1 Department of Anaesthesia and Intensive Care, Azienda Ospedaliero Universitaria "Policlinico-Vittorio Emanuele", Catania, Italy. Electronic address: filipposanfi@yahoo.it.
2 School of Anaesthesia and Intensive Care, University Hospital "G. Rodolico", University of Catania, Catania, Italy.
3 Pain Management Unit, St Thomas' Hospital, Guys and St. Thomas NHS Foundation Trust, London, UK.
4 Department of Anaesthesia and Intensive Care, Azienda Ospedaliero Universitaria "Policlinico-Vittorio Emanuele", Catania, Italy; School of Anaesthesia and Intensive Care, University Hospital "G. Rodolico", University of Catania, Catania, Italy; Department of General Surgery and Medical-Surgical Specialties, Section of Anesthesia and Intensive Care, University of Catania, Catania, Italy.