1 Department of Anesthesiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands.
2 Department of Anesthesiology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands; Department of Basic and Applied Medical Sciences, Ghent University, Ghent, Belgium. Electronic address: m.m.r.f.struys@umcg.nl.