title: Calorie delivery and clinical outcomes in the critically ill: a systematic review and meta-analysis.
abstract: OBJECTIVE
  To determine the effect of calorie delivery on hospital mortality among critically ill adults receiving enteral nutrition (EN). Secondary outcomes included the effect of calorie delivery on intensive care unit and hospital length of stay (LOS), duration of mechanical ventilation (MV) and incidence of new-onset pneumonia.
  
  
  METHODS
  We identified randomised clinical trials of EN, with or without supplemental parenteral nutrition (PN), involving adult ICU patients for whom mortality data were available, and when there was a significant difference in calorie supplementation between intervention arms (P < 0.05). We searched English language electronic databases (1946-2014), bibliographies of nutrition society guidelines and high-impact nutrition and critical care journals. We calculated summary odds ratio (OR) estimates and 95% confidence intervals using a random effects estimator, and used meta-regression to assess the effect on mortality of average calories delivered.
  
  
  RESULTS
  Of 1545 articles identified, 16 eligible studies involving 3473 patients were included. Five studies involved supplemental PN. Mean calorie delivery ranged from 126 kcal/day (SD, 115 kcal/day) to 2086 kcal/day (SD, 460 kcal/day). Mortality was 26.0% in the lower calorie delivery group and 26.5% in the higher calorie delivery group. There was no effect of increased calorie delivery on mortality (OR, 1.02; 95% CI , 0.85-1.24; P = 0.27; I2 = 16.3%). ICU and hospital LOS and incidence of newonset pneumonia did not differ between groups. Duration of MV was decreased with lower calorie delivery (weighted mean difference, 2.92 days; 95% CI, -4.49 to -1.35 days; P < 0.001; I2 = 14.7%). Meta-regression analysis did not show an overall effect on mortality of average calories delivered (P = 0.73; I2 = 40.8%).
  
  
  CONCLUSIONS
  Delivery of increased calories via the enteral route, with or without supplemental PN, was not associated with a survival benefit.
authors.affiliation: Department of Critical Care Medicine, Royal Hobart Hospital, Hobart, TAS, Australia. dr.harshel82@gmail.com.
authors.forename: Harshel G
authors.initials: HG
authors.lastname: Parikh
authors.affiliation: Critical Care Services, Royal Adelaide Hospital, Adelaide, SA, Australia.
authors.forename: Asaf
authors.initials: A
authors.lastname: Miller
authors.affiliation: Critical Care Services, Royal Adelaide Hospital, Adelaide, SA, Australia.
authors.forename: Marianne
authors.initials: M
authors.lastname: Chapman
authors.affiliation: Discipline of Acute Care Medicine, University of Adelaide, Adelaide, SA, Australia.
authors.forename: John L
authors.initials: JL
authors.lastname: Moran
authors.affiliation: Discipline of Acute Care Medicine, University of Adelaide, Adelaide, SA, Australia.
authors.forename: Sandra L
authors.initials: SL
authors.lastname: Peake
mesh_terms: D003422:Critical Care; D002149:Energy Intake; D006801:Humans; D018529:Nutritional Support; D017063:Outcome Assessment, Health Care