In modern anesthesia practice, anesthesiologists often need to choose a combination of multiple drugs according to the specific conditions and surgical needs of patients, which can not only achieve more fine anesthesia management, but also improve perioperative safety and patient comfort. In clinical practice, anesthesiologists will use etomidate combined with a small dose of remimazolam for anesthesia induction to obtain more stable hemodynamics, prevent intraoperative awareness, and relieve anxiety.However, what is the best dose ratio of etomidate combined with remimazolam, the current literature does not give clear indicators.

The experiment was divided into two steps. Step 1: Patients were randomly divided into group A (remimazolam induction group) and group B (etomidate induction group) according to the random number table, and group A was selected according to the literature. In group B, the initial dose was 0.2mg/kg, and 0.120mg/kg, and the ratio of successive doses was 1:0.8 and 1: 0.6, the ED50 of group A and group B was calculated by the sequential method, and the calculated remimazolam and etomidate were used as the initial doses of subgroups Step 2: According to the random number table, the patients were divided into group C (0.25ED50 remimazolam +0.75ED50 etomidate), group D (0.5ED50 remimazolam +0.50ED50 etomidate), group E (0.75ED50 remimazolam +0.25ED50 etomidate), and the dose of remimazolam in each group was fixed. The ED50 of etomidate in group C, group D and group E were calculated by sequential method.

Anesthesia methods: One hundred and twenty-five patients of both sexes, aged 18-60 yr, of American Society of Anesthesiologists physical status I-II, BIM: 18-30kg/m2, undergoing general anesthesia in the Second Hospital of Shanxi Medical University, were selected. Before operation, the patients were required to fast and drink, and had not received special preoperative medication. After the patient entered the room, blood pressure, heart rate, oxygen saturation and BIS were monitored and oxygen inhalation was given to the mask for 5L/min. After the tripartite verification was correct, intravenous access was established in the patient's upper limb, fluid infusion was opened, anesthesia was induced, remimazolam and etomidate were injected directly and slowly intravenously, and remimazolam and etomidate were injected for more than 10s according to the dosage of each group. Two drugs were injected at an interval of 10s or more. After the completion of one drug injection, 5ml normal saline was used to flush the tube, and the score was scored 2 minutes after intravenous injection. BIS value of 45-60 was considered as a positive response, and the dose gradient of the next patient was reduced. The observation was calculated as the first patient with positive to negative turning point, and the observation ended when the next patient with positive to negative reaction at the seventh turning point. The secondary outcome measures were the incidence of adverse reactions, changes in heart rate and blood pressure. At the end of the observation, if the patient showed a negative reaction, 0.08mg/kg etomidate was added for sedation, and then sufentanil and rocuronium were given for tracheal intubation in turn, and then surgery was performed.The demographic data of the patients were collected, including: gender, age, height, weight, BIM Statistical methods: probit model was used to calculate ED50 of each group, and the drug correlation coefficient was introduced as 1/(actual dose of remimazolam/ED50 of remimazolam + actual dose of etomidate/ED50 of etomidate). The measurement data with normal distribution were expressed as mean ± standard deviation (x±s). The measurement data with normal distribution between group A and group B were compared by two independent sample t test, and the comparison between group C, group D and group E was compared by one-way analysis of variance. Graphpad prism software was used to make five groups of sequential experimental plots and iso-radiation analysis plots when P<0.05 was considered statistically significant.

Inclusion Criteria:

1. Both sexes
2. aged 18-60 yr
3. ASA physical status I-II
4. BIM: 18-28kg/m²

Exclusion Criteria:

1. allergic to remimazolam and etomidate
2. in pregnancy or lactation
3. serious cardiovascular diseases, long-term alcoholism
4. used sedative drugs or opioids within 24 hours
5. severe mental illness and myasthenia gravis -