Clinical Research Directory

Dexmedetomidine-esketamine combination (1 μg/mL dexmedetomidine and 0.5 mg/mL esketamine) will be administered after anesthesia induction, firstly as a loading dose at a rate of \[0.4 x body weight (kg)\] mL/h for 30 minutes (0.2 μg/kg dexmedetomidine and 0.1 mg/kg esketamine), followed by a maintenance infusion at a rate of \[0.1 x body weight (kg)\] mL/h (0.1 μg/kg/h dexmedetomidine and 0.05 mg/kg/h esketamine) until one hour before the expected end of surgery. Postoperative patient-controlled analgesia will be established with a 100 mL mixture (containing 1.0 μg/mL sufentanil, 1.25 μg/mL dexmedetomidine, and 0.25 mg/mL esketamine in normal saline), programmed to deliver 2-mL boluses with an 8-minute lockout interval and an 1-mL/h background infusion, and provided for 48 hours (at least 24 hours).

Placebo (normal saline) will be administered after anesthesia induction, firstly as a loading dose at a rate of \[0.4 x body weight (kg)\] mL/h for 30 minutes, followed by a maintenance infusion at a rate of \[0.1 x body weight (kg)\] mL/h until one hour before the expected end of surgery. Postoperative patient-controlled analgesia will be established with a 100 mL mixture (containing 1.0 μg/mL sufentanil in normal saline), programmed to deliver 2-mL boluses with an 8-minute lockout interval and an 1-mL/h background infusion, and provided for 48 hours (at least 24 hours).

Active transcranial direct current stimulation (tDCS) will be administered using a battery-powered stimulator. The anode will be positioned over the left dorsolateral prefrontal cortex (DLPFC, F3) and the cathode over the right supraorbital region (Fp2). The stimulation intensity will be set at 2.0 mA, featuring a 30-second linear ramp-up at the beginning and a 30-second ramp-down at the end of each session. Each participant will receive a total of three 20-minute sessions of active tDCS. The first session will be provided at 40 minutes after extubation in the post-anesthesia care unit. Two other sessions will be provided on postoperative days 1 and 2 (between 10:00 and 12:00 am).

Sham transcranial direct current stimulation (tDCS) will be administered using a battery-powered stimulator. The anode will be positioned over the left dorsolateral prefrontal cortex (DLPFC, F3) and the cathode over the right supraorbital region (Fp2). To ensure blinding, the device will deliver a initial 30-second ramp-up to 2.0 mA followed immediately by a 30-second ramp-down to 0 mA. The device remains "ON" for the remaining 19 minutes with no effective current output, mimicking the peripheral scalp sensation without delivering cortical modulation. Each participant will receive a total of three 20-minute sessions of sham tDCS. The first session will be provided at 40 minutes after extubation in the post-anesthesia care unit. Two other sessions will be provided on postoperative days 1 and 2 (between 10:00 and 12:00 am).