Endometriosis and Pain Treatment by Intraoperative Administration of Low-dose Ketamine

Inclusion Criteria: * Patients undergoing surgery for endometriosis operation requiring general anaesthesia at the Inselspital, Bern University Hospital, University of Bern, Department of gynaecology and obstetrics. * Age ≥ 18 years * American Society of Anesthesiologist (ASA) physical status 1-3 * Patients with known or suspected endometriosis * Written informed consent. Exclusion Criteria: * Age \< 18 years * ASA physical status ≥4 * Higher-grade atrioventricular block without pacemaker * Severe hypovolemia or bradycardia * Uncontrolled hyper- or hypotension * Liver disease * Known malignant hyperthermia * Cardiovascular instability or severe heart failure (New York Heart Association classification (NYHA) \> III) * Myocardial infarction during the last 30 days prior to surgery * Increased intracranial or increased intraocular pressure * Limited peripheral autonomic activity, hypersensitivity to ketamine or propofol or its components * Pregnancy * Rejection or lack of consent of the patient or relatives