Abstract: AIM: To study the effects of anaesthesia on different encephalic regions with target controlled infusion of propofol using EEG nonlinear analysis method and to investigate its clinical significance. METHODS: 40 patients undergoing selected abdomen operations were randomly divided into propofol group A (3 μg /mL) and group B (4 μg /mL), n =20.EEG nonlinear parameters such as approximate entropy (ApEn), association dimension (D₂), complexity (Cx) were recorded using total intravenous anesthesia, and the changes of blood pressure (BP), heart rate (HR), pulse oxygen saturation (SpO₂) were observed. RESULTS: Nonlinear parameters were decreased at different encephalic regions after propofol sedation with statistical significance(P <0.05). Compared the nonlinear parameter of each group during the period of the operation, there were no significant differences between the two groups. In the process of achiving target propofol concentration, the encephalic region suppressed sequence were from frontal and parietal region to temporal lobe and occipital region, and after drug withdrawal, the excitation was recovered from temporal and occipital region to frontal and parietal region. CONCLUSION: During the operation, the nonlinar parameters are different at various stages and in the different encephalic regions. There is no statistical difference for the inhibitive effect on brain regions using 3 μg /mL and 4 μg /mL propofol respectively(P >0.05).

Key words: nonlinear electroencephalogram, approximate entropy, correlation dimensionality, complexity, propofol