Volume 13 Supplement 3
Serum glucose variability and brain-serum glucose ratio predict metabolic distress and mortality after severe brain injury
© BioMed Central Ltd 2009
Published: 23 June 2009
Cerebral glucose metabolism and energy production are affected by serum glucose levels. The objective of the present study was to assess whether serum glucose variability and the ratio between cerebral and serum glucose are associated with cerebral metabolic distress and outcome after severe brain injury.
We studied 46 consecutive patients that underwent multimodality monitoring with intracranial pressure, PbtO2 and microdialysis in a neurological ICU of a university hospital. The relationship between brain-serum glucose ratio and cerebral metabolic distress, as measured by microdialysis lactate/pyruvate ratio (LPR) ≥ 40, was analyzed for every hour of measurement. The relationship between daily serum glucose variability, as measured by the standard deviation (SD) and the mean amplitude glycemic excursions (MAGE), and metabolic distress was analyzed for every day of monitoring. Mortality was analyzed at hospital discharge. All analyses used general linear models of logistic function for dichotomized outcomes utilizing generalized estimating equations accounting for within-subject and between-subject effects.
The mean age was 55 years (IQR 42 to 64), 27 (59%) patients were female and the median admission Glasgow Coma Scale (GCS) was 7 (IQR 5 to 9). Diagnoses included sub-arachnoid hemorrhage (61%), intracerebral hemorrhage (22%), traumatic brain injury (13%) and cardiac arrest (4%), and 28% were dead at discharge. A total of 5,264 neuromonitoring hours and 300 days were analyzed. In a multivariable model, brain/serum glucose ratios below the median (12%) were independently associated with increased risk of metabolic distress (adjusted OR = 6.1 (4.5 to 8.2), P < 0.0001). In a similar multivariable model analyzing daily averaged data, increased serum glucose variability was also independently associated with higher risk of cerebral metabolic distress (adj OR = 1.8 (1.3 to 2.5), P < 0.0001 for SD; and adj OR = 1.2 (1.02 to 1.4), P = 0.03 for MAGE). Both analyses were adjusted for significant covariates such as GCS, cerebral perfusion pressure and serum glucose levels. An averaged brain/serum glucose ratio lower than the median and an increased serum glucose variability were independently associated with mortality at hospital discharge after adjusting for age and APACHE II score (adj OR = 6.9 (1.6 to 36.7), P = 0.01; and adj OR = 7.2 (1.3 to 41.7), P = 0.03, respectively).
The ratio between brain and serum glucose levels as well as serum glucose variability are associated with cerebral metabolic distress and increased mortality at hospital discharge in patients with severe brain injury.