Transesophageal echocardiography and orthotopic liver transplantation: general concepts.

T ransthoracic echocardiography is used extensively in the preoperative evaluation of patients undergoing liver transplantation and provides information about global cardiac function, valvular function, and presence of pericardial effusion. Dobutamine stress echocardiography and contrast-enhanced echocardiography are evolving into essential tools in the screening and/or evaluation of patients with possible coronary artery disease,1,2 pulmonary hypertension, or hepatopulmonary syndrome. Because of the potential for damage to esophageal varices with subsequent severe bleeding, transesophageal echocardiography (TEE) initially was used very reluctantly, but luckily this complication seems to be very uncommon, and, if it occurs, it is mild and self-limiting. Today, TEE is used more commonly in patients undergoing liver transplantation and has been helpful in the diagnosis and management of many conditions and complications.3 Patients with severe liver disease have a hyperdynamic hemodynamic system; most anesthesiologists believe high cardiac output has to be maintained perioperatively to maintain adequate perfusion of the tissues in the presence of peripheral shunting. Maintaining this high cardiac output can only be accomplished by maintaining preload. However, liver transplantation is associated with major changes in cardiac preload and afterload. Blood loss can be very significant, requiring the infusion of large amounts of fluids and blood products, potentially resulting in citrate toxicity. Graft reperfusion may lead to severe hypotension, usually the result of dramatic vasodilation, but in some patients, contractility changes are suspected to occur.4-6 Echogenic contrast material is seen entering the heart from the inferior vena cava on reperfusion in every patient,4 but clinically significant air embolism after reperfusion is uncommon. Although the interpretation of TEE remains mostly subjective, TEE has been helpful by providing additional information regarding preload and contractility. Filling pressures are not always reflective of preload because of significant changes in compliance.7 TEE may also help in the identification of the exact hemodynamic changes during postreperfusion syndrome.8,9 In addition, TEE has been used in the diagnosis and management of intraoperative complications, such as air embolism,10 thromboembolism,4,11,12 and the management of patients with unrelated cardiopulmonary disease, such as coronary artery disease, valvular pathological states, or idiopathic hypertrophic subaortic stenosis.13-15 Other patients with alcoholinduced cardiomyopathy, hemochromatosis, amyloidosis, or Wilson’s disease may benefit from intraoperative TEE monitoring. Pulmonary hypertension occurs more frequently in patients with severe liver disease; if it is decided to proceed with liver transplantation, TEE has proven to be an essential monitoring tool.16,17 TEE also allows the intraoperative diagnosis of hepatopulmonary syndrome in patients in whom the diagnosis was missed preoperatively.18-21 TEE has shown the presence of direct communications between portal vein and pulmonary veins.22 Finally, TEE allows for the intraoperative evaluation of the major vessels, including the suprahepatic inferior vena cava anastomosis; patients with previous LeVeen shunts may have narrowing or occlusion of the superior vena cava.23,24