1. Dept. of Anesthesiology, Rijnstate Hospital, Arnhem, The Netherlands;
2. International Pain Institute, Dept. of Anesthesiology, Lubbock, Texas, USA;
3. Whipps Cross University Hospital, London, UK;
4. Dept. of Anesthesiology, Onze Lieve VrouweGasthuis, Amsterdam,
The Netherlands