## 5 Conclusions  
The increase in average age and comorbidity of patients undergoing major abdominal surgery and LT predisposes them to the development of neurological and respiratory complications. PFO, a relatively frequent finding in general population, is a known risk factor for such complications. The occurrence of a right-to-left shunt related to hemodynamic alterations can lead to paradoxical embolism and respiratory complications during surgery. The proposed TCCD-TEE protocol, by identifying an unknown PFO, allowed us to monitor the shunt direction intraoperatively and guided the use of strategies to prevent the risk of paradoxical embolism in non-cardiac high embolic risk surgery. Further studies are needed to evaluate the correlation between the presence of PFO and the occurrence of neurological and respiratory postoperative complications. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Pts**} & **MELD Na\({}^{+}\)** & **Acute Diseases** & **MAP** & **Chronic** & **Ammonia** & **Na\({}^{+}\) Shift** & **Glucose Shift** \\  & [32; 33; 37; 38; 39; 40; 41; 42; 43] & [37; 44; 45; 46; 47; 48; 49; 40; 41] & [32; 44] & [37; 40] & [37; 40] & [37; 40] \\ \hline \multirow{2}{*}{**1**} & \multirow{2}{*}{30} & Preop-AKI & \multirow{2}{*}{\(<\)65} & & \multirow{2}{*}{43} & \multirow{2}{*}{5} & \multirow{2}{*}{39} \\  & Preo-infections & & & & & & \\ \hline
**2** & 19 & Preop-AKI & \(<\)65 & COPD & 118 & 4 & 168 \\ \hline
**3** & 9 & PRS & \(<\)65 \(>\)105 & & 50 & 2 & 98 \\ \hline
**4** & 15 & & & & 102 & 2 & 61 \\ \hline
**5** & 9 & PRS & \(<\)65 & COPD & 42 & 3 & 32 \\ \hline
**6** & 22 & Preop-infections & & & 49 & 6 & 153 \\ \hline
**7** & 17 & & & & 88 & 6 & \(-\)26 \\ \hline
**8** & 14 & Preop-infections & \(>\)105 & COPD & 64 & 16 & 61 \\ \hline
**9** & 11 & PO-AKI & \(<\)65 & CKD & 39 & 8 & 43 \\ \hline \multirow{3}{*}{**10**} & \multirow{3}{*}{//} & PO-AKI & \multirow{3}{*}{COPD} & \multirow{3}{*}{7} & \multirow{3}{*}{5} & \multirow{3}{*}{91} \\  & Preo-infections & & & & & \\ \cline{1-1} \cline{5-5}  & Peri-operative & & & & & \\ \cline{1-1} \cline{5-5}  & arrhythmias & & & & & \\ \hline \hline \end{tabular}  
* Pts: patients; Preo: pre-operative; AKI: acute kidney injury; COPD: chronic obstructive pulmonary disease; MELD Na\({}^{+}\): Mayo end-stage Liver Disease containing sodium; Na\({}^{+}\): sodium; CKD: chronic kidney disease; MAP: mean arterial pressure (peri-operative); PRS: post-reperfusion syndrome; PO-AKI: post-operative acute kidney injury.  
\end{table} 
Table 2: Main confounding factors of postoperative neurologic and respiratory complications in the studied cohort. **Author Contributions:** Conceptualization: [PERSON], [PERSON] and [PERSON]; methodology: [PERSON] and G.V. ; investigation: [PERSON] and M.R. ; data care: [PERSON] and L.G. ; writing: [PERSON], [PERSON], [PERSON] and L.G. ; review and editing: [PERSON] and [PERSON]; supervision: [PERSON] and [PERSON]. All authors have read and agreed to the published version of the manuscript. **Funding:** This research received no external funding. **Institutional Review Board Statement:** Subjects undergoing LT were included in the MEIO21 study (ethics committee approval no. CE-AVEC: 983/2021) involving the execution of planned intraoperative TEE-TCD monitoring in the surgery setting. The study was conducted in accordance with ethical guidelines of the World Medical Association's Declaration of Helsinki and guidelines for Good Clinical Practice. **Informed Consent Statement:** All patients signed the informed consent. **Data Availability Statement:** Data supporting reported results can be found at IRCCS Azienda Ospedaliero-Universitaria di Bologna, department of digestive, hepatic and endocrine-metabolic diseases. Post-Surgical and Transplant Intensive Care Unit. **Conflicts of Interest:** The authors declare no conflicts of interest.