Effects Of Different Depth Of Anesthesia On The Postoperative Cognitive Function And S-100β Protein Levels In Elderly Patients

Objective: To observe the effects of different depth of anesthesia on thePostoperative Cognitive Function（POCD） and the expressions of S^-100βprotein in the serum in elderly patients who were scheduled to receiveabdominal surgery，and provide a appropriate depth of anesthesia for elderlypatients.Methods: Eighty patients （ASAⅡ～Ⅲ,60～75years old） that werescheduled to receive abdominal surgery were randomly divided into2groups:one group was to receive lighter anesthesia （group L,n=40） and the othergroup was to receive deeper anesthesia （group D, n=40）.They were dividedat random with a number list.Exclusion criteria included: a history of surgery,ahistory of neurologic or mental disease,longterm use of large amounts ofsedatives or antidepressants, a history of alcohol abuse or a history of drugdependence, weight fluctuation range exceeds±25%,active liver disease,cardiac dysfunction, pulmonary dysfunction,inability to completeneuropsychologic testing.All selected patients were informed a consent.Group L was assigned to expected Narcotrend index（NTI）of47～64,Narcotrend stage（NTS）: D0～D1,group D was assigned to expected NTI of20～36,NTS:E0～E1.All patients did not use preoperative medication.Afterentering the operating room,patients were monitored by ECG,HR,SPO2andNarcotrend.Face mask oxygen was given conventionally by6L/min. Openvein fluid path and infuse Ringer. Local anesthesia for radial artery punctureand internal jugular veinpuncture,after the success of puncture,respectivelymonitor IBP and CVP. All patients were following the same steps.Afterintravenous injection of midazolam0.05mg/kg,infused propofol3mg·kg^-1·h^-1with the venous pump,each concentration increased0.5mg/kg intervals for 2min.When the expected NTI value was reached, intravenous injection offentanyl2～3ug/kg, rocuronium0.6mg/kg,and then finished with the trachealintubation.Using mechanical ventilation in anesthesia machines.Duringoperation,continuously intravenous infusion of propofol1～5mg·kg^-1·h^-1,remifentanil0.05～0.2ug·kg^-1·min^-1according to NTI increase or decreaseanaesthetics. The group L was expected NTI of47～64, NTS: D0～D1,thegroup D was expected NTI of20～36,NTS:E0～E1. The luctuation of meanarterial pressure （MAP） and heart rate （HR） was controlled to within20%ofthe preoperative value measured before surgery. If the MAP went outside thattarget range, it was increased with ephedrine, or decreased with urapidil. HRwas controlled to that target range by using atropine or esmolol. Rocuroniumwas discontinuously supplemented.Adjust fluid infusion speed according toCVP, no longer append rocuronium30minutes before the end of theoperation.At the end of surgery,stop pumping remifentanil and propofol. Allpatients using the same recipe for postoperative analgesia.Record generalsituation of patients,such as gender,age,educational level, hypertension,diabetes, duration of anesthesia, duration of surgery and so on.VAS was usedto measure the condition of pain.The changes of MAP, HR and NTI wereobserved at the time points of before induction（T₀）,afterinduction（T₁）,intubation moment（T₂）,at skin incision（T₃）,one hour duringsurgery（T₄）,two hour during surgery（T₅）,immediately after completion of theoperation（T₆）,extubation moment（T₇）.Using MMSE to evaluate postoperativecognitive function at the time of the day before surgery（T₀）,24h after surgery（T₁）.Sample blood from the internal jugular vein at the time of beforeinduction （T₀） two hours during surgery（T₁） immediately after completion ofthe surgery（T₂） two hours after surgery（T₃）24h after surgery（T₄）.Using theELISA method for detection of S^-100βprotein.Result: The general situation of the patients such as gender, body massindex,educational level, hypertension, diabetes,operation time, anesthesia timeand NTI that before induction and after surgery in two groups have nosignificant difference.In the two groups,after comparing with T₀,the MAP was lower at T₁and T₂,the difference was statistically significant（p<0.05）,the HRwas higher at T₂,the difference has statistically significant（p<0.05）.Nosignificant difference was found in MAP and HR between the two groups.Comparison doses of propofol between the two groups, L group wassignificant less than D group（p<0.05）.Comparison doses of remifentanilthere was on significant difference.POCD occurred in6patients （15%） whoreceived deeper anesthesia and14patients （35%） who received lighteranesthesia on24h after surgery（p<0.05）.In group D,after comparing withT₀,the levels of S^-100β protein were higher at T₁,T₂and T₃,the differencewas statistically significant （p<0.05）.In group L,after comparing with T₀,thelevels of S^-100β protein were higher at T₁,T₂,T₃andT₄,the difference wasstatistically significant （p<0.05）.The level of S^-100β protein from group Lwas higher at T₂,T₃and T₄than group D（p<0.05）.Conclusion：Compared with lighter anesthesia，deeper anaesthesia canreduce the incidence of Postoperative Cognitive Dysfunction and theexpressions of S^-100β protein in the serum in elderly patients.