The effects of continuous glucose infusion on blood, plasma, and brain glucose in anesthetized rats

In models of cerebral ischemia, it is important to rigidly control brain glucose in the peri-ischemic period because alterations in brain glucose can affect the severity of the postischemic injury. The following study evaluated the effect of a continuous glucose infusion as a means of producing stable increases in brain glucose that could be monitored by measuring either blood or plasma glucose. Fifty-four halothane-anesthetized rats were studied. Rats received either no treatment (control group; N = 6), saline 2 ml/h (N = 24), or glucose 1 g/kg per h in saline 2 ml/h (N = 24). In the latter two groups, samples of blood, plasma, and brain glucose were obtained at either 30, 60, 120, or 180 min of the infusion (N = 6 per group per sample period). Saline infusion had no effect on either blood, plasma, or brain glucose. In contrast, glucose infusion produced a significant increase in all three variables, achieving plateau increases during the 60-180 min measurement periods [blood glucose = 197 +/- 20 mg/dl (mean +/- S.D.) at 60 min, 220 +/- 34 mg/dl at 120 min, and 217 +/- 22 mg/dl at 180 min versus control blood glucose = 89 +/- 10 mg/dl]. Regardless of the treatment group, there was excellent correlation between blood and plasma glucose (r = 0.99; P much less than 0.001), blood and brain glucose (r = 0.96; P much less than 0.001), and plasma and brain glucose (r = 0.97; P much less than 0.001). The authors conclude that continuous glucose infusions are an effective method to produce stable increases in brain glucose in experimental models; and, in contrast to other methods for achieving brain glucose increases, the brain glucose increases can be accurately assessed by measuring blood or plasma glucose.