The Relationship And Associated Factors Between Metabolic Changes Of Cerebral Cortex And Postoperative Cognititive Dysfunction In Patients

Part One：Associated Factors Of Postoperative CognitiveDysfunction In Patients Undergoing OPCABBackground:POCD is a common postoperative complication in patients,and seriouslyimpact on their postoperative outcome and quality of life especially in thepatients undergoing cardiac surgery.Based on the previous studies, themechanism and causes of POCD remain unknown,but we can find theassociated risk factors. By analyzing relevant variables in patients undergoingOPCAB we try to identify risk factors for the occurrence of POCD.Methods:We enrolled30patients, aged50-85yr, ASA I-III, scheduled for off-pumpcoronary artery bypass surgery under general anaesthesia. Cognitive functionwas assessed with a battery of seven neuropsychological tests1-2day beforesurgery and1week after surgery.A Z-score of each test as well as thecomposite Z-score were obtained. When two Z-scores in the individual testsor the composite Z-score were higher than1.96, the patients were definedPOCD. We recorded preoperatively, the patients’sex,age,BMI,education,surgical history,past medi-cal history (hypertension,diabetes mellitus,COPD,smoking) and intraoperative factors:the operation time, hypotensiontime,blood loss,fluid infusion volume, vasoactive drugs usage (dopamine,nitroglycerin,milrinone, epinephrine, norepinephrine,phenylephrine, atropine), the values of blood lactate immediately afterinduction and during surgical procedures as well. Postoperative ICU stay andthe total days of hospitalization are also recorded. The variation of totalprotein,albumin were recoreded both preoperatively and1daypostoperatively. Using chi-square test and t test,wilconxon test to do theunivariate analysis.All univariate predictors with P<0.05were candidatepredictors for a logistic regression analysis to determine the risk factors ofPOCD in elderly patients undergoing OPCAB.Results:POCD was present in13of the30patients at one week after surgery. Theincidence of POCD in elderly patients undergoing OPCAB was43.3%.Onunivariate analysis, age, a second operation,operation time, hypotensiontime,dose of atropine using during surgery, length of postoperativestay,variation of plasma total protein and albumin concentration before andafter the surgery(P<0.05) were associated with an increased risk of POCD. Amultivariable logistic regression model indentified increasing age,hypotension time during surgery were the risk factors of POCD in elderlypatients undergoing OPCAB(P<0.05).Conclusion:Increasing age,a second operation,increasing operation time and hypotensiontime during surgery,using atropine during surgery, increasing length of stay,decrease of plasma total protein and albumin concentration after the surgeryare associated with an increased risk of POCD.Increasing age, increasinghypotension time during surgery are the risk factors of POCD in elderlypatients undergoing OPCAB (P<0.05). Part Two: The Effect of Metabolic Changes of CerebralCortex during Anesthesia And Surgery on PostoperativeCognitive FunctionBackground:To find the possible relationship between the metabolic changes of cerebralcortex during anesthesia and surgery and postoperative cognitive dysfunctionby using functional Near Infrared Spectroscopy (fNIRS).Methods:We studied the difference of quantitative changes of oxygenated hemoglobinconcentration of frontoparietal cerebral cortex between groups of POCD andno-POCD during surgery,at the time,we recorded the variation at the pointof incision(T1),5min of the first distal vessel anastomoses(T2),hypotension when moving the heart(T3) by using optical tomographysystem.We try to find the relationship between the difference presented by theETG and POCD.Results:Both groups of the patients showed lower average concentrations ofoxygenated hemoglobin in the frontal and parietal cortex at the point ofT2,T3than T1, especially T3moment fell the most significantly.The cerebralcortex showed lower metabolic activity. POCD group patients at all timepoints showed lower concentrations of oxygenated hemoglobin than the no-POCD group, and more sensitive to the change of blood pressure andperfusion.Conclusion:There is a close link between postoperative cognitive dysfunction andmetabolic changes of cerebral cortex during anesthesia recorded byfunctional Near Infrared Spectroscopy. It has potential value in the study ofmechanism of postoperative cognitive dysfunction.