【Abstract】Objective To determine whether change of ropivacaine plasma concentrations and analgesia role would be related to the pretreatment of lipid emulsion during epidural anesthesia in adults undergoing lower limb operations. Method Twenty-nine adult patients aged 18 to 65 years, ASAⅠ and Ⅱ, scheduled for elective lower limb operations under epidural anesthesia, were invited to participate in the study. The patients were randomized into three groups: control group (NS group, n=11); long chain fat emulsion group (LLE group, n=10); and medium and long chain fat emulsion group(MLE group, n=8). Three groups of patients were pretreated with 0.9 % saline, 20 % LLE or 20 % MLE, also at 2 ml•kg-1•h-1 for 30 min via left upper limb vein. 2 mg•kg-1(including the test dose) of ropivacaine was injected through the epidural catheter. Hemodynamic parameters were recorded during perioperation. Sensory block and the degree of motor block was determined. Ropivacaine plasma concentrations were measured from artery plasma samples at 1, 5, 10, 15, 30, 45, 60, 90, 120 minutes after total ropivacaine was given. Results No differences were observed between groups in onset time of sensory and motor block, time to maximum spread of sensory block, the segment of spinal nerve block, persistent time of sensory and motor block. The plasma ropivacaine concentration among all groups had no differences at each time. Conclusions Pretreatment of LLE and MLE had no effect on plasma concentration and pharmacodynamics of ropivacaine during epidural anesthesia in adults undergoing lower limb operations.