This study was approved by the Ethics Committee of Weifang People’s Hospital (KYLL20231126-1) and registered at the Chinese Clinical Trials Registry (ID: ChiCTR2400081688; Date:08/03/2024). Written informed consent was obtained from all patients before enrollment. The principles of Declaration of Helsinki were followed for this study. This manuscript adheres to the applicable CONSORT guidelines.

Fifty ASA I ~ II patients scheduled for elective day hysteroscopy under total intravenous anesthesia were selected. Exclusion criteria: patients with pregnancy, lactation, history of chronic pain, history of sedatives and analgesics, and allergy to any research drug. Exclusion criteria: patients with abnormal hearing; patients with blood pressure more than 180 / 110 after admission; there are patients who are allergic to drugs such as remimazolam and addicted to sedative drugs and alcohol; patients with cognitive impairment and low compliance; patients lost to follow-up after surgery, etc. According to the random number table method, they were divided into two groups: remimazolam tosilate group (group T) and remimazolam besylate group (group R), with 25 patients in each group.

The study drugs were prepared by an anesthesiology nurse, who had been given a detailed description of the programme and was aware of the patient’s distribution. Before the operation, the anesthesia nurse diluted the remimazolam besylate or remimazolam tosilate to 1 mg/ml and placed it in a sterile sealed bag. Anesthesiologists who did not know the specific types of drugs were given anesthesia by anesthesiologists when anesthesia was performed. Surgeons and patients were also unaware of the drugs administered. Data collection was performed by another independent anesthesiologist who was unaware of the group assignment.

The patients were routinely fasted and fasting, and no preoperative medication was given. After entering the room, the forearm vein channel of the upper limb was opened and the rapid infusion was performed. The ECG, SPO2, NIBP and BIS were monitored and the basic values were recorded. Before anesthesia induction, flurbiprofen 50 mg and dexamethasone 5 mg were intravenously injected. The two groups of patients were treated with the same anesthesia method, but the patients in each group were treated with different dosage forms of remimazolam. Anesthesia induction: Remimazolam 6mg / kg / h pump to sleep, and then given mivacurium chloride 0.2mg / kg and alfentanil 20ug / kg slow injection, 3min after the insertion of laryngeal mask. Anesthesia was maintained with intravenous infusion of remifentanil 1 mg / kg / h and alfentanil 40 ug / kg / h. The BIS value was maintained between 50 and 60, and mivacurium 0.1 mg / kg was injected intermittently when necessary. Ventilator-assisted breathing was performed during the operation. The parameters were set as follows: tidal volume 6-8ml / kg, respiratory rate 10–12 times / min, respiratory ratio 1: 2, and end-tidal CO2 maintained at 35–45 mmHg. After the operation, the drug was discontinued, and the tracheal tube was removed after fully awake and sent to PACU for observation for 2 h. When the Aldrete score was greater than 9 points, they were sent back to the ward.

The main observation index was the induction dose of remifentanil anesthesia; secondary observation indicators were sleep time, anesthesia maintenance time, recovery time, induction maintenance dose of alfentanil, maintenance dose of remimazolam, and incidence of adverse events during anesthesia (hypertension, hypotension, bradycardia, tachycardia).

Statistical methods SPSS25.0 software was used for statistical analysis, and the data were tested for normality and homogeneity of variance. The measurement data of normal distribution were expressed as mean ± standard deviation, independent sample T test was used for comparison between groups, and the median (interquartile distance) [M (Q1 ~ Q3)] was used for continuous variables of non-normal distribution, and rank sum test was used for comparison between groups. Counting data were expressed as a percentage, and the chi-square test was used for comparison between groups. P < 0.05 was considered statistically significant.