Cerebral physiology following general anaesthesia with sevoflurane or propofol in healthy volunteers - a randomised, single-blind cross-over trial

Although general anaesthesia is a very common medical procedure, knowledge of how the brain physiologically recovers remains limited. In this randomized cross-over trial, we investigated brain physiology during recovery from general anaesthesia with sevoflurane or propofol. Using magnetic resonance imaging (MRI) and magnetic resonance spectroscopy (MRS), we quantified cerebral blood flow (CBF), the cerebral metabolic rate of oxygen (CMRO 2 ), and concentrations of cerebral lactate and N-acetyl aspartate before and after anaesthesia. Twenty-one healthy volunteers (male:female 10:11, mean age 23(18-32) years) underwent two sessions of general anaesthesia with either sevoflurane or propofol, spaced at least four weeks apart. MRI scans were performed before anaesthesia and again four hours, one day, and eight days after anaesthesia. CBF increased by 5.7% four hours after sevoflurane general anaesthesia (p=0.040), possibly reflecting reduced haemoglobin concentration. CMRO 2 and N-acetyl aspartate concentrations did not change. In contrast, brain lactate was elevated four hours after both sevoflurane (14.7%, p=0.0006) and propofol (9.5%, p=0.01), and remained elevated one day after sevoflurane anaesthesia (13.2%, p=0.0008). This lactate increase occurred despite normal CMRO 2 and may indicate enhanced glycolytic activity during post-anaesthetic recovery.