1. Institute of Applied Health Sciences, Epidemiology Group, University of Aberdeen, NHS Grampian, department of Anaesthetics, Aberdeen, United Kingdom
2. Department of Anesthesiology, Centre Hospitalier de Wallonie Picarde (CHWAPI), Tournai, Belgium
3. Department of Anesthesiology, Cliniques universitaires Saint-Luc, Bruxelles, Belgium
4. Department of Anesthesiology, Centre Hospitalier Universitaire du Sart-Tilman, Liege, Belgium