Inclusion Criteria:  Adults, age ≥18 years, male or female American Society of Anaesthesiology (ASA) status I-III Patients undergoing elective craniotomy  Exclusion Criteria:  Patients unable to complete scale assessment Pregnant or lactating women Patients with preoperative chronic pain syndrome Patients with previous craniotomy history Patients with a history of mental illness who are receiving medication Patients with liver and kidney dysfunction Patients have taken pain medication within two weeks Patients with history of adverse reactions to pregabalin, ketamine and esticketamine Patients with history of drug abuse; BMI>35.0 kg · m - 2.