Lung transplantation (LTx) is a key therapeutic option for patients with end-stage pulmonary disease, particularly when other medical and interventional treatments-such as long-term oxygen therapy, pulmonary rehabilitation, pharmacological management (e.g., bronchodilators, corticosteroids) or noninvasive ventilation-fail to achieve adequate disease control (1). With advancements in anesthesia and surgical techniques in the past decades, short- and long-term survival have improved and the use of LTx has gradually expanded (2-4).

Anesthetic management involves specific challenges, particularly during the critical periods of LTx, such as the induction of anesthesia, the start of positive pressure ventilation, establishment and maintenance of single-lung ventilation, clamping and unclamping of the pulmonary artery (PA) and reperfusion of the transplanted lung (5). Tailoring anesthesia management to the underlying lung disease of the patient and the surgical process, with a particular emphasis on maintaining hemodynamic stability, is critically important (5). Although standard non-invasive monitoring-such as electrocardiography, non-invasive blood pressure measurement, pulse oximetry and capnography-is commonly used, hemodynamic monitoring during LTx must be tailored to the specific needs of each patient. PA catheters are a standard monitoring tool that provide valuable hemodynamic data, including PA pressure, cardiac output and mixed venous oxygen saturation, which are essential for guiding anesthesia and fluid management (6). However, transesophageal echocardiography (TEE) works by inserting a catheter with an ultrasound probe into the esophagus, enabling close-proximity, multi-plane scanning of cardiac structures. This allows for high-resolution, real-time imaging of cardiac anatomy, blood flow and functional status. In addition, during intraoperative extracorporeal membrane oxygenation (ECMO) support, hemodynamic measurements obtained via pulmonary artery catheters or other standard monitors may be compromised due to altered flow patterns and non-pulsatile circulation; however, TEE provides direct visualization of vascular structures and cardiac function, offering multidimensional parameters and thereby allowing for a more comprehensive and accurate hemodynamic evaluation (6).

TEE was first proposed in 1976, and can produce both two-dimensional (2D) and three-dimensional (3D) images with high resolution (5,7). This enables clinicians to detect critical intraoperative pathophysiological changes, such as right ventricular dysfunction or pulmonary vascular anastomotic abnormalities, at an early stage and to implement timely interventions to prevent serious complications (5). The guidelines established by the American Society of Anesthesiologists and the Society of Cardiovascular Anesthesiologists in 2020 recommend the use of TEE in the management of patients undergoing LTx (8). Notably, the latest guidelines from the International Society for Heart and Lung Transplantation for the first time classify the use of TEE in LTx as class I recommendation, indicating that there is evidence and/or general agreement that the procedure is beneficial, useful and effective in clinical practice (9). Current guidelines consistently recommend initiating TEE promptly, as standard hemodynamic assessments do not adequately inform clinical decision-making (7-9). As a multidisciplinary diagnostic and monitoring modality, the intraoperative application of TEE necessitates close collaboration among anesthesiology, surgical and critical care teams for integrated image interpretation and real-time decision support (10). Furthermore, TEE has been integrated into critical care ultrasonography protocols, particularly in mechanically ventilated patients, where its bedside evaluation of cardiac function has been widely validated (11). Perioperative use of TEE facilitates optimized hemodynamic management, thereby improves patient outcomes by enabling timely interventions, reducing perioperative complications, and supporting better organ perfusion (12). Nevertheless, comprehensive and updated evidence summarizing the role of TEE during LTx remains limited.

The present review summarizes the latest advances in the application of TEE in LTx, with a particular focus on its role in diagnosing and managing intraoperative complications. Compared with previous reviews, the present review provides updated insights into the integration of TEE in the intraoperative management of ECMO (13,14).

TEE provides comprehensive, real-time data that enable precise management tailored to each phase of LTx (8). Table I outlines the essential TEE monitoring contents recommended throughout the four main stages of the procedure (8,13,14). After anesthesia induction, initial hemodynamic fluctuations are common (5). Therefore, once hemodynamic stability is achieved during Period 1, a baseline TEE examination should be performed prior to chest opening, providing a reference for the assessment of subsequent changes (13). During Period 1, preparatory steps such as positive pressure ventilation and single-lung ventilation may also induce hemodynamic fluctuations, requiring close TEE monitoring to assess changes and adjust the management plan (13). Period 3, defined as the release of the PA and atrial [or pulmonary vein (PV)] clamps and subsequent reperfusion of the transplanted lung, occurs in rapid succession. Therefore, for monitoring and management purposes, they are considered as a single critical period (Table I) (13,14).

Due to the proximity of the probe to the heart and major blood vessels, TEE offers an ultrasonic window that facilitates detailed visualization of cardiac anatomy and hemodynamic characteristics during LTx (15). In 2021, the International Consensus Recommendations for Anesthetic and Intensive Care Management of LTx approved the use of TEE for hemodynamic monitoring during the preoperative, intraoperative, and postoperative phases of perioperative management (16).

The use of ECLS in LTx has steadily increased over the past decade, since the first successful LTx involving cardiopulmonary bypass (CPB) (59,60). In cases of limited donor availability and poor overall recipient condition, ECLS is used during LTx to ensure hemodynamic stability (61). The main advantage of ECLS is that it prevents volume overload and reperfusion injury in the first transplanted lung during bilateral LTx (62). The types of ECLS include CPB, venovenous ECMO (VV ECMO) and venoarterial ECMO (VA ECMO) (52).

ECLS is an important tool used to enhance surgical safety. The use of VV ECMO or VA ECMO as alternatives to CPB has become more popular (59). In 2022, the American Association of Thoracic Surgeons published an expert consensus document on the use of MCLS in LTx (59). This document provides 36 recommendations to guide professionals involved in the care of patients with end-stage lung disease who are considering transplantation. Among the recommendations, TEE is emphasized as a critical tool for evaluating ECMO dysfunction and related complications. These complications, including malpositioned cannulas, thrombosis, pericardial tamponade or inadequate ventricular unloading, require prompt and accurate assessment. The importance of TEE in this context is underscored by a strong consensus and a 92% agreement score among experts (59). Several studies have reported the use of TEE to guide ECMO; however, a comprehensive summary is lacking (63-65). Therefore, the present review summarizes the findings of the relevant studies.

ECMO involves cannulation of blood vessels to create a bypass circuit consisting of a pump and a membrane oxygenator (63). Bicaval VV ECMO is a well-recognized and validated therapy that requires the use of single or double peripheral venous access for the insertion of two different-sized cannulas to achieve adequate blood oxygenation (65). Traditionally, VV ECMO was performed using two cannulas [a femoral venous drainage cannula and an internal jugular (IJ), subclavian or second femoral venous cannula] to return blood to or near the right atrium (RA); however, the recently developed dual-lumen cannula can be used independently in the IJ vein (63). To ensure correct cannula positioning during surgery, TEE is an invaluable tool for both initial placement and continuous monitoring. Proper positioning requires the drainage port to reside in the superior vena cava (SVC) and the return port in the RA, with flow directed toward the TV (63). Using TEE, the mid-esophageal 4-chamber view can confirm the flow direction toward the TV, while the mid-esophageal SVC long-axis view verifies the location of the drainage port in the SVC (63). Additionally, the transgastric RV inflow-outflow view can confirm that the return port is in the RA without entering the right ventricle or contacting the atrial wall (63). In cases of malpositioning, TEE may reveal abnormal flow patterns, turbulence or mechanical compression of cardiac structures. These findings highlight the importance of continuous monitoring and adjustment to ensure optimal cannula function and prevent complications.

TEE provides guidance for all three key steps of cannulation: Wire placement, assessment of the precise depth of cannulation in the inferior vena cava (IVC) and orientation of the reperfusion port to the TV (66). Proper insertion and accurate positioning of the cannula are important for the safety and optimal performance of the dual-lumen cannula. Malpositioned cannulas can result in hemodynamic instability. For example, a misaligned return port may direct flow against the atrial wall, causing turbulence or inadequate flow (63). Similarly, an improperly placed drainage port may fail to fully capture venous return. TEE findings such as turbulence, low flow velocity or changes in chamber size (such as RV dilation) can indicate malpositioning (63). Structural injuries, such as atrial wall damage or vessel perforation, may be identified on TEE by the presence of hematomas, pericardial effusion or abnormal contact between the cannula and cardiac structures (63). Early detection of such issues allows for immediate correction of cannula position and, if necessary, surgical intervention to address injuries (67-69).

Thrombosis is the main complication associated with low ECMO flow (70). TEE is used to guide the diagnosis and treatment of thrombosis during ECMO (71-73). Obstruction of the cannula in ECMO is detected based on reduced blood flow velocity, hemodynamic instability and poor blood oxygenation. In addition, if refractory hypoxemia occurs during surgery after other causes (e.g., inadequate ECMO support due to insufficient flow, sweep gas failure or oxygenator dysfunction) have been excluded, TEE should be used for the early detection of a malpositioned cannula (63). In most cases, malpositioning of the cannula is predicted by deteriorating oxygenation during ECMO (63). TEE can be used to detect other complications related to cannulation such as hemothorax, pneumothorax and mediastinal or pericardial bleeding (63).

The risk of catheter malpositioning and tamponade may be higher in children than in adults because children have smaller, thinner blood vessels and smaller heart chambers (65,74). In addition, a particular concern in the pediatric population is the formation of a conduit loop, despite TEE images revealing the entry of the guidewire tip into the RV (63). After 2D TEE is used to guide the guidewire position, 3D TEE should be used to exclude the possibility of the formation of a guidewire loop during advancement. The oxygenation efficiency of the ECMO circuit depends on the flow rate of the pump relative to the cardiac output of patients. Accordingly, oxygenation in patients should be increased with increasing ECMO flow rate. If this does not occur, blood should be suspected to recirculate between the inflow and outflow cannulas, indicating the formation of a conduit loop (64). A case report of cardiac perforation during placement of a dual-lumen catheter in neonates highlighted that slight movement of the catheter in this population may lead to tip misalignment, and that using wire navigation to connect the RA to the IVC may be particularly difficult and dangerous (74). Direct contact between the tip of the wire or dilator and the IVC wall should be avoided. Neonatal experts recommend that TEE should be performed after catheter placement and before initiating ECMO to predict complications related to ECMO and to prevent cardiac arrest during immediate drainage (74).

A recent study has shown that TEE-guided ECMO is increasingly used in LTx due to its low radiation dose and bedside convenience (75). The present review summarizes specific monitoring of TEE in patients undergoing ECMO during LTx. However, studies on ECMO weaning during LTx and data validating the effectiveness of TEE in guiding ECMO are lacking.

Before LTx, the interatrial septum should be checked for the presence of a patent foramen ovale or an atrial septal defect (34). In the presence of a large atrial septal defect, RV pressure after LTx may lead to severe left-to-right shunting, resulting in high blood flow and transplant failure (76).

TEE can be used to detect the formation of a bronchovenous fistula (BVF) during LTx, especially in patients with severe pleural adhesions (77). BVF is a rare complication that can cause arterial gas embolism in important organs (including the heart and brain), leading to high mortality rates. Taguchi et al (77) reported that patients often receive high airway pressure ventilation during LTx and the surgical procedure can easily damage the bronchi and pulmonary vessels, leading to BVF. TEE can detect bubbles in the left side of the heart, facilitating early diagnosis and prompt treatment of BVF. The treatment goal is to maintain hemodynamic stability and minimize air entry into the bloodstream (reducing airway pressure and single-lung ventilation). Timely administration of pure oxygen can effectively treat hypoxemia and reduce air bubbles by eliminating nitrogen. TEE is an effective tool for the early diagnosis of BVF during LTx, which can improve the prognosis (77).

As mentioned in the 2020 Guidelines for the Use of TEE to Assist with Surgical Decision-Making in the Operating Room, TEE can help diagnose gas embolism in the left ventricle during reperfusion when the left atrial clamp is removed and the donor lung is implanted (8).

For certain specialized intraoperative support techniques, including the novel hybrid VA ECMO/CPB circuit, TEE monitoring can be utilized to adjust the ECMO flow rate and determine whether mode conversion is necessary (78,79).

After chest closure, TEE should be performed to determine the presence of atelectasis and pulmonary edema, or pulmonary tamponade occurring during severe emphysema or excessive lung inflation, providing a reference value for subsequent patient ventilation and volume management (80).

LTx is a complex procedure for both surgeons and anesthesiologists. Successful anesthesia during LTx can maintain hemodynamic stability and improve the prognosis. Therefore, anesthesiologists should possess expertise in TEE to manage intraoperative anesthesia and care. In addition, communication between anesthesiologists and LTx teams during surgery is crucial for achieving an optimal prognosis.

Current research primarily focuses on intraoperative monitoring, lacking comprehensive integration and analysis of continuous perioperative TEE data, thereby limiting a thorough evaluation of its clinical value and the assessment of multidisciplinary collaboration on patient outcomes (13,77). Future research should establish a robust multidisciplinary integration framework, spanning preoperative assessment, intraoperative monitoring, intensive care unit applications and postoperative follow-up. Such an integrative approach would not only provide cohesive support for perioperative decision-making but also identify dynamic clinical changes often overlooked by intermittent monitoring, ultimately optimizing patient management strategies and improving clinical outcomes.

Moreover, the application of TEE in pediatric LTx remains underexplored. Current practice in this population primarily relies on experience extrapolated from adult cases, with limited evidence from large-scale studies or pediatric-specific guidelines. Future investigations should focus on assessing the role of perioperative TEE in improving graft survival and reducing complications in children. Additionally, efforts are warranted to develop TEE probes and imaging modalities tailored to the unique anatomical features of pediatric patients.