1. Multidisciplinary Pain Center, Department of Anaesthesia and Intensive Care , Naestved Hospital , Næstved , Denmark
2. Multidisciplinary Pain Center, Department of Anaesthesia and Intensive Care Zealand University Hospital , Køge , Denmark
3. Department of Anaesthesia and Intensive Care , Zealand University Hospital , Lykkebækvej 1 , 4600 Køge , Denmark