Cerebral energy state and glycolytic metabolism during enflurane anesthesia in the rat

The effects of enflurane anesthesia on the cerebral cortical energy state and glycolytic metabolism were studied in rats. Twenty-four rats were divided into four groups with increasing concentrations of enflurane in the arterial blood, i.e. control (1.9 +/- 0.3 mg/dl, means +/- s.e.mean), level I (16.1 +/- 1.1 mg/dl), level II (26.0 +/- 1.6 mg/dl), and level III (32.9 +/- 0.9 mg/dl). At level I, high voltage 1-3 Hz slow waves superimposed on low voltage 10-12 Hz waves were predominant, and at levels II and III, spiking activity and burst suppression were recorded in the EEG. The duration of suppression at level III was significantly longer than that at level II. During enflurane anesthesia, there were no significant differences compared with the control group in the cerebral energy state or energy charge. Glycolytic metabolism remained unchanged except for an increase in glucose at levels II and III. Effects of hypocapnia and hypercapnia were examined in an additional 12 rats with an enflurane concentration in the blood similar to that at level II. Irrespective of PaCO2 levels, there were no significant changes in cerebral energy charge and glycolytic metabolites except for a decrease in glucose and an increase in lactate at hypocapnia. It was concluded that there was neither evidence of derangement of energy state nor increased anaerobic metabolism in the cerebral cortex during enflurane anesthesia.