The Effect of Intraoperative Infusion of Esketamine on Cholestatic Pruritus in Patients Undergoing Hepatobiliary Surgery

Inclusion Criteria: * 1\. Inclusion Criteria: 1. Patients with cholestasis caused by bile duct stones, gallbladder stones, bile duct strictures, pancreatic head cancer, cholangiocarcinoma, or periampullary carcinoma, etc. 2. Manifestations of cholestatic pruritus, typically with the palms and soles as the initial or most severely affected sites, which may extend to the limbs and trunk; possibly accompanied by jaundice (yellowing of the skin and sclera), dark urine (e.g., tea-colored), and clay-colored stools; often with a tendency to worsen at night. 3. Report of pruritus with an NRS score ≥ 4 (moderate to severe pruritus) twice within one week. 4. Scheduled for elective hepatobiliary surgery under general anesthesia, including but not limited to: partial hepatectomy, common bile duct exploration, choledocholithotomy, biliary-enteric anastomosis (e.g., Roux-en-Y anastomosis), pancreaticoduodenectomy (Whipple procedure), and radical resection of hilar cholangiocarcinoma. 5. American Society of Anesthesiologists (ASA) physical status classification I-III. 6. Age ≥ 18 years, body mass index (BMI) between 18 and 30 kg/m², regardless of gender. 7. Patients have fully understood the nature of the study, voluntarily agree to participate, and have signed the informed consent form. Exclusion Criteria: 1. Known allergy to any component of the study drug or history of allergic constitution; 2. History of allergy to general anesthetics, opioids, or non-steroidal anti-inflammatory drugs; 3. History of neurological disease; history of chronic pain; substance abuse or alcoholism; long-term use of opioids; administration of opioids within 48 hours prior to surgery; 4. ASA physical status classification IV; 5. Coronary heart disease, bronchial asthma, severe hypertension, severe hematologic dysfunction, renal dysfunction, or marked electrolyte abnormalities; 6. History of gastrointestinal diseases (peptic ulcer, Crohn's disease, ulcerative colitis); 7. Respiratory insufficiency or respiratory failure; 8. Preoperative diagnosis of severe liver failure of Child-Pugh class C or presence of hepatic encephalopathy; 9. Other pruritic disorders: uremic pruritus, polycythemia vera, cutaneous T-cell lymphoma, hypereosinophilia, drug eruption and drug-induced pruritus, as well as other pruritic diseases that may be easily confused, such as atopic dermatitis, pemphigoid, scabies, delusional parasitosis, dermatitis artefacta, etc.; 10. Pregnant or breastfeeding women; 11. BMI \< 18 kg/m² or BMI \> 30 kg/m²; 12. Poor compliance or inability to complete the study according to the protocol; 13. Participation in another drug clinical trial within the past 4 weeks; 14. Any other condition that, in the opinion of the investigators, makes the patient unsuitable for enrollment.