin E (22.26 +/- 1.61 /mL) concentrations were greater in the modified group. CONCLUSIONS: The modified vitamin regimen resulted in reduced riboflavin intake and plasma riboflavin concentration, suggesting plasma riboflavin concentration is partially dose dependent during the first postnatal month in VLBW infants. Modified group plasma vitamin A and vitamin E concentrations were greater during the first month, possibly because the vitamins were premixed with parenteral lipid emulsion. Because of the complexity of this protocol, the authors suggest that a parenteral multivitamin product designed for VLBW infants which uses weight-based dosing should be developed.     

积极的营养支持对住院期间早产儿的影响

目的 探讨生后早期积极的营养支持对住院期间早产儿的影响.方法 研究对象选择胎龄大于28周出生体重1000 g至2000 g、生后12 h内转入我院NICU、住院时间2周以上、无明显畸形且存活出院的早产儿,其中A组(2005年1月1日至2006年6月30日出生)81例,B组(2009年6月1日至2010年11月30日出生)79例.比较营养摄入、早产儿的生长速率及体重Z评分和血生化营养指标的差异.结果 B组生后第3、7天氨基酸用量明显高于A组[2.00(2.00,2.50) g/kg比1.50(1.50,2.00) g/kg,3.00(2.00,3.00) g/kg比2.00(1.80,2.60) g/kg,P均＜0.001].B组第3天奶量和总热卡摄入明显高于A组[9.41(2.66,18.74) ml/kg比14.47(4.23,30.77) ml/kg,P＜0.05,(64.87±16.04) kcal/kg比(55.62±17.68) kcal/kg,P=0.001].两组第1周后总热卡摄入相似.B组母乳强化剂使用率较前升高(62.8％比14.3％,P＜0.005).无论是出生体重1000～1499 g的早产儿,还是出生体重1500～2000 g的早产儿,B组生长速率均更快[(20.6±3.4)g/( kg·d)比(15.4±3.2)g/( kg·d),(20.3±9.1)g/(kg·d)比(14.3±4.9) g/(kg·d),P均＜0.001].A组生长迟缓的比例出院时较出生时增加(65.4％比40.7％,P＜0.05),B组差异无统计学意义.两组出生体重Z评分相似,而B组出院体重Z评分明显高于A组[(-1.24±0.79)比(-1.54±0.84),P＜0.05].出生时血清白蛋白、前白蛋白、尿素水平两组差异无统计学意义,而生后2周和出院前B组明显高于A组.结论 早产儿生后早期营养措施的改善有效促进了早产儿住院期间的生长和营养状况.     

Plasma and urine riboflavin during riboflavin-free nutrition in very-low-birth-weight infants

BACKGROUND: Very-low-birth-weight (VLBW; birth weight <1500 g) infants receive enteral and parenteral nutriture that provides greater daily riboflavin (vitamin B2) than does term infant nutriture, and elevated plasma riboflavin develops in these infants after birth. The purpose of this study was to measure plasma and urine riboflavin concentrations in VLBW infants during riboflavin-free nutrition. Our hypothesis was that elevated plasma riboflavin develops in VLBW infants because of high daily intake and immature renal riboflavin elimination. METHODS: Eighteen clinically healthy VLBW infants received parenteral nutrition and preterm infant formula during the first postnatal month. On postnatal days 10 and 28, the infants received specially prepared riboflavin-free enteral and parenteral nutrition for the 24-hour study period. Serial collections of plasma were made at time 0 and at 12 and 24 hours. Urine was collected continuously for the 24-hour period in 4-hour aliquots. Samples were analyzed for riboflavin concentration. RESULTS: During the 24-hour riboflavin-free study period on postnatal day 10, plasma riboflavin decreased 56% from 185 +/- 37 ng/mL (mean +/- SEM), and urine riboflavin decreased 75% from 3112 +/- 960 mg/mL. Similarly, on postnatal day 28, plasma riboflavin decreased 79% from 184 +/- 32 ng/mL, and urine riboflavin concentration decreased 91% from 5092 +/- 743 ng/mL during the 24-hour riboflavin-free study period. Riboflavin half-life (t(1/2)) was 18.5 hours on postnatal day 10 and decreased 48% by postnatal day 28. Riboflavin elimination was 145.1 +/- 20.6 mg/kg per day on postnatal day 10 and increased 40% by postnatal day 28. CONCLUSION: The VLBW infants who received parenteral nutrition and preterm infant formula had elevated plasma riboflavin on postnatal days 10 and 28. Plasma riboflavin t(1,2) was shorter and renal riboflavin elimination was greater on postnatal day 28 than on postnatal day 10. Plasma riboflavin was normal after 24 hours of riboflavin-free nutrition. The pattern of plasma and urine riboflavin in VLBW infants suggests a lower daily intake would maintain plasma riboflavin close to normal.     

Glutamine supplement with parenteral nutrition decreases whole body proteolysis in low birth weight infants

OBJECTIVES: To examine the effect of supplemental glutamine (0.6 g.kg -1 .d -1 ) on whole body protein/nitrogen and glutamine kinetics in low birth weight (LBW) infants receiving parenteral nutrition in the immediate neonatal period. STUDY DESIGN: Premature infants < or =32 weeks gestation with a birth weight from 694 to 1590 g were randomly assigned to either a glutamine-supplemented group (n = 10) or to a control group (n = 10). Tracer isotope studies were performed when the infants were 6 to 7 days old and had been receiving an amino acid intake of approximately 3.0 g.kg -1 .d -1 for at least 3 days. Whole body glutamine and nitrogen kinetics were measured with [5-15N]glutamine, [2H5]phenylalanine, [1-13C, 15 N]leucine, [15N2]urea, and GC-mass spectrometry. RESULTS: Supplemental glutamine was associated with a lower rate of appearance of glutamine ( P = .003), phenylalanine ( P = .001), and leucine C ( P = .003). There was no significant difference in leucine N turnover, urea turnover and plasma cortisol, and C-reactive protein levels in the 2 groups. CONCLUSION: Parenteral glutamine supplement in LBW infants was associated with lower whole-body protein breakdown. Because the decrease in whole body proteolysis is associated with protein accretion, parenteral glutamine supplement may be beneficial in selected populations of LBW infants.     

Cord blood and postnatal serum leptin and its relationship to steroid use and growth in sick preterm infants

OBJECTIVE: To study the effect of prenatal and postnatal glucocorticoids use on serum leptin and weight gain in sick preterm infants and its correlation with caloric intake. METHODS: Serum leptin was measured in 24 neonates at day 1 (cord), 14 and 28 by radioimmunoassay. Total caloric intake (enteral and parenteral) and weight were measured on days 14 and 28 of life. RESULTS: Mean birth weight and gestational age of study infants were 864 +/- 273 g (mean +/- SD) (range 520-1755 g), and 26.6 +/- 2.4 weeks (23-32 weeks) respectively. Cord blood leptin was greater in infants whose mothers received antenatal steroids (1.98 +/- 1.05 ng/ml vs 0.94 +/- 0.39 ng/ml, p=0.004). Serum leptin increased postnatally from 1.52 +/- 1.0 ng/ml at birth to 2.2 +/- 1.3 ng/ml on day 28 of life (p=0.03). Mean serum leptin had an inverse exponential relationship with postnatal weight gain by day 28 of life (R2=0.56). Total caloric intake on days 14 and 28 of life did not correlate with postnatal weight gain. CONCLUSIONS: Increased serum concentration of leptin following glucocorticoids may be associated with poor weight gain in sick preterm infants.     

Parenteral amino acids increase albumin and skeletal muscle protein fractional synthetic rates in premature newborn minipigs

OBJECTIVES: Early administration of parenteral amino acids increases whole body nitrogen retention in premature infants. Tracer kinetic studies suggest an increase in whole body protein synthesis as a possible mechanism for this increase in nitrogen retention. However, the effect of early parenteral amino acids on synthesis of specific proteins remains uncertain. Using premature newborn minipigs as a model for human premature newborns, we investigated the effects of parenterally administered amino acids on albumin and skeletal muscle protein fractional synthetic rates. METHODS: Fifteen Yucatan minipigs were delivered by cesarean section 6 days before the mean expected delivery date (day 106 of gestation; expected gestation, 111-113 days) and randomized to two groups immediately after birth: 7 piglets received a mixture of amino acids (0.4 g. kg. h ) and glucose (0.8 g. kg. h ) for 5 hours, and 8 piglets (control group) received glucose only. All piglets received a continuous primed infusion of 1-[ C]valine. Arterial plasma free C-valine enrichment was measured by gas chromatography/mass spectrometry, and protein synthetic rates were determined by measuring incorporation of C-valine into albumin and skeletal muscle protein using gas chromatography/combustion/isotope ratio mass spectrometry. RESULTS: Administration of amino acids increased albumin (87.0% +/- 42.1% [mean +/- SD] vs. 37.6% +/- 6.8% per 24 hours; < 0.05) and skeletal muscle fractional synthetic rates (11.60% +/- 6.9% vs. 6.5% +/- 1.5% per 24 hours; < 0.05). CONCLUSION: We conclude that parenteral amino acids increase albumin and skeletal muscle fractional synthetic rates in premature piglets on the first day of life.     

Effect of early low-volume enteral substrate on subsequent feeding tolerance in very low birth weight infants

To determine the effect of small enteral feedings on small bowel function, 46 infants with birth weight less than 1500 g, selected on the basis of risk factors for feeding intolerance, were assigned randomly to one of two feeding groups. Group 1 received low-volume enteral feeds (12 ml/kg/day) in addition to parenteral alimentation for 10 days beginning on day 8 of life; group 2 received parenteral alimentation alone until day 18 of life. After this trial period feedings were increased by 15 ml/kg/day in all infants. Four infants (9%) developed necrotizing enterocolitis (one prior to any feeds, two in group 1, and one in group 2); two others were dropped from the study for reasons unrelated to feeding. The remaining 18 infants in group 1 had improved feeding tolerance compared with the 22 in group 2, as manifested by fewer days that gastric residuum totalled more than 10% of feedings (1.3 +/- 0.5 days vs 3.2 +/- 0.6 days, respectively, p less than 0.05) and fewer days that feedings were discontinued because of feeding intolerance (2.7 +/- 0.8 days vs 5.5 +/- 0.9 days, respectively, p less than 0.05). Consequently, 17 of 18 (94%) infants who had received the early low-volume enteral feedings achieved an enteral intake of 120 kcal/kg/day by 6 weeks of life, whereas only 14 of 22 (64%) infants in the delayed feeding group reached this intake (p less than 0.05). Peak total serum bilirubin concentrations were comparable in the two groups. The initiation of hypocaloric enteral substrate as an adjunct to parenteral nutrition improved subsequent feeding tolerance in sick infants with very low birth weight.     

Effect of minimal enteral feeding on splanchnic uptake of leucine in the postabsorptive state in preterm infants

We conducted a controlled, randomized trial to study the effect of minimal enteral feeding on leucine uptake by splanchnic tissues, as an indicator of maturation of these tissues, in preterm infants in the first week of life. Within a few hours after birth, while receiving only glucose, a primed constant infusion of [1-(13)C]-leucine was started and continued for 5 h via the nasogastric tube, whereas 5,5,5 D3-leucine was infused intravenously (for both tracers, priming dose 2 mg/kg, continuous infusion 2 mg/kg/h). Patients were thereafter randomized to receive solely parenteral nutrition (C), parenteral nutrition and 20 mL breast milk/kg/d (BM), or parenteral nutrition and 20 mL formula/kg/d (F). On d 7, the measurements were repeated, after discontinuing the oral intake for 5 h. Fourteen infants were included in group C, 12 in group BM, and 12 in group F. There was no difference in energy intake or nitrogen balance at any time. On d 1, plasma enrichment for the nasogastric tracer was lower than for the intravenous tracer for all three groups, both for leucine and for alpha-keto-isocaproic acid. On d 7, the enrichment for leucine and alpha-keto-isocaproic acid for the nasogastric tracer was lower than for the intravenous tracer for the groups BM and F (BM: 3.65 +/- 1.20 nasogastric versus 4.64 +/- 0.64 i.v.; F: 4.37 +/- 1.14 nasogastric versus 5.21 +/- 0.9 i.v.). In the control group, there was no difference between tracers. The lower plasma enrichment for the nasogastric tracer compared with the intravenous tracer suggests uptake of leucine by the splanchnic tissues. We conclude that minimal enteral feeding--even in low volumes of 20 mL/kg/d--increases the leucine uptake by the splanchnic tissue. We speculate that this reflects a higher protein synthesis of splanchnic tissues in the groups receiving enteral nutrition.     

Net acid excretion during first week of life

Metabolic acidosis occurs frequently in newborns. Net acid excretion (NAE) in 34 preterm and 12 term infants was measured during the first week of life. Twenty preterm infants received breast milk or formula; the remaining infants received total parenteral nutrition (TPN) -- synthetic amino acids or casein hydrolysate solution. NAE for breast milk vs formula fed infants was 5.4 +/- 0.4 and 7.8 +/- 0.6 muEq/min/m2 (mean +/- SEM). The corresponding values for the two TPN solutions in preterm infants were significantly higher at 12.5 +/- 1.4 and 19.4 +/- 3.5 muEq/min/m2. Term infants produced even greater amount of net acid, 20.6 +/- 2.9 and 35 +/- 3.7 muEq/min/m2 respectively for the two TPN solutions. Milk fed infants are less prone to acidosis because of base generated from milk consumption. Due to its inherent acidogenic effect, TPN solutions induce acidosis more readily. Infants receiving TPN are therefore required to generate a higher NAE rate to maintain acid-base homeostasis compared to milk fed infants.     

Increased parenteral amino acid administration to extremely low-birth-weight infants during early postnatal life

BACKGROUND: Early administration of parenteral amino acids to infants with extremely low birth weight (birth weight < or = 1,000 g) has been encouraged to foster growth. However, excessive intravenous intake of amino acids may cause metabolic acidosis and uremia in extremely low birth weight infants. The hypothesis for this study was that extremely low birth weight infants would tolerate slightly increased early postnatal parenteral amino acid administration and benefit. METHODS: The peak daily parenteral amino acid dosage was increased from 3 g/kg (standard group) to 4 g/kg (modified group). The corrected parenteral amino acid dosage was computed to account for enteral protein intake and keep the combined daily intravenous amino acid and enteral protein intake at or below 3 g . kg -1 . d -1 in the standard group and 4 g . kg -1 . d -1 in the modified group. The primary outcome measure was plasma bicarbonate concentration as an indicator of acid-base status. Data were collected for patient demographics, nutritional intake, serum bicarbonate and serum urea nitrogen concentrations, and outcome. RESULTS: The corrected parenteral amino acid intake of the modified group was 16% greater at postnatal week 1 (3.30 +/- 0.83 g . kg -1 . d -1; mean, +/-1 SD) and 18% greater (3.86 +/- 0.94 g . kg -1 . d -1 ) at postnatal week 2 than the parenteral amino acid intake of the standard group. In the modified group, the mean serum bicarbonate concentration was 19.1 +/- 1.8 mEq/dL at week 1 and 23.9 +/- 2.9 mEq/dL at week 2, with no difference between the groups. At week 1, serum urea nitrogen concentrations were the same in both groups. The mean serum urea nitrogen concentration of the modified group at postnatal week 2 (18.2 +/- 8.8 mg/dL) was unchanged from postnatal week 1, but was greater than that of the standard group at postnatal week 2. Weight gain was the same in both groups. Corrected parenteral amino acid intake at postnatal week 1 correlated directly with weight gain from birth to postnatal week 2 ( P < 0.03) in both groups. CONCLUSIONS: Infants with extremely low birth weight tolerated parenteral amino acid intake of approximately 4 g . kg -1 . d -1. Mild increases of mean serum urea nitrogen concentration and mean weight gain were associated with increased parenteral amino acid administration without significant acidosis.     

Nutritional efficacy of preterm formula with a partially hydrolyzed protein source: a randomized pilot study.

BACKGROUND: Decreased nitrogen levels, calcium intestinal absorption rates, and plasma amino acid imbalances were reported for preterm infants who were fed partially hydrolyzed preterm formulas. In this pilot study, we evaluated a new formula with modified nitrogen and calcium sources. METHODS: During their second week of life, 16 preterm infants were randomly assigned to one of two groups: 9 were fed the new partially hydrolyzed formula and 7 were fed a conventional formula. Nutrient balance was performed at the end of the first month of life. Amino acid concentrations and anthropometric parameters were measured at theoretical term. RESULTS: Birth weight and gestational age (mean +/- SD) were similar in the two groups (28.9 +/- 7.0 weeks and 1183 +/- 242 g vs. 27.7 +/- 1.0 weeks and 1139 +/- 162 g). Median nitrogen absorption rates (85% vs. 89%; P = 0.03) and biological values (59% vs. 69%; P = 0.13) were lower for infants who were fed the new formula than for those fed the conventional formula. After correction for difference in nitrogen intake, there was no significant difference in nitrogen retained between the two groups (P = 0.11). Plasma amino acid concentrations were also similar in the two groups. Median calcium absorption tended to be higher in the new-formula group than in the conventional-formula group (54% vs. 45%, P = 0.19). At theoretical term, infants fed the conventional formula were heavier than infants fed the new formula (3559 +/- 362 g vs. 3193 +/- 384 g, P = 0.04). CONCLUSIONS: Because nitrogen content is 10% higher in hydrolyzed-protein formula than in entire-protein formula, appropriate nitrogen retention, plasma amino acid profile, and mineral use can be achieved with the new partially hydrolyzed formula. Further studies with larger groups are needed to evaluate the effect on growth.     

胃肠道外营养对早产儿肝胆功能的影响

目的：胃肠道外营养是提高早产儿成活率的主要手段之一,但由于早产儿肝肾功能、脂质清除等不成熟,胃肠道外营养的运用还存在某些争议的问题,胃肠道外营养时早产儿肝胆功能的损害已日益受到重视。该研究探讨胃肠道外营养对早产儿肝胆功能的影响。方法：对75例实行胃肠道外营养的早产儿及49例未实行胃肠道外营养的早产儿,各营养成分输入后的监测结果进行统计分析。结果：治疗后研究组及对照组谷草转氨酶、总胆红素、未结合胆红素均比治疗前明显下降,统计学差异有非常显著性(P<0.01);而谷丙转氨酶、结合胆红素则在治疗前后变化不明显,差异无显著性(P>0.05);治疗后研究组总胆汁酸(TBA)水平升高,差异有非常显著性(P<0.01),与胃肠道外营养持续时间呈正相关,与胎龄呈负相关;对照组治疗后总胆汁酸变化不明显,差别无统计学意义(P>0.05)。结论：早产儿胃肠道外营养时血清总胆汁酸(TBA)水平升高,应警惕胆汁淤积。