title: Circadian rhythm of blood glucose values in critically ill patients.
abstract: OBJECTIVE
  To test whether there is a circadian rhythm of blood glucose control in critically ill patients and whether morning blood glucose is an accurate surrogate of overall blood glucose control.
  
  
  METHODS
  Retrospective multiple-center observational study.
  
  
  METHODS
  Intensive care units of three tertiary hospitals and one affiliated private hospital.
  
  
  METHODS
  Cohort of 8,307 consecutive critically ill patients.
  
  
  METHODS
  Extraction of blood glucose values from electronically stored measurements. Extraction of demographic and outcome data from unit and hospital databases. Statistical assessment of variations in blood glucose control over each 24-hr cycle.
  
  
  RESULTS
  We studied 208,362 blood glucose measurements in 8,307 patients (5.5 measurements/day/person). In each hospital, there was a circadian rhythm of blood glucose control (p<.0001). The differences between highest and lowest blood glucose concentration in different time periods in each hospital were 0.27, 0.28, 0.95, and 0.22 mmol/L. There was also significant variation in the incidence and notional duration of hyperglycemia. The differences between the lowest and highest incidence of hyperglycemia in different time periods were 3.3, 2.7, 9.9, and 2.6% in each hospital. In all four hospitals, the average blood glucose value from 5:30 am to 6:30 am was significantly lower than the 24-hr average.
  
  
  CONCLUSIONS
  Blood glucose values and the incidence of hyperglycemia have a circadian rhythm in critically ill patients. Morning blood glucose may not be an accurate surrogate of blood glucose control over the daily cycle.
authors.affiliation: Department of Intensive Care, Austin Hospital, Heidelberg, Victoria, Australia.
authors.forename: Moritoki
authors.initials: M
authors.lastname: Egi
authors.forename: Rinaldo
authors.initials: R
authors.lastname: Bellomo
authors.forename: Edward
authors.initials: E
authors.lastname: Stachowski
authors.forename: Craig J
authors.initials: CJ
authors.lastname: French
authors.forename: Graeme
authors.initials: G
authors.lastname: Hart
authors.forename: Peter
authors.initials: P
authors.lastname: Stow
mesh_terms: D000368:Aged; D001786:Blood Glucose / Q000032:analysis*; D002940:Circadian Rhythm; D016638:Critical Illness; D005260:Female; D006801:Humans; D006943:Hyperglycemia / Q000097:blood / Q000453:epidemiology; D007003:Hypoglycemia / Q000097:blood / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
chemical_list: D001786:Blood Glucose