1. Department of Intensive Care, Medical Centre Leeuwarden, P.O. Box 888, 8901 BR Leeuwarden, The Netherlands
2. Department of Cardiothoracic Anaesthesiology, Medical Centre Leeuwarden, P.O. Box 888, 8901 BR Leeuwarden, The Netherlands
3. Department of Epidemiology, University Medical Centre Groningen, P.O. Box 30001, 9700 RB Groningen, The Netherlands
4. Department of Clinical Pharmacy and Clinical Pharmacology, Medical Centre Leeuwarden, P.O. Box 888, 8901 BR Leeuwarden, The Netherlands