Prospective Dose-Finding of Esketamine for Suppressing Cervical Dilation Response in Ambulatory Hysteroscopy Under Monitored Anesthesia Care.

BACKGROUND

Cervical dilation during ambulatory hysteroscopy often triggers somatic responses that challenge patient comfort and procedure smoothness. While esketamine's unique analgesic profile could address this, its effective dose within a dexmedetomidine-remifentanil monitored anesthesia care (MAC) protocol is undefined.

METHODS

In this prospective, double-blind, dose-finding study, 30 women received a standardized MAC protocol (dexmedetomidine 0.6 μg∙kg-1 loading dose followed by 0.4 μg∙kg-1∙h-1, with remifentanil 5 μg∙kg-1∙h-1). Esketamine was administered via Dixon's up-and-down sequential design (initial dose 0.3 mg∙kg-1; increments/decrements 0.02 mg∙kg-1) before cervical dilation. Positive response is defined as the absence of purposeful movement. The median effective dose (ED50) and 95% effective dose (ED95) were calculated using probit regression.

RESULTS

30 patients completed the study. The ED50 of esketamine was 0.36 mg∙kg-1 (95% CI 0.35-0.37) and the ED95 was 0.39 mg∙kg-1 (95% CI 0.37-0.42). Hemodynamic stability was maintained (mean arterial pressure change ≤15% from baseline) with no respiratory depression. Adverse events were self-limiting dizziness (66.7%) and nausea (6.7%). Recovery was swift, with a time to meet post-anesthesia care unit (PACU) discharge criteria of 17.93±3.30 min, and patient satisfaction was high (median score 9/10, IQR 8-10).

CONCLUSION

Under dexmedetomidine-remifentanil MAC, esketamine 0.39 mg∙kg-1 (ED95) effectively suppresses the cervical dilation response, promotes hemodynamic and respiratory stability, and facilitates a rapid, enhanced recovery after surgery (ERAS)-compliant recovery. This dose-finding study provides a practical and effective anesthetic combination for clinical implementation in ambulatory hysteroscopy.

CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov (identifier: NCT07034963). Principal Investigator: Lijuan Yan.