The trial was terminated early because additional sites did not recruit as planned, making the multicenter sample size infeasible. Enrollment ended after 117 participants were randomized at Nanfang Hospital, unrelated to safety, efficacy, or outcomes

Remimazolam besylate, as a new benzodiazepine drug, showing rapid clearance and moderate distribution of pharmacokinetic changes. The study will further explore the safety and effectiveness of remimazolam besylate n the sedation of mechanically ventilated patients after oral and maxillofacial surgery in the ICU.

Remimazolam besylate is a new type of ultra-short-acting benzodiazepine, showing rapid clearance and moderate distribution of pharmacokinetic changes. Remimazolam has been widely studied for programmed sedation in endoscopic procedures such as gastroenteroscopy and bronchoscopy. Remimazolam, as a short-acting sedative agent that is not metabolized by liver or kidney, can achieve rapid and reversible sedation and has the potential to shorten the duration of mechanical ventilation.

In the oral and maxillofacial surgical treatment, the use of microvascular free tissue transfer for reconstruction is one of the common operations. In order to avoid mechanical damage to the transplanted reconstructed tissue due to spontaneous movement, patients undergoing major head and neck reconstruction surgery are considered to require postoperative deep sedation for a certain period of time (RASS score required -4/-5 points). Deep sedation may cause hypotension and lead to reduced flap perfusion pressure, increasing the risk of hypoperfusion and flap necrosis, thus requiring close postoperative monitoring in the ICU.

Therefore, there is an urgent need for a sedative drug that can achieve rapid and sufficient sedation, does not inhibit breathing and can reduce the amount of patients or rapid recovery after drug withdrawal without increasing delirium. Based on the deficiencies of currently used sedatives and the potential advantages of remimazolam, we hypothesize that remimazolam can shorten the extubation time and lower the adverse reaction rate in patients with oropharyngeal cancer after mechanical ventilation sedation.

Therefore, we conducted a multicenter, randomized, non-inferiority pilot study to compare the efficacy and safety of remimazolam besylate, propofol, and midazolam in this patient population.

Inclusion Criteria:

• Age ≥18 years old;
• After undergoing oral and maxillofacial surgery, it is expected that a ventilator will be needed to assist with breathing;
• mechanical ventilation patients with expected ICU stay time <72h;
• People who need immediate sedative treatment;
• Obtain informed consent from subject or legal representative;

Exclusion Criteria:

• Pregnancy；
• Can not get RASS score from patients;
• Allergy to drugs;
• Proven acute and severe intracranial or spinal nerve disease due to vascular, infection, intracranial dilation, or injury;
• Uncompensated acute circulatory failure at randomization (severe hypotension with MAP<50 mmHg despite adequate fluid resuscitation and vasopressor therapy);
• Severe bradycardia (heart rate <50 beats/min) or degree II-III heart block (unless a pacemaker is installed);
• A history of long-term use of benzodiazepines or opioids;
• Subjects receiving sedation for indications other than to tolerate ventilators (e.g., epilepsy);
• Continuous sedation is unlikely to be required during mechanical ventilation (e.g. Guillain-Barre syndrome);
• Patients determined by the clinician to be unlikely to be removed from mechanical ventilation, such as diseases/injuries that primarily affect respirator neuromuscular function and conditions that clearly require long-term ventilation support (such as high spinal cord injury);
• Participation in any other interventional study (any study that assigns subjects to different treatment groups and/or performs unconventional diagnostic or monitoring procedures).