title: Risk factors and prediction of postoperative delirium in elderly hip-surgery patients: implementation and validation of a medical risk factor model.
abstract: OBJECTIVE
  To evaluate risk factors for postoperative delirium in a cohort of elderly hip-surgery patients and to validate a medical risk stratification model.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Medical school-affiliated general hospital in Alkmaar, the Netherlands.
  
  
  METHODS
  Six hundred three hip-surgery patients aged 70 and older screened for risk factors for postoperative delirium.
  
  
  METHODS
  Predefined risk factors for delirium were assessed on admission. One point was assigned for each of four risk factors present, resulting in three groups: low, intermediate, and high risk. Baseline screening and assessment included the Mini-Mental State Examination, the standardized Snellen test for visual impairment, chart review to determine Acute Physiological and Chronic Health Evaluation II score, and blood urea nitrogen to creatinine ratio. The primary outcome was postoperative delirium, as defined using Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, and Confusion Assessment Method criteria. All patients were screened daily for delirium.
  
  
  RESULTS
  Incidence of delirium was 3.8% in the low-risk group (P<.001), 11.1% in the intermediate-risk group (P=.27, relative risk (RR)=3.0), and 37.1% in the high-risk group (P<.001, RR=9.8). Cognitive impairment at admission had the highest predictive value for postoperative delirium (coefficient of determination=0.15). Contrary to previous findings, age was an independent predictive factor for delirium. Moreover, postoperative delirium was four times as frequent in acute patients as in elective hip-replacement patients.
  
  
  CONCLUSIONS
  The medical risk factor model is valid for elderly hip-surgery patients. Cognitive impairment, age, and type of admission are important risk factors for delirium in this surgical population.
authors.affiliation: Department of Geriatric Medicine, Medical Center Alkmaar, 1800 AM Alkmaar, the Netherlands. k.kalisvaart@mca.nl
authors.forename: Kees J
authors.initials: KJ
authors.lastname: Kalisvaart
authors.forename: Ralph
authors.initials: R
authors.lastname: Vreeswijk
authors.forename: Jos F M
authors.initials: JF
authors.lastname: de Jonghe
authors.forename: Tjeerd
authors.initials: T
authors.lastname: van der Ploeg
authors.forename: Willem A
authors.initials: WA
authors.lastname: van Gool
authors.forename: Piet
authors.initials: P
authors.lastname: Eikelenboom
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D015331:Cohort Studies; D003693:Delirium / Q000453:epidemiology*; D003863:Depression / Q000150:complications; D005260:Female; D006304:Health Status; D006615:Hip / Q000601:surgery*; D006760:Hospitalization; D006769:Hospitals, General; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D011183:Postoperative Complications; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D012307:Risk Factors