title: Indicators of lean body mass catabolism: emphasis on the creatinine excretion rate.
abstract: BACKGROUND
  The major stress response to critical illness leads to a catabolic state and loss of lean body mass.
  
  
  OBJECTIVE
  To test whether an increased rate of creatinine excretion might provide unique and timely information to monitor cell catabolism; to relate this information to balances of cell constituents (nitrogen, potassium, phosphate and magnesium); to evaluate the effectiveness of nutritional therapy to reverse this catabolic process.
  
  
  METHODS
  Prospective observational study.
  
  
  METHODS
  Children with severe traumatic brain injury admitted to the paediatric critical care units of The Hospital for Sick Children, Toronto, Canada and Hospital das Clínicas, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Brazil were studied. Complete 24 h urine collections were obtained for measurement of creatinine excretion rate and daily balances of nitrogen, potassium, phosphate and magnesium.
  
  
  RESULTS
  Seventeen patients were studied for 3-10 days. On Day 1, all had negative balances for protein and phosphate. Balances for these intracellular constituents became positive when protein intake was >/=1 g/kg/day and energy intake was >/=50% of estimated energy expenditure (P < 0.0001). Creatinine excretion rate was positively correlated with the urea appearance rate (r = 0.60; P < 0.0001), and negatively with protein balance (r = -0.45; P < 0.0001). Sepsis developed in four patients; before its clinical detection, there were negative balances for all intracellular markers and an abrupt rise in the excretion of creatinine.
  
  
  CONCLUSIONS
  Negative balances of intracellular components and an increase in rate of creatinine excretion heralded the onset of catabolism.
authors.affiliation: Department of Paediatrics, Hospital das Clínicas, Faculty of Medicine of Ribeirão, Preto, University of São Paulo, Av. dos Bandeirantes, 3900, 14049-900, Ribeirão Preto, SP, Brazil. carlotti@fmrp.usp.br
authors.forename: A P C P
authors.initials: AP
authors.lastname: Carlotti
authors.forename: D
authors.initials: D
authors.lastname: Bohn
authors.forename: A K
authors.initials: AK
authors.lastname: Matsuno
authors.forename: D M
authors.initials: DM
authors.lastname: Pasti
authors.forename: M
authors.initials: M
authors.lastname: Gowrishankar
authors.forename: M L
authors.initials: ML
authors.lastname: Halperin
mesh_terms: D000293:Adolescent; D015415:Biomarkers / Q000652:urine; D001823:Body Composition; D001930:Brain Injuries / Q000652:urine*; D001938:Brazil; D002170:Canada; D002648:Child; D002675:Child, Preschool; D003404:Creatinine / Q000652:urine*; D016638:Critical Illness; D006801:Humans; D008274:Magnesium / Q000652:urine; D008660:Metabolism / Q000502:physiology; D009584:Nitrogen / Q000652:urine; D010710:Phosphates / Q000652:urine; D011188:Potassium / Q000652:urine; D011446:Prospective Studies; D018709:Statistics, Nonparametric
chemical_list: D015415:Biomarkers; D010710:Phosphates; D003404:Creatinine; D008274:Magnesium; D009584:Nitrogen; D011188:Potassium