Anesthesia for Obese Patients: Desflurane Versus Xenon

Inclusion Criteria: * American Society of Anesthesiologists (ASA) I to III * requires bariatric surgery * body mass index (BMI) \>= 35 kg/m2 * patient speaks and writes French * patient has signed consent form * patient enrolled in a social security program Exclusion Criteria: * patient refuses to sign consent * ASA IV or more * patient is pregnant or breastfeeding * history of hyperthermy (or suspicion, or family history thereof) * history of liver disease, icterus, unexplained fever, or eosinophilia after administration of a halogen anesthesia * patient has symptomatic gastro-oesophagean reflux * patient has hypersensitivity to one or more of the following substances: propofol, remifentanil, celocurine, cisatracurium, rocuronium, desflurane, xenon, paracetamol, ketoprofen, nefopam, tramadol * patient has obstructive respiratory failure (chronic obstruction pneumopathy, asthma) or has heart disease with severly altered cardiac function * patient has high intracranial pressure * patient requires high concentrations of oxygen (fio2\>40%) * patient has a neuro-sensorial deficient which prevents reading, writing, or response to simple oral commands (severe deafness, language impairment...)in the absence of a prothesis * patient has a psychiatric pathology, or chronically consumes alcohol or other mind-altering substance * patient has had general anesthesia in the last 15 days * patient under guardianship * impossible to correctly communicate information to the patient * absence of efficient contraception for women of childbearing age * participation in another study within the last 3 months