Correlation Between Perioperative EEG Variability and Postoperative Delirium Incidence.

Inclusion Criteria: 1. Patients undergoing general anaesthesia with single-lumen endotracheal tube placement; 2. Age ≥65 years, gender unrestricted, body mass index (BMI) 18-28 kg/m²; 3. Normal mouth opening and head/neck mobility; 4. Pre-anaesthesia American Society of Anaesthesiologists (ASA) physical status classification of I or II and Mallampati airway classification of I or II. Exclusion Criteria: 1. Individuals with psychiatric disorders, literacy issues, or communication difficulties who are unable to cooperate with POD screening; 2. Patients with severe lesions in vital organs, such as the heart, lungs, brain, liver or kidneys. 3. Those undergoing cardiac or neurosurgical procedures during this admission; 4. A history of alcohol abuse or recent use of sedatives or opioids; 5. haemoglobin \<100 g/L; 6. Participation in any clinical research studies within the past 3 months.