title: Elevation of blood urea nitrogen is predictive of long-term mortality in critically ill patients independent of "normal" creatinine.
abstract: OBJECTIVE
  We hypothesized that elevated blood urea nitrogen can be associated with all-cause mortality independent of creatinine in a heterogeneous critically ill population.
  
  
  METHODS
  Multicenter observational study of patients treated in medical and surgical intensive care units.
  
  
  METHODS
  Twenty intensive care units in two teaching hospitals in Boston, MA.
  
  
  METHODS
  A total of 26,288 patients, age ≥ 18 yrs, hospitalized between 1997 and 2007 with creatinine of 0.80-1.30 mg/dL.
  
  
  METHODS
  None.
  
  
  METHODS
  Blood urea nitrogen at intensive care unit admission was categorized as 10-20, 20-40, and >40 mg/dL. Logistic regression examined death at days 30, 90, and 365 after intensive care unit admission as well as in-hospital mortality. Adjusted odds ratios were estimated by multivariable logistic regression models.
  
  
  RESULTS
  Blood urea nitrogen at intensive care unit admission was predictive for short- and long-term mortality independent of creatinine. Thirty days following intensive care unit admission, patients with blood urea nitrogen of >40 mg/dL had an odds ratio for mortality of 5.12 (95% confidence interval, 4.30-6.09; p < .0001) relative to patients with blood urea nitrogen of 10-20 mg/dL. Blood urea nitrogen remained a significant predictor of mortality at 30 days after intensive care unit admission following multivariable adjustment for confounders; patients with blood urea nitrogen of >40 mg/dL had an odds ratio for mortality of 2.78 (95% confidence interval, 2.27-3.39; p < .0001) relative to patients with blood urea nitrogen of 10-20 mg/dL. Thirty days following intensive care unit admission, patients with blood urea nitrogen of 20-40 mg/dL had an odds ratio of 2.15 (95% confidence interval, 1.98-2.33; <.0001) and a multivariable odds ratio of 1.53 (95% confidence interval, 1.40-1.68; p < .0001) relative to patients with blood urea nitrogen of 10-20 mg/dL. Results were similar at 90 and 365 days following intensive care unit admission as well as for in-hospital mortality. A subanalysis of patients with blood cultures (n = 7,482) demonstrated that blood urea nitrogen at intensive care unit admission was associated with the risk of blood culture positivity.
  
  
  CONCLUSIONS
  Among critically ill patients with creatinine of 0.8-1.3 mg/dL, an elevated blood urea nitrogen was associated with increased mortality, independent of serum creatinine.
authors.affiliation: Department of Genetics, Harvard Medical School, Massachusetts General Hospital, Boston, MA, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Beier
authors.forename: Sabitha
authors.initials: S
authors.lastname: Eppanapally
authors.forename: Heidi S
authors.initials: HS
authors.lastname: Bazick
authors.forename: Domingo
authors.initials: D
authors.lastname: Chang
authors.forename: Karthik
authors.initials: K
authors.lastname: Mahadevappa
authors.forename: Fiona K
authors.initials: FK
authors.lastname: Gibbons
authors.forename: Kenneth B
authors.initials: KB
authors.lastname: Christopher
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D015415:Biomarkers / Q000097:blood; D001806:Blood Urea Nitrogen; D015331:Cohort Studies; D016001:Confidence Intervals; D003404:Creatinine / Q000097:blood*; D003422:Critical Care / Q000379:methods; D016638:Critical Illness / Q000401:mortality*; D017052:Hospital Mortality / Q000639:trends*; D006784:Hospitals, Teaching; D006801:Humans; D007362:Intensive Care Units; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011237:Predictive Value of Tests; D012189:Retrospective Studies; D016019:Survival Analysis; D013997:Time Factors
chemical_list: D015415:Biomarkers; D003404:Creatinine