The Correlation Between EEG Spectrum Pattern And Postoperative Cognitive Dysfunction In Elderly Patients

Background:Postoperative cognitive dysfunction(POCD)refers to the disorder of cognitive ability,which is included memory,orientation,attention,thinking and social activity,after surgery.It usually lasts from several weeks to several months.The risk factors of POCD are numerous and complicated,namely,the patient's age,chronic diseases,surgical methods,anesthesia methods and depth of anesthesia.Among them,age is an independent risk factor.Studies show that the incidence of POCD at 7 days postoperatively in elderly non-cardiac surgery patients is as high as 20%.With the advent of an aging society,there will be more and more elderly patients undergoing surgery.Therefore,POCD is a critical complication which influences the long-term outcome of postoperative recovery.As a measure of brain activity,EEG plays an important role in measuring patient's consciousness,cognitive function and emotion.In clinical practices,anesthesiologists often reason the state of consciousness of the patient to control the depth of anesthesia through monitoring patients' EEG.A recent study suggests that the qualitative form of the EEG shows prominent alpha oscillation and slow-delta oscillation after anesthesia-induced loss of consciousness,and there is a positive correlation between age and attenuation of alpha oscillation.Considering the correlation between age and POCD,we hypothesize that the lack of intraoperative alpha oscillation is associated with postoperative cognitive impairment.Objective:We try to find out the correlation between EEG pattern and POCD,in order to provide an approach for screening high-risk groups of POCD from a new perspective,and provide clues for the study of the mechanism of POCD.Method:This study recruited patients who were hospitalized at Xijing Hospital between November 2017 and February 2018,aged 65 to 75 years,and scheduled to undergo surgery under general anesthesia.On the day before surgery,patients were recruited according to the inclusion and exclusion criteria.The preoperative general data collection was completed,and MMSE was used to assess cognitive function.During the operation,anesthesia depth monitor was used to collect the patient's EEG information and record the patient's intraoperative information.The patient was tested for MMSE 7 days after surgery or on the day of discharge,again.Patients with POCD were screened based on the difference in preoperative and postoperative MMSE scores.The comparisons of the EEG changes before and after anesthesia were performed between POCD patients and non-POCD patients to investigate the correlation between EEG pattern and POCD.Result:1.A total of 50 patients completed the study,including 11 in the POCD group and 39 in the non-POCD group.There was no statistical difference in gender,age,BMI,preoperative MMSE score,type of surgery,and time of surgery between the two groups.2.In the POCD group and non-POCD group,the percentage of total power in the delta oscillation decreased after the anesthesia,and the percentage of theta oscillation,alpha oscillation and beta oscillation increased.In the gamma oscillation,only the non-POCD group has changed.3.Under anesthesia,the percentage of delta oscillation in POCD group was significantly higher than that in non-POCD group.4.The decrease in the percentage of alpha oscillation power and the spectral power of alpha oscillation may not be the risk factor for POCD.Conclusion:There is a difference in the EEG pattern between POCD patients and non-POCD patients,but the decrease of the percentage of alpha oscillation spectral power and the alpha oscillation spectral power may not be the risk factor for the occurrence of POCD.