Rectus sheath block (RSB) is a kind of anterior abdominal wall block. It has postoperative analgesic effect for abdominal surgery with midline incision. Robotic gynecologic surgery is accompanied by significant postoperative pain and usually IV-PCA is used to manage the pain.The purpose of this study is to investigate the analgesic effect of ultrasound-guided RSB to single-port robotic gynecologic surgery which has incision site at umbilical area. Patients will randomly assigned to two groups, RSB group and Control group. Each patients will assessed for time to first rescue analgesia, verbal numerical rating pain scores, number of rescue analgesic demands, and postoperatively opioids use by IV-PCA by a blinded investigator at 0, 1, 6, 12, 24 and 48 hours postoperatively.

Patients of RSB group will be performed ultrasound-guided bilateral RSB after induction of general anesthesia. The procedure will be performed bilaterally and 15 ml on each side, total 30 ml of 0.25% ropivacaine will be injected. After the procedure, a surgery scheduled will be proceeded. Patient of Control group will be proceeded the surgery after induction of anesthesia. All patients will use total 100 ml of IV-PCA containing 800 µg of fentanyl for 48 hours postoperatively. If a patient complains pain more intense than VNRS 4 or demands an analgesic drug, a rescue analgesic would be allowed.

Inclusion Criteria:

• Robotic single-port gynecologic surgery
• American society of Anesthesiologists (ASA) physical status classification I-II
• Age: 21-60

Exclusion Criteria:

• Gynecologic cancer operation
• History of previous abdominal surgery
• Allergy to local anesthetics(ropivacaine)
• Opioid tolerance
• Coagulopathy
• Infection at the needle insertion site
• Difficulty to cooperating