The Addition of a Saddle Block With Intrathecal Morphine for Analgesia in Transgender Patients Undergoing Penile Inversion Vaginoplasty: A Randomized Double-blind Placebo-controlled Trial

PIV is a TRS offered for male-to-female transition associated with severe postoperative pain despite contemporary analgesic strategies, including opioid-based multimodal systemic analgesia and local anesthetic-based pudendal nerve block. Intrathecal opioids directly target the nociceptors in the spinal cord and can provide potent analgesia for abdominopelvic procedures, including PIV, but are associated with important dose-related adverse effects with rostral spread within the cerebrospinal fluid.

Motor-sparing saddle block using ultra-low dose hyperbaric spinal anesthesia has been successfully implemented as the standard of care for anesthesia in patients undergoing ambulatory perianal procedures at WCH. Saddle block produces reliable sensory anesthesia and long-lasting analgesia of the perineum ("saddle") as the hyperbaric local anesthetic preferentially blocks the small pain fibers of the sacral nerve roots with gravity when the patient is placed in the seated position. With the aim to directly target the opioid nociceptors in the sacral roots and limit rostral opioid spread (and associated opioid-related adverse effects), we recently began to offer a presurgical saddle block with a low dose of intrathecal morphine (100mcg) to patients undergoing PIV at WCH with excellent anecdotal results. Therefore, we are undertaking the present randomized placebo-controlled study to determine whether or not the addition of a saddle block with IT morphine to multimodal systemic analgesia and surgeon-administered pudendal nerve block provides superior analgesia to multimodal systemic analgesia and surgeon-administered pudendal nerve block alone.