The modern era of ultrasound was ushered into the scientific community during the late 1930s with the advent of metal flaw detectors and World War II, when interest in advanced detection technology such as sound navigation and ranging and radio detection and ranging peaked.1 Later, application of ultrasound to medicine led to greater understanding of human anatomy, physiology, and pathology.2 In the past 20 years, evolution of the microprocessors enabled the miniaturization of large cumbersome ultrasound devices to hand-held, even pocket-sized instruments. The size, cost, availability, and quality of these smaller ultrasound devices have placed point-of-care ultrasound in the noncardiologist physician’s armamentarium. The purpose of this article is to describe the concept of focused cardiac ultrasound (FoCUS), its diagnostic targets, indications, benefits, and limitations. Training and equipment required to perform FoCUS are also discussed.
WHAT IS FOCUSED CARDIAC ULTRASOUND?
Many terms are used to describe a narrowed ultrasound examination of the cardiovascular system including, but not limited to, hand-held, point-of-care, bedside, quick-look cardiac ultrasound, or ultrasound stethoscope. These multiple synonyms are compounded by the variety of acronyms applied to bedside ultrasound protocols, such as FAST, FATE, FEEL, and RUSH, which are defined and described in Table 1.3 To avoid any confusion, the term FoCUS will be used for the remainder of this article.
FoCUS, as defined by the American Society of Echocardiography, is a “focused examination of the cardiovascular system performed by a physician using ultrasound as an adjunct to the physical examination to recognize specific ultrasonic signs that represent a narrow list of potential diagnoses in specific clinical settings.”4 The essential features of FoCUS are summarized in Table 2.4
FoCUS is used as an adjunct to the physical examination when a patient’s symptoms suggest an abnormality of cardiovascular structure or function. It is important to note that FoCUS is not comprehensive, but is instead concentrated on improving the understanding of the underlying cardiovascular pathophysiology. Making a definitive diagnosis is not the objective of FoCUS. With FoCUS, the bedside physician is gathering crucial information to assess the patient’s physiologic status, refine the differential diagnoses, and choose interventions that can change the course of management.5 FoCUS is used to facilitate point-of-care decisions by answering critical questions in a binary fashion, that is, yes/present or no/absent. This simplifies the cardiac ultrasound examination because neither measurements nor quantifications are performed.6 The agreement between qualitative data obtained by FoCUS and comprehensive standard echocardiography is good.6–8 The simplicity of the FoCUS examination also lends itself to point-of-care application. The equipment used is usually portable, and the examination is quick and noninvasive and performed by the physician responsible for making real-time clinical decisions that may change management strategies.
The clinical indications to perform a FoCUS examination are shown in Table 3.4,9 The ability of the physician to make timely and appropriate medical decisions when using FoCUS is increased.10–17 Kanji et al17 found that 28-day survival was improved in patients suffering from subacute shock whose management was guided by “limited” transthoracic echocardiography (TTE). Of note, their echocardiographic examination was comprised of the exact same views as the FoCUS examination.
Cardiovascular data that can be obtained from a FoCUS examination are summarized in Table 4.9 Because of the limited diagnostic targets, only a select number of views are acquired during a FoCUS examination. The FoCUS examination typically comprises (1) parasternal long axis, (2) parasternal short axis, (3) apical 4-chamber, (4) subcostal 4-chamber, and (5) subcostal inferior vena cava views18 (Figure 1). With the FoCUS examination, each cardiac structure is imaged in more than one view, to avoid errors of omission, validate findings, and ensure that ultrasound artifacts are not mistaken for abnormalities. However, in critical or life-threatening situations, that is, cardiac arrest, critical clinical decisions can be made with data obtained from a single view.10
Despite its potential, FoCUS, as any diagnostic tool, has important limitations (Table 5). The most important of those is the experience and skill set of the physician performing the examination.3 If the images acquired during the FoCUS examination are of poor quality or cluttered with artifact, little actionable information can be gleaned. It is paramount that the physician performing the FoCUS examination realizes the difference between a “good” image and an image that contains insufficient information to make sound clinical decisions. The onus is on the performing physician to understand his limitations and to recognize when consultation with a more experienced colleague is required. Second, FoCUS is a qualitative examination and the grading of the severity of disease processes, such as aortic stenosis, is not its scope. Third, FoCUS is limited by the type of ultrasound equipment used to perform the examination. Although FoCUS can be performed with high-end ultrasound machines with full capabilities, it is much more likely that it will be performed on machines that have fewer modalities, that is, 2 dimensional, M-mode, and basic color flow Doppler only. However, the small size of these ultrasound systems provides for increased portability and real-time use by the bedside, thus outweighing their limited functionality.
FOCUS VERSUS LIMITED TRANSTHORACIC ECHOCARDIOGRAPHY
Because of the heterogeneity of terms used to describe FoCUS, there may be confusion regarding how FoCUS differs from limited TTE. These differences can be pared down to one word, scope. Limited TTE requires ultrasound equipment with full functionality, training for image acquisition, obligatory knowledge for image analysis and interpretation, as well as accreditation for the safe and appropriate use of echocardiography in a broad scope of practice. FoCUS, on the other hand, has a narrower scope of practice and is restricted by the equipment used and the skill set of the physician performing the examination. The scope of practice of FoCUS may vary from a specific patient population (intensive care unit patients) to a clinical setting (preoperative assessment clinic). A limited TTE examination refers to a small number of images that are obtained by an expert echocardiographer (registered ultrasound technician or physician), which enable the physician to evaluate and discriminate between disease processes and severities. On the other hand, the FoCUS examination has a narrowed scope and can only address specific clinical questions4,9 (Table 6).
THE ANESTHESIOLOGIST AND FOCUS
FoCUS is simply the application of a common technology in a new and innovative way. Much like the electrocardiogram may be considered a narrowly focused cardiac electrophysiologic technique, FoCUS may provide the anesthesiologist with timely data on the patient’s anatomy and physiology, allowing him/her to construct more precise differential diagnoses and management strategies. The value of point-of-care ultrasound in comparison with or as an adjunct to the physical examination has been investigated.19–23 Kobal et al19 found that the accuracy of cardiovascular diagnoses by medical students, who had limited echocardiographic training and used a small hand-carried ultrasound device, was superior to that of experienced board-certified cardiologist using standard physical examinations. Patients with high cardiac risk who had surgery for hip fracture had lower mortality when treated by anesthesiologists who used a point-of-care, “focused” TTE.24
Several specialties such as Trauma Surgery, Emergency Medicine, and Critical Care Medicine25 have already embraced the use of ultrasound, including FoCUS, and have incorporated ultrasound education into formal training programs. The skills required to perform FoCUS can be obtained by noncardiology physicians with limited training. Cowie et al26 demonstrated that echocardiography-naive anesthesiology trainees could rapidly and successfully be trained to recognize clinically significant aortic stenosis by using TTE.
There is scant information regarding the appropriate training for FoCUS in anesthesiology. The Society of Critical Care Anesthesiologists has suggested learning goals for critical care basic ultrasound, which are, however, broader than what is needed for FoCUS.25 Ramsingh et al27 developed a point-of-care ultrasound curriculum for general anesthesiology residents that blended traditional didactic lectures with hands-on model and simulation experience. Ideally, a curriculum for FoCUS designed for board-certified anesthesiologists would consist of (1) a core didactic curriculum, (2) access to an archive of images and clinical cases, and (3) hands-on model and simulation workshops supervised by expert teachers. Once the teaching sessions have been completed, the trainees would perform, capture, and interpret independent studies, which also need evaluation and validation. Finally, the trainees should prove and maintain competency.
The various ultrasound platforms used to perform echocardiography include: (1) large, fully functional systems, (2) small platforms with basic functions, (3) hand-carried, and (4) pocket-sized systems (Table 7). Full functional systems are used in echocardiography laboratories and in the cardiac operating theater. They are bulky in size, difficult to maneuver, and expensive, thus less than ideal for the performance of FoCUS examination. Small ultrasound platforms typically retain much of the functionality, are cart-based, easier to maneuver, and less expensive. Hand-carried devices are typically the size of a laptop computer, readily carried to the bedside, and have standard ultrasound modalities only. Pocket platforms are small enough to fit in a laboratory coat pocket, but their functionality is restricted.4,9
Although implementation of FoCUS in daily practice is with hand-carried or pocket-sized platforms, it can be performed with any ultrasound machine. The recommendations from the American Society of Echocardiography are that ultrasound equipment used for FoCUS examinations meet 5 basic criteria: (1) a transducer with frequency appropriate for adult patients (typically 2–6 MHz), (2) minimal display requirements that include the ability to label images with at least 2 patient identifiers, as well as the date and time the examination was performed, (3) markers to indicate scale or image depth, (4) 2-dimensional gray-scale imaging and ability to adjust depth and gain, and (5) the ability to store images in a retrievable location in the Digital Imaging and Communications in Medicine format.4,9 (Table 8)
In the United States, billing is based on Current Procedural Terminology codes. Currently, although there is a Current Procedural Terminology code for limited TTE, no such code exists for FoCUS. It is inappropriate to bill a FoCUS examination as a limited TTE.4,9
The appropriate application of FoCUS by anesthesiologists may potentially alter management and affect outcomes for a wide range of patients. FoCUS and point-of-care ultrasound should be incorporated into our skills set and everyday practice.28 Training for FoCUS should be ideally based on a national curriculum.
Name: Bradley J. Coker, MD.
Contribution: This author is the primary author and corresponding author of the manuscript.
Name: Josh M. Zimmerman, MD, FASE.
Contribution: This author was involved in writing and editing the manuscript.
This manuscript was handled by: Nikolaos J. Skubas, MD, DSc, FACC, FASE.
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© 2017 International Anesthesia Research Society
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