title: Empirical relationships among oliguria, creatinine, mortality, and renal replacement therapy in the critically ill.
abstract: OBJECTIVE
  The observation periods and thresholds of serum creatinine and urine output defined in the Acute Kidney Injury Network (AKIN) criteria were not empirically derived. By continuously varying creatinine/urine output thresholds as well as the observation period, we sought to investigate the empirical relationships among creatinine, oliguria, in-hospital mortality, and receipt of renal replacement therapy (RRT).
  
  
  METHODS
  Using a high-resolution database (Multiparameter Intelligent Monitoring in Intensive Care II), we extracted data from 17,227 critically ill patients with an in-hospital mortality rate of 10.9 %. The 14,526 patients had urine output measurements. Various combinations of creatinine/urine output thresholds and observation periods were investigated by building multivariate logistic regression models for in-hospital mortality and RRT predictions. For creatinine, both absolute and percentage increases were analyzed. To visualize the dependence of adjusted mortality and RRT rate on creatinine, the urine output, and the observation period, we generated contour plots.
  
  
  RESULTS
  Mortality risk was high when absolute creatinine increase was high regardless of the observation period, when percentage creatinine increase was high and the observation period was long, and when oliguria was sustained for a long period of time. Similar contour patterns emerged for RRT. The variability in predictive accuracy was small across different combinations of thresholds and observation periods.
  
  
  CONCLUSIONS
  The contour plots presented in this article complement the AKIN definition. A multi-center study should confirm the universal validity of the results presented in this article.
authors.affiliation: Department of Anesthesia, Critical Care and Pain Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, 1 Deaconess Rd. CC-470, Boston, MA 02215, USA.
authors.forename: Tal
authors.initials: T
authors.lastname: Mandelbaum
authors.forename: Joon
authors.initials: J
authors.lastname: Lee
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Scott
authors.forename: Roger G
authors.initials: RG
authors.lastname: Mark
authors.forename: Atul
authors.initials: A
authors.lastname: Malhotra
authors.forename: Michael D
authors.initials: MD
authors.lastname: Howell
authors.forename: Daniel
authors.initials: D
authors.lastname: Talmor
mesh_terms: D058186:Acute Kidney Injury / Q000097:blood* / Q000150:complications / Q000401:mortality* / Q000628:therapy; D003404:Creatinine / Q000097:blood*; D016638:Critical Illness; D036262:Empirical Research; D017052:Hospital Mortality; D006801:Humans; D009846:Oliguria / Q000097:blood* / Q000209:etiology / Q000401:mortality*; D017582:Renal Replacement Therapy; D012189:Retrospective Studies
chemical_list: D003404:Creatinine