| IntroductionPostoperative.cognitive dysfunction means changes of personality the ability of social intercourse , congnition and skill after anesthesia and surgery. After extracorpereal circulation, 79 percent of cognitive dysfunction occured, 20 percent of them last over six months, Study shows the incidence of cognitive dysfunction is 25. 8 percent after a week of noncardiac surgery, and 9.9 percent after three months. Postoperative cognitive dysfunction doesnt favored to the patients, particularly to the treatment for the elderly patients around the operations. Many factors can lead to postoperative cognitive dysfunction, including cardippulmonary bypass, general anesthetic medicine, hypoxemia, hypocapnica and hypotensive etc. With increasing of critical surgeries and the number of elderly patients, the incidence of complication of cerebral oxygen metabolism and incidence of cerebral blood vessels increase on perioperations, monitory methods of function of cerebral oxygenation and clinic uses are increasing. Oxygenation states of jugular venous bulb oxygen saturation and lactate concentration can hint the state of cerebral oxygen supply and consumption indirectly, which direct anesthesia during the surgery and predict the nerve system function. In our study, by investigating the effects of propofol and isoflurane on jugular venous bulb oxygen saturation ,lactate difference between venous blood and arterial blood, postoperative cognitive dysfunction as well in elderly patients, evaluate correlation the cerebral metabolism and postoperative cognitive dysfunction.MaterialsInstruments: Detex - Omeda 110 anesthesia machine (USA) ; Hp monitor(USA) ; Bayer blood gas analysis machine (USA) ; Qiang sheng auto chemical analysis machine 250 ( USA) ; Brawn intravenous transfusion pump ( Germany).Medicine: Isoflurane ( ABBOTTO LABORATORIES) ; Propofol ( Astrazen-eca).MethodsPatient; we studied 40 patients from surgery of orthopedic department, ASA I - II , undergoing hip joint replacement, knee joint replacement, thoracic and lumbar vertebral surgery, fixation of the fracture of femora etc. They have no neuropsychiatric disease or history of taking correspording medicines and other vasodilator medicines. The patients were divided into two groups randomly. I propofol group ( n = 20 ) ; II Isoflurane group ( n = 20 )Anesthesia methods: all patients were given valium lOmg, po. and atropine 0.5mg im. 30 minutes before operation. After induction with propofol 1.5 -2. 0mg kg"1, fentanyl 3jxg kg"1 ,midazolan 0. 05mg * kg"1 vecoroniun 0. lmg kg"1 iv, endotracheal intubation was performed and controlled ventilations, propofol was given 6 - 12mg kg"1 h"1 with infusor in I group, 2 -4% isoflurane was inhaled continuosly in group II , fentanyl and vecuronium intermittent iv. to maintain anesthesia in two groups.Sample take and conduct: At the time of before intubation ( To) , after intubation (T,) ,30 minutes after intubation (T2) , 60 minutes (T3) and the point of taking out the tube ( T4 ) , arterial and jugular venous blood samples 4 ml were taken for measurement immediately of PjvO2PaO2SjvO2SaO2b and lactate concentration. Calculated CaO2 CjvO2 Ca - jvO2and OER according to Fick formula. Mini - Mental state ( MMS) was used to survey the patient' s congni-tive function at the time of before induction (Ta) , 6 hours after operation ( Tb ) , 12 hours (Tc), 24 hours (Td) and 3 days (Te) after operation respectively.Data analysis: all datas were expressed as mean sd, statistical comparative in the group were performed with paired t - test, and comparative between group with two sample t -test. A level of p <0.05 was considered statistically signifi-cant.ResultsSjvO2 increased significantly at T3 T4 in group II , and the value of lactate and that difference of venous and arterial blood was higher than To, which were all higher than those of the same time in group I ; Ca - jvO2and OER decreased significantly at T3 T4 in group II , and lower than those of the same time in group I ; MMS score was lower at TTTj in group II , and at TbTc in group I ; The incidence of postoperative cognitive dysfunction was 10/17 (59% ) and 3/23 (13% ) respectively during the surgery with disturbance of cerebral oxygen supply and consumption and without disturbance of that.DiscussionAs china is becoming an aging society, more and more old patients need to be operated, the incidence of disorder of cerebral metabolism, accidence of cerebral vessels are increasing during the operations. In this study, blood samples were drawn from jugular vein bulb to be performed blood gas analysis and calculated SjvO2 Ca - jvO2 OER lactate, which could reflect cerebral oxygen supply and consumption. There had no change in SjvO2 Ca - jvO2 and OER in group I , also they were in normal range, at the same time lactate concentration and the difference of lactate of encephalic blood had no remarkable change, which mean cerebral oxygen supply and consumption could maintain the balance with propofol anesthesia, and there had no cerebral tissues anoxia. In group H , there exist some obstacles on using oxygen of cerebral tissues and cerebral blood doesnt well -distributed, which may be aroused from cerebral blood dilator, an increase in cerebral vessel blood, cerebral excessive perfusion and an increase in fermenting without oxygen.The incidence of postoperative cognitive dysfunction in elderly patients after operation and anesthesia is higher significantly than that in younger. Cognitive dysfunction do harm to the patient, particularly to the treatment for old patientsperioperation.Selection of agent for general anesthesia is also affect postoperative cognitive dysfunction, propofol and isoflurane were selected in our study to observe their affects on congnitive function. MMS score decreased significantly at 6h,, 12h, after operation in group I , which there had no remarkable change to baseline in 24h later; MMS score decreased significantly at 6h 12h 24h after operation in group II , while there had no remarkable change to baseline 3 days later. In our study, the patients' age, gender proportion, education time, dept of anesthesia, hypotension etc. which may affect postoperative congnitive function were controlled strictly, so we could conclude the difference cause from general anesthesia agent. The result of the study is similar to Anthony's study, they found inhaled agents can inhibit significantly peripheral nerve taking in acetylcholine , so as to limited acetylcholine's synthesis speed. Acetylcholine is an important matter exists intensively in the brain, which closely related to learning and memory. So isoflurane could weaken ability of directional and understanding , while after propofol anesthesia, the patients have more strongly self - control ability, whose internal memory was normal, and nerve function doesn 't change. In this study, index were all in normal range, with two anesthetic a-gents, and MAP were maintain over 70mmHg, which assured cerebral perfusion , but the result showed that 58 percent patients showed up postoperative cognitive dysfunction in those who have presented cerebral oxygen metabolism imbalance, which similar to the study of Monk. The study demonstrate that only increasing cerebral perfusion or decreasing cerebral oxygen metabolism couldnt acquire ideal cerebral protecting effect, only when oxygen balance is reached. Above all the postoperative cognitive dysfunction in elderly patients are related to the disorder of cerebral oxygen metabolism, so monitoring jugular venous and arterial blood gas and lactate, correctly judging the state of cerebral oxygen metabolism can help management during surgery and maintain cerebral oxygen metabolism to prevent or decrease incidence of the nervous system complication.
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