From the Paediatric Intensive Care Unit, Department of Intensive Care, Leiden University Medical Centre, Leiden, The Netherlands (AW), Department of Anaesthesiology, University Hospital Brugmann and Queen Fabiola University Children's Hospital, Brussels, Belgium (SA, DS, PVL)

Correspondence to Ariane Willems, Paediatric Critical Care Medicine, Department of Intensive Care, Leiden University Medical Centre, Albinusdreef 2, 6333 ZA Leiden, The Netherlands. Tel: +31 71 526 16 77; e-mail: [email protected]