“An invasion of armies can be resisted, but not an idea whose time has come.”
In this review, we describe the evolution of physician- performed ultrasound in anesthesia and critical care medicine, including the relevance of developments in technology. The concept of an expertise pyramid and levels of proficiency are discussed. Uses of point-of-care ultrasound are detailed for transesophageal echocardiography (TEE), transthoracic echocardiography (TTE), lung ultrasound, vascular access, regional anesthesia, and goal-focused TTE. The final section addresses training and future directions.
ULTRASOUND FOR NONCARDIOLOGISTS—WHERE DID IT START?
The first ultrasound machines were developed in the 1950s, based on sonar technology developed in World War II.1 Over the next 3 decades, this technology was developed commercially and became widely adopted by cardiologists, radiologists, and obstetric physicians. The equipment was bulky and very expensive, and the imaging was of relatively poor quality compared with today’s standards. This limited the technology to major facilities such as diagnostic laboratories or the cardiac surgery operating room. Ultrasound entered anesthesiology practice in the late 1980s with the introduction of intraoperative TEE for cardiac surgery.2 Paradoxically, this delayed the widespread adoption of ultrasound into anesthesiology practice because of the invasive nature of TEE and its complications.3,4 The requirement for sedation or anesthesia, and the need for a high level of diagnostic knowledge by the cardiac anesthesiologists5,6 equivalent to cardiologists tended to exclude physicians who wished to use ultrasound at a more qualitative level. Those unable to perform a full cardiologist level diagnostic study were considered inadequately trained and therefore should be prevented from accessing the technology. Thus, perioperative echocardiography was seen as the domain of the expert, who generally was the cardiac anesthesiologist.
Smaller, robust, less-expensive, yet high-quality ultrasound machines were a necessary precursor to greater use of ultrasound, but equally important was a mindset change to consider surface ultrasound applications, including TTE and ultrasound-guided procedures, as important areas for noncardiac anesthesiologists. In parallel, but somewhat delayed in time, other acute care specialties adopted similar changes in view and ultrasound usage.
The changing role of ultrasound can be viewed in evolutionary terms. The early stage is when discreet ultrasound examinations are performed by diagnostic laboratories, usually by technologists and reported by cardiologists or radiologists, and the treating clinician subsequently reviews a written report. These tend to be comprehensive examinations that are interpreted in-depth by highly trained physicians, but with often considerable delay in delivery of the information to the treating physician. The middle stage is the current practice of point-of-care ultrasound examination. The big transition has been the use of ultrasound at the point-of-care by the treating physician rather than by a cardiology or radiology service. In cardiac anesthesiology, this involves comprehensive TEE during the operation by the anesthesiologist. For the acute care specialties, this includes goal-focused TTE7 and TEE, ultrasound-guided regional anesthesia8 (including neuraxial9,10 and truncal11 blocks), vascular access,12 and lung13 and pleural scans.14 For the emergency physician, this could also include the FAST abdominal scan (Focused Assessment with Sonography for Trauma).15 The next stage of evolution will be when we incorporate ultrasound into everyday practice rather than performing separate ultrasound examinations, i.e., ultrasound-assisted examination and ultrasound-guided procedures. Consequently, goal-focused TTE becomes “ultrasound-assisted examination of the heart,” a lung scan becomes “ultrasound-assisted examination of the chest,” whereas nerve blocks, vascular access, and pleural drainage become “ultrasound-guided procedures.” With this evolution, the range and uses of ultrasound will expand dramatically to improve examination of the abdomen, joints, legs (for deep vein thrombosis), airway, and examinations to help guide physicians during resuscitation and trauma. Expertise in ultrasound by the anesthesiologist may also be useful in assisting the surgeon intraoperatively for direct organ imaging such as of the aorta, liver, kidneys, and lymph nodes, because the skill set of ultrasound use and knowledge is transferable to examination of other body areas. Equally, the surgeon may use the same skill set preoperatively when assessing the patient, or transfer these techniques for direct imaging of internal organs during the operation by placing the probe in a sterile sheath.
THE ROLE OF TECHNOLOGY IN THE EVOLUTION OF ULTRASOUND USE
There is little doubt that advances in ultrasound technology including reduced equipment size and price have had a major role in the expansion of its use outside of cardiology or radiology. The concept of limited training and the “ultrasound stethoscope” is not new, but required small, portable technology with adequate image fidelity.
The first generation of portable devices (large desktop computer–sized machines built into a console with wheels) were used principally for TTE and general ultrasound in patients in intensive care, who were too sick to transport to other departments. Inferior imaging ability made more difficult by mechanical ventilation mostly limited their use to abdominal, pelvic, and vascular ultrasound or to office-based TTE. The second generation mobile machines were smaller (laptop computer sized and detachable from a trolley) and had improved imaging capability, notably harmonic imaging, which was a key step forward in mobile TTE. Unfortunately, further miniaturization into hand-carried ultrasound (HCU) systems weighing typically <6 pounds had inferior image quality and lacked echocardiographic modalities used for quantification (particularly spectral pulsed and continuous wave Doppler). There was a greater risk of missing clinically important pathology than by cart-based systems, and this raised concern that the use of this technology could lead to patient harm. A position paper was released by the American Society of Echocardiography in 2002, cautioning practitioners to restrict the level of interpretation to the ability of the HCU device.16 This position statement was remarkable in that it predicted many developments that have occurred since then. Importantly, the American Society of Echocardiography task force endorsed the concept of ultrasound-assisted examination stating that it “believes that this technology will extend the concept of the ‘complete physical examination,’ allowing more rapid assessment of cardiovascular anatomy, function, and physiology.” Furthermore, the evolution of portable ultrasound systems was predicted: “Because the small HCU device may evolve into a full diagnostic device, its use and dissemination will not rest simply on the size of the instrument but on the individual user and his or her understanding of and response to the information imparted.” In a more recent position paper on focused cardiac ultrasound in the emergent setting,17 the American Society of Echocardiography acknowledged the use of HCU in ultrasound-assisted examination by noncardiologists. The consensus group recommended choice of ultrasound platform to be “scaled” to the expertise of the operator and intended uses, including noncardiac (e.g., vascular, abdominal, pelvic), which may not be available yet in the HCU devices. The predictions in 2002 have largely been correct with regard to the enormous technological advancement, such that the portable machines of today are fully capable echocardiography systems capable of multiple imaging applications. The limitations imposed by technology in 2002 are largely irrelevant in 2012. In very recent times, however, there has been introduction of even smaller ultrasound systems, capable of fitting into a coat pocket or palm. This latest evolution holds the greatest promise for integration of ultrasound into bedside examination, because of the enhanced portability. However, as in 2002, these HCU devices have limited abilities and the evidence of their utility is still emerging.
THE EXPERTISE PYRAMID
The concept of an expertise pyramid is shown in Figure 1. Ultrasound-assisted examination is at the broad base of the pyramid, and it is envisaged that the majority of acute care specialists should be able to obtain this level of expertise. At the top of the pyramid are the highly trained and qualified experts in ultrasound. It is likely that high-level expertise will be restricted to one specific area, such as echocardiography (TTE or TEE), abdominal ultrasound, or chest ultrasound, and will include specialists from acute care disciplines as well as radiologists and cardiologists. The achievement of high-level expertise will be dependent on the level of ultrasound training rather than traditional specialist craft groups. The middle of the pyramid is a space where physicians may develop moderately advanced skill and knowledge in a specific area (such as TTE) with good general knowledge and skills in ultrasound. It is also a transition zone, as practitioners start at the ultrasound-assisted examination level, increase the expertise to become a “good basic sonographer” before ultimately becoming “an expert.” It is envisaged that supervision and mentorship will be provided by practitioners who are at one level higher in experience than the trainee.
The concept of an expertise pyramid is widely incorporated into recommendations by learned societies and accreditation bodies on what is required to achieve competency. A summary of these recommendations is shown in Table 1. The majority of published recommendations are heavily focused on number of cases performed and various levels of supervision, and requirement for examinations. There are some recommendations in which knowledge and practical skills are separated, for example, the diploma of diagnostic ultrasound by the Australian Institute of Ultrasound. Achieving competency in knowledge (as distinct from practical skill) is tested either via an examination process or via completion of approved short courses. The Australian and New Zealand College of Anaesthetists’ recommendation, PS46 for TEE competency, is an example of this for which there are multiple pathways available for achieving the knowledge base.a These include recognized fellowships, the University of Melbourne Postgraduate Diploma course, or completion of the NBE PTEeXAM.
Recently, several roundtable consensus statements have been published on recommendations for ultrasound use by intensive care physicians, which define competencies and support the concept of the expertise pyramid. Mayo et al.18 report on consensus definitions for general and cardiac ultrasound, including basic and advanced applications, and the competencies required to achieve each level. The International Expert Statement on training standards for critical care ultrasonography19 was a consensus of 29 societies, and recommended categories of general ultrasound and basic and advanced cardiac ultrasound. There was complete agreement among the participants that general critical care ultrasound and “basic” critical care echocardiography should be mandatory in the curriculum of intensive care unit (ICU) physicians. Volpicelli et al.20 reported on a consensus agreement on the implementation of lung ultrasound. The ideal training pathway for physician-performed ultrasound, irrespective of the modality and scope of practice, would include supervised acquisition and assessment of knowledge base, practical skill, and interpretation of images. Ultimately, the specific pathways for achieving competence will be determined by specialist societies and credentialing requirements for practice at individual institutions.
For anesthesiology, the historical development of ultrasound use excluded the majority of practitioners. The major problem with the expertise pyramid is that echocardiography started with TEE for cardiac surgery, which required a full diagnostic level of knowledge and expertise to be gained in the first instance. Essentially, the pyramid was turned upside down so that one had to be at the top of the pyramid in expertise to commence using the technology. This had the profound effect of limiting opportunity for noncardiac anesthesiologists to adopt the technology, because the time and effort to achieve competency was well beyond their clinical scope or opportunity. Furthermore, in the operating room, TEE rapidly became “the domain of the cardiac anesthesiologist,” whereas TTE and other surface ultrasound applications remained the domain of cardiologists and radiologists.
This paradigm, however, is changing with the incorporation of point-of-care ultrasound use.21 In this middle stage of evolution, point-of-care applications that are well established include ultrasound-guided regional anesthesia, goal-focused TTE (e.g., Hemodynamic Echocardiography Assessment in Real Time [HEART] scan22 or Focused Assessed Transthoracic Echocardiography [FATE]23), and abdominal scanning for trauma (e.g., Focused Assessment with Sonography in Trauma [FAST]15 or Rapid Ultrasound in Shock [RUSH]24) with other uses, such as lung imaging,25 deep vein thrombosis assessment,26 and soft tissue injury27 assessment, developing as the emerging uses. A summary of named goal-focused studies is shown in (Table 2). Importantly, there is a change in emphasis toward accepting a limited knowledge base and use of pattern recognition of pathology, and a reduced number of cases in training to achieve competence for goal-focused examination. This has facilitated the uptake of ultrasound technology at a basic level by a much wider group of acute care specialists. Goal-focused echocardiography, however, is not intended to be a state-of-the-art, comprehensive echocardiography assessment, but is about identifying clinically important cardiac pathology to determine whether patients are at risk for hemodynamic compromise and to guide specific hemodynamic treatment.
Ultimately, broad-base integration of ultrasound technology into clinical practice requires teaching and acceptance at a medical school level, and this is gaining popularity. An ultrasound curriculum was successfully implemented across all 4 years of medical school at the University of South Carolina School of Medicine in 2006.28 The curriculum was based on a point-of-care program that was developed for emergency medicine physicians with a broad coverage of ultrasound specialties. It was well received by the students and teachers, and similar programs have since been increasingly implemented at other institutions from the entire curriculum29 to shorter teaching programs.30–35 The rapid, widespread uptake of ultrasound into undergraduate teaching was presented at the inaugural world congress on ultrasound in medical education in 2011.36
IS USING ULTRASOUND EFFECTIVE?
Point-of-care ultrasound examination provides diagnostic information to the clinician, which may aid clinical assessment and decision-making, hence ultrasound machines are not considered a therapeutic device. In terms of efficacy, there are 3 aspects to consider: is diagnosis improved, does improved diagnosis lead to change in decision-making, and do changes in decision-making lead to better patient outcome? The controversy starts earlier: even if diagnosis is improved, it is up to the user to decide on subsequent changes, if any, to management.
The last aspect is the most controversial, because even with correct knowledge, the practitioner may not initiate appropriate or best therapy. In the literature, there are very few randomized studies or outcome data investigating the use of ultrasound in critical care applications. Therefore, in this review, we focus on diagnostic accuracy and decision-making.
Most of the literature aims to identify the incidence of new findings that were not detected by either clinical or other cardiac tests. There are 2 focus areas: elective use in cardiac surgery, and use in the ICU for hemodynamically compromised patients. A summary of findings is shown in Table 3, consistently reporting the high rate of influences of TEE on diagnosis and management. In cardiac surgery, the use of routine TEE leads to identification of new findings sufficient to change the operation in approximately 5% of patients.37–39 Most of these changes relate to a clinically relevant difference from preoperative assessment of anatomical abnormalities, such as moderate or severe valve disease. In studies in which TEE was used in selected patients, such as in patients at increased risk or enduring hemodynamic instability, the frequency of change is much higher (14%–21%).40–42
In the ICU, where the principal indication for TEE was hemodynamic compromise, the TEE led to a change in diagnosis and management in 40% of cases.43–58 The majority of changes were in hemodynamic treatment (vasopressor, inotrope infusions, and fluid management) but a significant proportion relate to surgical decision-making (such as diagnosis or exclusion of pericardial tamponade and aortic dissection).
On the basis of these observational, and largely proof-of-concept studies, TEE has become incorporated into routine practice in cardiac surgery and postoperative care. Given the potential serious complications of esophageal injury, however, the decision to use TEE must be justified, and approved indications are published by governing bodies.59,60 There are, however, no outcome studies in which TEE has been randomized as an intervention to assess patient outcome.
Most of the literature on the use of TTE outside of cardiology laboratories relates to the diagnostic superiority of TTE over clinical examination, especially when performed by novices and with handheld ultrasound technology.61–65 Initially, the literature compared the image quality of held echocardiography with comprehensive systems, and subsequently reported its clinical applications. It is this literature that best supports the concept of “ultrasound-assisted examination.” A common finding was the influence on clinical management of the new cardiac diagnoses revealed by echocardiography.
A summary of publications in critical care is shown in Table 4. With the recent and considerable improvements in technology, TTE now rivals TEE as the investigation of choice for hemodynamic instability,66 because adequate imaging is now feasible in most mechanically ventilated patients (95%–98%)23,67,68 and is noninvasive. The summarized data show frequent changes in diagnosis and management with TTE in patients requiring noncardiac surgery, admission to the ICU, and the emergency department. Taken together, it is apparent that a junior doctor equipped with minimal training in echocardiography and a portable ultrasound machine will outperform an experienced cardiologist with a stethoscope.69 Vignon et al.70 recently investigated the efficacy of a brief echocardiography training program (12 hours) for intensive care residents, who subsequently demonstrated a high level of competence in diagnosis of basic hemodynamic disorders using TTE. Royse et al.71 evaluated the training course used to teach the HEART scan goal-focused TTE study on interpretation of pathology using recorded videos and found a high agreement with course students and experts. Importantly, there are no studies in which clinical examination outperformed echocardiography.
In anesthesiology, there are few data evaluating the effect of echocardiography diagnosis on clinical decision-making, and these are mostly series of case reports or proof-of-concept observational studies. However, in patients who have or are at risk of cardiac disease, the detection rate of clinically significant pathology is in the order of 25% of patients, which leads to changes in perioperative management.72,73 In prospective observational studies by Canty et al.72–74 and Cowie,75 the therapeutic impact from focused TTE was 39% to 82%, which was principally before anesthesia (90%) for noncardiac surgery, but also during and after surgery in mechanically ventilated patients. Important management changes were identification of high cardiac risk patients and alteration in preoperative assessment and level of postoperative care (10%–15%), but surgery was changed for a small proportion of patients (2%) as a result of the new information from TTE. The majority of changes were in hemodynamic management (30%–40%), including more rational use of invasive monitoring and fluid and vasopressor use. In a study by Canty et al.,72 during which goal-focused TTE was used in the preadmission clinic setting, the overall effect was to step down planned treatment (based on a reassurance from normal TTE findings) in more patients than to step up treatment based on clinically significant pathology. The effect on workflow was to reduce the intensity of treatment and resource use. This, however, has not been subjected to economic or outcomes analysis.
These publications mirror the earlier work with TEE, showing strong proof of concept that either goal-focused or comprehensive TTE may change our practice in the preadmission clinic in a large proportion of patients. The incidence of abnormal findings by limited echocardiography is similar to that of comprehensive echocardiography studies in the preadmission setting. Faris et al.76 investigated the incidence of cardiovascular pathology in patients attending a preadmission clinic, where the indication for TTE was based on appropriate use criteria guidelines issued by the American Society of Echocardiography. They reported that 27.6% of patients considered appropriate for TTE had at least moderate or severe cardiac pathology. However, many of these studies are “proof of concept,” and the clinical use of the new information was determined by the treating clinician. Further research is required to determine whether the change in diagnosis or management leads to improvement in outcomes.
Lung ultrasound imaging is an emerging discipline that has widespread application to surgery, anesthesiology, and intensive care and has been incorporated into the focused TTE protocols FATE23 and RUSH.24 Certain diagnoses, such as detection of pneumothorax and pleural effusion are widely recognized and easy to obtain.13,25 Pleural effusion size is reasonably accurately assessed by measuring pleural fluid dimensions with ultrasound when compared with drainage volume.77,78 The size of pneumothorax can be estimated by measuring the “contact point” where the probe is moved around the chest to see where the lung joins the pleural space.79 Despite demonstration of improved safety of pleural drainage with point-of-care ultrasound,14,80 uptake into clinical use has been slow.14,81,82 The emerging areas of interest, however, are to correlate lung imaging with patterns of pathology such as alveolar-interstitial syndrome83 (including pulmonary edema), consolidation and collapse,84 abscess, emphysema, and even pulmonary embolus.85 Lichtenstein and Meziere13 reported effective and rapid diagnosis of these disorders in critically ill patients with acute respiratory failure using lung ultrasound, demonstrating a very high sensitivity and specificity compared with computed tomography. The routine use of lung ultrasound in critical care has the potential to substitute for computed tomography and chest radiography, particularly for repeated examinations, and thus reduce radiation exposure to patients and staff.86
ULTRASOUND-GUIDED VASCULAR ACCESS
Real-time use of ultrasound to guide vascular access is well established as a point-of-care application of ultrasound. This is the one area in which there is high-level evidence of benefit, but mostly for internal jugular vein cannulation. In 2011, a combined task force of the American Society of Echocardiography and the Society of Cardiovascular Anesthesiologists published recommendations supporting the routine use of ultrasound-guided internal jugular vascular access “whenever possible,” which was based on 30 level 1 studies supporting its use.87 The National Institute for Clinical Excellenceb (United Kingdom) published similar recommendations in 2002 and a subsequent audit demonstrated reduced central venous catheter–related complications in 284 patients since its implementation at a single institution.88
ULTRASOUND-GUIDED REGIONAL ANESTHESIA
The use of ultrasound to guide regional blockade is now widely accepted throughout the world. The literature covers 3 phases: the first was to describe how to perform the block and to describe the sonographic anatomy; the second was to show performance advantage such as faster onset of block, less local anesthetic used, or high rate of efficacy; and the third phase was to identify whether it makes a clinical difference such as improved success, longer duration, and reduced morbidity compared with the anatomical landmark or nerve stimulator-guided techniques. Soeding et al.92 demonstrated faster onset and more complete onset of brachial plexus blocks with an ultrasound-guided technique compared with blind technique. Improved analgesia was reported with ultrasound-guided regional anesthesia in 2 recent meta-analyses.89,90 There was insufficient evidence to draw conclusions on improved outcome, but a reduction in surrogate morbidity including vascular puncture and diaphragmatic paralysis was demonstrated in the meta-analysis by Neal et al.90 Importantly, there are no reports showing that ultrasound is inferior to blind techniques, and significant morbidity from peripheral nerve blockade is very rare.91 Adoption of ultrasound has without doubt led to a rapid expansion in regional blockade in acute and chronic pain medicine and to new techniques including a variety of vertebral (neuraxial),9,10 paravertebral, and truncal (e.g., transverses abdominus plane11,93) blocks.
GOAL-FOCUSED TTE: SEPARATING “THE GOOD, THE BAD, AND THE UGLY”
The incorporation of goal-focused TTE is perhaps the greatest challenge for anesthesiologists and critical care physicians in the next few years. It is also a necessary step in the evolution of clinical ultrasound before it evolves to “ultrasound-assisted examination.” There are several paradigm shifts that are necessary for widespread adoption of goal-focused TTE. We must accept that novices can perform goal-focused TTE.94 A further paradigm shift is that diagnosis of pathology is largely based on pattern recognition rather than detailed knowledge base and formal quantification. This is not full diagnosis, but rather answering clinical questions in real time, with referral to more experienced practitioners for full diagnosis at a later stage. An example is the identification of aortic stenosis, whereby pattern recognition can be used to determine clinically important stenosis, whereas formal quantification to assess the severity requires the use of spectral Doppler particularly. The presence of heavily calcified and restricted aortic valve leaflets is one pattern that rapidly identifies potentially clinically significant aortic stenosis.
In a study of interpretative ability of novices after a training course to teach the HEART scan, novices reported on 5 videotaped echocardiography cases in which only 2-dimensional (2D) and color flow Doppler images were available.71 The agreement between novice and expert was very high for hemodynamic state and valve severity. In particular, few clinically important valve lesions were misdiagnosed, whereas there was a tendency to overcall the severity of mild valve lesions. Using continuous wave Doppler, Cowie and Kluger95 studied the ability of novices to measure peak aortic gradients from the apical 5-chamber view and compared it with that of expert cardiac anesthesiologists. There was very high agreement of significant aortic stenosis (based on valve morphology) and good agreement (based on peak velocity alone (κ 0.8–1), reinforcing the importance of pattern recognition of aortic stenosis on 2D imaging.
In recent years, the concept of portable ultrasound is less relevant because most portable echocardiography systems had all basic echocardiographic modalities and approached cart-based machines in image quality. However, this is not true of the palm-sized echocardiography machines and these may have limitations in their ability to perform goal-focused studies. Furthermore, one must overcome the fear that the clinician may “miss something important” when doing a limited versus comprehensive study, that is, the notion that a missed diagnosis outweighs any positive prospect of new or correct diagnoses. There are 2 polar opinions to this statement. One view is that misdiagnosis by ultrasound could lead to patient harm, and the best way to avoid that is to ensure that only practitioners who are expert in performing and interpreting echocardiography are given access to high-level equipment and allowed to perform echocardiography. The alternative view is that clinical diagnosis is frequently incorrect compared with echocardiography, and even accepting that practitioners with limited training and experience will miss or misdiagnose pathology on occasions, that ultrasound-assisted examination will reduce the incidence of incorrect diagnosis compared with physical examination alone,22,65 and that there could be a clinical consequence to not performing echocardiography. Practice is likely to lie between the 2 poles and should be directed by evidence.
The Australian experience may provide insights into the likely mode of adoption and education in ultrasound in acute care medicine. In 2004, the University of Melbourne Postgraduate Diploma of Perioperative and Critical Care Echocardiography was released with the predominant focus on TEE for cardiac anesthesiology, and the majority of students had no interest in TTE. In 2012, the course is now in 2 levels: the first level concentrates more on TTE and surface ultrasound but with basic TEE, and the second level is devoted to diagnostic knowledge base and emphasis on both TTE and TEE. The distribution by specialty is now overwhelmingly in favor of noncardiac acute care specialties, with fewer than 25% of students being cardiac anesthesiologists (personal communication, University of Melbourne Ultrasound Education Group, 2012). The majority of noncardiac anesthesiologists do not perform TEE and have no interest in it. In North America, the move toward limited echocardiography has been in the form of “basic TEE,” although it is likely that a paradigm shift toward limited TTE will occur given the noninvasive nature of this technology and removal of the need for sedation or anesthesia to perform the study.
In general, normal or mild pathology is unlikely to lead to hemodynamic compromise under anesthesia. Examples of “good, bad, and ugly” are shown in Figure 2. Acute care physicians will be reassured if the ejection systolic murmur they heard on auscultation is only aortic sclerosis. However, they will be alerted if it is moderate or severe aortic stenosis, and alarmed if a patient who is short of breath has severe pulmonary hypertension and right heart failure. See online supplemental digital content for examples of normal (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A451, and Video 2, see Supplemental Digital Content 2, http://links.lww.com/AA/A452), aortic stenosis (Video 3, see Supplemental Digital Content 3, http://links.lww.com/AA/A453, and Video 4, see Supplemental Digital Content 4, http://links.lww.com/AA/A454), and right ventricular failure (Video 5, see Supplemental Digital Content 5, http://links.lww.com/AA/A455, and Video 6, see Supplemental Digital Content 6, http://links.lww.com/AA/A456).
There are many published goal-focused studies, and each has a catchy acronym. They range in scope from very simple (2D only) studies to assess ventricular function in a peri-arrest situation (Table 4), to more extensive yet still limited studies incorporating 2D and color flow Doppler to evaluate valve and ventricular function (HEART scan22,71). The common feature is to concentrate on either 2D only, or 2D and color flow Doppler analysis, and to avoid formal quantification using pulsed wave or continuous wave Doppler. Another common feature is an emphasis on pattern recognition of pathology rather than extensive quantification. The scanning ability and level of knowledge required to be proficient in quantification and spectral Doppler is much higher than that required to view 2D imaging, or with color flow Doppler. Removing spectral Doppler also reduces the time taken to perform the study, such that a goal-focused study can be performed and reported in 10 minutes or less. The ability to discriminate hemodynamically significant from nonsignificant aortic stenosis is important, because it is a significant risk factor for postoperative mortality,96 is poorly assessed clinically,97,98 and may be asymptomatic even if severe.99 This has been achieved by focused TTE performed by anesthesiologists72–74 and others100–102 using 2D assessment of valve cusp separation without the use of quantitative spectral Doppler (standard with comprehensive TTE).
Although acronym, goal-focused examinations define a particular sequence of study views, the point-of-care physician must ultimately determine what structures to look at first, according to clinical requirement. For example, the subcostal view is most appropriate during an arrest situation because images can be obtained without interrupting chest compression.
HOW DO WE ACHIEVE ULTRASOUND FOR EVERYONE?
To achieve full evolution, training in ultrasound should be incorporated into medical school teaching. It should be viewed as part of clinical assessment and examination. There are some centers already adopting this approach.
Within acute care medical disciplines, the logical approach is to start with limited TTE and surface ultrasound applications, and then to progress up the pyramid of expertise. Learned societies and credentialing organizations should produce guidelines to identify what knowledge is required and how many studies should be performed to ensure competency.18,19 Such recommendations should seek to be consistent across specialty craft groups.
The barriers to adoption of ultrasound for everyone revolve in part around education and equipment. In the past decade, there has been a major shift in focus from static and large cart-based ultrasound machines to portable, yet high-quality, ultrasound systems. Although the cart-based machines are the most sophisticated and provide the best image quality, they are not well suited to many areas of critical care practice. The smaller, portable machines are easier to move and position next to patients, whether in the ICU, the anesthesia induction room, or in the preadmission clinic. The cost is also reduced considerably, such that an echocardiogram machine in 1995 was the cost of a house ($250,000), whereas today a very capable portable machine is the cost of a car ($30,000–$60,000). This has allowed providers to increase the number of machines available. However the “silo” mentality between medical specialty craft groups has limited cross-discipline training opportunities.
Australia is a good model for how education can lead a change in practice. The adoption of TEE in cardiac surgery in the mid-1990s was relatively slow and ad hoc, with the early adopters going overseas or getting limited training within Australia. There was a deficiency of training courses and even textbooks on TEE. Those wishing to adopt the technology had to work very hard to obtain the knowledge and practice to become proficient. This produced a need for a high-quality and extensive knowledge to cater to the diagnostic-level interpretive skills required in cardiac surgery. This led to the production of the University of Melbourne distance education courses. These courses provided access to knowledge for those wishing to become skilled in TEE, with the consequence that many Australian anesthesiology or cardiothoracic surgery departments insisted that cardiac anesthesiologists complete the Postgraduate Diploma or an equivalent fellowship or examination such as the NBE PTEeXAM. This approach was endorsed by the Australian and New Zealand College of Anaesthetists. However, this approach limited the echocardiography knowledge to cardiac anesthesiologists performing TEE. In response to demand, the TEE-based course split into 2 parts in 2009, with the first half aimed at the noncardiac anesthesiologist, emergency, and intensive care physicians, where TTE would be the first and most frequently used echocardiography modality, complemented by a basic level of TEE. Clinicians can limit their echocardiography training and graduate with a postgraduate certificate or continue to the level of diploma where the focus is TEE and diagnostic-level knowledge. The delivery of these courses is entirely via distance education, which allows clinicians to study in their own time and place, thereby facilitating access to information. In addition, formalized training workshops were established to teach the HEART scan goal-focused study. The impact on clinical practice has been dramatic. In Australia and New Zealand, where there are approximately 5000 anesthesiologists or critical care physicians, 1375 have completed the workshops, more than 400 have completed the certificate level, and more than 500 have completed the diploma level. The predominant use of echocardiography among anesthesiologists and critical care physicians is now goal-focused TTE, with TEE remaining predominantly the domain of the cardiac anesthesiologist (personal communication, University of Melbourne Ultrasound Education Group, 2012). The importance of distance-based education is to make it easy for clinicians to work through a process to acquire the knowledge in a structured and graded manner. These courses are now run as professional development programs for the Society of Cardiovascular Anesthesiologists (SCA ON-CUE levels 1 and 2), increasing availability to North American and worldwide practice.
It is likely that education platforms that are tailored to physician needs and practice environments will facilitate a high rate of adoption of ultrasound into clinical practice. There are already many short courses, workshops, texts, and electronic material to aid learning. A selection of iPhone apps and websites are shown in Table 5, which will aid the practitioner as reference guides, aide-memoires, pocket books, or calculators and report forms as well as platforms for e-learning. However, integration of ultrasound into everyday practice (ultrasound for everyone) will only be accomplished when it is part of the curricula of medical schools and specialist training organizations. A recent expert panel on intensive care training36 recommended unanimously that general critical care ultrasound and basic echocardiography should be a core part of the ICU curriculum. Other societies, boards, and colleges will produce training and practice guidelines to help steer the path of education, practice guidelines, and competency assessment.
IS THERE A DANGER IN WIDESPREAD ADOPTION OF ULTRASOUND?
There is certainly widespread consensus from noncardiology specialties that ultrasound should be an integral part of their practice.19 There is, however, a paucity of outcome data on the use of routine ultrasound in anesthesiology, intensive care, or emergency medicine. As a comparative example, it took 15 to 20 years after widespread adoption of the pulmonary artery catheter before research questioned whether the balance was harm or benefit.103,104 Research is likely to direct appropriate use, and better define clinical situations in which benefit clearly outweighs risk of harm. This research, combined with expert consensus leads to recommendations for the performance and appropriate use of echocardiography.105,106 Education, definition of competency, and quality assurance programs are likely to evolve to reduce the risk of harm. This is a dynamic topic, which is likely to change as we move toward widespread adoption of ultrasound into everyday practice.
Ultrasound is becoming an integral part of anesthesiology and acute care medical practice. What started out as TEE for cardiac surgery has spread to ultrasound-guided regional anesthesia and vascular access, goal-focused TTE, and emerging use of lung, abdominal, vascular, and soft tissue imaging. The multiple roles of ultrasound have many complementary components, and the future direction is to consider ultrasound as simply part of clinical assessment and an aid to guide procedures.
Name: Colin F. Royse, MBBS, MD, FANZCA.
Contribution: This author helped prepare the manuscript.
Conflicts of Interest: Employee of University of Melbourne; involved in the development of course materials described (Postgraduate Certificate and Diploma of Clinical Ultrasound and HEART scan), Director of Heartweb, which conducts the SCA ON-CUE courses.
Name: David J. Canty, MBBS, FANZCA, PGDipEcho.
Contribution: This author helped prepare the manuscript.
Conflicts of Interest: Employee of University of Melbourne; involved in the development of course materials described in the text (Postgraduate Certificate and Diploma of Clinical Ultrasound and HEART scan).
Name: John Faris, MBChB, DAvMed, FAFOM, FFOM, FANZCA, BA, ASCeXAM, PGDipClinUs.
Contribution: This author helped prepare the manuscript.
Conflicts of Interest: Involved in the development of course materials described in the text (Postgraduate Certificate and Diploma of Clinical Ultrasound and HEART scan).
Name: Darsim L. Haji, MBChB, FACEM, PGDipEcho.
Contribution: This author helped prepare the manuscript.
Conflicts of Interest: Involved in the development of course materials described in the text (Postgraduate Certificate and Diploma of Clinical Ultrasound and HEART scan).
Name: Michael Veltman, MBBS, FANZCA, ASCExam, FASE.
Contribution: This author helped prepare the manuscript.
Conflicts of Interest: Involved in the development of course materials described in the text (Postgraduate Certificate and Diploma of Clinical Ultrasound and HEART scan).
Name: Alistair Royse, MBBS, MD, FRACS, FCSANZ.
Contribution: This author helped prepare the manuscript.
Conflicts of Interest: Employee of University of Melbourne; involved in the development of course materials described in the text (Postgraduate Certificate and Diploma of Clinical Ultrasound and HEART scan), Director of Heartweb, which conducts the SCA ON-CUE courses.
This manuscript was handled by: Martin J. London, MD.
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