Effects of Minimal-Flow Sevoflurane and Multimodal Analgesia in Head and Neck Cancer Surgery

Inclusion Criteria: * Age 18-99 years * Scheduled for head and neck cancer tumor resection and free flap reconstruction surgery Exclusion Criteria: * Preoperative tracheostomy * History of previous head and neck cancer tumor resection * Anemia (hematocrit \<30% or recent transfusion) * Hypertension on ACEI/ARB medications * Significant medical conditions (e.g., NYHA class 3 or 4 heart failure, eGFR \<60 ml/min/1.73 m², Child B or C liver failure, severe respiratory disorders, pre-existing cognitive impairment) * ASA physical status 4 or 5 * Allergies to sevoflurane, dexmedetomidine, ketamine, or lidocaine