Intensive care medicine is vital in managing patients after cardiac surgery with endotracheal intubation，in order to provide extensive monitoring to assure clinical stabilization. During this time of recovery, sedation is frequently employed. However, prolonged sedation risks negative sequelae.At present,propofol, benzodiazepines, and dexmedetomidine are typical drugs used for sedation of patients in intensive care unit.Each has its own advantages and disadvantages.The investigators try to find near-ideal agents for sedation,characterized by good sedative effect,minimal adverse effects and rapid awakening facilitating earlier extubation.Remimazolam appeared to be an effective and safe sedative for short term sedation. Study participants were predicated on age (> 18 years), admission following cardiac surgery, still mechanical ventilation within 48 hours,and prior informed consent.Participants were randomized to receive remimazolam besylate or propofol in a 1:1 ratio for sedation with a target sedation depth before extubation.Finally，the investigators will compare the sedation effect and safety between the 2 groups ，to prove if remimazolam is appropriate for sedation in patients after cardiac surgery in intensive care unit.

Inclusion Criteria:

1. age ≥ 18 years ;
2. admitted to the intensive care unit after cardiac surgery with techanical ventilation；
3. expected to extubation within 48hours ；
4. participant has given informed consent

Exclusion Criteria:

1. pregnant or lactating women
2. known or suspected hypersensitivity to the study drug
3. history of impaired consciousness or psychiatric illness
4. severe bradycardia with a heart rate of < 50 beats per minute
5. systolic blood pressure < 90 mmHg with fluid resuscitation and vasopressor maintenance
6. atrioventricular block（II or III degree）, Left ventricular ejection fraction(LVEF) <30%
7. participated in other clinical studies within 3 months

After the study results are published

You can explain the reason and contact the study initiator via email to request the data. The email address is:yuwenqiao1980@zju.edu.cn