Randomization
Computer-generated randomization tables were used to establish randomization. The group assignment was concealed in serially numbered, sealed, opaque envelopes. Patients were assigned at random to one of three equal groups (n = 20): group I (placebo group) received 0.9% normal saline, group II (dexmedetomidine group) received 1 µg/kg dexmedetomidine, and group III (ketamine group) received 1 mg/kg ketamine. An investigator who was not involved in patient anesthesia or outcome evaluation prepared the study drug in a standardized syringe with the same volume (50 ml) for all groups. The patients, the researcher who performed anesthesia, and the data collectors were blinded to the group assignment.