Figure 21-10 Relationship between changes in the cerebral metabolic rate for glucose (CMRg) and cerebral blood flow (CBF) in the motor-sensory cortex in rats during isoflurane anesthesia. Most of the CMR suppression caused by isoflurane had occurred by 1.0 minimum alveolar concentration (MAC), and in this concentration range CBF is not increased. Thereafter, additional isoflurane causes little further reduction in CMR, and cerebral vasodilation occurs. These data (±SD), from Maekawa and colleagues,^[27] suggest the importance of metabolic coupling in determining the CBF effects of isoflurane.