Objective To investigate the influence of stroke volume variation (SVV)-guided fluid therapy on postoperative cognitive function in elderly patients undergoing the unilateral total knee arthroplasty(UTKA).Methods One hundred patients undergoing the UTKA were randomly di-vided into two groups,group A(SVV 4%-9%)and group B(SVV 10%-14%).The liquid manage-ment,serum markers (CRP,IL-6)and the incidences of deflating-tourniquet-related hypotension and preoperative, 5 d after surgery of the occurrence of POCD in two groups were recorded. Results There was no significant difference in general information between the two groups. Compared with group B,group A needed more fluid transfusion and had a higher 24 h urine volume. The CRP and IL-6 was significantly higher in group B than that in group A;The incidence of defla-ting-tourniquet-related hypotension in group A [22(44%)]was also lower than that in group B [43 (86%)].However,there was no significant difference in the incidence of POCD between the two groups.Conclusion Sufficient blood volume can help to reduce the incidence of deflating-tourniquet-related hypotension,and reduce the inflammatory reaction in elderly patients.