1. Department of Anesthesiology, University Medical Center Goettingen, 37075 Goettingen, Germany
2. Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, 20251 Hamburg, Germany
3. Department of Neurology and Neurophysiology, University Medical Center Freiburg, 79106 Freiburg, Germany
4. Department of Anesthesiology and Intensive Care Medicine, Klinikum Region Hannover, 30459 Hannover, Germany
5. Department of Anesthesiology, Asklepios Hospitals Schildautal, 38723 Seesen, Germany