These results demonstrate that CBF/CMRO2 ratio is markedly increased above normal and maintained during prolonged inhalation of volatile anesthetics in humans. It is impossible to determine whether these data indicate a stable CBF or whether CBF and CMRO2 are changing in parallel during the observation period. The unchanging electroencephalographic pattern suggests that the former possibility is more likely and that the increase of CBF produced by volatile anesthetics is maintained over time without decay, which has been reported in several animal studies. It also is suggested that isoflurane possesses greater capability to maintain global CBF relative to CMRO(2) than does halothane or sevoflurane. time.)

The results indicate that there was no decay in Vmca over time during prolonged (3 h) inhalation of volatile anesthetics at 1.5 MAC in humans. The fluctuation of Vmca during burst suppression on EEG at 1.5 MAC indicates that the flow-metabolism coupling occurred.

Deepening anesthesia from 0.5 to 1.0 MAC was maintained with no difference between the two agents during 4h of neurosurgery.

Low-flow isoflurane-nitrous oxide anaesthesia offers substantial economic advantage over high-and medium-flow isoflurane-nitous oxide anaesthesia. Acta Anaesthesiol Scand 37: 50512, 1993 2) Curatolo M, Derighetti M, Peterse-Felix S, et al. Fuzzy logic control of inspired isoflurane and oxygen concentrations using minimal flow anaesthesia.