The Effects of Propofol Anesthesia on Local Cerebral Glucose Utilization in the Rat

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Abstract
The autoradiographic 14C-2-deoxy-D-glucose method was used to determine local cerebral glucose utilization (LCGU) during propofol anesthesia and recovery in 52 regions of the rat brain. Control rats intravenously received 5 ml .cntdot. kg-1 .cntdot. h-1 of the egg-oil-glycerol emulsion that constitutes the vehicle for propofol. Anesthesized animals received an iv bolus of propofol (20 mg/kg) followed by continuous infusion of the anesthetic at 12.5, 25, and 50 mg .cntdot. kg-1 .cntdot. h-1 for 1 h prior to injection of 14C-2-deoxy-D-glucose and for the following 45 min. In addition, a fifth group of animals were studied immediately after awakening from a 20 mg/kg bolus of propofol as indicated by the first reappearance of head lift. All rats were spontaneously breathing room air throughout the experimental procedure. The general pattern of the cerebral metabolic response to propofol anesthesia was a dose-related, widespread depression of LCGU. At the three infusion rates of propofol tested, overall mean LCGU was reduced by 33%, 49%, and 55%, respectively, and significant decreases were observed in 60%, 85%, and 90% of the regions assayed. These effects were rapidly reversible, since in the recovery group, LCGU returned to near control values in the majority of the brain areas. Although all of the anatomofunctional systems (sensorimotor, extrapyramidal, limbic, and reticular) were involved, forebrain structures showed a greater sensitivity to the depressant action of propofol than did hindbrain regions. The only structures in which glucose use was spared, even when the highest dose of propofol was infused, were the nuclei related to the auditory-vestibular system (cochlear and vestibular nuclei, lateral lemniscus, and superior olive). The pattern of metabolic changes produced by propofol resembles that observed after barbiturates, Althesin, and etomidate.