A Study Evaluating Sedation of Intravenous Administration of HSK3486 Injectable Emulsion in ICU Patients Undergoing Mechanical Ventilation

Inclusion Criteria: 1. Patients who require tracheal intubation for mechanical ventilation are expected to require 6-24 h of sedation after randomization; 2. The target RASS for the required sedation of patients ranges from +1 to -2 points; 3. Aged ≥ 18 and \< 80 years old, with no gender requirement; 4. 18 kg/m2 ≤ BMI ≤ 30 kg/m2; 5. The patients or their family members fully understand the objectives and significance of this study, and voluntarily participate in this clinical study and sign the informed consent form. Exclusion Criteria: 1. Patients known to be allergic to eggs, soy products, opioids and their antidotes, and propofol; patient having contraindications to propofol, opioids and their antidotes; 2. Patients who have received sedation for more than 3 days in the ICU or in the general ward before being transferred to the ICU before signing informed consent form; 3. Patients having the following medical history or evidence of any of the following at screening, which may increase sedation/anesthesia risk: 1. Cardiovascular system: New York Heart Association (NYHA) Class III and IV heart failure, Adams-stokes syndrome; acute coronary syndrome (ACS) that occurs within 6 months before screening; bradycardia requiring medication and/or heart rate ≤ 50 beats/min; a history of severe arrhythmia such as II-III degree atrioventricular block (excluding patients using pacemakers); acute and chronic myocarditis; patients who require vasoactive drugs to maintain a normal blood pressure; 2. Patients with mental system disorders (such as schizophrenia, depression, etc.) and cognitive disorders; patients with a history of abuse of psychotropic drugs and anesthetics; patients with a history of alcohol abuse within 3 months prior to screening; patients with a history of drug abuse; patients with a history of long-term use of psychotropic drugs, etc.; 3. Severe hepatic and renal insufficiency (liver function: refer to child-pugh grade C, the scale is shown in Appendix 6; renal function: glomerular filtration rate eGFR ≤ 30 mL/(min•1.73 m2) \[eGFR is calculated using the Modification of Diet in Renal Disease (MDRD) equation: eGFR = 175 × serum creatinine (SCr)-1.234 × age-0.179 × 0.79 (females)\]; patients undergoing dialysis; 4. Grand mal epilepsy and convulsion; craniocerebral injury, intracranial hypertension, cerebral aneurysm; a Glasgow coma scale (GCS) of ≤ 12 points (see Appendix 4 for the scale); a SOFA scale of \> 9 points (see Appendix 5 for the scale); patients with high paraplegia and general paralysis; 5. Expected survival of ≤ 72 h. 4. Pregnant or lactating females; women or men of child-bearing potential who are unwilling to use contraception through the study; subjects who are planning pregnancy within 1 month after the study (including male subjects); 5. Have participated in any other clinical trials within 1 month prior to screening; 6. Other conditions that patients are judged by the investigator to be unsuitable for participating in the study.