The purpose of this study is to evaluate the efficacy and safety of Remimazolam Tosilate for Injection for prolonged sedation(≥72h) during mechanical ventilation in the ICU.

Inclusion Criteria:

1. Patients or their guardians are able to provide a written informed consent
2. Subjects have been treated with endotracheal intubation and mechanical ventilation, and is expected to receive sedation after randomization. The target level and duration of sedation meet the criteria
3. Age ≥ 18 and ≤ 80 years, male or female
4. Body mass index (BMI) > 18 and < 30 kg/m2

Exclusion Criteria:

1. participants (other than in endotracheal intubation) who are expected to require neuro-muscle blockers during sedation；
2. Suffering from mental disorders (such as schizophrenia, depression, etc.) and cognitive dysfunction;
3. Organ failure during screening period；
4. Subjects who were receiving dialysis during the screening period or who were expected to require dialysis treatment during the study period;
5. History of epilepsy or status epilepticus;
6. Subjects with a history of drug abuse；
7. Myasthenia gravis or a history of myasthenia gravis;
8. severe arrhythmias or heart disease;
9. Subjects after neurosurgery operation；
10. participants who did not require continuous sedation during mechanical ventilation for endotracheal intubation;
11. Abnormal values of the laboratory examination
12. Subjects who required vasopressor medication to maintain normotensive blood pressure during the screening period (excluding subjects who used vasopressor medication only during surgery);
13. Allergic to relevant drugs ingredient or component;
14. Pregnant or nursing women;
15. Subjects who has participated in clinical trials of other interventions recently;
16. Other conditions deemed unsuitable to be included.