1. Institute for Medical Biometry, Informatics and Epidemiology, University Hospital Bonn, 53127 Bonn, Germany
2. Department of Anesthesiology and Intensive Care Medicine, University Hospital Bonn, 53127 Bonn, Germany
3. Institute for Experimental Hematology and Transfusion Medicine, University Hospital Bonn, 53127 Bonn, Germany
4. Department of Neurosurgery, University Hospital Bonn, 53127 Bonn, Germany
5. Department of Neurosurgery, University Hospital Leipzig, 04103 Leipzig, Germany
6. Department of Anesthesiology and Pain Management, The University of Texas Southwestern Medical Center, Dallas, TX 75390, USA