Current literature suggests that the use of critical care ultrasound has enhanced technical proficiency among critical care providers; has improved procedural outcomes and in some instances, facilitated more timely diagnosis of medical problems than traditional radiographic methods. Furthermore, experiential reflection over time on the inherent advantages and pitfalls of bedside ultrasound has facilitated more judicious and efficacious application of this technology. Published guidelines now exist to define the ideal use of bedside ultrasound in various diagnostic and treatment algorithms. The enhanced safety profile of ultrasonography, in comparison to invasive or radiation-emitting techniques, has made it an attractive alternative across a broad range of clinical scenarios, including pulmonary, cardiac, and traumatic conditions.
Overview of Current Practice
Bedside chest ultrasound is now used almost routinely to assess pleural effusions at least as an adjunct to chest radiographs and in some cases for primary evaluation. It is also useful for the assessment of pneumothorax and with sufficient resolution, for evaluation of and differentiation between other alveolar or interstitial lung pathology. There presently exist hand-carried ultrasound devices used for intensive care patients that some now even advocate can be used as part of the daily, routine bedside evaluation of pulmonary disease. Given that thoracic ultrasound has both diagnostic and therapeutic benefits, it can serve to reduce the overall expenditures by use of a single study when appropriate. Recently, international guidelines were described to provide evidence-based consensus regarding the use of “point-of-care” lung ultrasound. Among the key statements was first, that chest ultrasonography more accurately assists in the diagnosis of pneumothorax than chest radiographs and secondarily that in pediatric patients, lung ultrasound is as accurate as chest radiography in diagnosing pneumonia. The consensus group further concluded that pulmonary ultrasonography is also valuable in monitoring aeration changes across the spectrum of parenchymal lung disease.
Although not as widespread as lung ultrasound, the role of “FADE” (Fast Assessment Diagnostic Echocardiography) continues to grow in critical care medicine. Previously solely a procedural skill retained by cardiologists, intensivists and anesthesiologists both have begun to utilize rapid, focused echocardiography for the assessment of volume status, myocardial function, pericardial and valvular pathology, and hemodynamics. It is unlikely that bedside diagnostic echocardiograms can ever replace the sophistication of formal echocardiography; however, in acute situations, it may prove of benefit, especially when sub-specialty expertise outside of the ICU is not imminently available. A specific inherent challenge of training noncardiologists to perform echocardiography is the variability in ascertaining procedural competence and maintenance of skill. Unlike cardiologists, who routinely perform this skill and thus have the ready opportunity to update and finesse their technical expertise, less frequent operators, such as intensivists, may rather place patients at risk if their diagnostic abilities are suboptimal. Moreover, unlike thoracic ultrasound for which there are fewer potential anatomical variants, subtle deviations from the normal in cardiac anatomy, particularly in children or after cardiac surgery, may distort the planes of view and thus, compromise diagnostic accuracy for the point-of-care ultrasonographer.
The utilization of focused assessment with sonography for trauma (termed “FAST”) is broadly accepted and in many instances has become the standard of practice across emergency medicine and trauma departments, particularly in patients who are clinically unstable and for whom transfer to an area outside of the emergency department may result in greater morbidity, FAST is a useful tool for identifying the sequelae from blunt abdominal or thoracic injury in posttraumatic patients and guiding rapid intervention and therapy. Given the highly specific and moderately sensitive nature of this tool, it can help clinicians to stratify risk assessment and the need for follow-up care, especially in those patients who have borderline findings. Those educational studies which do exist claim that incorporation of focused ultrasound training in surgical and emergency medicine training programs is feasible with an acceptable level of competency attained by trainees.
Nowhere are these findings more relevant than in the case of neonates and children. Pediatric populations are especially vulnerable to procedural error and failure given their relatively small body habitus in comparison to adults; the frequent distortion of normal anatomical landmarks secondary to overlying vessels and their anatomical size; and their inability to readily cooperate with necessary positioning in the absence of substantive sedation and its associated risks. When critically ill, infants and children typically have lower thresholds for respiratory and hemodynamic collapse that may result from their primary disease process and are further exacerbated by the physiologic stress of painful procedures and the systemic effects of requisite sedation and analgesia. Additionally, while most parents will support and facilitate any intervention needed to help care for their sick child, even the most patient individuals are likely to become disheartened and unwilling when multiple procedural unsuccessful attempts are made. It is no wonder that ultrasound guidance for central vascular access in children has so quickly gained favor across most neonatal and pediatric critical care units.
Challenges of Critical Care Ultrasound
Despite the clear benefit of intensive care ultrasound on patient care, provider quality, and system efficiency, the inherent risks associated with this emerging technology cannot be ignored. There are potential hazards associated with training highly skilled, yet undifferentiated practitioners in novel techniques. Although critical care physicians undergo years of training to become clinical subspecialists and possess extensive procedural expertise, adult learners are notoriously difficult to reeducate once they have moved from novice to master learners. New skills portend new technical, conceptual, and intellectual challenges that not all clinicians are willing to take the needed time to surmount. Additionally, maintenance of practical skill is difficult: first, when there are limited opportunities for skill mastery when one is outside of formal training, and second, when the motivation may be limited if in essence the existent practice “is not (thought to be) broken” in the first place.
As one can imagine, there is a learning curve for any new application or skill. Unfortunately, given the paramount consequences of misdiagnosis or clinical misadventures in critical care medicine, the margin of error is quite narrow. That being said, as practitioners seek to improve their ultrasound abilities, it is unclear how many patients may inadvertently suffer the undesirable consequences of time-delay, inaccurate or incomplete diagnosis, or direct injury all the while the learner hones his or her skills.
There exists also an inherent tension between those providers, who traditionally provided ultrasound services—radiologists, cardiologists, and sonographers, for example—and intensivists, who may try to mimic the same diagnostic or therapeutic outcomes; however, with far less training or expertise. One cannot ignore the potential adverse financial impact of this less costly, less invasive imaging modality on those who previously singularly provided these services. Arguably, equipping more providers to be able to perform this service can have clinical and even fiscal benefit for the larger health system; however, potentially at the expense of other sectors of the medical system.
Provider Training and Education
Formal instruction in critical care ultrasound has taken various forms, from proprietary supplemental courses to the informal bedside “see one, do one, teach one” philosophy to high-fidelity simulation. In each of these formats, participants range from senior physicians to advanced practitioners and graduate medical trainees. What is typically common to the formal educational experience is a theoretical discussion surrounding ultrasound physics and technique, introduction to the direct application of ultrasound in the ICU, hands-on demonstration and/or experience with mannequins or observed media, and some form of certification or accreditation by the conclusion of the experience. Such courses are widely variable in academic and clinical rigor, the distribution of didactic versus practical experience, as well as in cost. In reality, the more pervasive approach to ultrasound education is through direct observation of (experienced) critical care operators with subsequent trial and error by the learning providers. Although the advantage of this method is that it provides real-life, real-time patient experience, the detriment lies in the inability to truly quantify competency and consistency among a range of providers.
Clearly, the introduction of bedside ultrasound into critical care units has altered the manner in which intensive care is delivered. Most proponents of best practice would advocate the use of ultrasound guidance when available for vascular access and as a ready adjunct, if not primary tool for the diagnosis of certain critical conditions, including lung pathology, cardiac abnormalities, and traumatic injury. That being said, discrepancies exist between how ultrasound training and continuing education is provided in addition to the anticipated variance in provider proficiency and utilization of this tool. Naturally, further study of the benefits of intensive care ultrasound to the critically ill patient should consider factors, such as interprovider reliability, standardization of education for ultrasound training, and alternative uses of this technology to help facilitate better use of this tool in critical care practice.