Transcatheter aortic valve implantation (TAVI) is an alternative for patients, that are considered to be too sick for conventional aortic valve replacement. There is no conclusive opinion about the best anesthesiologic management of these patients. Sedation and general anaesthesia are both adequate and the current literature shows no benefit towards one of these methods.

This study wants to investigate the influence of these two anesthesiologic managements on the cerebral oxygen saturation during the "rapid pacing"-period during valvuloplasty. The patients are randomised allocated to one of these two anaesthesiological managements. The investigators use the Near-Infrared Spectroscopy (NIRS) to measure the cerebral oxygen saturation. Parallel there will be a measurement of cerebral biomarkers to monitor cerebral hypoxia.

Inclusion Criteria:

• informed consent
• transcatheter aortic valve implantation

Exclusion Criteria:

• denial by patient
• denial by screening anaesthesist
• active neurodegenerative disease