Objective To investigate the effects of inhalation of different concentrations of isoflurane on global and regional cerebral glucose metabolic rate (CMRglu) in healthy volunteers using positron emission tomography (PET) scan.Methods The study was approved by the ethic committee of the hospital. After obtaining written informed consent we studied eight right-handed healthy volunteers (3 male, 5 female), aged 21-28 yrs. Each volunteer underwent 3 PET scans.They were fasted for 8 h prior to study. The PET scan was performed when conscious, at 0.5 and 1.0 MAC isofluraneanesthesia. The interval between two PET scans was 1 week. Scans were obtained with a MASEP CPET Plus scanner (2.0 mm resolution-FWHM) using the 18 fluorodeoxyglucose technique. Results The whole brain CMRglu averaged 30.0?1.1 ?mol?100 mg-1?min-1 when the volunteer was awake. Isofluraneanesthesia significantly reduced whole-brain CMRglu by 24% to 23.3?1.4 ?mol?100 mg-1?min-1 at 0.5 MAC and by 41% to 18.4?0.9 ?mol?100mg-1?min-1 at 1.0 MAC (P