Korean J Anesthesiol Introduction Combined spinal epidural anesthesia (CSE) is now in widespread use because it can reduce or eliminate some of the disadvantages of spinal and epidural anesthesia while also preserving their advantages. It offers the speed of onset, efficacy, and minimal toxicity of a spinal block combined with the potential of improving an inadequate block or prolonging the duration of anesthesia with epidural supplements, and extending the analgesia into postoperative period [1]. These advantages make the CSE useful to surgical anesthesia in total knee replacement arthroplasty (TKRA). However, patients undergoing TKRA are usually elderly, and they often have concomitant diseases that compromise cardiovascular and pulmonary function and spinal stability. On occasion, the anatomical deformity caused by a degenerative change of the vertebral column or by morbid obesity, the uncompensated hemodynamic response to CSE-induced physiologic changes resulting from severely decreased cardiac function, and the antiplatelet and anticoagulant therapy preventing ischemic cardiac events make CSE inappropriate to surgical anesthesia for TKRA [2]. These factors even prevent general anesthesia practices from being conducted [3]. With the presence of these factors, alternative anesthetic techniques are needed to perform TKRA. There are many reports about femoral/sciatic nerve block as a postoperative analgesia after TKRA, but few reports about femoral/sciatic nerve block as surgical anesthesia. We therefore compared the efficacy of femoral/sciatic nerve block with lateral femoral cutaneous nerve block (FSNB) and CSE during the perioperative period. Materials and Methods After obtaining approval from the institutional review board, and informed consent, the observational study was carried out on 84 consecutive patients undergoing elective unilateral TKRA. The anesthetic technique used was based on surgeon, anesthesiologist, and/or patient preference. All TKRAs were performed under CSE (n = 42) or FSNB (n = 42). In the CSE group, the epidural space below L2 was identified using a loss of resistance to saline. Next, an extra long 27-gauge pencil-point spinal needle was introduced through the Tuohy needle. When correct placement of the spinal needle had been confirmed by free flow of cerebrospinal fluid (CSF), 1.3 ml of 0.5% hyperbaric bupivacaine was injected, and the spinal needle was then withdrawn. After withdrawing the spinal needle, 10 ml of 0.75% ropivacaine was injected, and a catheter was introduced, about 4-5 cm into the epidural space through the Tuohy needle. In the FSNB group, femoral nerve block was performed www.ekja.org Kim, et al. using Winnie’s technique. Following contraction of the qua- driceps femoris muscle and movement of the patella with 0.5 mA at 1 Hz using nerve stimulator, 20 ml of 1.5% mepivacaine were injected. The lateral femoral cutaneous nerve block was performed by the injection of 5 ml of 1.5% mepivacaine, 2.5 cm medial, and 2.5 cm caudal to the anterior superior iliac spine. The sciatic nerve block was based on Labat’s technique. After contractions of the gastrocnemius (foot plantar flexion) and/ or tibialis anterior (foot dorsi-flexion) using a stimulus of 0.5 mA at 1 Hz, 20 ml of 1.5% mepivacaine were injected. Urinary catheters were placed in all patients and were continued until 48 hours postoperatively. In the event of an incomplete blockade, intravenous injection of 30 mg of ketorolac, 100 μg of fentanyl, and a continuous infusion of propofol (3 mg/kg/hr) with 1 mg/kg of bolus were used sequentially for additional analgesia as common practice in our institution. If systolic blood pressure and heart rate were decreased below 100 mmHg and 50 bpm, 10 mg of ephedrine and 0.5 mg of atropine were administered, respectively. In the event of shivering, 25 to 50 mg of meperidine was administered intravenously, and intravenous administration of ondansetron (4-8 mg) or ramosetron (0.1-0.2 mg) was used when the patient complained of nausea or vomiting. At the end of surgery, the epidural catheter in the CSE group was removed, and intravenous patient-controlled analgesia (IV PCA) composed of 1,000 μg of fentanyl, 150 mg of ketorolac, and 0.3 mg of ramosetron, with a total volume of 100 ml, was initiated for postoperative analgesia, without any supplemental blockades, and was maintained for 48 hours. And the IV PCA settings were a bolus of 1 ml, a lockout interval of 15 minutes with no limit, and 2 ml/hr of background infusion. For each group, time from the start of drape for anesthetic procedure to the end of local anesthetic injection (preparation time), duration of surgery and time elapsed from the end of local anesthetic injection to the end of the surgery (total anesthetic time) were described. In addition, intraoperative side effects, such as hypotension (systolic blood pressure < 100 mmHg), bradycardia (< 50 bpm), shivering, nausea/vomiting, for example, and frequency of use of intraoperative medi- cations for managing these side effects were also described. Postoperatively, all the patients were tracked to determine the time lasting from the end of local anesthetic injection to complete resolution of sensory and motor block (complete resolution time), the rate of satisfaction with the surgical anesthesia and the postoperative analgesia, where 0 means extremely dissatisfied and 100 means extremely satisfied, the willingness to recommend the same surgical anesthesia and postoperative analgesia to others, duration of IV PCA use, and remaining amount of IV PCA. And visual analog scale (VAS) pain scores, where 0 indicates “no pain” and 10 indicates 449