Sodium Lactate and Brain Relaxation (LSD)

Inclusion Criteria: * Patients with ASA 1, ASA 2 ou ASA 3, meaning they don't have any unstable comorbidities which could be a threat to life. * Scheduled surgery for resection of supratentorial brain tumors by craniotomy under general anesthesia * Unilateral brain tumor * Deviation of the falx cerebri \> 3mm on the preoperative imaging * Pharmacological brain relaxation required by the neurosurgeon in charge of the patient. * Patient who has been informed and who signed the free informed consent to participate to the study. Meaning the patient understood the purpose and the procedures required by the study and agreed to participate and obey the requirements and restrictions of this study. * Affiliation to a social security system or recipient of a such system. Exclusion Criteria: * Emergency surgery * Age \< 18 years old or \> 75 years old * ASA score IV-V * Legal incapability or limited legal capacity * Patient who will unlikely cooperate to the study and/or poor cooperation foreseen by the investigator * Preoperative Glasgow score \< 13 * Pregnant woman and/or breastfeeding * Body index masse\< 18 kg.m-2 ou \> 30 kg.m-2 * Preoperative hyponatremia \< 130mmol/l or hypernatremia \> 145 mmol/l * Osmotherapy in the 24 hours prior to the surgery (Mannitol, Hypertonic saline, Sodium lactate) * Congestive heart failure * Moderate ou severe chronic kidney disease, defined by a creatinine clearance (MDRD) \< 60 ml/min * End-stage liver disease (Child Pugh ≥ B7) * Myasthenia gravis * External ventricular drain or ventriculoperitoneal shunt of cerebrospinal fluid * Allergy to Mannitol 20% or one of his excipients * Allergy to Sodium Lactate or one of his excipients * Contraindication for propofol * Allergy to anesthetic agents (propofol, remifentanil, cisatracurium) * Refusal of consent * Patient within the exclusion period of another study or planned by the "national file of volunteers" * Medical history of cognitive disorders or demencia