title: Frequency of acute changes found on head computed tomographies in critically ill patients: a retrospective cohort study.
abstract: OBJECTIVE
  The frequency of positive findings on computed tomography (CT) of the head in critically ill patients who develop neurologic dysfunction is not known.
  
  
  METHODS
  Cohort study of head CTs for patients admitted to 3 intensive care units from 2005 to 2010. We documented the frequency of acute changes for all head CTs and for the subgroup of patients with altered mental status (AMS). We also examined associations between patient characteristics or medications administered before head CT and the odds of an acute change on head CT using multivariate logistic regression.
  
  
  RESULTS
  During 11 338 intensive care unit admissions, there were 901 eligible head CTs on 706 patients (6% of patients). Among head CTs, 155 (17.2%) assessed concern of new focal deficit, 99 (11.0%) concern for a seizure, and 635 (70.5%) for AMS. Acute changes were found on 109 (12.1%; 95% confidence interval [CI], 10.0%-14.2%) of all head CTs, and 30% (22.4%-36.9%) of patients with focal deficits, 16.2% (8.8%-23.5%) of patients with seizures but only 7.4% (5.4%-9.4%) for patients with AMS. A diagnosis of sepsis was associated with a decreased odds of an acute change on head CT for all head CTs (odds ratio 0.61; 95% CI, 0.40-0.95; P = .028) but was not significantly associated with a decreased risk among the cohort of head CTs for AMS (odds ratio 0.82; 95% CI, 0.41-1.62; P = .56). No other factors were associated with an altered risk of acute change on head CT for all patients in our cohort or for those with AMS.
  
  
  CONCLUSIONS
  Acute changes on head CTs performed for concern regarding new focal neurologic deficit or seizures are frequent compared with those performed for AMS with a nonfocal examination. No specific patient characteristics or medications were associated with a large change in the likelihood of finding an acute change for patients with AMS.
authors.affiliation: General Internal Medicine, Whipps Cross University Hospital, London, UK. Electronic address: shaila311@googlemail.com.
authors.forename: Shaila
authors.initials: S
authors.lastname: Khan
authors.affiliation: Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, NY. Electronic address: cg2397@columbia.edu.
authors.forename: Carmen
authors.initials: C
authors.lastname: Guerra
authors.affiliation: Department of Radiology, College of Physicians and Surgeons, Columbia University, New York, NY. Electronic address: agk3@columbia.edu.
authors.forename: Alexander
authors.initials: A
authors.lastname: Khandji
authors.affiliation: Department of Anesthesiology, University of Wisconsin School of Medicine and Public Health, Madison, WI, USA. Electronic address: rbauer2@wisc.edu.
authors.forename: Rebecca M
authors.initials: RM
authors.lastname: Bauer
authors.affiliation: Department of Critical Care Neurology, College of Physicians and Surgeons, Columbia University, New York, NY. Electronic address: jc1439@cumc.columbia.edu.
authors.forename: Jan
authors.initials: J
authors.lastname: Claassen
authors.affiliation: Department of Anesthesiology, College of Physicians and Surgeons, Columbia University, New York, NY; Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY. Electronic address: hw2125@cumc.columbia.edu.
authors.forename: Hannah
authors.initials: H
authors.lastname: Wunsch
mesh_terms: D000328:Adult; D000368:Aged; D001281:Atrial Fibrillation / Q000175:diagnosis; D001921:Brain / Q000000981:diagnostic imaging* / Q000187:drug effects; D016893:Carotid Stenosis / Q000175:diagnosis; D016001:Confidence Intervals; D003244:Consciousness Disorders / Q000000981:diagnostic imaging* / Q000209:etiology; D016638:Critical Illness; D005260:Female; D006801:Humans; D007362:Intensive Care Units; D007902:Length of Stay; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D012044:Regression Analysis; D012189:Retrospective Studies; D012640:Seizures / Q000000981:diagnostic imaging*; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data
keywords: CT scan, x-ray; Critical care; Decision making; Intensive care unit; Radiation