Chapter 25. The Nuts and Bolts of a Perioperative TEE Service

Over the past decade, the practice of perioperative transesophageal echocardiography (TEE) has evolved to the point that many anesthesiology departments own and operate their own ultrasound equipment and offer comprehensive perioperative TEE services, rather than “borrowing” equipment from cardiology colleagues or requesting their professional assistance in the operating room. The successful initiation and delivery of perioperative TEE services requires attention to a number of organizational details. First, practitioners with adequate training should be credentialed by the hospital for performance of perioperative TEE. Additionally, each program requires building a system for report generation and data storage, allocation of capital resources as well as skilled technical personnel to maintain and operate equipment, and implementation of a Continuous Quality Improvement (CQI) process. Finally, an efficient reimbursement infrastructure will ensure the program's fiscal viability. Although specific organizational details will depend on the individual institution and setting, the current chapter provides practical general guidelines that may be implemented to achieve success.

The TEE probe in use today has changed little in concept from that originally introduced by Hisanaga in 1977.1 Most probes are a modified gastroscope with an ultrasound transducer mounted on the tip. They are 80 to 100-cm long with a shaft diameter of 10 mm, a tip width of 12 to 14 mm, and are latex-free. Newer three-dimensional (3D) probes are approximately 1 mm wider at the tip than existing two-dimensional (2D) probes. Rotary dials in the handheld housing control a series of cables sealed within the shaft that allow flexion and extension as well as side-to-side lateral bending of the tip. Range of motion of the tip varies slightly among manufacturers but is approximately 60° up and down as well as 60° to the right and left. Buttons on the side of the housing electronically steer the ultrasound transducer at the tip, providing full 180° rotation.

A grounded shield covers all active circuits distal to the control housing, making electrical injury highly unlikely unless the outer layer of the shaft is cracked. However, the probe should always be disconnected prior to external defibrillation, as any minor defect in the covering could allow secondary arcing, potentially causing severe burns. Generally, the probe should be disconnected if left in place and unused for extended periods of time, such as during cardiopulmonary bypass, to prevent thermal injury or interaction with electrosurgical units. Electrical integrity of the TEE probe should be tested by a qualified technician as part of preventive maintenance, according to the manufacturer's protocol. This includes conducting frequent “bite hole” inspections as well as annual temperature calibration and current-leakage tests.

Current ultrasound machines are equipped with safety features to minimize risks of injury to the patient. Units will “time out” after a designated period, often 10 minutes, of inactivity to avoid probe overheating. In addition, there is an auto-cool feature that will interrupt ultrasound transmission if the transducer becomes excessively hot. Current models will freeze scanning at 41°C, although this can be overridden, usually to a maximum of 42.7°C. At this point, scanning will freeze until a designated cooler threshold is reached. In addition, scanning is frozen at less than 18°C. Although no bioeffects have been demonstrated at acoustic output levels used during echocardiography, it is prudent to maintain ultrasound energy exposure at ALARA (as low as reasonably allowable) levels.2 As such, the power settings should be set at the lowest level compatible with adequate image acquisition.

Handling of the TEE probe requires care and attention as the fragile elements in the tip must be protected from accidental damage. Prior to connecting the probe to the ultrasound machine, it is important to inspect the entire probe for damage to the probe covering and test the motion of the probe tip. Excessive motion of the tip is indicative of a malfunctioning probe. The contact pins should also be quickly examined to ensure that none are broken or bent. Successful connection is confirmed when the appropriate probe icon appears on the ultrasound machine screen. Multiplane probes autocalibrate each time the probe is connected—a process that is most efficient when the probe shaft is straight.

When used in the operating room, some mechanism should be used to secure the housing in a fixed position, allowing continuous monitoring of a particular view while preventing injury to the patient and keeping the probe from dropping to the floor. A variety of sheaths to cover the probe are available to protect it from contamination, although clear benefit from these has not been demonstrated.

Cleaning procedures for the TEE probe should follow manufacturer's recommendations. The probe is disconnected from the machine and the shaft soaked in mild soapy water to remove all organic matter. Enzymatic cleaners with a moderate pH work well, but iodine-containing solutions should be avoided. Furthermore, use of these enzymatic cleaners helps prevent accumulation of residue from the disinfecting solutions that can turn the patient's lips and tongue black. The shaft and tip should be wiped carefully with gauze pads, and the housing and shaft inspected for cracks, dents, holes, or bumps. Disinfection procedures follow, most often using glutaraldehyde-based solutions or various hydrogen peroxide solutions. Manufacturer's instructions should be carefully followed concerning dilution and soak times. Exceeding these guidelines will weaken the covering of the probe shaft. Disinfectants such as 70% isopropyl alcohol, phenol, benzoyl peroxide, or benzothonium chloride should not be used on the tip or the shaft. Probes should never be autoclaved or disinfected by ultraviolet radiation, steam, gas, or heat sterilization systems. After disinfection, the shaft should be rinsed copiously with sterile water and dried with a soft cloth, while the housing and steering mechanism are wiped down with 70% alcohol. Following cleaning and disinfection, the probe is stored with shaft and tip straight, shielded from direct sunlight and extremes of temperature. The case provided by the manufacturer should only be used for transportation to avoid prolonged storage in a coiled position.

General organization of a TEE service must be based on the needs and resources of each specific department. Many institutions are able to fulfill their clinical needs with several probes but fewer ultrasound machines. In such cases, two or more patients may have TEE probes in place, and a single ultrasound machine is transported wherever it is needed next. With due diligence and care, this can be done safely and allows maximal flexibility and patient service in a world of limited resources. Furthermore, with currently available equipment that incorporates multiple ultrasound modalities with extremely small footprint units, the ability to share between locations and even between services is greatly enhanced.

If ultrasound equipment is shared with the cardiology department, probes are ideally cleaned, disinfected, and stored in a single location by dedicated technicians familiar with these procedures. In this case, transportation of the probes to and from the operating room may best be done in the carrying case if the distance is far, or by hand with the tip protector in place. Transporting probes that are resting on top of a cart carries a high risk of costly damage to the probe and should not be done.

Competent technical assistance is a key element to a successful perioperative TEE service. For anesthesiology departments, it is often the anesthesia technicians that are responsible for cleaning and maintaining TEE probes, as well as ordering supplies and identifying problems. Also, log books should be kept of probe and machine maintenance activity along with written protocols for equipment cleaning and sterilization. While rarely employed in the operating room setting, a skilled sonographer is invaluable in other critical care settings. Space is often limited, and it is frequently necessary for the machine to be on the opposite side of the bed from the physician performing the exam. A skilled assistant speeds the examination, as the physician can concentrate on manipulating the probe rather than constantly switching hands to operate the ultrasound machine. Regardless of the setting, all TEE exams require the focused attention of the physician performing the procedure. A collaborative relationship with sonographers and cardiologist-echocardiographers often improves the quality of the perioperative TEE service.

In all clinical settings outside of the operating room, there should always be at least one assistant to monitor the patient's vital signs, administer medications, suction secretions, and otherwise attend to the patient's needs. Sonographers are not typically credentialed to monitor the sedated patient or administer medications, and therefore the presence of a skilled nurse or another physician is usually required. In the operating room, the anesthesiologist- echocardiographer may be responsible for performing the TEE examination and administering the anesthetic. However, owing to the significant workload and attention required of both tasks, a resident anesthesiologist, nurse anesthetist, or other technical assistant is extremely valuable, especially during busy moments.

Written informed consent for TEE outlining the risks and benefits, as well as the indication for the examination, is necessary outside of the operating room. In addition, a thorough discussion of the procedure improves patient cooperation for those studies performed in awake patients. Relative and absolute contraindications must be assessed and discussed with the patient, including a history of gastric or esophageal pathology and abnormalities of the airway and pharynx. In the operative environment, current recommendations are that informed consent be obtained and documented in the patient's chart, either separately or as part of the general anesthetic consent.3

In all settings in which TEE is performed, additional required equipment includes suction apparatus, supplemental oxygen, emergency cart with airway equipment and resuscitation drugs, monitors, bite guards, intravenous access supplies, and universal precautions equipment for the staff. Oxygen supplementation is advisable whenever patients are sedated.4

Monitoring for all patients should include continuous electrocardiographic and pulse oximetry recording and intermittent blood pressure measurements, in accordance with guidelines for conscious sedation.4 Patients should have been fasting for at least 6 hours and dentures should be removed. An intravenous catheter should be inserted even if sedation is not anticipated, since it will provide immediate vascular access if needed for resuscitation. When possible, the patient is placed in the left lateral decubitus position to reduce the risk of aspiration.

Topical anesthesia of the mouth and pharynx facilitates all TEE examinations performed in patients who are not heavily sedated or under general anesthesia. Most often viscous lidocaine (2%) gargle or atomized lidocaine (4%) are used as topical agents and carry significantly less risk of methemoglobinemia compared to benzocaine-containing local anesthetics.5 Superior laryngeal nerve blocks may be performed, or lidocaine-soaked gauzes may be placed in the piriform sinuses with Krause forceps. Adequacy of topical anesthesia can be tested with a tongue blade or suction tip. Successful TEE examination in the awake patient is most likely if adequate time is allowed for the topical anesthesia to become effective.

Intravenous sedation is administered to most patients undergoing elective TEE outside of the operating room, and has been shown to decrease procedure-associated retching as well as post-procedure sore throat.6 Choice of agents and depth of sedation must be tailored to the patient. Most commonly, fentanyl and midazolam in small doses are administered prior to attempted placement of the probe. Although an unusually cooperative patient may be able to swallow the TEE probe without sedation, a more apprehensive patient may require heavy sedation or even a short-acting hypnotic. Interestingly, additional sedation is rarely required after initial placement of the probe.

Endocarditis temporally related to TEE has been described in only one case report.7 In contrast, a very low incidence of bacteremia induced by TEE examination was found in several studies (4 out of 500 patients in total).8–12 A recent editorial noted that most of the organisms isolated in these studies were skin commensals, probably representing contamination rather than true TEE-related bacteremia.13 Authors of a recent review of 17 databases comprising more than 42,000 adult patients have recommended prophylaxis “in cases of poor oral hygiene, prolonged or traumatic TEE procedures, or in subjects undergoing TEE in the first two months after valve replacement.”14 In contrast, the updated American College of Cardiology/American Heart Association guidelines for management of valvular heart disease do not recommend antibiotic prophylaxis before any gastrointestinal procedure, including TEE.15

Following attention to the preparatory details of informed consent, topical anesthesia, and intravenous sedation described above, the TEE probe is inserted with ease in the majority of adequately prepared awake patients. The probe's control wheels should be tested prior to insertion, to confirm proper function. A bite guard should be used in all patients with teeth to prevent injury to the patient or the probe shaft, even when used in anesthetized patients. Appropriate acoustic coupling gel should be placed on the probe tip prior to insertion to optimize imaging. Although any glycerol or other water-based lubricating medium is acceptable, mineral oil or other oil-based coupling gels will damage the probe's outer covering. After insertion of the bite block, the lubricated probe is introduced into the patient's pharynx, at a depth of approximately 15 to 20 cm from the teeth. Gentle steady pressure to advance the probe is applied, and the patient is asked to swallow. For many patients, this verbal instruction is all that is required—swallowing will close the vocal cords and relax the cricopharyngeus muscle.14 Flexing the patient's neck or slight flexion of the probe tip may assist its passage past the base of the tongue. Neck flexion also prevents stretching of the esophagus, a condition which might increase the risk of a mucosal tear or perforation.14 Under no circumstances should the TEE probe be forced into the esophagus. It may also be helpful to hold the small wheel on the housing at a neutral position, to avoid undesirable lateral bending during probe insertion. The large wheel, controlling flexion/extension, should never be locked. If there are feeding or nasogastric tubes in place, the TEE probe can usually be placed alongside these devices, but often they must be removed to allow adequate imaging. Prior to introducing the TEE probe in tracheally intubated patients, many physicians place an orogastric tube to evacuate the stomach contents.

When an endotracheal tube is in place, the TEE probe is placed most easily by manually distracting the patient's mandible by inserting a gloved thumb behind the lower molars and lifting the jaw upward. This maneuver, also known as the Esmarch-Hein maneuver, opens the pharynx and allows the tip of the probe to be guided with ease directly into the mouth, pharynx, and esophagus. On occasion, turning the patient's head to the right or left will be helpful. While the use of direct laryngoscopy is not usually necessary for probe placement, a recent study did show that its use results in successful placement with fewer attempts and reduces complications like odynophagia and minor oropharyngeal injuries.16

It should be kept in mind that unsuspected pathology may impede advancement of the probe. Any unusual resistance to probe insertion should prompt abandonment of the procedure. Failure to place the probe is rare. Chee et al found a 1.2% rate of failure among 901 TEE exams.17 In another review, 98.5% of failures were due to lack of cooperation or lack of operator experience, while only 1.5% were due to anatomic abnormalities.18 Other authors have identified prominent vertebral spurs associated with cervical spondylosis as a common cause (16 of 40) of failure of probe placement.19 In intubated patients, briefly deflating the endotracheal tube cuff should be considered as this may ease passage of the probe tip.14

When unusual resistance is encountered during attempts to advance or withdraw the probe, the physician should consider that the tip may have “folded” 180° onto itself, so called “buckling” of the probe.14 This mechanical problem should be suspected when probe movement is difficult, image quality is very poor, and the control wheels are bound and difficult to move. If the physician believes this has occurred, the probe should be advanced gently into the stomach, the tip straightened, and the probe removed and inspected. Under the rare circumstance that the TEE probe cannot be moved without exerting undue force, a radiograph may help determine the probe position and guide the next intervention. In very unusual circumstances, if the deflector mechanism is completely jammed inside the patient and all efforts to release it have failed, the probe should be removed from the unit, and the entire probe shaft should be cut with heavy-duty pliers or other suitable tool. This will release the deflecting mechanism, allow the tip to straighten, and facilitate probe removal.2

Indications for performance of a TEE examination are very broad and vary according to practice locations. General indications for perioperative TEE include definition of ventricular and valvular function, identification of intracardiac masses and sources of embolization, evaluation of intracardiac shunt, and assessment of aortic pathology. The most common indication for urgent TEE examination is differential diagnosis of severe hemodynamic instability, including cardiac compression and tamponade following cardiac surgery, suspected pulmonary embolus, acute myocardial ischemia, or aortic dissection. In 2010, the American Society of Anesthesiologists (ASA) and the Society of Cardiovascular Anesthesiologists (SCA) updated the practice guidelines for perioperative TEE (Table 25–1).20

The first area in which perioperative TEE achieved routine use was the cardiac surgical operating room. In this setting, TEE is most useful for evaluating ventricular function, detecting wall motion abnormalities indicative of acute myocardial ischemia, and evaluating native or prosthetic valve function immediately following valve replacement or repair (see Table 25–1).20,21 TEE also has an especially important role in the intraoperative management of surgery for congenital heart disease.22

In a large prospective cohort study, Mishra et al found that 36% of 5016 cardiac surgical patients benefited from the pre-cardiopulmonary bypass TEE study and a similar number from the post-bypass study.23 The TEE examination was most useful for the identification of intracardiac thrombus, aortic atheroma, mitral leaflet configuration, changes in valvular function, and in guiding de-airing procedures prior to separation from bypass. It was also judged essential for transmyocardial laser revascularization and port-access procedures.23 In some centers, TEE has replaced transthoracic echocardiography (TTE) as the preferred initial imaging study in post-cardiac surgery patients requiring emergent evaluation owing to the superior image quality of TEE compared with chest wall echocardiography. In one report, the average time to reach a diagnosis was 11 minutes, and the etiology of refractory hypotension was clearly identified in 76% of patients.24

As more anesthesiologists become skilled in the performance and interpretation of TEE, its use during noncardiac surgery has increased (see Table 25–1). Suriani et al reported the use of TEE in 123 orthotopic liver transplants.25 In 15% of cases, TEE was critical in altering surgical or anesthetic technique, treating life-threatening events, or directing further postoperative evaluation. In this population, TEE can also be useful in diagnosing hepatopulmonary syndrome by identification of bubbles in the pulmonary veins after a bubble test.26 TEE is of immense value in managing intraoperative hemodynamic instability. Feierman reported the use of intraoperative TEE to identify unsuspected dynamic left ventricular outflow tract obstruction, allowing crucial redirection of management strategy.27 Brandt et al reviewed 66 cases in which intraoperative TEE was emergently requested to diagnose severe left ventricular dysfunction, aortic dissection, new myocardial wall motion abnormalities, patent foramen ovale, localized cardiac tamponade, and right ventricular dilatation consistent with a pulmonary embolism.28

TEE use is becoming more and more common in critical care areas, sometimes performed by cardiologists, but more frequently by anesthesiologists and intensivists.29 Two recent studies examined the indications for and impact of TEE studies in the intensive care unit (ICU). In a total of 379 studies, the most common indications were for evaluation of unexplained hypotension, left ventricular function, pulmonary edema, and suspected endocarditis. The TEE studies had an immediate impact on management in 30% to 50% of the cases.30,31 Others have reported using TEE in intensive care units to guide central line placement, evaluate patients with unexplained hypoxemia, or to evaluate potential heart donors.32,33

In the setting of hemodynamically significant pulmonary embolism, both TEE and transthoracic echocardiography will demonstrate signs of cor pulmonale, including right ventricular dilatation, right ventricular dysfunction, tricuspid regurgitation, and pulmonary hypertension. TEE will be able to demonstrate emboli in the main or right pulmonary artery with a high degree of sensitivity. However, TEE is not sensitive enough for detection of left pulmonary artery or lobar pulmonary artery emboli.34 Therefore, in a patient with cor pulmonale and suspected pulmonary embolism, TEE can rapidly confirm the diagnosis; however, a negative TEE study should be followed by computed tomography (CT) angiography to rule out left lung or peripheral pulmonary emboli.29

The proximity of the esophagus to the aorta allows precise and accurate diagnosis of certain types of aortic pathology using TEE, and this application has found a specific niche in the emergency room. Minard et al compared TEE with aortography to evaluate possible aortic disruption.35 Diagnosed abnormalities included intimal flaps, pseudoaneurysms, intra- or extraluminal hematomas, and gross dissections with identification of false and true lumens. However, the sensitivity and specificity of TEE were lower than aortography, most likely due to the inability of TEE to image the distal third of the ascending aorta and the aortic arch.35,36 While some forms of aortic pathology are not completely assessed with TEE, this technique is very valuable in ruling out aortic dissection. Yalcin et al reported TEE to be 98% sensitive and 99% specific for detection of aortic dissection.37 In addition, of significant importance is the fact that TEE is often safer than other imaging modalities in hemodynamically unstable patients. Overall, despite its known deficiencies, TEE remains the first-line test for evaluation of aortic pathology, owing to its portability, low cost, low level of invasiveness, rapidity, and low complication rate. In the presence of a negative study, however, it is often necessary to proceed to further radiologic imaging if the clinical suspicion of aortic pathology remains high.36–39

There are very few absolute contraindications to TEE, and an individualized cost/benefit analysis must influence each decision. Esophageal pathology is probably the most controversial source of risk. Problems such as severe esophageal reflux disease, dysphagia, and odynophagia are considered to be relative contraindications in some centers. However, there are reports of the safe use of TEE even in patients with known esophageal varices. Generally, the presence of esophageal masses, strictures, and large varices are considered strong contraindications to performing TEE. Other conditions such as unstable cervical spine injuries, a history of mediastinal radiation, or upper airway pathology (eg, severe facial trauma or pharyngeal tumors) should be considered relative contraindications. Recent oral intake or an uncooperative patient can make performance of the TEE difficult and may result in a higher rate of complications or an inadequate study. When TEE is being considered as an important diagnostic test and the patient is known to have a history of significant esophageal pathology, it is reasonable to request endoscopic evaluation of the esophagus by a gastroenterologist prior to performing TEE. However, a normal endoscopic evaluation does not eliminate the risk of TEE- induced gastrointestinal injury.40 In a patient with partial or total gastrectomy, it would be prudent to limit the TEE examination to the upper and midesophageal views and avoiding insertion of the probe to the depth of the surgical site.14

In contrast to the benign nature of TTE, TEE is an invasive procedure, albeit of minimal degree. Furthermore, perioperative TEE is often performed in patients who are either critically ill or are undergoing major surgery and more likely to suffer a variety of adverse events. While a low rate of complications would be expected based upon the similarity of TEE to upper gastrointestinal endoscopy (UGED), there are several pertinent factors that may make TEE fundamentally different from UGED. Many patients undergoing UGED have suspected local pathology, while TEE is avoided in such patients, thereby reducing the risk of probe-induced injury. On the other hand, the TEE probe is inserted blindly rather than under fiberoptic guidance. Furthermore, patients undergoing TEE tend to have more advanced cardiopulmonary disease.18 Taken together, these factors would indicate that the risk of TEE should probably not be based on generalizations from UGED.

Most descriptions of the complications of TEE are based on published case reports. These can be broadly divided into complications related to upper airway and gastrointestinal injury during probe insertion and manipulation, those related to compression and pressure by the probe on adjacent organs, those related to the sedation used to facilitate the study in non-anesthetized patients, and those complications resulting from the hemodynamic responses to the procedure (Table 25–2).14 Case reports, however, are deceiving for two main reasons. First, case reports of complications do not identify the prevalence of the complication. Second, some complications ascribed to TEE during cardiac surgery may have another etiology. For example, in one study, the incidence of recurrent laryngeal nerve injury after cardiac surgery was similar with and without TEE.41 Another study has reported 10 cases of upper gastrointestinal bleeding in 8559 patients undergoing cardiac surgery without the use of TEE (0.1%).42 Had TEE been used in these cases, the observed gastrointestinal bleeding would likely have been attributed to this procedure.

With the limitations of case reports clearly in mind, several large series have examined complications related to TEE in different settings (Table 25–3). Overall, the risk of major complications in adults was 0.07% to 0.2%, and the risk of all complications was 0.2% to 0.7%. In addition to the studies mentioned in Table 25–3, another large series of 2070 TEE studies performed in a cardiology laboratory described several complications including laryngospasm, hypotension, pulmonary edema, and one death from cardiac arrest possibly related to sedation, for an overall rate of major complications of 0.5%.43

In contrast to these relatively favorable studies, other studies have emphasized a significant risk of TEE-induced major gastrointestinal injury. A 2006 literature review described 12 case reports of major esophageal injury after perioperative TEE.44 In a series of 860 patients undergoing cardiac surgery, Lennon et al reported a 1.2% incidence of major complications in patients who had TEE compared to 0.3% in those who did not have TEE done.45 These complications included partial thickness tears or perforations of the esophagus or stomach, as well as upper gastrointestinal (GI) bleeding requiring transfusion and/or endoscopic or surgical interventions. Two-thirds of the complications were not evident until more than 24 hours after surgery. In a recent retrospective database study including more than 16,000 patients undergoing cardiac surgery with TEE, the incidence of esophageal or gastric tears and perforation was small (0.09%) but carried a significant 20% mortality rate.46

Other studies have demonstrated an eightfold increase in the risk of transient dysphagia associated with intraoperative use of TEE.47 Barium studies have confirmed that swallowing abnormalities after cardiac surgery were more common when TEE was used intraoperatively, and these were associated with an increased risk of pneumonia and prolonged mechanical ventilation and ICU stay.48 Both the incidence of failure to insert the probe and the risk of complications appear to be lower for intraoperative TEE compared to TEE performed in the nonoperative setting. The most likely explanation for these findings is that patients undergoing intraoperative TEE are anesthetized and paralyzed, have their airways protected, and are invasively monitored. However, it should be stressed that an anesthetized patient is not able to assist with probe insertion by swallowing and will not complain of pain as a warning sign of impending injury.

The incidence of minor complications depends to a large extent on the way these are defined and diagnosed. For example, in a case-control series of 664 patients undergoing TEE mostly in the cardiology lab and ICU, changes in blood pressure and hemoglobin oxygen saturation were strictly defined and closely monitored.49 These authors reported transient hypotension in 5.4% of the examinations, transient hypertension in 8.6%, and desaturation in 3.2%. The overall incidence of minor complications (defined as those not requiring therapy or those reversed by simple interventions) was 16.3%, with only three major complications (0.45%).

Compared to adults, pediatric patients are at a higher risk from TEE, both for failure of probe insertion as well as for complications (see Table 25–3). The child's small oropharynx and the proximity of the relatively large TEE probe to the more pliable great vessels and airway most likely explain the high incidence of hypotension from vascular compression or airway problems like unintentional tracheal extubation and right main-stem bronchial intubation.50 Fortunately, these problems are easily recognized and resolve with TEE probe removal.

The risk of TEE exams might be higher in other settings and with special patient populations. Critically ill patients may be at a higher risk of complications owing to unstable hemodynamics and coagulopathy. However, in one report of 308 TEE studies performed in critical care units, only two patients developed hypotension requiring pharmacological support, one had a clinically evident aspiration, and one had an oropharyngeal bleeding.30 In a smaller series of 62 TEE examinations in critical care patients, one patient developed hypotension, one vomited, and one patient with known seizures receiving anticonvulsant therapy had a grand mal seizure soon after start of the TEE study.51 Generally, it appears that TEE can be performed safely in the intensive care unit.

In contrast, TEE performed in the emergency room (ER) appears to be associated with an increased risk, probably related to the precarious clinical status of the patients and possibly associated with the failure to secure the airway prior to the TEE examination. One study reported 142 TEE examinations performed in the ER with complications occurring in 18 (12.6%).38 One patient died from rupture of a thoracic aneurysm during the TEE study, seven developed respiratory insufficiency, four required tracheal intubation, and 10 patients suffered other minor complications. When clinically feasible, it may be safer to admit these patients to the ICU and stabilize them prior to performing the TEE study.

Obesity is considered to be a possible risk factor for increased complications after TEE. A case-control study has shown a 2.7-fold increased risk of transient hypoxemia in obese patients.49 Increased heart size, especially left atrial dilatation, which may compress and distort the esophagus and gastroesophageal junction, has been reported to increase the risk for major gastrointestinal injury during TEE.44 A recent large study has found significantly increased risk for esophageal and gastric injury in women compared to men, especially those older than 70 years of age.46

Traditional videotape libraries of echocardiograms are rapidly becoming relegated to the dusty backrooms of medical records departments for a variety of reasons, most importantly because the crucial value of rapid acquisition, retrieval, manipulation, and comparison has been recognized. Despite the obvious technical issues, digital studies do not degrade over time, they can be easily tracked over time to evaluate disease progression, they are available for teaching and research, and they are rapidly searchable in a way not dependent on the memory of the reader or investigator.

Echo signals emerge from the ultrasound transducer in an analog format as continuous voltage signal patterns. These are immediately translated into digital form by a scan converter and undergo a series of transformations. Such signal processing varies between manufacturers but generally improves image quality by screening out superficial structures and improving fine detail, contrast resolution, and spatial focusing. Images are captured at a rate of 25 to 30 frames per second, the minimal rate required for the human eye to perceive smooth motion.52,53 Historically, the ultrasound machine then converts the image back to analog format for display on the monitor and directs similar analog signals to the video output for recording on videotape. In newer systems, the digital signal is directly stored on a hard drive or optical disc and then transmitted to a distant site for storage on a common server or workstation via network connection.

The advantages of a digital system are immediately obvious and include the ability to record a single image and view it as a continuous loop, review multiple loops on the screen simultaneously, and even compare similar loops from separate studies. Furthermore, the latest systems allow the reviewer to perform off-line spectral Doppler and M-mode analysis at a distant workstation, and some manufacturers allow off-line analysis in non-scanned planes (eg, M-mode scanning in any direction within the 2D scan plane). Studies are immediately available for viewing by the referring physician, and can be transmitted with ease to distant sites for additional opinions or even “tele-cardiology” consults when an expert echocardiographer is not available. The stability of binary code also prevents degradation of data over time. Study archiving and retrieval is tremendously simplified, as patient identifiers included in study information can be stored in databases. Studies are also directly available for educational purposes, as databases can include any quantitative or descriptive information the managers choose to include. Such global digitization of echo studies has been shown to decrease physician interpretation time by greater than 30%.54 Digital structured reporting, which merges qualitative and quantitative reporting by automatically populating as much data as possible directly from the machine and providing a format for the rest of the report from drop-down menus, showed dramatic improvements in productivity. This advance has been seen for individuals, as well as departments as a whole, even though some variability among physicians remained.55 All perioperative echocardiographers are therefore urged to move toward this digital standard by incorporating the Digital Imaging and Communications in Medicine (DICOM) format, high-speed networking, and permanent storage with built-in redundancy.3

The issue of digital storage capacity deserves special mention in the setting of a digital echo library. Each image requires approximately 1 Mb of memory per frame, or 30 Mb per second for digital storage. For an average 10-minute study, this is 18 gigabytes of memory, exceeding the storage capacity of 28 CD discs or 4 DVDs!56 In addition, transmitting this amount of data over a T1 network line would require approximately 7 hours.57

Therefore, data compression strategies have been developed to improve the efficiency of data storage and transfer. One such method preserves the ability to reconstruct the image exactly from the compressed data and is known as “lossless” compression. Only very limited degrees of compression are possible with lossless methods (eg, 3:1 up to possibly 7:1).56 Alternatively, in “lossy” compression techniques, some information is lost and exact replication of the image is not possible. Joint Photographic Experts Group (JPEG) is an example of a lossy format that can compress in the range of 5:1 and up to 80:1.58 Further compression is possible with Moving Pictures Expert Group (MPEG) compression. Such lossy techniques take advantage of redundant information both within and between frames and can compress data at rates of up to 200:1 with little degradation in diagnostic content. Such compression decreases the time required for data transmission from hours to minutes. Several studies have compared compressed images and digital video and have shown excellent concordance in visible image quality and diagnostic accuracy.57,59

For purposes of standardization, the American College of Radiology and the National Electrical Manufacturers Association formed a joint committee in 1983 to develop the Digital Imaging and Communication in Medicine (DICOM) standard.58 The latest version (3.0) was released in 1993, and has been endorsed by the American Society of Echocardiography (ASE), the American College of Cardiology (ACC), and the European Society of Cardiology.54 DICOM specifies how images are to be stored and transmitted over networks, as well as ways to incorporate patient information and image calibration data. The latest systems marketed by TEE manufacturers are able to export images in a variety of formats, including JPEG, Audio Video Interleave (AVI), and MPEG compression.

In a world of increasing reliance on electronic data management, it is important to keep several points in mind when choosing a software platform.

1. Comprehensiveness. All potentially useful data fields should be included in the original design. Published TEE examination guidelines are a useful starting point to decide upon these fields.60

2. Recording. Traditionally, a dedicated medical clerk enters test results from hand-written forms completed by the echocardiographer, a system plagued by clerical errors and inefficiencies. Alternatively, the echocardiographer can enter data directly into the database using a Web-enabled application at the time of interpretation or some handheld device at the time of the examination itself. The data input interface can be optimized for efficient data entry and minimal requirement for textual input using check boxes, drop boxes, and shortcuts for repetitive data (eg, “no change” between the pre-operative and post-operative TEE studies). Options can be programmed as mutually exclusive to prevent errors in data entry.61 The report can even be signed electronically.

3. Flexibility. The database should allow insertion of new fields in the future, as methods and study techniques evolve.

4. Connectivity. Ideally, the TEE images are digitally archived and a linking field can be used to couple the database record with matching images from the TEE archive.

5. Security. Like all medical databases, security measures should conform to current HIPPA regulations.

When a TEE examination is performed in the operating room, the main findings are always communicated directly to the surgeon and anesthesiologist caring for the patient. Similarly, a TEE performed in the ER or in the ICU is often performed for a specific diagnostic question that needs an urgent answer, and therefore the TEE findings should again be conveyed orally to the appropriate caregivers. However, a signed, written report should always follow any TEE examination for all the standard reasons of officially documenting any medical procedure (Table 25–4).62 Furthermore, producing a report is one of the requirements for proper training in echocardiography.63 When a trainee performs a TEE, the supervising echocardiographer should confirm the findings and co-sign the report. A copy of the report should be placed in the patient record, whether in electronic or paper-based format. Ideally, the report should be completed within 24 hours of performing the study.3

The SCA and the ASE have published recommendations for the content of a perioperative TEE report, including a sample report template (Table 25–5).64 The report should reflect the comprehensive adult perioperative TEE examination guidelines published by the SCA and ASE,60 and include an assessment of the degree of severity of any detected abnormality. Although specific quantitative measurements are not required by this practice guideline, these measurements should be performed and recorded as needed to create a complete description of any cardiac abnormality and its severity. Left ventricular regional wall motion should be evaluated and described according to standard nomenclature.62,65 A graphic representation of regional ventricular function facilitates transforming the real-time echocardiographic loops into an easily interpreted picture of left ventricular function.65

Published practice guidelines describe the indications and contraindications,20 training requirements,63 study performance procedures,60 report generation,64 and clinical competence evaluation66 for perioperative TEE. Drawing on these documents and on previously published guidelines for CQI in general echocardiography,67 the ASE and SCA have recently developed and published guidelines for a CQI program in perioperative echocardiography.3 It is strongly recommended that all practitioners take part in the CQI process to enhance their individual as well as departmental improvement.

The aim of any CQI program is to enable the involved practitioners to identify possible problems early, analyze their causes, develop solutions, and test them. 67 The primary tenets of a CQI program are having an ongoing, continuous process that strives to do the right thing in the right way and results in ongoing practice improvement. Table 25–6 lists the main components of a CQI program adapted for the practice of perioperative TEE.3 It is important that all practitioners who perform echocardiography participate in the CQI process and that these activities be documented. Although the emphasis placed on various numerical requirements that appear in CQI recommendations has been questioned, these numbers, derived from expert opinion, can serve as a reasonable guide to ensure staff proficiency and allow early detection of clinical problems.68

The cost of establishing and maintaining a perioperative TEE service is significant, and appropriate reimbursement is required to ensure the long-term viability of the service. As stated by the ASA, intraoperative TEE is a new diagnostic tool and service that “extends beyond the scope of standard perioperative anesthesia care.” It is “in addition to the anesthesia service being provided,” and is not “incorporated within the usual basic or time units of the ASA Relative Value Guide.”69 It comes as no surprise, then, that a study examining Medicare policies for perioperative TEE reimbursement has shown marked variation between local carriers. Only two-thirds had a specific policy for intraoperative TEE performed by an anesthesiologist, and almost half of the carriers denied all payments for this procedure. Reimbursement uncertainties are also shared by anesthesiologists. Almost 30% of those practicing in states where reimbursement does exist have reported that they never bill for TEE. Attesting to the integrity and professionalism of these anesthesiologists, TEE utilization rate was not affected by the availability of reimbursement.70

Billing for intraoperative TEE is done using specific Current Procedural Terminology (CPT) codes (Table 25–7). Different codes describe the purpose of the exam (diagnostic vs monitoring), the specific task performed (probe insertion or image acquisition, interpretation, and report, or both), and the modality employed (2D echo vs color-flow Doppler or pulsed-wave/continuous-wave Doppler). For reimbursement of any CPT code, the patient must have a condition corresponding to one or more of 100-plus listed International Classification of Diseases, Ninth Revision, Clinical Modification (ICD9-CM) diagnosis codes (Table 25–8), and these codes should be listed as well on the billing sheet.

The CPT codes for TEE are commonly bundled into the anesthesia codes. The “59” modifier should therefore be used to override the bundling in cases where intraoperative TEE is performed by the same individual responsible for the rest of the anesthesia care. In such cases, the TEE is a reimbursable service under Medicare guidelines only when it was performed for specific diagnostic purposes and a written report is generated. Use of TEE for monitoring is described by CPT code 93318, which does not require a written report. This code is particularly controversial with regard to Medicare billing. Most carriers view this use of TEE as an integral part of anesthesia care and therefore bundled with the base units of anesthesia and not separately reimbursable. Some carriers, however, will allow billing for probe placement in this situation (CPT codes 93313/93316), and some may even opt to allow full payment for the 93318 code.

Most Medicare carriers will require the provider of TEE services to be specifically credentialed in echocardiography. Since these policies change regularly and depend on the local Medicare carrier, every anesthesiologist should be familiar with the most updated local policies for reimbursement.