1. Department of Anesthesiology, Intensive Care Medicine and Pain Therapy, University Hospital Frankfurt, Theodor-Stern Kai 7, 60590 Frankfurt, Germany
2. Main-Kinzig-Clinic, Department of Anesthesia, Intensive Care Medicine and Pain Therapy, Herzbachweg 14, 63571 Gelnhausen, Germany
3. Clinic of Anesthesiology, Intensive Care and Pain Therapy, Orthopedic Clinic Friedrichsheim, Marienburgstraße 2, 60528 Frankfurt am Main, Germany
4. Evangelical Hospital Oldenburg, Department of Anesthesia, Intensive Care Medicine and Pain Therapy, Steinweg 13-17, 26122 Oldenburg, Germany