The objective of this study is to evaluate the incidence of Post-Operative Delirium (POD), diagnosed with the Confusion Assessment Method (CAM), in elderly patients undergoing hip fracture surgery under general anaesthesia with xenon or sevoflurane, for a period of four days post-surgery.

Inclusion Criteria:

• Elderly patient (≥ 75 years)
• Patient with planned hip fracture surgery within 48 hours after the hip fracture
• Patient willing and able to complete the requirements of this study including the signature of the written informed consent

Exclusion Criteria:

• Patient suffering from multiple fractures, pelvic fractures proximal, pathological fractures, femur fractures (i.e., fractures of the middle or distal femur)
• Disabling neuropsychiatric disorders (severe dementia, Alzheimer's disease, schizophrenia, depression)
• Brain trauma within 12 months prior to selection, history of stroke with residuals
• Patient suffering from delirium (CAM diagnosis) at selection
• Patient who cannot complete the pre-operative mental tests (CAM and/or MMSE) of this clinical trial
• Patient with Mini-Mental State Examination (MMSE) score < 24 at selection
• Patient known to susceptible to malignant hyperthermia
• Patient with elevated intra-cranial pressure
• Patient with a risk of high oxygen demand
• Patient with recent or ongoing myocardial infarction / damage
• Patient with severe cardiac failure, or patient with severe impaired left ventricular systolic function
• Patient with known severe lung and/or airway disease, or severe chronic respiratory insufficiency, or a sustained homecare oxygen therapy
• Contra-indication (serious illness or medical conditions) for general anaesthesia
• Known allergy or hypersensitivity to any drugs administered during this clinical trial
• Previous participation in this clinical trial
• Participation in another clinical trial within 4 weeks prior to selection
• History of alcohol or drug abuse or psychiatric disorders which would impair the understanding of the necessary information or render medically or legally unable to give written informed consent