1 Department of Cardiothoracic Anaesthesia and Intensive Care Medicine, Azienda Ospedaliero Universitaria Pisana, Via Paradisa 2, 56123 Pisa, Italy. Electronic address: f.guarracino@ao-pisa.toscana.it.
2 Department of Cardiothoracic Anaesthesia and Intensive Care Medicine, Azienda Ospedaliero Universitaria Pisana, Via Paradisa 2, 56123 Pisa, Italy.