Abstract: Objective To study the feasibility and safety of peripheral nerve(lumbar plexus-sciatic nerve) block in total knee replacement for elderly patients. Methods Eighty patients who underwent unilateral knee replacement in our hospital from June 2011 to June 2012 were randomly divided into general anesthesia(GA) group and peripheral nerve block(NB) group(40 in each group).The systolic blood pressure(SBP),diastolic blood pressure(DBP),heart rate(HR),SpO₂,and the beginning,peak and maintenance time of sensory and motor nerve block were recorded in two groups before anesthesia(T0),immediately after tracheal intubation(T1),skin cut(T2),decollement and osteostomy(T3),60 min after use of tourniquet(T4),5 min after removal of tourniquet(T5).Anesthesia-related adverse reactions were detected in two groups. Results Onset of sensory and motor block was 10.3±4.6 min and 13.1±4.8 min.The maintenance of sensory and motor block was 610±145 min and 322±90 min,P<0.05.The SBP and DBP were lower in GA group than in peripheral NB group at T3 and higher in GA group than in peripheral NB group at T4 and T5(P<0.05).The HR was lower in peripheral NB group at T2 than at T0(P<0.05).Motor reactions were observed in 2 patients of peripheral NB group at osteostomy.The incidence of nausea and vomiting was lower in peripheral NB group than in GA group after operation.No anesthesia-related adverse reaction occurred in two groups. Conclusion Lower extremity never block is safe and effective in unilateral knee replacement for elderly patients,especially for those receiving anticoagulant therapy and those not fit for general anesthesia.