title: Association Between Nighttime Discharge from the Intensive Care Unit and Hospital Mortality: A Multi-Center Retrospective Cohort Study.
abstract: BACKGROUND
  We aimed to determine the impact of nighttime discharge from the intensive care unit (ICU) to the ward on hospital mortality and readmission rates in consecutive critically ill patients admitted to five Canadian ICUs. We hypothesized that hospital mortality and readmission rates would be higher for patients discharged after hours compared with discharge during the day.
  
  
  METHODS
  A multi-center retrospective cohort study was carried out at five hospitals in Edmonton, Canada, between July 2002 and December 2009. Nighttime discharge was defined as discharge from the ICU occurring between 07:00 pm and 07:59 am. Logistic regression analysis was used to explore the associations between nighttime discharge and outcomes.
  
  
  RESULTS
  Of 19,622 patients discharged alive from the ICU, 3,505 (17.9%) discharges occurred during nighttime. Nighttime discharge occurred more commonly among medical than surgical patients (19.9% vs. 13.8%, P < 0.001) and among those with more comorbid conditions, compared with daytime discharged patients. Crude hospital mortality (11.8% versus 8.8%, P < 0.001) was greater for nighttime discharged as compared to daytime discharged patients. In a multivariable analysis, after adjustment for comorbidities, diagnosis and source of admission, nighttime discharge remains associated with higher mortality (odds ratio [OR] 1.29; 95% CI, 1.14 to 1.46, P < 0.001). This finding was robust in two sensitivity analyses examining discharges occurring between 00:00 am and 04:59 am (OR 1.28; 1.12-1.47; P < 0.001) and for those who died within 48 h of ICU discharge without readmission (OR 1.24; 1.07-1.42, P = 0.002). There was no difference in ICU readmission for nighttime compared with daytime discharges (7.4% vs. 6.9 %, p = 0.26). However, rates were higher for nighttime discharges in community compared with tertiary hospitals (7.7% vs. 5.7%, P = 0.023).
  
  
  CONCLUSIONS
  In a large integrated health region, 1 in 5 ICU patients are discharged at nighttime, a factor with increasing occurrence during our study and shown to be independently associated with higher hospital mortality.
authors.affiliation: Division of Critical Care Medicine, Faculty of Medicine and Dentistry, University of Alberta, 2-124E Clinical Sciences Building, 8440-122 Street, Edmonton, AB, T6G 2B7, Canada. lucianoazevedo@uol.com.br.|Department of Critical Care Medicine, Alberta Health Services, Edmonton Zone, 2-124E Clinical Sciences Building, 8440-122 Street, Edmonton, AB, T6G 2B7, Canada. lucianoazevedo@uol.com.br.|Research and Education Institute, Hospital Sírio-Libanês, São Paulo, Brazil. lucianoazevedo@uol.com.br.|Emergency Medicine Department ICU, University of São Paulo, São Paulo, Brazil. lucianoazevedo@uol.com.br.
authors.forename: Luciano C P
authors.initials: LC
authors.lastname: Azevedo
authors.affiliation: Division of Critical Care Medicine, Faculty of Medicine and Dentistry, University of Alberta, 2-124E Clinical Sciences Building, 8440-122 Street, Edmonton, AB, T6G 2B7, Canada. ivens_s@hotmail.com.|Department of Critical Care Medicine, Alberta Health Services, Edmonton Zone, 2-124E Clinical Sciences Building, 8440-122 Street, Edmonton, AB, T6G 2B7, Canada. ivens_s@hotmail.com.|Research and Education Institute, Hospital Sírio-Libanês, São Paulo, Brazil. ivens_s@hotmail.com.
authors.forename: Ivens A
authors.initials: IA
authors.lastname: de Souza
authors.affiliation: Division of Critical Care Medicine, Faculty of Medicine and Dentistry, University of Alberta, 2-124E Clinical Sciences Building, 8440-122 Street, Edmonton, AB, T6G 2B7, Canada. zygun@ualberta.ca.|Department of Critical Care Medicine, Alberta Health Services, Edmonton Zone, 2-124E Clinical Sciences Building, 8440-122 Street, Edmonton, AB, T6G 2B7, Canada. zygun@ualberta.ca.
authors.forename: David A
authors.initials: DA
authors.lastname: Zygun
authors.affiliation: Departments of Critical Care Medicine, Medicine and Community Health Sciences, Institute for Public Health, University of Calgary, Calgary, Canada. tstelfox@ucalgary.ca.
authors.forename: Henry T
authors.initials: HT
authors.lastname: Stelfox
authors.affiliation: Division of Critical Care Medicine, Faculty of Medicine and Dentistry, University of Alberta, 2-124E Clinical Sciences Building, 8440-122 Street, Edmonton, AB, T6G 2B7, Canada. bagshaw@ualberta.ca.|Department of Critical Care Medicine, Alberta Health Services, Edmonton Zone, 2-124E Clinical Sciences Building, 8440-122 Street, Edmonton, AB, T6G 2B7, Canada. bagshaw@ualberta.ca.
authors.forename: Sean M
authors.initials: SM
authors.lastname: Bagshaw
mesh_terms: D000328:Adult; D039602:After-Hours Care; D000368:Aged; D002170:Canada; D015331:Cohort Studies; D015897:Comorbidity; D003422:Critical Care; D016638:Critical Illness; D005260:Female; D017052:Hospital Mortality; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D010360:Patient Transfer; D012189:Retrospective Studies