Exploration Of Neuroimaging And Biochemical Prognostic Indicators For Post-operative Cognitive Dysfunction After Coronary Artery Bypass Graft

The lifespan of Chinese population has been extended with the advance in socialdevelopment and living quality. On international common opinion, a country can beconsidered in aging society when the proportion of people over age of60constitutesmore than10%of the overall population. In2013, the elderly are more than200million,proportion rising from13.26%(the result of Sixth National Census) to14.8%. Priorstudies have proved that the incidence of CHD is related to age and increases with age. Atpresent, coronary artery bypass surgery is one efficient method to treat coronary heartdisease (CHD).Some may suffer POCD (postoperative cognitive dysfunction), one of the mostserious complications, which is defined as impaired memory, abstract thinking, directiondiscernment emerging and decline in social skills several days after operation. Caused bydifferent research targets and research protocols, prior studies yielded no consensus inincidence of POCD which even over60%in some results. Sequences of POCD, such as delayed recovery, increased clinical costs, deteriorated living quality and exaggeratedsocial burdens are big concerns. Available studies show that old age is a major cause forPOCD. The incidence of AD (Alzheimer’s Disease，AD) among patients with POCD ismuch higher than normal people. With the aging of Chinese population, POCD hasbecome a major challenge for the society. As there is no efficient treatment presently,how to prevent POCD and find its early-warning marker becomes major issue.MRI (Magnetic Resonance Imaging) has been widely applied to check and diagnoseMCI (mild cognitive impairment) and AD in prior studies. Some researches proved thecorrelation between the hippocampal volume and AD. Previous studies have confirmedthe highly increase of IL-6after the surgery, associated with cognitive dysfunction.Hence, the following experiment is designed.Objective:1. To investigate the correlation between the hippocampal volume and postoperativecognitive dysfunction (POCD) in patients undergoing cardiac surgery by measuringthe hippocampal volume with MRI2. To discuss the relationship between the cognitive dysfunction, peripheralinflammation and brain damage factors in patients who under coronary artery bypasssurgeryMethods:Choose58patients who are undergoing coronary artery bypass grafting and another51healthy objects in middle or old ages. The patients were assessed withneuropsychological tests and MRI scans on the day before surgery, andneuropsychological tests again on the7th postoperative. The healthy group was assessedwith neuropsychological tests in the same interval. The results were dealt with the “Zscoring method”. The MRI machine3.0T superconducting magnetic resonance (Siemens,German) was used to scan the hippocampal. Then we measured the hippocampal volumeby computer. All the patients were divided into POCD group and non-POCD group byneuropsychological tests. Then we calculate the incidence of POCD and the hippocampalvolume and analysize the relationship between the hippocampal volume and POCD. 4ml blood was taken from the healthy objects for one. Then we take4ml blood fromthe patient group every time for five times (before surgery,2h after surgery,1d aftersurgery,3d after surgery and7d after surgery). Put the blood into tubs with serumthrombotic accelerator and separation gel and keep them in fridge at the temperature of4℃for30minutes. Centrifuge them, take the serum and keep the serum in the fridge atthe temperature of-80℃. Use ELISA(enzyme linked immunosorbent assay) to test IL-6,NSE and S100β.Results:All the patients completed the whole battery of neuropsychological tests and MRIscans. The result shows that the general condition between the patients and the healthyages had no statistically difference. According to the neuropsychological tests,4healthyaged people in control group were diagnosed with POCD, so the false positive rate of theneuropsychological tests is7.8%.32patients were diagnosed with POCD, a ratio of55.2%. MRI scan shows that the hippocampal volume in POCD group(5.64±0.26cm3)was significantly smaller than those in non-POCD group (5.81±0.35cm3，P<0.05).The hippocampal volume had negative correlation with neuropsychological tests.Patients undergoing coronary artery bypass surgery had a higher IL-6than healthysubjects. Subjects above the age of60showed higher IL-6、NSE和S100β than youngersubjects. Patients with POCD above the age of60show higher IL-6. Biological markersin the blood of patients indicate that surgery led to the increase of IL-6、NS and S100β,which would decrease gradually after the surgery.2hours after the surgery, thepresentation amount of POCD group is obviously higher than the pocd non-POCD group.The presentation amount of NSE shows no difference between POCD group andnon-POCD group. There is no difference in S100β.Conclusion:There is a higher risk of suffering POCD in patients undergoing cardiac surgery.Meanwhile, we find that the hippocampal volume is smaller in POCD patients bypreoperative MRI scans. The hippocampal volume of patients undergoing coronary arterybypass bridging surgery had negative correlation with POCD, which indicates that hippocampal volume can be a risk factor of POCD. This could be an objective andmacroscopic imaging bases for early prevention for postoperative cognitive dysfunction.With the surgical influence, IL-6and NSE are increased in the blood, but they willdecrease to the normal level with time goes by. IL-6and NSE in the blood of old subjectsshow a higher level than young subjects. People above the age of60with IL-6higherthan104.651pg/ml have a higher risk of POCD.SummaryThe objects of our study are the patients undergoing cardiac surgery and healthyone in middle or old ages. Firstly，two groups were assessed with neuropsychologicaltests and the hippocampal volume measuring before surgery. We found that thehippocampal volume in POCD group is smaller than it in non-POCD group. Secondly,we measure the IL-6、NSE and S100β in blood of two group. We found that theexpression level of the IL-6、NSE、S100β was substantial increase after surgery. BetweenPOCD group and non-POCD group, the expression of IL-6and NSE were statisticaldifferences, but only the IL-6before surgery could be used as an indicator to predicatePOCD.