Abstract： Objective To observe the application effect of fascia iliaca block under the guidance of ultrasound in the total hip replacement(THR)in the elderly patients with Alzheimer's disease(AD).Methods A total of sixty elderly patients with AD who were admitted in our hospital from January,2019 to December,2020 for THR due to hip joint fracture were included in the study and randomized into the general anesthesia group and the combination group with thirty cases in each group.The patients in the general anesthesia group were given the routine general anesthesia to complete the operation,while the patients in the combination group were giv-en fascia iliaca block under the guidance of ultrasound before general anesthesia induction.The changes of HR and MAP before anesthesia(T0),30 min during operation(T1),60 min during operation(T2),and after op-eration(T3)in the two groups were compared.The radial artery and jugular venous blood in the above timing points in the two groups was collected to analyze CaO2,SjvO2,D(a-jv)O2,CjvO2,and CERO2.VAS was used to evaluate the pain in a motion and resting state 4,8,12,and 24h after operation.Results MAP in the combi-nation group at T1 was significantly elevated when compared with that at T0(P＜0.05),while the compari-son of HR among each timing point was not significantly different(P＞0.05).MAP and HR at T1,T2,and T3 in the general anesthesia group were significantly elevated when compared with before anesthesia(P＜0.05).MAP and HR at T1,T2,and T3 in the combination group were significant lower than those in the gen-eral anesthesia group(P＜0.05).SjvO2 and CjvO2 at T1,T2,and T3 in the two groups were significantly higher than those at T0(P＜0.05),but D(a-jv)O2 and CERO2 were significantly lower than those at T0(P＜0.05).SjvO2 and CjvO2 at T1,T2,and T3 in the combination group were significantly higher than those in the general anesthesia group(P＜0.05),while D(a-jv)O2 and CERO2 were significantly lower than those in the general anesthesia group(P＜0.05).VAS score at each timing point in the combination group was signifi-cantly lower than that in the general anesthesia group(P＜0.05).Conclusion Fascia iliaca block under the guidance of ultrasound in combined with general anesthesia can alleviate the intraoperative stress levels and cerebral oxygen metabolic levels in elderly AD patients undergoing THR,with postoperative analgesic effect more superior to the pure general anesthesia,which is more beneficial to perform the operation and facilitate the postoperative operation.