Inclusion Criteria:  Patient undergoing elective spinal cord neoplasms resection; Ages between 18 and 65 years old; American Society of Anaesthesiology (ASA) status I-III; Signed informed consent.  Exclusion Criteria:  Previous adverse reaction to ketamine, s-ketamine or pregabalin; Patients with a diagnosed history of severe chronic pain; Patients with long-term analgesic treatment(gabapentin/opioids/ketamine); Patients with aphasia or inability to cooperate with the pain assessments; Known sever insufficiency of vitals(such as heart failure/renal dysfunction/hepatic failure); Patients with a diagnosed history of psychiatric disorder; Patients treated with gabapentin/pregabalin in the last three months; Drug abuse; Body mass index (BMI) > 35 kg/m2 ; Pregnancy or lactation.