A total of 92 children undergoing adenotonsillectomy , aged 3-7 years , were randomly allocated to receive either low-doseketamine 0.15 mg/kg followed by dexmedetomidine 0.3 g/kg i.v. ( KETODEX , n = 45 ) or volume-matched normal saline ( Control , n = 47 ) , about 10 min before the end of surgery .