Most patients in ICU are treated with a combination of analgesics and sedatives in most cases. Due to the different mechanism of different sedative and analgesic drugs, different antagonistic or synergistic effects may occur when combined with drugs, resulting in different clinical effects, especially significant effects on ventilators for patients with assisted breathing. Therefore, this study hopes to compare the effects of different sedative and analgesic drug combinations on the duration of mechanical ventilation for patients with ventilators, so as to guide the clinical adoption of a more reasonable sedative and analgesic scheme.

Inclusion Criteria:

• Adults who are treated with sedation and analgesia for invasive mechanical ventilation

Exclusion Criteria:

• they have baseline severe cognitive impairment; were pregnant or breast-feeding; were blind, deaf ; had second-degree or third-degree heart block or bradycardia requiring intervention; had an allergy to the experimental drugs; had an indication for benzodiazepines; were anticipated to have immediate discontinuation of mechanical ventilation; were expected to have neuromuscular blockade for more than 48 hours; were in a moribund state; or had received mechanical ventilation for more than 96 hours before meeting all inclusion criteria.