This study aims to find effective dose of remimazolam for inducing loss of consciousness in children aged 2 to 8 years old. We will explore ED90 of remimazolam for loss of consciousness in 2 minutes after intravenous injection, via a up-and-down method with biased-coin design.

We will administer remimazolam intravenously to the study participants. Remimazolam will be infused in 30 seconds to the participants, and we will wait for 2 minutes for the participants be sedated.

When a participant was not sedated in 2 minutes, dose of remimazolam in the next participant will be escalated by 0.05mg/kg. When a participant was sedated in 2 minutes, dose of remimazolam in the next participant will be decreased by 0.05mg/kg or maintained as same. The probability of decrement and maintenance will be 90% and 10% respectively. The dose of remimazolam in the first participant of the study will be 0.05mg/kg.

We will collect the results and obtain ED90 of remimazolam for loss of consciousness in children aged 2 to 8 years old.

Inclusion Criteria:

• Children scheduled to undergo general anesthesia or sedation
• American Society of Anesthesiologist Physical Status of 1 or 2

Exclusion Criteria:

• Presence of Upper respiratory tract infection or any pulmonary disease
• Presence of subglottic stenosis, laryngomalacia, or tracheomalacia
• History of hypersensitivity to benzodiazepines or propofol
• History of hypersensitivity to beans or peanut
• History of seizure
• Presence of arrhythmia, tachycardia, or bradycardia
• Presence of acute closed-angle glaucoma
• Patients with unstable vital sign
• Presence of sleep apnea
• Presence of galactose intolerance, Lapp lactase deficiency, or glucose-galactose absorption disorder
• History of hypersensitivity to dextran 40
• Refusal to enroll by one or more parents or legal guardian
• Other conditions the researchers regarded as inappropriate to enroll