title: Energy metabolism, nitrogen balance, and substrate utilization in critically ill children.
abstract: BACKGROUND
  Critically ill patients are characterized by a hypermetabolic state, a catabolic response, higher nutritional needs, and a decreased capacity for utilization of parenteral substrate.
  
  
  OBJECTIVE
  We sought to analyze the relation between a patient's metabolic state and their nutritional intake, substrate utilization, and nitrogen balance (NB) in mechanically ventilated, critically ill children receiving parenteral nutrition.
  
  
  METHODS
  This was a cross-sectional study in which resting energy expenditure (REE) and NB were measured and substrate utilization and the metabolic index (MI) ratio (REE/expected energy requirements) were calculated.
  
  
  RESULTS
  Thirty-three children (mean age: 5 y) participated. Their average REE was 0.23 +/- 0.10 MJ x kg(-1) x d(-1) and their average MI was 1.2 +/- 0.5. Mean energy intake, protein intake, and NB were 0.25 +/- 0.14 MJ x kg(-1) x d(-1), 2.1 +/- 1 g x kg(-1) x d(-1), and -89 +/- 166 mg x kg(-1) x d(-1), respectively. Patients with an MI >1.1 (n = 19) had a higher fat oxidation than did patients with an MI <1.1 (n = 14; P < 0.05). Patients with lipogenesis (n = 13) had a higher carbohydrate intake than did patients without lipogenesis (n = 20; P < 0.05). Patients with a positive NB (n = 12) had a higher protein intake than did patients with a negative NB (n = 21; P < 0.001) and lower protein oxidation (P < 0.01).
  
  
  CONCLUSIONS
  Critically ill children are hypermetabolic and in negative NB. In this population, fat is used preferentially for oxidation and carbohydrate is utilized poorly. A high carbohydrate intake was associated with lipogenesis and less fat oxidation, a negative NB was associated with high oxidation rates for protein, and a high protein intake was associated with a positive NB.
authors.affiliation: Sections of Critical Care, Gastroenterology and Nutrition, Texas Children's Hospital, Houston, TX 77030, USA. jorgec@bcm.tmc.edu
authors.forename: J A
authors.initials: JA
authors.lastname: Coss-Bu
authors.forename: W J
authors.initials: WJ
authors.lastname: Klish
authors.forename: D
authors.initials: D
authors.lastname: Walding
authors.forename: F
authors.initials: F
authors.lastname: Stein
authors.forename: E O
authors.initials: EO
authors.lastname: Smith
authors.forename: L S
authors.initials: LS
authors.lastname: Jefferson
mesh_terms: D000293:Adolescent; D001481:Basal Metabolism; D002153:Calorimetry, Indirect; D002648:Child; D002675:Child, Preschool; D016638:Critical Illness; D003430:Cross-Sectional Studies; D004040:Dietary Carbohydrates / Q000008:administration & dosage / Q000378:metabolism*; D004041:Dietary Fats / Q000008:administration & dosage / Q000378:metabolism*; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D004734:Energy Metabolism; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D009584:Nitrogen / Q000378:metabolism*; D009751:Nutritional Requirements; D010288:Parenteral Nutrition; D012121:Respiration, Artificial; D013379:Substrate Specificity
chemical_list: D004040:Dietary Carbohydrates; D004041:Dietary Fats; D004044:Dietary Proteins; D009584:Nitrogen