By ORM Staff
The use of transesophageal echocardiography (TEE) has become ubiquitous in cardiac surgery and has rapidly expanded in noncardiac surgery, including liver transplantation. A recent survey of anesthesiology directors at U.S. liver transplant centers, by Zerillo et al, found 90% of respondents have at least one team member who uses TEE and 66% employ it for all cases (Semin Cardiothorac Vasc Anesth. 2018 Jun;22(2):137-145). Nearly 85% of respondents agreed that this imaging modality provides unique and clinically valuable information that cannot be obtained easily with other monitoring tools.
In addition to facilitating hemodynamic management during liver transplantation, TEE has been shown to assist with rapid identification of life-threatening conditions and to help anesthesiologists feel confident about their choice of interventions.
For a closer look at the latest applications of TEE in adult liver transplantation, and how it may help to optimize outcomes in these highly-complex patients, Dinesh Kurian, MD and Govind Rangrass, MD], shared their experience and expertise. Both assistant professors in the Department of Anesthesia and Critical Care at the University of Chicago Pritzker School of Medicine.
ORM: What kind of anesthetic challenges do today’s liver transplant patients present?
Dr. Rangrass: UNOS’ [United Network for Organ Sharing] “Share 35” policy has dramatically changed organ allocation by increasing the distance from which livers can be procured for sicker patients, specifically patients with MELD [Model for End-Stage Liver Disease] scores of 35 or greater. Liver transplant programs have evolved in their sophistication to take care of sicker patients who might not have been deemed candidates for surgery in the past. Compared with five or 10 years ago, we’re seeing many more patients with diabetes, coronary heart disease, morbid obesity and other comorbidities that raise their risk for intraoperative complications.
ORM: For which transplant patients do you find TEE most useful?
Dr. Kurian: At our center, we perform about 75 liver transplants annually and use TEE for all of them unless there are absolute contraindications, such as active bleeding or recently banded esophageal varices or distinct esophageal pathology. TEE is particularly useful for the management of patients with hepatopulmonary syndrome, right ventricular dysfunction, patent foramen ovale, atrial septal defect and high right-sided pressures in the heart due to volume overload or portopulmonary hypertension.
The sicker the patients are, the more likely they are to have worse heart function and over time, to develop cardiac cirrhotic cardiomyopathy. Being able to obtain a real-time assessment of heart function with TEE can help an anesthesiologist decide whether or not, at least transiently, to use inotropes to support heart function during the surgery and whether those inotropes would be sufficient to maintain hemodynamics and perfuse the new organ and prevent congestion of the newly transplanted liver.
ORM: What kind of clinically valuable information does TEE provide at the start of surgery that might be difficult to obtain with other monitors?
Dr. Rangrass: Before the transplant starts, we often place the TEE probe to get a baseline assessment of the heart for valvular disorders and signs of hypervolemia related to right-sided heart pressures. That is of particular importance since the right heart is often stressed during the course of the surgery. The left ventricle is also assessed with the expectation that in an advanced cirrhotic patient with low systemic vascular resistance, the left ventricle will have a hyperdynamic performance.
TEE is also valuable in showing us hypovolemia and can help us avoid the use of invasive monitors, such as the Swan-Ganz catheter, to directly measure the pressures of the heart. We can visually see underfilling of the heart during the dissection phase, which begins with the drainage of ascites, and may be complicated by bleeding. This may be as much as 5 to 10 L of fluid in a patient with severe portal hypertension, which, once drained, can suddenly precipitate hypotension. TEE would show us if there is hypovolemia and inform us of the need to begin volume resuscitation.
Dr. Kurian: The baseline assessment can also reveal unexpected information. Maybe an [echocardiogram] a few weeks earlier looked fairly reassuring, but the patient had a subsequent decompensation and presents with worsening heart function. Now we have a liver that has already been procured brought into the room and general anesthesia has already been induced when TEE reveals a clinically significant difference in heart function. That could inform us how to do the case and prompt a discussion with the surgeon about whether the transplant should be performed on venovenous bypass.
ORM: As surgery progresses, how does TEE facilitate hemodynamic management?
Dr. Rangrass: When the IVC [inferior vena cava] is clamped during the anhepatic phase, most patients have an acute drop in preload to the heart. However, there is considerable variability because there are venous collaterals that build up over time and there are limited methods of quantifying the degree to which patients are collateralized. With different pathologic states, you can generally assume that there’s very little collateralization and that the IVC cross-clamping is going to be very difficult to manage.
That’s the point when TEE could reveal relative underfilling of the ventricles and prompt additional volume resuscitation. TEE also helps you understand if it’s safe to remove the native liver out at that moment. Sometimes, if there is significant hemodynamic instability, the hepatectomy is aborted. But one of the goals of using TEE to guide hemodynamic management is to avoid that scenario and be able to proceed safely with the surgery.
ORM: Have you encountered situations in which TEE provided lifesaving information that would not have been possible to obtain with other monitors?
Dr. Kurian: The neohepatic phase is the most critical moment during the entire surgery when TEE provides real-time information. There are a number of catastrophic and really important events that require immediate action to maintain the stability of the patient during this phase and avoid a disastrous cardiac arrest. In terms of lifesaving moments, we had one [recently]. Right after the IVC was unclamped, there was a sudden cardiac arrest with asystole. This was before the liver was reperfused, which is when we’d normally expect a massive hemodynamic catastrophe to occur.
Using TEE, our anesthesiologist in the room was quickly able to identify that the heart was full of air due to a massive arterial gas embolism. He alerted the surgeons, who identified a defect in the IVC, occluded it to prevent further air entrainment, and proceeded to repair it. Meanwhile, the anesthesiologist administered inotropes and the assisting surgeons performed cardiac massage through the diaphragm. Within a minute, the patient was back, with a perfusing rhythm.
ORM: What impact does the use of TEE have on outcomes for adult liver transplant patients?
Dr. Rangrass: Along with helping us navigate decision trees during true lifesaving emergencies and intraoperative rescue of critically ill patients, this imaging tool allows us to take a more targeted approach to volume resuscitation, where patients can be managed in a way to prevent end-organ damage such as acute kidney injury, pulmonary edema or liver congestion.
Trying to resuscitate to such fine end points is challenging, especially during liver transplantation where there are such large fluid shifts. Compared with pressure monitors, TEE is a better way to calibrate the utilization of one’s tools because one can actually see the size of the heart and assess myocardial function, and help put these extremely sick patients on a faster trajectory to recovery after this major surgery. That’s why I consider TEE to be part of the best possible care I can provide for these complex and challenging patients.