1 Unit of Cardiovascular Anesthesia and Critical Care, Department of Medical Biotechnology, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
2 Unit of Anesthesia and Critical Care for General, Vascular and Transplantation Surgery, Azienda Ospedaliera Universitaria Pisana, Pisa, Italy - g.biancofiore@med.unipi.it.