2.3. Randomization and blinding
Patients who met the inclusion criteria were assigned randomly into 2 groups with a ratio of 1:1. Randomization was done using random numbers created in SPSS 26.0 (IBM, Chicago, IL). Seventy-three patients were assigned to the control group, and 74 were assigned to the esketamine group. A biostatistician who was blinded to patients prepared sealed opaque envelopes for each patient. Before the surgery, independent researchers who did not participate in the analysis opened the envelopes and assigned each patient according to the envelope and prepared the placebo (normal saline—identical in appearance) or esketamine in syringes according to the assigned group of the patient. Anesthesiologists then unknowingly, administered the placebo or esketamine to the patient, blinded to the contents of the syringe.