1 Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany. bernd.saugel@gmx.de.
2 Outcomes Research Consortium, Cleveland, OH, USA. bernd.saugel@gmx.de.
3 Department of Anesthesiology, Center of Anesthesiology and Intensive Care Medicine, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
4 Department of Anaesthesiology, University Hospital LMU Munich, Munich, Germany.
5 Department of Health Science, Section of Anesthesia and Critical Care, University of Florence, Florence, Italy.
6 Department of Anesthesia and Critical Care, Azienda Ospedaliero-Universitaria Careggi, Florence, Italy.