Renal Protection

This study evaluates the anesthetic-sparing and renal protection effects of minimal-flow sevoflurane anesthesia combined with multimodal analgesia using dexmedetomidine, ketamine, and lidocaine in head and neck cancer patients undergoing free flap microvascular surgery. The 2x2 factorial randomized controlled trial aims to compare sevoflurane usage and renal function changes with different fresh gas flow rates and multimodal analgesia.