Can a nerve block during surgery reduce pelvic pain and opioid use in women with endometriosis?

Intervention Name: Arm 1 – SHP Block: Intraoperative Superior Hypogastric Plexus (SHP) block with local anaesthetic Arm 2 – Placebo Control: Intraoperative sham injection with normal saline Intervention Description (Arm 1 – SHP Block) Brief name: Intraoperative Superior Hypogastric Plexus (SHP) block with 0.25% bupivacaine Materials: Standard surgical supplies, including 10–20 mL of 0.25% bupivacaine, 22G spinal needle, and syringes. No additional patient-facing materials are used. Procedures: After induction of general anaesthesia, participants randomised to the intervention group will receive an SHP block performed under direct laparoscopic visualisation. Using a 22G spinal needle, the surgeon will inject 10–20 mL of 0.25% bupivacaine into the retroperitoneal space at the location of the superior hypogastric plexus, typically just inferior to the aortic bifurcation, anterior to the L5 vertebral body. Provider and expertise: Administered by a consultant gynaecological laparoscopic surgeon or a trained fellow with experience in pelvic nerve blocks under supervision. Mode of delivery: Face-to-face during surgery under general anaesthesia. Delivered individually to each participant. Timing and dose: A single dose of bupivacaine (10–20 mL of 0.25%) is administered once intraoperatively. Location: Operating theatres at Mater Mothers Hospital, Brisbane, within the Advanced Laparoscopy Gynaecological Unit. Adaptation: The intervention is not titrated or adapted. Standard volume and technique are used in all patients. Fidelity and adherence: Fidelity will be assessed by surgical documentation, intraoperative photography, and adherence to the standardised SHP block protocol. Fidelity checks will be conducted periodically by the principal investigator.