Inclusion Criteria:  Patients or their guardians are able to provide a written informed consent 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 Meet the age criteria, male or female Meet the BMI criteria  Exclusion Criteria:  Deep sedation is required, or continuous sedation is not needed during the study process Subjects with a history of severe cardiovascular disease, or cerebrovascular disease, or neurological disease, or mental illness Subjects with a history of drug abuse Subjects after neurosurgery operation Organ failure before randomization Abnormal values of the laboratory examination Abnormal blood pressure and heart rate during screening Allergic to relevant drugs ingredient or component Pregnant or nursing women Subjects who has participated in clinical trials of other interventions recently