Circadian rhythm of blood glucose values in critically ill patients.
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.
Egi
Moritoki
M
Department of Intensive Care, Austin Hospital, Heidelberg, Victoria, Australia.
Bellomo
Rinaldo
R
Stachowski
Edward
E
French
Craig J
CJ
Hart
Graeme
G
Stow
Peter
P
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
D001786:Blood Glucose