Effects Of General Anesthesia On The Postoperative Cognitive Function Of Elderly Patients With Nerve Block Combined With Different Depth Of Anesthesia

Objective:To compare the effects of general anesthesia on the postoperative cognitive function of elderly patients with nerve block combined with different depth of anesthesia.Methods:60 ASA Ⅰ-Ⅱ pa tients aged 65 to 80 years,with BMI 18-25kg/m² and MoCA>23 poi nts,scheduled for lower limb surgery,were randomly divided into tw o groups according different depth of anesthesia.Group Ⅰ:low sedation group（BIS55-65）;Group Ⅱ:highly sedation group（BIS40-50）.The femoral nerve combined with tibial and fibular nerve was identified and blocked respectively guided with ultrasound before the induction of anesthesia.After 20min,acupuncture site was made to ensure that every patient was painless（VAS<3）.Induction of routine anesthesia was performed,then intubated AmbuLaryngeal mask and ventilated（VT8ml/kg,RR8-12bpm,I:E=1:1.5,PetCO₂ 30-40mmHg）.Anesthesia was maintained with inhalation of sevoflurane（MAC0.3）,intravenous infusi on of propofol.The infusion rate of propofol was adjusted to BIS r espectively.Stop the inhalation of sevoflurane and propofol at the e nd of operation,administer antagonize residual neuromuscular blocka ge with Neostigmine and atropine until VT>5ml/kg,RR12-16bpm,th en pull out the laryngeal mask and to the recovery room.Cognitive f unction and pain were assessed using the MoCA and VAS respective ly at 1d before anesthesia and 1d、3d、7d after surgery.Three month s later,the patients were telephoned to inquire the effect of anesthesi a on their memory and attention.At the same time,hemodynamics,e xtubation time and the recovery time,and the differences of the dos age of propofol,fentanyl and vasoactive drugs in two groups were c ompared.Result:1.65 patients include the study,but five subjects could not complete the protocol and were discharged.In group Ⅰ,2 case s did not coorperate with POCD test,1 case failured nerve block,;I n Ⅱ group,1 case did not cooperate with POCD test,1 case chan ged into tracheal intubation because of Laryngeal mask leakage.The re were no significant differences in gender,age,body weight,educat ion and operation time between two groups（table-1）.2.MoCA scores:In group Ⅰ:25.00±1.23 scores at 1d before anesthesia,1d、3d、7d a fter surgery were respectively 24.73±1.31 scores,24.77±1.07 scores,24.90±1.06 scores;In group Ⅱ:25.03±1.00 scores at 1d before anesthesi a,1d、3d、7d after surgery were respectively 24.83±0.91 scores、24.87±1.07 scores、24.93±0.91 scores（table-3）.Three months later,ther e are three patients to think that the anesthesia had some effects on their memory,including 1 case in group Ⅰ and 2 cases in group Ⅱ.3.The dosage of propofol was significant difference between two grou ps.Group Ⅱ>Group Ⅰ.Group Ⅰ was 2.88±0.6mg/kg/h and group Ⅱ was 4.56±1.2mg/kg/h.During the operation,the dosage of fentanyl in group Ⅰ was 5.79±1.2mg,Ⅱ group 4.74±3.0mg,and there was no statistical difference between two groups（table-4）.4.Compared with group Ⅰ,the time of extubation and recovery in group Ⅱ was longer.The time of extubation was 5.77±3.01min in group Ⅰ,and 12.16±2.58 min in group Ⅱ.The time of comeback of directional ability was6.17±3.23 min in group Ⅰ,and 13.47±3.14 min in group Ⅱ.5.No stat istical difference between two groups in vasoactive drugs,hemodyna mic change（table-5and table-6）and postoperative VAS score（tabl e-7）.All patients have no intraopertive awareness.Conclusion:Different depth of anesthesia during combined generalanesthesia with nerveblockhave no effects on postoperative cognitive dysfunction in elderly patients undergoing lower limb surgery,but it can shorten extubation time,accelerate the recovery of orientation and reduce the dosage of anesthetic in low sedation state（BIS55-65）than highly sedation sate（BIS40-50）.