Study On The Changes Of Cerebral Oxygen Supply-demand Balance And Brain Autoregulation Function And Its Influencing Factors In Patients Undergoing Open Surgery Under Intravenous Anesthesia

Background: Post operative cognitive dysfunction（POCD）is a kind of disease characterized by postoperative neurocognitive defects.Imbalance of cerebral oxygen supply and demand and impaired autoregulation are risk factors for POCD.Regional cerebral oxygen saturation（rSO₂）and tissue hemoglobin concentration index（THI）measured by near infrared spectroscopy,It can effectively evaluate the balance of cerebral oxygen supply and demand.Propofol is a vasoactive intravenous anesthetic.It is worth studying whether it affects the balance of cerebral oxygen supply and demand before and after anesthesia.By calculating the continuous linear Pearson correlation coefficient between rSO₂ and MAP（mean arterial pressure）,the cerebral oximetry index（COx）was obtained.The continuous linear Pearson correlation coefficient between THI and MAP（mean arterial pressure）was calculated to obtain total hemoglobin reactivity index（THx）.Cerebral autoregulation（CA）platform can be monitored by COx and THx.Previous studies have reported that age has an effect on CA,the duration of surgery has an effect on rSO₂,and the hemodynamics of patients fluctuate greatly during hilar occlusion.It is of research significance to explore whether there are differences in cerebral oxygen supply and demand balance and brain autoregulation function in patients with different ages,operation duration and whether or not hilar occlusion is performed.The results of this study can provide some reference for clinical anesthesia management.Objective To investigate whether there are differences in cerebral oxygen supply and demand balance before and after intravenous propofol anesthesia and the influencing factors of cerebral oxygen supply and demand balance and automatic brain regulation platform.Methods From June 2020 to October 2020,we monitored the regional cerebral oxygenation of 53 patients who underwent laparotomy in Department of Hepatobiliary Surgery in our hospital from entering the operating room to the end of surgery.RSO₂,Tissue hemoglobin concentration index（THI）,mean arterial pressure（MAP）.RSO₂ and THI were used to evaluate brain oxygenation.Then,the moving linear Pearson correlation coefficient（COx）between rSO₂ and MAP was calculated throughout the procedure,and the moving linear Pearson correlation coefficient（THx）between THI and MAP was calculated.COx and THx were used to explore the upper and lower limits and plateau length of brain autoregulation.Blood gas analysis was collected intermittently,and all patients were administered standardized anesthesia.Finally,the rSO₂ and THI were compared before and after anesthesia by paired t-test.The rSO₂ and THI of the left and right brain were grouped according to age,hilar blockade and operation time,and compared by two-sided t-test.The upper and lower limits of CA,as defined by COx and THx,and the range of adjustment were also grouped according to age,hilar blockade,and duration of surgery,and were compared by two-sided t-test.Results There were significant differences in brain rSO₂ before versus after anesthesia in 53 patients（left side P=0.000,right side P=0.000）.There were statistically significant differences in THI between the left and right sides before and after anesthesia（left P=0.000,right P=0.000）.There was no significant difference in rSO₂ and THI between the left and right sides according to whether the age was more than 50 years old,whether the hilar was blocked or not,and whether the operation time was more than 360 minutes（P > 0.05）.The linear correlation curve showed that the THI of left and right brain decreased gradually with the increase of age（left brain THI with age r=-0.2618,P=0.0583;Right brain THI with age r=-0.2836,P=0.0396）.The lower limit,upper limit and range of CBF autoregulation were（82.46±12.87）mm Hg,（93.67±13.69）mm Hg and（11.22±8.38）mm Hg,respectively,defined by COx under propofol intravenous anesthesia.The lower limit,upper limit and range of CBF autoregulation defined by THx were（79.98±10.56）,（93.77±12.34）and（13.79±8.63）mm Hg,respectively.The upper limit,lower limit and adjustment range of CA defined by COx and THx were compared according to whether the age was more than 50 years old,whether the hilar was blocked,and whether the operation time was more than 360 minutes,and there was no significant difference（P > 0.05）.Conclusion In patients with open hepatobiliary surgery under propofol intravenous anesthesia,rSO₂ and THI of left and right brain decreased compared with before anesthesia,and THI of left and right brain decreased with age.Intravenous anesthesia with propofol usually results in a shortening of the brain’s automatic regulatory platform.The lower limit and upper limit of automatic CBF regulation and the range of automatic CBF regulation may not be affected by whether the age is more than 50 years old,whether the portal is blocked or not,and whether the operation duration is more than 360 minutes.Intraoperative rSO₂ and THI monitoring should be strengthened and brain protection measures should be taken in time to achieve the balance of oxygen supply and demand and the stability of automatic brain regulation function.