Objective To observe the impacts of lumbar plexus block combined with sciatic nerve block on postoperative cognitive function and plasma S100βlevel in eldly patients undergoing hip surgeries.Methods Sixty patients of ASA Ⅱ or Ⅲ aged 65-85 years,undergoing selective hip sur-geries,were randomly divided into 2 groups (n=30 each).Group G received general anesthesia with tracheal intubation,while group L received ultrasound-guided lumbar plexus block and parasacral sci-atic nerve block combined with general anesthesia.The mini-mental state examination (MMSE)score was recorded before anesthesia,1 d,3 d and 7 d after operation.The plasma S100βlevel was detected before anesthesia,1 h and 7 d after operation.Results The MMSE scores declined on 1 d after oper-ation in both groups(P <0.05),and the value was lower in group G(P <0.05).There were 18 (56.7%)patients diagnosed with POCD in group G at the first day postoperatively,while it was 10 (33.3%)in group L,and the difference was significant(P<0.05).The MMSE scores were still low-er at 3 d after operation (P<0.05).The concentrations of plasma S100βincreased in both groups at 1 h after operation,and it was more obviously in group G (P <0.05).Conclusion Lumbar plexus block combined with parasacral sciatic nerve block might reduce the stress reaction and dosages of general anesthetics in eldly patients undergoing hip surgeries,minimize the damages of central nervous system,protect the cognitive function and reduce the incidence of POCD.