The Study Of Drug-Neural Effects Modeling And Cerebral Oxygen Metabolism In Anesthesia

Human brain and its related physiological changes has always been the hot and difficult topic in scientific studies. As yet, the mechanisms of general anesthesia remain largely unclear. Because of the complexity of the brain and the difficulty of anesthesia mechanism study, the widely-used and convincing method used to explain anesthesia mechanisms is to study from as many as possible aspects, such as modeling the brain and investigating the changes of brain oxygen. The existing studies have some shortcomings, like incomplete modeling and data analysis, lack of cerebral oxygen metabolism studying. To solve the above problems, this thesis was devoted to building an anesthesia electroencephalographic model and exploring the cerebral oxygen changes under general anesthesia to explain anesthesia mechanisms, combined theory with actual data. The content is as follows:Firstly, for the modeling study of anesthetic effect mechanisms, based on the anesthetic drug propofol, we built a model that was able to reproduce the macroscopic EEG. Combined with the pharmacokinetics model, based on the propofol drug infusion rate, the effect-site concentration dependent on time can be derived. Taking the propofol effect-site concentration as the input of a neural mass model, the output is the anesthesia electroencephalogram(EEG) signal. The neural mass model used here adopted the equivalent circuit of neurons, considering the physiological and anatomical structure of the cerebral cortex, and the connectivity and interaction among the neurons in the cerebral cortex, outputted the anesthesia EEG signal. In our study, the EEG data of nine subjects under general anesthesia experiment was compared with the simulated EEG data in respect to spectrum, permutation entropy and relative power spectral density. The results showed that the simulated EEG data could reflect some main features of real EEG data.Secondly, for the cerebral oxygen metabolism study of anesthesia mechanisms, applying the functional near-infrared spectroscopy(f NIRS) technique to monitor general anesthesia operation. The characteristics of the blood and oxygen(oxy-hemoglobin, Hb O2 and deoxy-hemoglobin, Hb) in the cerebral cortex under different anesthesia states were analyzed. The results showed that the concentration changes of oxy-hemoglobin and deoxy-hemoglobin under different states exhibited significant differences, that is to say, based on the two indices different anesthesia stats can be differentiated. The study first investigated to use the concentration changes of oxy-hemoglobin and deoxy-hemoglobin to estimate anesthesia states using f NIRS device. It provided important reference for determining the depth of anesthesia in clinical.Finally, we compared the research results of modeling and cerebral oxygen metabolism with the existing findings in terms of anesthesia mechanisms.