A POSITRON-EMISSION-TOMOGRAPHY STUDY OF CEREBRAL BLOOD-FLOW AND OXYGEN-METABOLISM IN HEALTHY MALE-VOLUNTEERS ANESTHETIZED WITH ELTANOLONE

Background: The effects of eltanolone anaesthesia in humans on regiona l cerebral blood now, regional cerebral metabolic rate of oxygen and o xygen extraction ratio were to be evaluated using positron emission to mography (PET). Methods: Six healthy male volunteers were studied. Ser ies of PET-measurements with O-15 and (H2O)-O-15 were carried out in t he awake state (baseline) (n=6), during eltanolone anaesthesia (n=5) a nd during early recovery (n=5), when the subjects were oriented with r espect to person, place and time. Eltanolone was given as a programmed infusion. Results: Cerebral blood flow (rCBF) was reduced in almost a ll cortex regions studied by 31+/-16% (mean+/-SD, P<0.01). During reco very rCBF increased to 109+/-26% of pre-anaesthetic baseline levels (P <0.01). Eltanolone in the doses administered lowered oxygen metabolism (rCMRO(2)) by 52+/-8% (P<0.01) in cortex regions. During recovery rCM RO(2) increased to 90+/-13% of baseline (P<0.01). The oxygen extractio n (OER) in cortical regions decreased by 32+/-23% (P<0.01) during anae sthesia and returned to 82+/-10% of baseline (P<0.01) during recovery. Less reduction in cortical blood flow during eltanolone anaesthesia w as seen in the uncus (P<0.01), though no differences in the depression of oxygen metabolism were seen. Oxygen extraction remained homogeneou s throughout the brain. Conclusion: Eltanolone anaesthesia was shown t o reduce cerebral oxygen metabolism and cerebral blood flow in healthy volunteers. There were no signs of ischaemic effects. (C) Acta Anaest hesiologica Scandinavica.