Randomization and group allocation
Patients were randomized into either remimazolam group or routine group at 1:1 ratio with a block size of 4 and stratified by study centers by an independent biostatistician (SAS 9.2. SAS Institute, Cary, NC). Random numbers were sealed in sequentially numbered opaque envelopes and stored at study centres until the end of the study. A researcher was designated to allocate random number 30 min before anesthesia and prepared trial drugs per protocol. This researcher was not involved in administration of intervention, follow-up, and data collection.