title: The association between ICU level of care and mortality in the Netherlands.
abstract: OBJECTIVE
  The relationship between the number of patients admitted to an intensive care unit (ICU) volume and mortality is currently the subject of debate. After implementation of a national guideline in 2006, all Dutch ICUs have been classified into three levels based on ICU size, patient volume, ventilation days, and staffing. The goal of this study is to investigate the association between ICU level and mortality of ICU patients in the Netherlands.
  
  
  METHODS
  We analyzed data from 132,159 patients admitted to 87 ICUs between January 1, 2009 and October 1, 2011. Logistic GEE analyses were performed to assess the influence of ICU level on in-hospital mortality and 90-day mortality in the total ICU population and in different ICU subgroups while adjusting for severity of illness by APACHE IV.
  
  
  RESULTS
  No significant differences were found in the adjusted in-hospital mortality of the total ICU population and in different subgroups admitted to level 1, 2 and 3 ICUs. In-hospital mortality in level 2 and 3 ICUs as opposed to level 1 ICUs was 1.06 (0.93-1.22) and 1.10 (0.94-1.29), respectively, and 90-day mortality was 0.92 (0.80-1.06) and 1.01 (0.88-1.17).
  
  
  CONCLUSIONS
  We demonstrated that ICU level was not associated with significant differences in the case-mix adjusted in-hospital and long-term mortality of ICU patients. This finding is in contrast with some earlier studies suggesting a volume-outcome relationship. Our results may be explained by the successful implementation of nationwide mandatory quality requirements and adequate staffing in all three levels of ICUs over the last years.
authors.affiliation: Department of Intensive Care, Slotervaart Hospital, Amsterdam, The Netherlands, Georg.Kluge@gmail.com.
authors.forename: Georg Heinrich
authors.initials: GH
authors.lastname: Kluge
authors.forename: Sylvia
authors.initials: S
authors.lastname: Brinkman
authors.forename: Giel
authors.initials: G
authors.lastname: van Berkel
authors.forename: Johannes
authors.initials: J
authors.lastname: van der Hoeven
authors.forename: Crétien
authors.initials: C
authors.lastname: Jacobs
authors.forename: Yvonne E M
authors.initials: YE
authors.lastname: Snel
authors.forename: John P W
authors.initials: JP
authors.lastname: Vogelaar
authors.forename: Nicolette F
authors.initials: NF
authors.lastname: de Keizer
authors.forename: Emiel S
authors.initials: ES
authors.lastname: Boon
mesh_terms: D018806:APACHE; D000368:Aged; D015331:Cohort Studies; D003422:Critical Care / Q000379:methods*; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D007902:Length of Stay / Q000706:statistics & numerical data*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009426:Netherlands