Anesthetic regimen
The anesthetic regimen was standardized for all participants. None of the patients received any preanesthetic medication. Standard anesthetic monitoring, including electrocardiography, noninvasive blood pressure, pulse oximetry, capnography, and bispectral index, was implemented.In the hypnotic-remifentanil groups, that is, the Thio-Remi and Pro-Remi groups, thiopental sodium or propofol was initially infused at a rate of 350 mL/h using an infusion pump (Agilia®, Fresenius Vial, France) until LOC was achieved (no response to verbal command “open your eyes”). Thereafter, the target Ce was set at 3 ng/mL using a TCI pump (Orchestra® Base Primea, Fresenius Vial, France), in which the Minto model was pre-programmed, in effect-site targeting mode. Remifentanil was initially infused using a TCI pump in the remifentanil-hypnotic groups (Remi-Thio and Remi-Pro groups). When a predetermined Ce of 3 ng/mL was achieved, thiopental or propofol was administered in the same manner as in the hypnotic-remifentanil groups.The total dose of hypnotics administered until LOC and elapsed time to LOC were recorded. Moreover, vital signs, including peripheral oxygen saturation (SpO