Postoperative pain control after TKA Introduction With the growth of the aging population and regressive disorders, the need for total knee arthroplasty (TKA) has grown. However, its postoperative pain is severe and 60% of the patients complain of severe pain and 30% complain of moderate pain [1]. The postoperative pain of TKA prevents the use of physical therapy and rehabilitation therapy, which is intensive in the early period. This ultimately results in a bad prognosis [2]. Therefore, many studies have attempted to design method to reduce the postoperative pain of TKA. The commonly used intravenous patient controlled analgesia (IVPCA) is easy to set up, but a large dose of opioids is used to control the pain at the local surgical site or a small dose of opioids is used due to the anxiety of side-effects from overuse. However, these approaches led to cases of failure in pain control [3-5]. On the other hand, continuous nerve blocks have been shown to decrease pain, produce fewer side-effects, and decrease the lengths of hospital stays and rehabilitation when compared to IVPCA [3,6]. The continuous psoas compartment block (PCB), which unilaterally affects a vast area of the lower extremity, is one of the continuous nerve blocks. In this study, continuous PCB was compared to IVPCA with the goal of evaluating their effectiveness in postoperative pain control and their side-effects in TKA patients. Materials and Methods The study was performed on 40 patients who were below the age of 80, American Society of Anesthesiologists (ASA) class I and II, and were undergoing TKA. After the present study received the permission from the Institutional Review Board, the authors told the patients and guardians the purpose of the study, explained to them the possible side-effects, and got their informed consent. The patients were randomly grouped as follows: patients with IVPCA were placed into Group IVPCA (n = 20), patients who got a PCB by approaching the area of the 3rd lumbar nerve were put into Group PCB (n = 20). Patients who had allergies to the drugs used in the study such as local anesthetics, a severe liver or kidney disorder, contraindications to having a peripheral nerve block (infection, coagulation disorder, or a disorder of the nervous system affecting the lower extremities), or a BMI of 30+ were excluded from the study. All the patients underwent general anesthesia. In Group IVPCA, 100 μg of fentanyl, 0.5 mg of hydromorphone, 15 mg per 10 kg body weight of keromin and normal saline in a total volume of 45 ml were used. Continuous intravenous administration was applied at a 0.5 ml/hr rate using patient- controlled analgesia [Ambix anaplusⓇ, E-Wha Fresenius Kabi, Korea]. The IVPCA was set so that the patient could have an 48 Vol. 62, No. 1, January 2012 infusion at each occurrence of pain with a 0.5 ml bolus dose and a 15 min lockout time. The IVPCA was maintained until 48 hours after the surgery. The continuous PCB was performed before the surgery. The patients were put into the prone position. Using a C-arm [Exposcop 8000, Ziehm imaging GMBH, Germany], the location of the 4th lumbar vertebra body was confirmed, and 1/3 of the outer area of the transverse process on the same side of the knee receiving surgery was set as the puncture site. At the puncture site, the skin wheel was made using local anesthetics. An epidural needle [Tuohy 18G, PerifixⓇ, B.Braun, Germany] was then inserted vertically into the skin and when the needle touched the transverse process, it was slightly taken out and was advanced parallel to the spine in the direction of the head at a degree of 10-20. At this point, the loss of resistance was confirmed using the air syringe. Afterwards, when the spreading of the contrast agent [IopamiroⓇ300, Bracco, Italy] around the psoas compartment was confirmed (Fig. 1), a catheter [20 G, PerifixⓇ, B.Braun, Germany] was inserted 2-3 cm deeper via a needle, and then the needle was removed. To prevent the movement of the catheter and reduce the risk of infection, subcutaneous tunneling was performed. 0.25% ropivacaine at a bolus dose of 20 ml was infused via the catheter before the surgery. The nerve block was then confirmed using a pinprick test and a cold sense loss. After the surgery, continuous PCB boxter [AutoFuserⓇ, Acemedical, Korea] using 0.2% ropivacaine at a rate of 8 ml/hr was infused while leaving the catheter in place for 48 hours after the surgery. Pain scores were measured using verbal numeric rating scales (VNRS) with a 0 to 100 range at 6 hrs, 24 hrs, and 48 hrs after surgery. During the hospital stay the patients were checked Fig. 1. C-arm images showing that the dye (IopamiroⓇ300) spread over the psoas compartment shadow. www.ekja.org