title: Risk of postoperative acute kidney injury in patients undergoing orthopaedic surgery--development and validation of a risk score and effect of acute kidney injury on survival: observational cohort study.
abstract: OBJECTIVE
  What is the predicted risk of acute kidney injury after orthopaedic surgery and does it affect short term and long term survival?
  
  
  METHODS
  The cohort comprised adults resident in the National Health Service Tayside region of Scotland who underwent orthopaedic surgery from 1 January 2005 to 31 December 2011. The model was developed in 6220 patients (two hospitals) and externally validated in 4395 patients from a third hospital. Several preoperative variables were selected for candidate predictors, based on literature, clinical expertise, and availability in the orthopaedic surgery setting. The main outcomes were the development of any severity of acute kidney injury (stages 1-3) within the first postoperative week, and 90 day, one year, and longer term survival.
  
  
  CONCLUSIONS
  Using logistic regression analysis, independent predictors of acute kidney injury were older age, male sex, diabetes, number of prescribed drugs, lower estimated glomerular filtration rate, use of angiotensin converting enzyme inhibitors or angiotensin receptor blockers, and American Society of Anesthesiologists grade. The model's predictive performance for discrimination was good (C statistic 0.74 in development cohort, 0.70 in validation cohort). Calibration was good in the development cohort and after recalibration in the validation cohort. Only the highest risks were over-predicted. Survival was worse in patients with acute kidney injury compared with those without (adjusted hazard ratio 1.53, 95% confidence interval 1.38 to 1.70). This was most noticeable in the short term (adjusted hazard ratio: 90 day 2.36, 1.94 to 2.87) and diminished over time (90 day-one year 1.40, 1.10 to 1.79; >1 year 1.28, 1.10 to 1.48). The model used routinely collected data in the orthopaedic surgery setting therefore some variables that could potentially improve predictive performance were not available. However, the readily available predictors make the model easily applicable.
  
  
  CONCLUSIONS
  A preoperative risk prediction model consisting of seven predictors for acute kidney injury was developed, with good predictive performance in patients undergoing orthopaedic surgery. Survival was significantly poorer in patients even with mild (stage 1) postoperative acute kidney injury.
  
  
  BACKGROUND
  SB received grants from Tenovus Tayside, Chief Scientist Office, and the Royal College of Physicians and Surgeons of Glasgow; PT receives grants from Novo Nordisk, GlaxoSmithKline, and the New Drugs Committee of the Scottish Medicines Consortium. No additional data are available.
authors.affiliation: Renal Unit, Ninewells Hospital, NHS Tayside, Dundee DD1 9SY, UK samira.bell@nhs.net.
authors.forename: Samira
authors.initials: S
authors.lastname: Bell
authors.affiliation: Department of Clinical Epidemiology, Leiden University Medical Centre, Leiden, Netherlands.
authors.forename: Friedo W
authors.initials: FW
authors.lastname: Dekker
authors.affiliation: Division of Population Health Sciences , School of Medicine, University of Dundee, Dundee, UK.
authors.forename: Thenmalar
authors.initials: T
authors.lastname: Vadiveloo
authors.affiliation: Division of Population Health Sciences , School of Medicine, University of Dundee, Dundee, UK.
authors.forename: Charis
authors.initials: C
authors.lastname: Marwick
authors.affiliation: Division of Population Health Sciences , School of Medicine, University of Dundee, Dundee, UK.
authors.forename: Harshal
authors.initials: H
authors.lastname: Deshmukh
authors.affiliation: Division of Population Health Sciences , School of Medicine, University of Dundee, Dundee, UK.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Donnan
authors.affiliation: Department of Clinical Epidemiology, Leiden University Medical Centre, Leiden, Netherlands.
authors.forename: Merel
authors.initials: M
authors.lastname: Van Diepen
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood / Q000209:etiology* / Q000401:mortality*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000009:adverse effects*; D015415:Biomarkers / Q000097:blood; D015331:Cohort Studies; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005919:Glomerular Filtration Rate; D006801:Humans; D019637:Orthopedic Procedures / Q000009:adverse effects* / Q000401:mortality*; D011183:Postoperative Complications / Q000209:etiology / Q000401:mortality; D011237:Predictive Value of Tests; D018570:Risk Assessment; D012307:Risk Factors; D012606:Scotland / Q000453:epidemiology
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine