Nutritional practices in the neonatal intensive care unit: analysis of a 2006 neonatal nutrition survey.

OBJECTIVE: The goal of this investigation was to determine how current parenteral nutrition and enteral nutrition practice intentions for preterm infants compare with published recommendations and previous feeding practices. METHODS: A survey of feeding strategies for 3 preterm infant weight groups was sent to NICU directors, neonatal fellowship directors, neonatologists, neonatal nurse practitioners, and neonatal dieticians. A total of 775 surveys were distributed by both electronic and standard mail services. RESULTS: There were 176 survey responses (23%). The majority of practitioners initiated parenteral nutrition for very preterm infants in the first day of life. Ninety-one percent of respondents increased protein delivery daily. Most respondents increased lipid delivery at a fixed rate, rather than on the basis of triglyceride levels. Insulin was used in 98% of units, but only 12% of the time as a nutritional adjuvant to increase weight gain. Across all birth weight categories, breast milk was prescribed most commonly for the first enteral feeding. Enteral feedings were started earlier and increased faster than in the past, especially for extremely low birth weight infants (<1000 g). The majority of respondents prescribed enteral feedings for infants with indwelling umbilical arterial (75%) and umbilical venous (93%) catheters. Despite data that more rapid feeding advancement is safe, >80% of respondents increased feedings at rates of 10 to 20 mL/kg per day across all weight categories. CONCLUSIONS: Clinicians reported that they are initiating parenteral and enteral nutrition earlier and in larger volumes than in the past, reflecting increased knowledge about best nutritional practices in very preterm neonates. The data suggest that the persistent extrauterine growth failure of preterm infants is not attributable to a lack of best nutritional practice knowledge and intention.

Achieving positive protein balance in the immediate postoperative period in neonates undergoing abdominal surgery.

OBJECTIVES: To determine whether neonates undergoing major abdominal surgical procedures in the first day of life could achieve a positive protein balance without protein toxicity in the immediate perioperative period by using parenteral amino acids and fentanyl analgesia. STUDY DESIGN: Newborns undergoing major surgery for gastroschisis in the first 24 hours of life (n = 13) were alternately allocated to immediate postoperative parenteral administration of 1.5 g/kg(-1)/day(-1) versus 2.5 g/kg(-1)/day(-1) amino acids. Protein balance was determined at 1.6 to 2.6 days postoperatively with both nitrogen balance and leucine stable isotope methodology. Statistical analyses were conducted with the unpaired t test and linear regression. RESULTS: Protein balance was significantly different in the 2 groups with both nitrogen balance and leucine stable isotope methodology. There was no evidence of protein toxicity as determined with blood urea nitrogen, creatinine, and ammonia concentrations. CONCLUSIONS: Neonates undergoing the metabolic stress of abdominal surgery shortly after birth are able to achieve a net positive protein balance with parenteral amino acid administration without evidence of protein intolerance.

Early aggressive nutrition in very preterm infants.

Despite numerous advances in the nutrition of preterm infants, the increasing survival at lower birth weights is resulting in a new frontier of extrauterine nutritional support of these vulnerable infants. The extremely low birth weight infant has endogenous energy to maintain energy balance for only 3-4 days without an exogenous energy supply. Nevertheless, many clinicians are still hesitant to introduce substrates at high rates early in life secondary to concerns of intolerance and toxicity. Current feeding practices appear to be resulting in significant postnatal growth failure in very preterm neonates. Optimizing nutritional support in these infants is critical to avoiding adverse growth and neurological outcomes. There is a need for scientifically based feeding strategies to achieve normal in utero growth rates postnatally. Important areas for research include determination of safe and efficacious upper limits of energy and amino acid intake, identification of markers for protein toxicity, better characterization of the effect of various neonatal illnesses and the neonatal stress response on nutritional metabolism, development of enteral feeding strategies that will allow for more rapid enteral feeding advance while reducing the risk of necrotizing enterocolitis, and understanding the benefits and risks of both over- and undernutrition in the extremely low birth weight infant.

Special circumstances: trophic feeds, necrotizing enterocolitis and bronchopulmonary dysplasia.

There are many unresolved issues regarding how to feed the extremely-low-birth-weight (ELBW) infant. Trophic feedings of small volumes of breast milk or formula do not appear to increase the incidence of necrotizing enterocolitis (NEC). For prevention of NEC, breast milk, antenatal steroids and fluid restriction each confers a benefit. Because the incidence of NEC is relatively low, to determine if a particular prevention strategy is effective, large numbers of infants would need to be enrolled in a prospective, randomized controlled trial, and such trials are rare. Candidate therapies for NEC prevention that warrant further study include oral immunoglobulins, probiotics, long-chain polyunsaturated fatty acids and arginine. Suboptimal nutrition in ELBW infants is common in the early postnatal period. This is also the most critical time for the development of bronchopulmonary dysplasia, when even brief periods of malnutrition have significant effects on lung development and growth.

The neonatologist's dilemma: catch-up growth or beneficial undernutrition in very low birth weight infants-what are optimal growth rates?

As the threshold of viability decreases, clinicians who care for preterm neonates increasingly are faced with making decisions regarding feeding in a population for which there are no clear guidelines and minimal scientific data to inform optimal nutritional strategies. It is becoming more apparent that the amount of nutrition, as well as the timing of nutrient delivery, may affect long-term growth and metabolic outcomes. Both overnutrition and undernutrition at critical growth periods may have adverse effects. The risks and benefits of nutrient delivery designed to achieve "catch-up" growth need to be further identified. This article reviews both established concepts and more recently identified issues that need to be considered by the neonatologist when making feeding decisions in the very preterm neonate.

Blood urea nitrogen concentration as a marker of amino-acid intolerance in neonates with birthweight less than 1250 g.

OBJECTIVE: Currently blood urea nitrogen (BUN) is commonly used as a marker of protein intolerance in very preterm infants. The purpose of this study was to evaluate the relationship between amino-acid intakes and BUN concentrations during the early neonatal period in preterm neonates. STUDY DESIGN: Retrospective review of BUN concentration data from 121 infants with birthweight

Effect of low versus high intravenous amino acid intake on very low birth weight infants in the early neonatal period.

Greater protein intakes are required than have been commonly used to achieve fetal in utero protein accretion rates in preterm neonates. To study the efficacy and safety of more aggressive amino acid intake, we performed a prospective randomized study in 28 infants [mean wt, 946 +/- 40 g (SEM)] of 1 (low amino acid intake, LAA) versus 3 g.kg(-1).d(-1) (high amino acid intake, HAA) at 52.0 +/- 3.0 h of life. After a minimum of 12 h of parenteral nutrition, efficacy was determined by protein balance and was significantly lower in the LAA versus HAA groups by both nitrogen balance (-0.26 +/- 0.11 versus 1.16 +/- 0.15 g.kg(-1).d(-1), p < 0.00005) and leucine stable isotope (0.184 +/- 0.17 versus 1.63 +/- 0.20 g.kg(-1).d(-1), p < 0.0005) methods. Leucine flux and oxidation and nonoxidative leucine disposal rates were all significantly higher in the HAA versus LAA groups (249 +/- 13 versus 164 +/- 8, 69 +/- 5 versus 32 +/- 3, and 180 +/- 10 versus 132 +/- 8 micro mol.kg(-1).h(-1), respectively, p < 0.005), but leucine appearance from protein breakdown was not (140 +/- 15 in HAA versus 128 +/- 8 micro mol.kg(-1).h(-1)). In terms of possible toxicity with HAA, there were no significant differences between groups in the amount of sodium bicarbonate administered, degree of acidosis as determined by base deficit, or blood urea nitrogen concentration. Parenteral HAA versus LAA intake resulted in increased protein accretion, primarily by increasing protein synthesis versus suppressing protein breakdown, and appeared to be well tolerated by very preterm infants in the first days of life.

Aggressive nutrition of the very low birthweight infant.

We propose an approach to nutrition of the VLBW infant that aims at minimizing the interruption of nutrient uptake engendered by premature birth. Our approach is aggressive in that it goes beyond current practice in several key aspects. The gap in nutrient intakes between the proposed aggressive approach and current practice will most likely disappear over the next few years as today's aggressive practice becomes tomorrow's standard practice. As the gap diminishes, so will the threat that nutritional deprivation poses to growth and development of VLBW infants.

Ovine placental and fetal arginine metabolism at normal and increased maternal plasma arginine concentrations.

Arginine (A) may play a significant role in fetal growth, by stimulating insulin secretion and as a precursor for both polyamine synthesis and nitric oxide production. To determine whether increased maternal plasma A concentrations can enhance delivery of A to the fetus, uterine, umbilical, and net uteroplacental (UP) A uptake rates were measured in 12 pregnant ewes at 129.6 +/- 0.4 d gestation (mean +/- SEM) during normal and after 3 h of increased maternal plasma A concentrations. With a 2.7-fold increase in maternal plasma A concentrations (p < 0.001), there were significant increases in uterine A uptake (13.8 +/- 1.0 to 41.3 +/- 7.7 micromol/min, p < 0.005), umbilical A uptake (3.3 +/- 0.5 to 5.2 +/- 0.8 micromol.min(-1).kg(-1) fetus, p < 0.005), UP A uptake (17.8 +/- 6.2 to 89.2 +/- 20.3 micromol.min(-1).kg(-1) placenta, p < 0.01), fetal arterial A concentration (98.7 +/- 6.3 to 137.1 +/- 9.9 microM, p < 0.001), maternal A disposal rate (143.7 +/- 9.4 to 217.0 +/- 6.7 micromol/min, p < 0.001), fetal A disposal rate (7.9 +/- 0.8 to 9.9 +/- 1.1 micromol.min(-1).kg(-1), p < 0.05), fetal A oxidation rate (1.31 +/- 0.24 to 1.84 +/- 0.36 micromol.min(-1).kg(-1), p < 0.05), and plasma insulin concentration in both fetus (16 +/- 2 to 20 +/- 2 microU/mL, p < 0.001) and mother (24 +/- 3 to 32 +/- 4 microU/mL, p < 0.001). Thus, increased maternal plasma A concentration increases maternal, UP, and fetal A net uptake, and increases insulin secretion in mother and fetus. The 4.2-fold larger increase in UP than net fetal A uptake could represent preferential UP A metabolism relative to fetal A metabolism, relatively limited placental-fetal A transport capacity compared with uterine A uptake capacity, or both; responsible mechanisms remain unknown.