The purpose of this study is to evaluate the efficacy and safety of fospropofol disodium for injection compared to propofol for sedation in mechanically ventilated ICU patients.

This is a randomized, open-label, small sample study using fospropofol disodium and propofol for sedation in mechanically ventilated ICU patients. Subjects are randomized to different treatment groups (including 1 for fospropofol disodium and 1 for propofol). Remifentanil is co-administered with fospropofol or propofol. Efficacy and safety profiles of fospropofol disodium are to be evaluated.

Inclusion Criteria:

• Patients aged >= 18 and <= 75 years; Endotracheal intubated; Patients currently on mechanical ventilation <= 96 hours and expected to be mechanically ventilated >= 24 hours; Demand for light/moderate sedation (a RASS score of -3 to 0).

Exclusion Criteria:

• Informed Consent is unsigned； Participated in any other interventional research within 3 months; Tracheostomy; BMI <= 18 and >= 35 kilograms per square meter Pregnant; Lactant; Known or suspected allergy to various components of the study drug or to opioids and their salvage drugs, or other diseases (such as pancreatitis associated with hyperlipidemia) for which lipid emulsion should not be used; Patients who cannot be evaluated for RASS for various reasons (such as mental illness, acquired or congenital mental retardation, deafness, severe neuromuscular disease, Parkinson's disease, Huntington's disease, Alzheimer's disease, cerebrovascular disease, coma, or severe cognitive impairment due to structural diseases such as stroke, intracranial hemorrhage, head injury, malignancy, hypoxic brain injury, or cerebral edema); Patients with an expected survival period of less than 48 hours; Severe hepatic insufficiency (CTP score is 10-15 points); Chronic kidney disease (CKD grade 3 above); Unstable angina pectoris or acute myocardial infarction; Left ventricular ejection fraction <= 30%; Heart rate < 50bpm(intravenous pumping of isoproterenol <4ug/min, heart rate ≥50bpm may not be excluded); Type 2 second-degree or third-degree atrioventricular block (except those implanted a pacemaker); Two vasoconstrictors are used to maintain SBP above 90mmHg after sufficient fluid resuscitation; Myasthenia gravis; Patients with a history of drug abuse, drug abuse, alcohol abuse and long-term use of psychotropic drugs within 2 years before the screening period. Binge drinking is defined as regular drinking more than 14 times per week (1 time = 150ml of wine or 360ml of beer or 45ml of spirits);