Total intravenous anesthesia in combination with remimazolam and remifentanil without a neuromuscular blocking agent: a prospective observational study

Background: A novel short-acting benzodiazepine, Remimazolam, has recently been approved for general anesthesia and sedation. Hence, we investigated the feasibility and safety of remimazolam during the induction and maintenance of general anesthesia without using a neuromuscular blocking agent (NMBA) in patients undergoing hysteroscopic surgery. Methods: : This prospective observational study included 38 patients undergoing hysteroscopic surgery. Remimazolam and remifentanil were the main anesthetic agents without an NMBA, and a supraglottic airway was inserted to protect the airway. The induction time, amount of each anesthetic agent used during anesthesia, intraoperative bispectral index (BIS) hemodynamic parameters, and recovery profiles were measured. Results: : General anesthesia was successfully administered to 37 patients using remimazolam and remifentanil without NMBA. The induction doses of remimazolam and remifentanil were 0.4 mg/kg (interquartile range [IQR] 0.34–0.47 mg/kg) and 1.07 μg/kg (IQR, 0.90–1.29 μg/kg), respectively. Additionally, the maintenance doses of remimazolam and remifentanil were 1.14 mg/kg/h (IQR, 0.88–1.55 mg/kg/h) and 0.06 μg/kg/min (IQR, 0.04–0.08 μg/kg/min), respectively. Intraoperative BIS values had risen temporarily >60 in eight patients (21.6%) despite administration of 2 mg/kg/h of remimazolam; thus, they were treated with supplementary midazolam. The median recovery time was 7 min (IQR, 5–8 min) after approximately 40 min (IQR, 40.0–57.5 min). There was no correlation between the infusion dose of remimazolam and recovery profiles, such as recovery time, recovery BIS, modified observer assessment of alertness/sedation (OAA/S) scale in the post-anesthesia care unit (PACU), post-anesthesia recovery (PAR) score in the PACU, and length of stay in the PACU (all P >0.05). Conclusion: Remimazolam can be combined with remifentanil without an NMBA in female patients who undergo hysteroscopic surgery, during which a supraglottic airway is a feasible method to protect the airway. Trial registration: The study protocol was registered at ClinicalTrials.gov (NCT05025410) on 27/08/2021.