1. Department of Neurosurgery in Linköping University Hospital Linköping Sweden
2. Department of Biomedical and Clinical Sciences Linköping University Linköping Sweden
3. The Swedish National Patient Insurance Company (Löf) Stockholm Sweden
4. Department of Anaesthesiology and Intensive Care Vrinnevi Hospital Norrköping Sweden
5. Department of Thoracic and Vascular Surgery and Department of Medical and Health Sciences Linköping University Linköping Sweden
6. Department of Anaesthesiology and Intensive Care University Hospital Linköping Sweden