EC50 and EC95 of Epidural Ropivacaine for Intraoperative Analgesia During High-Intensity Focused Ultrasound for Adenomyosis: A Prospective Double-Blind Up-and-Down Concentration-Finding Study.

PURPOSE: Regarding anesthesia management for high-intensity focused ultrasound (HIFU) treatment of uterine adenomyosis, existing research is limited. While considered non-invasive, HIFU ablation carries risks such as thermal injury to adjacent structures like nerves if the focused energy deviates from the target. Therefore, the procedure requires that patients remain perfectly still while retaining sufficient consciousness to immediately report warning sensations like cutaneous burning or radiating leg pain. This unique requirement renders conventional anesthetic approaches inadequate. General or neuraxial anesthesia impair sensory feedback, while traditional intravenous sedation presents challenges in balancing analgesia with respiratory safety and patient communication. Epidural analgesia with low-concentration ropivacaine offers a potential solution due to its favorable sensory-motor dissociation, which can maintain analgesia and immobility while preserving the patient's ability to communicate. Previous studies support the efficacy of this approach, but the optimal drug concentration remains undefined. This study aimed to determine the median effective concentration (EC50) and 95% effective concentration (EC95) of ropivacaine combined with sufentanil (0.5 µg/mL) for epidural analgesia during HIFU treatment of adenomyosis.

PATIENTS AND

METHODS

This prospective study ultimately included 29 patients with adenomyosis undergoing HIFU with intraoperative epidural analgesia. The epidural solution contained ropivacaine (concentrations determined through an up-and-down sequential method, starting at 0.06% for the first patient) and sufentanil 0.5 µg/mL. After a 5 mL test dose, a 15 mL bolus was administered, followed by 10 mL maintenance doses every 40 minutes. Successful analgesia was defined as an intraoperative visual analog scale (VAS) score < 4.

RESULTS

The EC50 of epidural ropivacaine with sufentanil 0.5 µg/mL was 0.079% (95% CI, 0.075-0.084%), and the EC95 was 0.089% (95% CI, 0.084-0.118%).

CONCLUSION

These findings provide critical dose references for optimizing intraoperative analgesia during HIFU for adenomyosis.