In addition to its role as an intraoperative diagnostic tool, transesophageal echocardiography (TEE) has been shown to be increasingly useful in the critical care setting. Patients in the critical care unit may have impaired cardiac function due to comorbidities or as a result of their critical illness. Indeed, cardiac dysfunction is one of the most common causes of hemodynamic instability and death in critically ill patients.1 Unlike many other diagnostic modalities available to the intensivist, TEE is minimally invasive and can be rapidly performed at the bedside. It can be used to provide valuable information on cardiac function, guide resuscitation and management, and diagnose a wide range of pathologies that may have a negative impact on the critically ill patient (Table 22–1). TEE was initially applied in the intensive care unit (ICU) for the postoperative evaluation of unstable cardiac surgery patients. However, TEE has also been shown to be beneficial in the general ICU setting, changing management in up to two-thirds of cases.2,3 In addition to the fact that the use of echocardiography has a positive impact on the management of patients in the general ICU,4 there is also evidence to support its therapeutic impact and its value in predicting mortality.5 Surprisingly, despite all these advantages, echocardiography is still not yet available in most ICUs, being largely limited by the availability of trained providers.5

The indications for TEE, as previously discussed in this manual, also apply to critically ill patients. The ACC/ AHA/ASE guidelines define hemodynamic instability and suspected aortic dissection as class I indications for echocardiography in the ICU (ACC/AHA/ASE 2003 guidelines) (Table 22–2). Acutely ill trauma patients should also undergo an echocardiographic evaluation if they are suspected to have cardiac tamponade or aortic injury. The most common indication for which TEE is performed in the ICU is hemodynamic instability, followed by endocarditis, assessment of ventricular function, aortic pathology, and miscellaneous others.2

In the general population, transthoracic echocardiography (TTE) is typically the first modality used, as it is noninvasive and more widely available. In the ICU population, however, up to one-half of mechanically ventilated patients cannot be imaged adequately via TTE.6 Barriers to adequate TTE imaging include mechanical ventilation with positive end-expiratory pressure, wounds and dressings, and body habitus. In addition, many ICU and trauma patients may be too unstable to be positioned in the left lateral decubitus position for TTE imaging. In a study comparing TTE to TEE in patients with unexplained hypotension in the ICU, TTE images were inadequate in over 60% of cases, while TEE provided new, clinically significant diagnoses in 28% that were not seen by TTE.7 The American College of Cardiology deems TEE a reasonable first test (versus TTE) in patients who are intubated, recently postoperative, or who have chronic obstructive pulmonary disease (COPD) or chest wall abnormalities, which may impair TTE examinations.8

In addition, there are certain structures and pathologies that are best visualized using TEE. These include the mitral valve, prosthetic valves, great vessels, and atria, as well as endocarditis and intracardiac thrombi (Table 22–3).8,9 This is particularly important in trauma patients who may be at risk of cardiac tamponade, aortic injuries, and traumatic valvular disruption or septal defects. Finally, TEE is indicated in critically ill patients requiring echocardiographic evaluation in whom TTE images are inadequate.

As with TEE in the general population, transesophageal echocardiography has a very low incidence of complications in critical care patients.2,10 Excluding feeding tube dislodgement, TEE had a complication rate of 2.6% in a review comprising 2508 examinations in the ICU.2 The most common complications included oropharyngeal mucosal lesions (0.7%), hypotension (0.6%), and coughing (0.3%). TEE should not be performed in any patient with esophageal perforation or in whom esophageal pathology or other comorbidities prevent safe and atraumatic insertion of the TEE probe.

Patient Preparation

Prior to performing a TEE examination, appropriate equipment for airway management, suctioning, and resuscitation should be available. Standard monitoring should be used including pulse oximetry, invasive or noninvasive blood pressure monitoring, and continuous electrocardiogram. It may be beneficial to have a second physician present to assist with management during the examination of hemodynamically unstable patients.

For elective TEE examinations, the patient should fast for 4 hours prior to the procedure to facilitate gastric emptying. Topical anesthesia with aerosolized or viscous local anesthetic should be performed prior to probe insertion. Judicious sedation may be used at the intensivist’s discretion, depending on the patient’s clinical presentation. Small titrated doses of benzodiazepines and/or opioids are commonly used, with reversal agents readily available.

For emergent TEE, gastric contents should first be suctioned via orogastric or nasogastric tube if in situ. In a patient with cardiopulmonary instability and an unsecured airway, endotracheal intubation prior to TEE may be clinically indicated. While TEE can be an invaluable tool for diagnosis, its use should not delay appropriate resuscitation and management of the unstable patient.

Imaging

Many TEE studies in the ICU are performed to facilitate diagnosis and management of an unstable patient, or to rule out a specific disease such as tamponade or endocarditis. Thus, while a comprehensive TEE exam as described in the ASE/SCA guidelines should be performed in all cases,11 the intensivist performing echocardiography should initially focus the exam based upon the patient’s clinical status and suspected diagnosis. The following is a brief summary of the intensivist’s echocardiographic approach to various clinical presentations and diagnoses—a thorough discussion of each topic can be found in earlier chapters.

Hypovolemia and Preload Assessment

Significant hypovolemia is seen on TEE as decreased left ventricular (LV) filling and commonly demonstrated by obliteration of the LV cavity (“kissing” papillary muscles) in the transgastric (TG) midpapillary short-axis (SAX) view. However, systolic cavity obliteration may also occur in the setting of reduced afterload and/or increased ejection fraction in 20% of cases, and may not reflect hypovolemia.12 Furthermore, visual detection of small (< 10%) yet potentially important changes is difficult and more objective measurements of LV volumes are required, especially in patient with compromised ventricular function (see Chapter 21). A left ventricular end-diastolic area (LVEDA) in the TG SAX view less than 6.3 cm2/m2 (women) or 7.5 cm2/m2 (men) could be consistent with hypovolemia as these values define the lower limits of normal in subjects under general anesthesia.13 Unfortunately, there is a wide range of normal values and as a consequence, visual estimation of LV volume is limited to the extremes—cavity obliteration or marked ventricular dilation.