1 From the Department of Anaesthesiology, Pain Medicine and Procedural Sedation and Analgesia, Martini General Hospital Groningen, Groningen, The Netherlands (HDdeB), the Department of Anaesthesia and Pain Medicine, Royal Surrey NHS Foundation Trust, Guildford, UK (WJF), the Department of Anesthesiology and Critical Care Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA (MJS).