title: Protein balance in the first week of life in ventilated neonates receiving parenteral nutrition.
abstract: BACKGROUND
  Protein intake is frequently delayed in ill neonates because of concerns about their ability to metabolize substrates.
  
  
  OBJECTIVE
  We aimed to determine the factors affecting protein balance in ventilated, parenterally fed newborns during the first week of life.
  
  
  METHODS
  Leucine kinetic studies were performed in 19 neonates by using the [1-(13)C]leucine tracer technique after 24 h of a stable total parenteral nutrition (TPN) regimen. TPN intakes were prescribed by rotating attending physicians, enabling assessment of protein metabolism over a range of clinically used nutrient intakes.
  
  
  RESULTS
  Mean (+/-SD) birth weight was 1.497 +/- 0.779 kg, gestational age at birth was 30.3 +/- 4.0 wk, and age at study was 3.9 +/- 1.4 d. Amino acid intakes (AAIs) ranged from 0.0 to 2.9 g x kg(-1) x d(-1). Based on leucine kinetic data, protein balance was calculated as the difference between protein synthesis and catabolism. By multiple regression analysis, AAI was the only predictor associated independently with protein balance (P < 0.01); energy intake, lipid intake, glucose intake, birth weight, and gestational age were not. Both leucine oxidation and nonoxidative leucine disposal rates were significantly correlated with leucine intake (P < 0.0005 and P < 0.01, respectively). Of the 12 infants with AAIs > 1 g x kg(-1) x d(-1), only 1 infant was significantly catabolic (protein balance <-1 g x kg(-1) x d(-1)). There was no evidence of protein intolerance as determined by elevated creatinine (69 +/- 31 micromol/L), plasma urea nitrogen (6.7 +/- 2.53 mmol/L), or metabolic acidosis (pH: 7.36 +/- 0.05).
  
  
  CONCLUSIONS
  Ill neonates can achieve a positive protein balance in the first days of life without laboratory evidence of protein toxicity.
authors.affiliation: Department of Pediatrics, University of Colorado Health Sciences Center, Denver 80262, USA. patti.thureen@uchsc.edu
authors.forename: P J
authors.initials: PJ
authors.lastname: Thureen
authors.forename: A H
authors.initials: AH
authors.lastname: Anderson
authors.forename: K A
authors.initials: KA
authors.lastname: Baron
authors.forename: D L
authors.initials: DL
authors.lastname: Melara
authors.forename: W W
authors.initials: WW
authors.lastname: Hay
authors.forename: P V
authors.initials: PV
authors.lastname: Fennessey
mesh_terms: D000596:Amino Acids / Q000008:administration & dosage / Q000378:metabolism; D001724:Birth Weight; D002153:Calorimetry, Indirect; D004044:Dietary Proteins / Q000378:metabolism*; D005865:Gestational Age; D006801:Humans; D007227:Infant Nutritional Physiological Phenomena; D007230:Infant, Low Birth Weight / Q000378:metabolism; D007231:Infant, Newborn / Q000378:metabolism*; D007930:Leucine / Q000493:pharmacokinetics; D010289:Parenteral Nutrition, Total; D011506:Proteins / Q000378:metabolism; D012044:Regression Analysis; D012121:Respiration, Artificial; D012720:Severity of Illness Index
chemical_list: D000596:Amino Acids; D004044:Dietary Proteins; D011506:Proteins; D007930:Leucine