This randomized clinical trial aims to evaluate the effectiveness of scalp nerve blocks and dexmedetomidine in reducing opioid use and preventing postoperative delirium in patients undergoing supratentorial brain tumor surgery. A total of 2000 patients will be randomly assigned to one of four groups, receiving either active treatments, placebos, or their combinations. The main outcome measured will be the amount of opioid pain medication needed after surgery.

This single-center, double-blind, placebo-controlled trial employs a 2x2 factorial design to evaluate two non-opioid interventions: preoperative scalp nerve blocks and perioperative dexmedetomidine infusion. Eligible patients scheduled for elective supratentorial tumor resection will be randomized into four groups: 1) scalp nerve blocks plus placebo dexmedetomidine infusion; 2) placebo scalp nerve blocks plus dexmedetomidine infusion; 3)both active treatments; and 4) double placebo. The primary outcomes are cumulative sufentanil consumption via patient-controlled analgesia during the first 48 postoperative hours. Secondary outcomes include the incidence of postoperative delirium within 3 days assessed using CAM-ICU/3D-CAM, pain scores, total perioperative opioid use, quality of recovery, and persistent incisional pain. Results will provide evidence for optimizing analgesia while minimizing opioid-related complications in neurosurgical patients.

Inclusion Criteria:

• Aged from 18 to 65 years
• American Society of Anesthesiologists physical status I to III
• Scheduled to undergo elective supratentorial tumor resection

Exclusion Criteria:

• Incision-area skin infection
• A history of previous craniotomy
• Allergy to study medications
• A history of preoperative change in consciousness or cognitive function
• Inability to communicate,
• Preoperative pain in the surgical region
• Severe hepatic or renal dysfunction
• Severe bradycardia (heart rate<40 beats/min)
• Sick sinus syndrome or second- to-third degree atrioventricular block