Femoral Nerve Block: Single Injection versus Continuous Infusion for Total Knee Arthroplasty

BACKGROUND AND OBJECTIVES: This study was conducted to ascertain whether there is any advantage to the continuous-infusion femoral 3-in-1 nerve block over the single-injection femoral nerve block for postoperative analgesia after total knee arthroplasty. METHODS: A double-blind, randomized, controlled study was made of 33 patients undergoing total knee arthroplasty, who were randomized into three groups. Group 1 received a single-injection femoral 3-in-1 nerve block with 20 mL 0.5% bupivacaine with 1:200,000 epinephrine. Group 2 had a catheter placed in the femoral nerve sheath, through which a continuous femoral 3-in-1 nerve block was established. Group 3 patients served as controls. All blocks were performed and assessed prior to induction of standardized general anesthesia. All patients received morphine via patient-controlled analgesia. Pain was recorded on a 100-mm visual analog scale at rest and with motion of the knee. Opioid consumption and side effects were recorded; P = .05 was considered statistically significant. RESULTS: In the recovery room, pain scores with motion were lower in the single-injection and continuous-infusion groups (P < .05). There were no significant differences between any of the groups regarding pain scores or morphine requirements beyond the recovery room. The incidence of nausea was higher in the control group. There were no differences between the groups with respect to overall patient satisfaction. CONCLUSIONS: We were unable to confirm improvements in analgesia provided by continuous-infusion femoral 3-in-1 nerve block for total knee arthroplasty except in the recovery room.