Francesco Formica1, Fabio Guarracino2. 1. Cardiac Surgery Unit, Department of Medicine and Surgery, Parma General Hospital, University of Parma, Parma, Italy. 2. Department of Anaesthesia and Critical Care Medicine, Cardiothoracic and Vascular Anaesthesia and Intensive Care, Azienda Ospedaliero Universitaria Pisana, Pisa, Italy.