title: The attributable mortality of acute kidney injury: a sequentially matched analysis*.
abstract: OBJECTIVE
  Acute kidney injury in the critically ill is an independent risk factor for adverse outcome. The magnitude of the impact of acute kidney injury on outcome, however, is still unclear. This study aimed to estimate the excess mortality attributable to acute kidney injury.
  
  
  METHODS
  We performed a sequentially matched analysis according to the day of acute kidney injury diagnosis after ICU admission. Patients with acute kidney injury and those without acute kidney injury were matched according to age, sex, ICU admission diagnosis, Simplified Acute Physiology Score II without renal and age components, and the propensity to develop acute kidney injury at each of the four matching time points.
  
  
  METHODS
  Cohort of 16 participating ICUs from the prospective Finnish Acute Kidney Injury study.
  
  
  METHODS
  Cohort of 2,719 consecutive patients with either emergency admission or elective postsurgical patients with an expected ICU stay greater than 24 hours.
  
  
  METHODS
  None.
  
  
  RESULTS
  Of the 2,719 patients included in the study, acute kidney injury developed in 1,081 patients (39.8%) according to the Kidney Disease: Improving Global Outcomes-definition during ICU treatment on days 1-5. Of these, 477 patients were successfully matched to 477 patients who did not develop acute kidney injury. The 90-day mortality of the matched patients with acute kidney injury was 125 of 477 (26.2%) compared with 84 of 477 (17.6%) for their matched controls without acute kidney injury. Thus, the absolute excess 90-day mortality attributable to acute kidney injury was estimated at 8.6 percentage points (95% CI, 2.6-17.6 percentage points). The population attributable risk (95% CI) of 90-day mortality associated with acute kidney injury was 19.6% (10.3-34.1%).
  
  
  CONCLUSIONS
  In general ICU patients, the absolute excess 90-day mortality statistically attributable to acute kidney injury is substantial (8.6%), and the population attributable risk was nearly 20%. Our findings are useful in planning suitably powered future clinical trials to prevent and treat acute kidney injury in critically ill patients.
authors.affiliation: 1Intensive Care Units, Division of Anaesthesia and Intensive Care Medicine, Department of Surgery, Helsinki University Central Hospital, Helsinki, Finland. 2Department of Clinical Sciences, University of Helsinki, Helsinki, Finland. 3ANZIC Research Centre, Department of Epidemiology and Preventive Medicine, School of Public Health and Preventive Medicine, Monash University, Melbourne, VIC, Australia. 4Division of Intensive Care, Kuopio University Hospital, Kuopio, Finland. 5Department of Intensive Care, North Karelia Central Hospital, Joensuu, Finland.
authors.forename: Suvi T
authors.initials: ST
authors.lastname: Vaara
authors.forename: Ville
authors.initials: V
authors.lastname: Pettilä
authors.forename: Kirsi-Maija
authors.initials: KM
authors.lastname: Kaukonen
authors.forename: Stepani
authors.initials: S
authors.lastname: Bendel
authors.forename: Anna-Maija
authors.initials: AM
authors.lastname: Korhonen
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
authors.forename: Matti
authors.initials: M
authors.lastname: Reinikainen
mesh_terms: D058186:Acute Kidney Injury / Q000401:mortality*; D000368:Aged; D016638:Critical Illness / Q000401:mortality*; D005260:Female; D005387:Finland / Q000453:epidemiology; D006801:Humans; D007362:Intensive Care Units / Q000706:statistics & numerical data*; D008297:Male; D008875:Middle Aged; D057216:Propensity Score; D011446:Prospective Studies; D012307:Risk Factors