Effect of remimazolam on MACBAR of sevoflurane in gynecological laparoscopic surgery: a randomized controlled trial

Background: Previously, our study revealed that remimazolam effectively reduces end-expiratory sevoflurane minimum alveolar concentration (MAC) values during laryngeal mask placement in adults. However, the combined effect of remifentanil and sevoflurane in MAC for blocked adrenergic response (MACBAR) remained unclear. In this study, we aimed to investigate the effects of different doses of remimazolam combined with remifentanil on sevoflurane MACBAR in patients undergoing gynecological laparoscopic surgery. Methods: Overall, 120 patients, aged 20–45 years, with elective gynecologic laparoscopic surgery and categorized under the American Society of Anesthesiologists grade were selected. They were then randomly categorized into one control group (R0) and three remimazolam groups (R1, R2, and R3), each comprising 30 patients, using a randomized numeric table method. Anesthesia was induced in all patients through intravenous injection of propofol (2 mg/kg), cisatracurium (1.5 mg/kg), and remifentanil (3 ng/ml) via target-controlled infusion. Mechanical ventilation was performed after tracheal intubation, and anesthesia was maintained by inhaling sevoflurane. The plasma concentration of remifentanil was adjusted to 1 ng/mL via target-controlled infusion. Group R0 pumped an equal volume of saline, while groups R1, R2, and R3 continuously pumped remimazolam at 1.0 mg/kg/h, 1.5 mg/kg/h, and 2 mg/kg/h, respectively. The end-expiratory sevoflurane concentration for patients in each group was adjusted to the preset value for at least 20 min. Heart rate and mean arterial pressure were recorded at several time points: before induction of anesthesia, 3 and 1 min before, and 1 and 3 min after pneumoperitoneum induction in all four groups. The sevoflurane MACBAR was determined using sequential and up-and-down methods. Results: The MACBAR of sevoflurane in groups R0, R1, R2 and R3 were (2.46 ± 0.18)%, (2.18 ± 0.16)%, (1.81 ± 0.15)% and (1.47 ± 0.18)%, respectively. Compared to the R0 group, the R1, R2, and R3 sevoflurane MACBAR were significantly lower (P < 0.05). Conclusions: Remimazolam reduced sevoflurane MACBAR in patients undergoing gynecologic laparoscopic surgery and increased in a dose-dependent manner.