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.