Group allocation
loss of consciousness
Participant group allocation was based on the administration sequence of hypnotics and remifentanil (hypnotic-remifentanil and remifentanil-hypnotic groups), and further subdivision was based on the type of hypnotic administered, that is, thiopental or propofol. Consequently, participants were randomly assigned to one of four groups in a 1:1:1:1 ratio using computer-generated random numbers. In the Thio-Remi group, thiopental was administered first until loss of consciousness (LOC), followed by remifentanil infusion via target-controlled infusion (TCI) at an effect-site concentration (Ce) of 3 ng/mL. In the Pro-Remi group, propofol was administered first until LOC, followed by remifentanil at a Ce of 3 ng/mL. In the Remi-Thio group, remifentanil was first infused at a Ce of 3 ng/mL using a TCI pump, followed by thiopental until LOC. In the Remi-Pro group, remifentanil and propofol were administered in that order and in the same manner.