Inclusion Criteria:  Children aged 3-7 years, American Society of Anesthesiologists Physical Status I-II, scheduled for elective surgery in Peking University First Hospital.  Exclusion Criteria:  Preterm patients; Height and weight not within the standard ranges for respective ages; Surgery for head or heart; Operation duration of <20min or >2h; Patients with muscular, neurologic or psychiatric diseases; Patients with Congenital anomaly or hereditary diseases; Patients with medication abuse; Allergy to medication including propofol, sevoflurane, and ketamine; Allergy to beans; Refusal to participate the study by guardians.