Transesophageal Echocardiography in Noncardiac Thoracic Surgery

Introduction

The use of transesophageal echocardiography (TEE), performed by the anesthesiologist, has become commonplace in cardiac surgery operating rooms in recent years. This has been especially prominent as the use of Swan-Ganz catheters has diminished at the same time. Outside of the cardiac surgery operating room the use of TEE has, thus far, largely been reserved for cases of unexplained hypotension/hypoxia/instability or so-called “rescue TEE.” However, this is changing, and more providers are electing to use TEE for hemodynamic monitoring in general surgery cases. The use of TEE in the thoracic surgery room is a natural evolution of its use in the cardiac surgery operating room because of TEE trained cardiac anesthesiologists often times providing the anesthetic for thoracic surgery patients, and the obvious interplay between the pulmonary and cardiovascular systems. In addition, as the surgical cases grow more complex and challenging, or rely on advanced therapies, such as extracorporeal membrane oxygenation (ECMO), there is an avenue to expand the use of TEE in this arena.

Thus far there is no consensus on indications for the use of TEE in thoracic surgery, save for the “rescue TEE,” like there is for its use in cardiac surgery. However, practice patterns are evolving in a way that make TEE a powerful tool for guiding management of this challenging patient population.

Indications for Transesophageal Echocardiography Use

The accepted guidelines by the Society of Cardiovascular Anesthesiologists published jointly with the American Society of Echocardiographers (ASE) state that the use of TEE in noncardiac surgery is indicated for patients who have known or suspected cardiovascular pathology that may impact the outcome of the surgery. The American Society of Anesthesiologists (ASA) expands on this to state that TEE may be indicated when the patient’s cardiovascular pathology may result in severe hemodynamic, pulmonary, or neurologic compromise. In addition, the ASA indicates that the use of TEE is warranted in cases of unexplained life-threatening hemodynamic compromise refractory to corrective measures. In cardiac surgery, the indications for TEE remain broad to include all patients undergoing open heart and in particular valvular surgeries and thoracic aortic procedures, while being indicated for select coronary artery bypass grafting (CABG) procedures. With the advent of transcatheter-based intracardiac procedures, the role of TEE has expanded to include procedural guidance during these procedures.

Beyond these, more indications for perioperative TEE are being pursued. There is growing use of TEE in the field of liver transplantation and the American Association for the Study of Liver Disease has issued a recommendation that TEE be used during orthotopic liver transplantation (OLT) to assess for the following: intracardiac chamber sizes, ventricular hypertrophy, systolic function, diastolic function, valvular function, and left ventricle (LV) outflow tract obstruction. Wax et al. conducted a survey of anesthesiologists at centers performing more than 40 OLTs per year and found TEE use at least occasionally in 86% of cases and 13% of respondents use TEE for every case. Furthermore, TEE findings during various phases of transplantation have been shown to be predictive of major adverse cardiac events (MACE) following surgery. For instance, the finding of intraoperative biventricular dysfunction was shown to be three times more likely than controls to suffer MACE and those with intracardiac thromboemboli were nearly five times more likely to suffer a cardiac event. Most institutions that perform liver transplantation require the providers to be ­certified in basic TEE certification.

TEE is also used for monitoring purposes in some urologic surgeries. Recently, a published randomized controlled trial (RCT) compared TEE use during radical cystectomy to current standard of care. In that study, the authors randomized 80 patients and found that the cohort who had TEE-based monitoring received fewer central lines, had shorter durations of mechanical ventilation with fewer pulmonary complications, and showed a lower rate of cardiac arrhythmias. Of course, as is the pattern nationally, one limitation of this study is that only cardiac anesthesiologists with training in advanced perioperative TEE, rather than basic, were included as the primary anesthesiologists and these results may be because of anesthesiologists selection as opposed to TEE use per se. Regardless, this highlights the search for novel uses and recognition of the value of TEE as a monitoring tool. In other urologic surgeries, such as resection of renal cell carcinoma with tumor thrombus of the inferior vena cava, TEE is used to evaluate for tumor location and extension, need for cardiopulmonary bypass, and also as a monitor for tumor embolization during the procedure.

In the emergency setting, point-of-care cardiac ultrasound (US) has been widely adopted in the setting of peri- and intracardiac arrest. Systematic reviews and meta-analysis have shown US to have a high level of accuracy for identifying reversible causes and an upwards of 95% accuracy for predicting short-term survival. Alternatively, the absence of cardiac activity on US is also highly predictive of the failure to achieve return of spontaneous circulation. In the operating room, the so-called “rescue TEE” has been a well-established tool to evaluate refractory hemodynamic instability. This is likely caused by the high accuracy of the images obtained despite ongoing resuscitation. Diagnoses such as pericardial tamponade, pulmonary embolism (PE), aortic dissection, biventricular dysfunction, and volume status are all accurately assessed using TEE. It is no surprise then that TEE during intraoperative cardiac arrests carries with it a similar benefit. This is largely because of the benefits stated previously regarding accuracy of imaging despite ongoing resuscitation. Of specific benefit to TEE over transthoracic echocardiography (TTE) is that accurate image acquisition is not impeded by ongoing cardiopulmonary resuscitation and requires no interruption of chest compressions.

Despite these multiple indications, some backed up with clear evidence, there exist no randomized trials of TEE as a monitor for noncardiac thoracic surgery. Regardless, it appears that TEE can be a powerful tool in aiding both the anesthesiologist and the surgeon in managing complex patients.

Transesophageal Echocardiography asa Monitor

The ASA first directly addressed the topic of “vigilance” in a 1992 panel at the annual meeting, and this concept has evolved to make up a large portion of how the specialty is viewed. This idea of vigilance in monitoring our patients in the operating room has driven countless technologic advancements seeking to allow physicians to better monitor, interpret, and respond to physiologic changes encountered (and ideally predicted) in the course of surgery. Classically, the pulmonary artery catheter (PAC) has represented the monitor of choice, though there has been growing interest in noninvasive cardiac output monitors, arterial waveform analysis, and TEE. At this time, however, the PAC remains the hemodynamic monitor most commonly used beyond the standard ASA required monitors. This use seems to persist despite lack of evidence for benefit of their use, and in at least one study potential for harm.

The goal of hemodynamic monitoring is to integrate information provided about patient variables into a plan of action that improves the outcome of the patient. In the case of PACs there has yet to be compelling evidence that supports their use in regards to improved outcomes. The Evaluation of Heart Failure and Pulmonary Artery Catheterization Effectiveness Trial (ESCAPE), published in 2005 randomized patients with heart failure to either receive a PAC to guide management or management based on clinical assessment. This study showed that patients receiving PACs were no more likely to be alive at 6 months, or did they have shorter hospitalizations. This finding is congruent with multiple reports from the critical care literature showing no apparent benefit to using PACs in patient management. These studies are in agreement with the 2003 publication evaluating the use of PACs in high-risk elderly patients undergoing noncardiac surgery which showed no improvement in 6-month mortality, and showed an increased rate of PE in the treatment group. Subgroup analysis of the sampled group even showed a possible increase in mortality in the group undergoing thoracic surgery, which should lend even more scrutiny to the use of PACs in thoracic surgery.

In light of this evidence showing that pulmonary artery (PA) catheters are not beneficial in managing heart failure and high-risk patients, then a natural question is “Of what benefit would echocardiography be?” This is an especially pointed question considering the large variability seen in the literature comparing PACs and TEE in one simple monitoring modality: measuring cardiac output. Su et al. in 2002 did a direct comparison of esophageal Doppler and PACs in patients undergoing CABG surgery and found an excellent linear correlation between cardiac output values obtained with a PAC and that with TEE. There are retrospective studies comparing the two which showed lower levels of correlation though these have their limitations sufficient to say that with qualified users TEE can get similar values as that of PACs. More recently, there has been an emphasis on noninvasive cardiac output monitors, which appear promising. At least one group compared one device (LIDCO) to TEE and PAC during the prebypass phase of surgical aortic valve replacement for aortic stenosis and found a high degree of reliability in the device for trending cardiac output. There are many more groups currently evaluating these devices and how they respond under various physiologic conditions during different phases of cardiac surgery.

Despite the results however, there is information that TEE provides the physician that a PAC or noninvasive cardiac output monitors would not provide. TEE is the only monitor that can provide instantaneous feedback about valve pathology or ventricular function. While the other monitors can provide the cardiac output, TEE has the ability to show the physician how that cardiac output is generated and if there are wall motion abnormalities or diastolic dysfunction. TEE is crucial in evaluating for pericardial disease and effusion, which goes undetected on PACs and other monitors. In addition, in the case of lung transplant TEE can provide information on the pulmonary venous anastomosis, and also indicate the function of the right ventricle (RV). In thoracic aortic surgery, TEE will evaluate for dissection and aneurysm which will of course go unnoticed on other monitors.

Clearly, there are other monitors that may provide useful information. However, the effect of these monitors (PACs) are dubious at best while some provide only very limited information (noninvasive cardiac output monitors). TEE, however, despite no RCT to validate its effect on patient outcomes, provides robust information that can help guide not only patient management by the anesthesiologist, but also surgical planning and execution with a low level of risk.

Risks of Transesophageal Echocardiography

Certainly the use of TEE carries great potential benefit, although we would be remiss if we did not speak about the potential harm of TEE use. The vast majority of the inherent risk of TEE use is related to the insertion of the echocardiogram probe into the oropharynx, around the base of the tongue, and subsequently into the esophagus. The complication that is most worrisome is direct damage to the esophagus. There are multiple reports of esophageal perforation associated with the insertion of the TEE probe. Reportedly, these most feared complications happen in 0.03% to 0.09% in large case series. The majority of these injuries (54.3%) occur in the thoracic esophagus with smaller proportions occurring in the pharyngeal or cervical regions (11.8% and 20.6%, respectively). The majority of these patients in one case series underwent repair of the perforation, though with a significant mortality of (28%) as the direct result of their injuries.

Although damage to the esophagus is very worrisome, this remains a safe procedure, especially so when the patient is anesthetized in the intraoperative setting. One large case series of intraoperative TEE was done in 2001 and included over 7000 patients. These authors showed an incidence of esophageal injury of 0.01% and of upper gastrointestinal bleeding of 0.03%. In addition, they showed a low mortality rate associated with TEE of 0%. From this case series, we also see that the more common complications that arise tend to be relatively minor with odynophagia occurring in 0.1% of cases and dental injuries occurring in 0.03%. More recently in 2007, Piercy et al. evaluated roughly 10,000 cardiac surgical patients and found similar rates of major complications with an incidence of about 1/1000.

In light of these potential complications, which are nonzero risks, it is important to discuss safety surrounding the use of TEE and ways to avoid these potentially devastating complications. First, as with any procedure in medicine, safety begins with the physician performing a detailed history and physical exam. Largely, this interview and exam will focus on elucidating potential gastrointestinal pathology that would prevent a barrier to passing the TEE probe. A history of esophageal or stomach surgery, or a history of difficulty swallowing should raise the physician’s suspicion of possible complications. If an interview elicits evidence of significant, noninvestigated, dysphagia then a barium swallow test remains the gold standard method of investigation to confirm or refute the presence of esophageal strictures or diverticula which otherwise might result in complications. In addition, some attention must be given to questioning the benefit of placing the TEE probe. As discussed earlier, this can be a powerful tool that can lead in certain conditions to a change in surgical planning. However, the possibility of this must be weighed against the potential chance of causing a complication.

Safe handling of the TEE probe is a must. Once the proper screening is done, safe handling by the physician is the last line of defense in preventing a complication. Once the patient is adequately anesthetized, important as the passage of the TEE can be a strong stimulus, intubation of the esophagus can occur under direct visualization or blindly. Under direct visualization, the jaw may be thrust and tongue pulled out to expose the oropharynx through which the probe may be guided, or if done blindly one hand may insert the probe while the other guides it along the back of the tongue and into the esophagus. Occasionally, there is difficulty in passing the TEE probe necessitating direct laryngoscopy to expose the esophagus through which the probe may be inserted. In small patients or those with dysphagia, one consideration would be the use of a pediatric TEE probe, as this has a smaller bore and theoretically is less likely to cause trauma. The probe should be lubricated to reduce friction and an inserted probe should always be unlocked and in a neutral position when inserted or removed ( Fig. 55.1 ).