[PERSON]  
3 Department of Medical and Surgical Sciences (DIMEC), University of Bologna, 40138 Bologna, Italy; [EMAIL_ADDRESS] (S.R. ); [PERSON] (I.S.Z. ); [PERSON](L.G. ); [PERSON]S] (M.C. ); [EMAIL_ADDRESS] (M.R.) [PERSON]  
3 Department of Medical and Surgical Sciences (DIMEC), University of Bologna, 40138 Bologna, Italy; [EMAIL_ADDRESS] (S.R. ); [PERSON] (I.S.Z. ); [EMAIL_ADDRESS] (L.G. ); [EMAIL_ADDRESS] (M.C. ); [EMAIL_ADDRESS] (M.R.) [PERSON]  
3 Department of Medical and Surgical Sciences (DIMEC), University of Bologna, 40138 Bologna, Italy; [EMAIL_ADDRESS] (S.R. ); [PERSON] (I.S.Z. ); [EMAIL_ADDRESS] (L.G. ); [PERSON]S] (M.C. ); [EMAIL_ADDRESS] (M.R.) [PERSON]  
3 Department of Medical and Surgical Sciences (DIMEC), University of Bologna, 40138 Bologna, Italy; [EMAIL_ADDRESS] (S.R. ); [PERSON] (I.S.Z. ); [EMAIL_ADDRESS] (L.G. ); [EMAIL_ADDRESS] (M.C. ); [EMAIL_ADDRESS] (M.R.) [PERSON]  
3 Department of Medical and Surgical Sciences (DIMEC), University of Bologna, 40138 Bologna, Italy; [EMAIL_ADDRESS] (I.S.Z. ); [PERSON](L.G. ); [PERSON]S] (M.C. ); [EMAIL_ADDRESS] (M.R.) [PERSON]  
3 Department of Medical and Surgical Sciences (DIMEC), University of Bologna, 40138 Bologna, Italy; [EMAIL_ADDRESS] (I.S.Z. ); [EMAIL_ADDRESS] (I.S.Z. ); [EMAIL_ADDRESS] (L.G. ); [EMAIL_ADDRESS] (M.C. ); [EMAIL_ADDRESS] (M.R.) [PERSON]  
3 Department of Medical and Surgical Sciences (DIMEC), University of Bologna, 40138 Bologna, Italy; [EMAIL_ADDRESS] (S.R. ); [PERSON] (I.S.Z. ); [EMAIL_ADDRESS] (L.G. ); [EMAIL_ADDRESS] (M.C. ); [EMAIL_ADDRESS] (M.R.) [PERSON]  
3 Department of Medical and Surgical Sciences (DIMEC), University of Bologna, 40138 Bologna, Italy; [EMAIL_ADDRESS] (S.R. )-PFO can also cause hypoxemia and platypnea-orthodeoxia syndrome due to right-to-left shunting of deoxygenated blood [5]. Standard PFO diagnostic techniques include contrast-enhanced transthoracic echocardiography (cTTE), contrast-enhanced transesophageal echocardiography (cTEE) and transcranial color Doppler ultrasound (TCCD). TEE is the best tool for obtaining an anatomical confirmation of PFO and essential details such as the PFO measure, degree and direction of the shunt, presence of atrial septal aneurysm and prominent Eustachian valve. TCCD, although more sensitive than cTTE in detecting PFO (96.1% vs. 45.1%), is unable to distinguish between intracardiac and extractardiac shunts [6]. A bubble test is recommended before and after the Valsala maneuver with TCCD and echocardiography. cTTE confirmed the PFO diagnosis when the left ventricular bubble appeared within the first 3-5 cardiac cycles after right ventricular opacification. TCCD confirms the diagnosis when at least one bubble appears <25 s after injection with stirred saline [7,8]. Preoperative PFO screening is not routinely performed, although PFO was significantly associated with an increased risk of postoperative ischemic stroke [4]. Guidelines recommend antiplatelet therapy for secondary prevention of stroke in patients with PFO, but no definitive recommendations exist for the management of incidental PFO diagnosed perioperatively. Closure of an incidental PFO is reasonable in high-risk surgery, such as heart transplantation, ventricular assisted-device implantation or in surgical procedures involving atriotomy [9]. In non-cardiac high-embolic-risk surgery, such as liver transplantation (LT), the risk of PFO-related paradoxical embolism is expected to increase due to perioperative hemodynamic changes [10]. Despite such considerations, there are currently no indications of preoperative PFO closure in asymptomatic patients [11]. Since the intraoperative evaluation of a PFO shunt is essential to guide the anestheological conduct in real-time, and reduce the risk of stroke, we proposed a PFO diagnostic and monitoring protocol. The objective of this study was to describe the feasibility and utility of the proposed protocol in patients undergoing non-cardiac major surgery with a high risk of embolic events.