Anesthesia for total knee replacement for FSNB since there are no convincing evidence that dosage over 700 mg is safe from systemic toxicity of local anesthetics. Accordingly, the quality of surgical anesthesia in the FSNB group was thought to be unreliable in that the use of intra- operative antihypertensives, analgesics, and sedatives was more frequent (P < 0.05) in the FSNB group than in the CSE group, possibly because of an insufficient blockade of the obturator nerve. In some patients in the FSNB group, analgesia was adequate until a specific time, after which discomfort occurred when the surgeon started hammering for the purpose of fitting prosthesis to the bones. Intravenous midazolam and/or propofol with a secure airway were effective in providing sedation in these patients. The slightly higher rate of satisfaction with surgical anesthesia in the FSNB group (though nonsignificantly, P = 0.078), and no significant difference of the willingness to recommend the same surgical anesthesia to others between the two groups support the effectiveness of the intravenous midazolam and/or propofol in supplementing the insufficient block of the obturator nerve. Pain after TKRA is marginally treated with IV PCA. After TKRA, VAS scores range from 40-80 (of 100) during the immediate postoperative period and slowly decline by the first operative day [14-16]. In this study, it can be assumed that the effects of single- injection blockades of the two groups lasted for over 2 hours postoperatively, when total anesthetic time was subtracted from the complete resolution time (165.8 ± 16.24 in the CSE group and 126.0 ± 27.70 in the FSNB group, P = 0.208). No significant change in postoperative VAS scores suggests that IV PCA provided appropriate analgesia during the period when residual effects of the initial blockades were fading out. In addition, no significant differences in duration of IV PCA use and remaining amount of IV PCA representing the postoperative analgesic consumption, postoperative VAS score of each postoperative hour, the rate of satisfaction with postoperative analgesia, and willingness to recommend the same postoperative analgesia to others between the two groups mean that FSNB achieved a similar degree of the postoperative analgesia in CSE. The fact that the incidence of intraoperative hypotension and bradycardia is higher in the CSE group than in the FSNB group reflects the more frequent use of ephedrine and atropine in the CSE group than in the FSNB group, though no statistically significant differences of the incidence and the frequency of use were found between groups. Chelly et al. [17] demonstrated that hypotension and bradycardia during surgery was significantly decreased with the use of 3-in-1 paravascular and sciatic blocks compared with epidural anesthesia, and Capdevila et al. [18] also reported a significantly elevated incidence of postoperative arterial hypotension in the continuous epidural infusion group, in comparison with the continuous femoral block group. In addition, the incidence of hypotension was higher in patients 452 Vol. 62, No. 5, May 2012 receiving epidural block than in patients receiving CSE [19], so it could be explained that relatively better hemodynamic stability in CSE compared with epidural block made incidence of intraoperative hypotension and bradycardia between the two groups in this study statistically indifferent. The incidence of postoperative side effects, such as dizziness, sedation, postoperative nausea and vomiting (PONV), and pruritus, was similar between the two groups in the present study. Urinary retention, which is one of the most common side effects related to neuraxial blockade, could not be evaluated, because placement of urinary catheters were continued until 48 hours postoperatively in this observational study. Likewise, Davies et al. [20], who did not include urinary retention in the list of side effects, found no significant difference between the two methods. On the contrary, Zaric et al. [21], Singelyn et al. [22], Capdevila et al. [18], and Chelly et al. [17], who included urinary retention in the list of side effects, found less side effects occurred in the patients with a single-shot FSNB or continuous femoral nerve block. Recently, introduction of ultrasound imaging techniques to peripheral nerve blocks decreases the dose of local anesthetics required to produce a successful surgical block and the time required to perform the procedures, and also provides improve- ments in onset and success of sensory block. Nevertheless, nerve stimulation should be an essential part of ultrasound guided technique, as ultrasound alone only had a 60% success rate [23]. Further, ultrasound-aided peripheral nerve stimulated block is perhaps the optimal way to achieve a successful block, especially at the beginning of a learning process [24]. Thus, unavailability of ultrasound at the time of FSNB implies the limitation of our study. By decreasing the dose of local anesthetics required for FSNB under ultrasound guidance, it should have been possible to perform an additional obturator block, which could not be blocked consistently by femoral 3 in 1 block. At this point, we are expecting that using ultrasound imaging techniques in performing FSNB and obturator block in the patient undergoing TKRA will yield more positive results than the present study. Finally, there are no significant differences of intraoperative and postoperative parameters that we measured except intra- operative use of antihypertensives, analgesics, and sedatives. The results of this study demonstrate that FSNB in addition to a sophisticated use of intraoperative medications, such as sedatives, antihypertensives, and analgesics, provides effective unilateral anesthesia in patients undergoing TKRA as much as CSE. And early postoperative analgesia of single-shot FSNB performed at the beginning of the surgery was also similar to single-shot CSE. However, FSNB cannot be the first choice for TKRA, such as CSE or general anesthesia. It should be used as a third alternative for the situation where CSE or general www.ekja.org