Abstract
The aim of this study was to investigate the dose-related effect of propofol on brain electrical activity and the cerebral pial arterioles in cats. Seven cats were anesthetized and a closed cranial window was made over the left parietal region. After baseline (isoflurane 0.8%, 0.5 MAC) measurement of the diameter of the pial arteriole and the cortical electroencephalogram (EEG), an intravenous infusion of propofol at a rate of 5mg·kg-1·hr-1 was started for 20min before all measurements were obtained using this dose of the drug. Subsequently, the infusion rate was increased to 10mg·kg-1·hr-1 for 20min, 20mg·kg-1·hr-1 for 20min and then 30mg·kg-1·hr-1 for 20min, and all measurements were obtained at each of the experimental conditions. EEG changed from fast activity (baseline, 0.5 MAC isoflurane) to a mixture of fast and slow activities (5mg·kg-1·hr-1), slow high amplitude activity (10mg·kg-1·hr-1), burst and suppression or suppression (20mg·kg-1·hr-1) and complete suppression (30mg·kg-1·hr-1). The baseline diameters of the pial arterioles were 100.1±17.4μm. The arteriolar diameters at 5, 10 and 20mg·kg-1·hr-1 decreased significantly compared with baseline diameters (P<0.05). The diameters were 92.9±14.2μm (5mg·kg-1·hr-1), 92.7±13.4μm (10mg·kg-1·hr-1) and 88.8±14.2μm (20mg·kg-1·hr-1). When the infusion rate was increased from 20mg·kg-1·hr-1 to 30mg·kg-1·hr-1, four of seven arterioles dilated. At 30mg·kg-1·hr-1, the diameters were 90.2±18.4μm. Our results suggest that the diameter of the pial arteriole in cats was influenced directly by propofol and indirectly by decreased brain electrical activity during propofol infusion.
