Long-term Sedation With Remimazolam Besylate in Critically Ill Patients

Inclusion Criteria: * Age ≥ 18 and ≤ 80 years; * Intubated and mechanically ventilated ≤96 hours before enrollment； * Expected to require continuous invasive ventilation and sedation ≥24 hours; * Requirement for light to moderate sedation (a RASS score of -3 to 0) Exclusion Criteria: * Body mass index (BMI) \<18 or \>30 kg/m2; * Allergy or unsuitabilty to any composition of study drugs or remifentanil; * Living expectancy less than 48 hours； * Possible surgey in the operating room in 24 hours； * Myasthenia gravis; * Serious hepatic dysfunction (CTP 10-15); * Chronic kidney disease with glomerular filtration rate (GFR) \< 29 ml/min/1.73m2; * Systolic blood pressure less than 90 mm Hg after appropriate intravenous volume replacement and continuous infusions of 2 vasopressors; * Acute severe neurological disorder and any other condition interfering with RASS assessment; * Pregnancy or lactation; * Unstable angina or acute myocardial infarction; * Left ventricular ejection fraction less than 30%; * Heart rate less than 50 beats/min; * Grade 2 , second degree or third degree atrioventricular block in the absence of a pacemaker; * Abuse of controlled substances or alcohol; * Other conditions deemed unsuitable to be included;