title: The impact of low preoperative fat-free body mass on infections and length of stay after cardiac surgery: a prospective cohort study.
abstract: OBJECTIVE
  Several studies have shown low fat-free mass index to be a stronger predictor for mortality than low body mass index. The main aim of this study was to assess the still unknown association between preoperative low fat-free mass index and adverse cardiac surgical outcomes.
  
  
  METHODS
  In a prospective observational study, fat-free mass index was determined by bioelectric impedance spectroscopy on hospital admission. Associations between low fat-free mass index and postoperative infections and mortality, as well as prolonged intensive care unit and hospital stays, were analyzed with logistic and Cox regression techniques.
  
  
  RESULTS
  Between February 2008 and December 2009, 325 adult patients admitted for elective heart surgery were included. Analyses showed that low fat-free mass index, present in 8.3% of patients, was independently associated with occurrence of infections after cardiac surgery (18.5% vs 4.7%; adjusted odds ratio, 6.9; 95% confidence interval, 1.8-27.7; P = .01). Low fat-free mass index also tended to be associated with higher risk of longer postoperative intensive care unit stay (adjusted hazard ratio, 0.7; 95% confidence interval, 0.4-1.1; P = .09). When classifying patients as undernourished by traditional methods (body mass index ≤21.0 kg/m(2) or ≥10% weight loss in preceding 6 months), half of patients with low fat-free mass index were misclassified as well nourished.
  
  
  CONCLUSIONS
  Low fat-free mass index is associated with increased occurrence of adverse outcomes after cardiac surgery. We advocate fat-free mass index as the leading parameter in classifying and treating undernourished cardiac surgical patients, which might improve recovery rates after cardiac surgery.
authors.affiliation: Department of Dietetics, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands. l.m.vanvenrooij@amc.uva.nl
authors.forename: Lenny M W
authors.initials: LM
authors.lastname: van Venrooij
authors.forename: Rien
authors.initials: R
authors.lastname: de Vos
authors.forename: Evelien
authors.initials: E
authors.lastname: Zijlstra
authors.forename: Mieke M M J
authors.initials: MM
authors.lastname: Borgmeijer-Hoelen
authors.forename: Paul A M
authors.initials: PA
authors.lastname: van Leeuwen
authors.forename: Bas A J M
authors.initials: BA
authors.lastname: de Mol
mesh_terms: D050154:Adiposity; D000368:Aged; D015992:Body Mass Index; D006348:Cardiac Surgical Procedures / Q000009:adverse effects* / Q000401:mortality; D003141:Communicable Diseases / Q000209:etiology* / Q000401:mortality; D017558:Elective Surgical Procedures; D017097:Electric Impedance; D005260:Female; D006331:Heart Diseases / Q000150:complications / Q000401:mortality / Q000601:surgery*; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay; D016015:Logistic Models; D008297:Male; D044342:Malnutrition / Q000150:complications* / Q000401:mortality / Q000503:physiopathology; D008875:Middle Aged; D009426:Netherlands; D016017:Odds Ratio; D010343:Patient Admission; D016016:Proportional Hazards Models; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013997:Time Factors; D016896:Treatment Outcome