1. Department of Neurosurgery, Justus Liebig University Giessen, D‑35392 Giessen, Germany
2. Department of Neurosurgery, University Hospital Muenster, D‑48149 Muenster, Germany
3. Department of Anesthesiology, University Hospital Heidelberg, D‑69120 Heidelberg, Germany
4. Department of Visceral, Thoracic and Vascular Surgery, Philipps University Marburg, D‑35034 Marburg, Germany