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 << 0.001), blood and brain glucose (r = 0.96; P << 0.001), and plasma and brain glucose (r = 0.97; P << 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.