Automated Administration of Fluids Guided by Dynamic Parameters and Cardiac Output During General Anesthesia

Inclusion Criteria: * The patient must have given his/her informed and signed consent * The patient must be insured or beneficiary of a health insurance plan * The patient will receive general anesthesia for a surgical procedure with the following characteristics: ----- planned abdominal surgery by laparotomy or laparoscopy with a probable duration\> 2 hours ----- invasive monitoring of blood pressure ----- administration of crystalloid and colloid (HEA PM \<150 kDa) Exclusion Criteria: * The patient is participating in another study * The patient is in an exclusion period determined by a previous study * The patient is under judicial protection, under tutorship or curatorship * The patient refuses to sign the consent * It is impossible to correctly inform the patient * The patient is pregnant, parturient, or breastfeeding * The patient has a contraindication for a treatment used in this study: ----- Contraindications to the administration of HES MW \<150 kDa ----- Patient classified NYHA\> 2 ----- Allergy to HEA * The patient has a pacemaker * Surgery with cardiopulmonary bypass * Surgery on the skull * Dementia * Patients with brain pathology (tumor, stroke, Parkinson's disease, ...) * Patients with a psychiatric disorder, severe depression or psychosis, as well as those receiving antipsychotic treatment * Limitations concerning the use of respiratory pulse pressure variation: cardiac arrhythmia, spontaneous ventilation, using a volume flow \<7 ml / kg