Comparison of the analgesic effects continuous epidural anesthesia and continuous rectus sheath block in patients undergoing gynecological cancer surgery: a non-inferiority randomized control trial

Purpose We investigated the non-inferiority of continuous rectus sheath block to continuous epidural anesthesia for postoperative analgesia of gynecological cancer patients. Methods One hundred ASA-PS 1–2 patients via a median incision up to 5 cm above the navel were randomized into a continuous epidural anesthesia (CEA) group and a continuous rectus sheath block (CRSB) group. Following surgery, they have controlled with intravenous patient-controlled analgesia (IV-PCA) as basal postoperative analgesia. For patients in the CEA group were administered 0.25% levobupivacaine at 5 mg/h. Patients in the CRSB group, catheters were inserted on both sides of the posterior rectus sheath after surgery. They received 0.25% levobupivacaine on both sides at 7.5 mg/h. To determine whether CRSB is non-inferior to CEA in postoperative treatment, pain at rest and movement was assessed using the Numerical Rating Scale (NRS). The non-inferiority margin of NRS difference between CRSB and CEA was set at 1.3 difference in means. The primary outcome was non-inferiority comparisons of NRS at rest/at movement after surgery, while the secondary outcome included the frequency of requesting IV-PCA and rescue drugs. Results NRS at rest in the CRSB group was not inferior to that in the CEA group. On the other hand, the NRS at movement at 4, 6, 8, 12 h following surgery in the CRSB group was inferior to CEA. There was no difference in the frequency of requesting IV-PCA and rescue drugs. Conclusions CRSB showed the non-inferiority to CEA for postoperative analgesia at rest, while CRSB was not non-inferior to CEA at movement in gynecological cancer patients. CRSB would be a substitute when CEA is contraindicated as a component of postoperative multimodal analgesia.