title: Volume of activity and occupancy rate in intensive care units. Association with mortality.
abstract: OBJECTIVE
  Mortality after many procedures is lower in centers where more procedures are done. It is controversial whether this is true for intensive care units, too. We examined the relationship between the volume of activity of intensive care units (ICUs) and mortality by a measure of risk-adjusted volume of activity specific for ICUs.
  
  
  METHODS
  Prospective, multicenter, observational study.
  
  
  METHODS
  Eighty-nine ICUs in 12 European countries.
  
  
  METHODS
  During a 4-month study period, 12,615 patients were enrolled.
  
  
  METHODS
  Demographic and clinical statistics, severity at admission and a score of nursing complexity and workload were collected.
  
  
  RESULTS
  Total volume of activity was defined as the number of patients admitted per bed per year, high-risk volume as the number of high-risk patients admitted per bed per year (selected combining of length of stay and severity of illness). A multi-step risk-adjustment process was planned. ICU volume corresponding both to overall [odds ratio (OR) 0.966] and 3,838 high-risk (OR 0.830) patients was negatively correlated with mortality. Relative mortality decreased by 3.4 and 17.0% for every five extra patients treated per bed per year in overall volume and high-risk volume, respectively. A direct relationship was found between mortality and the ICU occupancy rate (OR 1.324 and 1.351, respectively).
  
  
  CONCLUSIONS
  Intensive care patients, whatever their level of risk, are best treated where more high-risk patients are treated. Moreover, the higher the ICU occupancy rate, the higher is the mortality.
authors.affiliation: Istituto di Anestesiologia e Rianimazione, Università di Milano, Azienda Ospedaliera-Polo Universitario San Paolo, Via A Di Rudinì 8, 20142 , Milan, Italy. g.iapichino@unimi.it.
authors.forename: Gaetano
authors.initials: G
authors.lastname: Lapichino
authors.affiliation: IRCCS Ospedale Maggiore, Milan, Italy.
authors.forename: Luciano
authors.initials: L
authors.lastname: Gattinoni
authors.affiliation: Servizio Anestesia e Rianimazione, Ospedale Civile, Legnano, Italy.
authors.forename: Danilo
authors.initials: D
authors.lastname: Radrizzani
authors.affiliation: GiViTi Coordination Centre, Istituto di Ricerche Farmacologiche "Mario Negri, Ranica, Bergamo, Italy.
authors.forename: Bruno
authors.initials: B
authors.lastname: Simini
authors.affiliation: GiViTi Coordination Centre, Istituto di Ricerche Farmacologiche "Mario Negri, Ranica, Bergamo, Italy.
authors.forename: Guido
authors.initials: G
authors.lastname: Bertolini
authors.affiliation: Istituto di Anestesiologia e Rianimazione, Università di Milano, Azienda Ospedaliera-Polo Universitario San Paolo, Via A Di Rudinì 8, 20142 , Milan, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Ferla
authors.affiliation: Istituto di Anestesiologia e Rianimazione, Università di Milano, Azienda Ospedaliera-Polo Universitario San Paolo, Via A Di Rudinì 8, 20142 , Milan, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Mistraletti
authors.affiliation: Istituto di Anestesiologia e Rianimazione, Università di Milano, Azienda Ospedaliera-Polo Universitario San Paolo, Via A Di Rudinì 8, 20142 , Milan, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Porta
authors.affiliation: Foundation for Research on Intensive Care in Europe, University Hospital, Groningen, The Netherlands.
authors.forename: Dinis R
authors.initials: DR
authors.lastname: Miranda
mesh_terms: D016638:Critical Illness; D005060:Europe; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units / Q000592:standards / Q000706:statistics & numerical data*; D016015:Logistic Models; D011446:Prospective Studies; D011785:Quality Assurance, Health Care; D016526:Workload