ASHOT E. SARGSYAN, MICHAEL BLAIVAS and DIMITRIOS KARAKITSOS

Overview

The approaches to examination of patients by clinical providers has evolved with the growth of medical knowledge and expectations of quality care. Though still primarily relying on their senses, physicians have been adding basic equipment (e.g., scale, stethoscope) and more complex devices (e.g., scopes, sphygmomanometer) to patient evaluation standards. In the intensive care unit (ICU), the diagnostic process is rather complex and continuous, and physical examination is deprived of several basic elements, such as pain assessment and general patient cooperation. Therefore, intensivists tend to rely on adjunctive diagnostic tools. The addition of critical care ultrasound (CCU) to the patient examination arsenal has been a major development during the last decade. The method fits naturally in the logic of the initial assessment process and, because of its repeatability, also in the continuous monitoring of these highly variable patients. As a generous source of real-time information, CCU shares a pedestal only with the physical examination itself.^1,2

Notwithstanding the ample supporting evidence vividly exhibited throughout this volume, implementation of CCU is still in its early stages. Further large-scale growth depends on recognition of the evidence, acceptance by leading organizations, further development and miniaturization of equipment and data-handling facilities, training and cross-pollination of expertise, clarification of administrative and financial aspects, and other factors. Physicians are gradually recognizing the benefits of implementation of CCU for themselves and for their patients. Gradual implementation of CCU will eventually lead to stratification of physicians and facilities into those that know and use the advanced CCU support and those that do not.

One overarching and powerful measure capable of tipping the balance toward accelerated maturation and phasing in of CCU is the development and promotion of a high-level, conceptually strong, and realistic approach. This chapter does that by further analyzing the holistic approach (HOLA) concept of CCU imaging that was introduced in Chapter 1. The HOLA concept defines CCU as part of the patient examination by a clinician to visualize all or any parts of the body, tissues, organs, and systems in their live, anatomically and functionally interconnected state and in the context of the whole patient’s clinical circumstances. The term “holistic” in the HOLA acronym is used in its original meaning in ancient Greek: to emphasize the importance of the whole and the interdependence of its parts. The term and the acronym must not be confused with “holistic medicine,” which has a different patient population, scope, and methodology. The authors of this chapter define the following overarching principles that should drive implementation of a HOLA-based CCU model in the ICU:

Scope of critical care ultrasound

One of the prevalent misconceptions regarding physician-performed ultrasound is the concern that it is done in lieu of comprehensive (referred) sonographic studies. Another source of confusion is the lack of a clear distinction between focused emergency ultrasound and CCU.

The scope of CCU is not to replace comprehensive sonography. CCU does not substitute for “radiologic” sonography, very much like Foley catheter placement does not make the urology service irrelevant; CCU replaces only studies that are largely futile in their solely retrospective significance. CCU performed by intensivists or other members of the ICU team augments the physical examination and has an instant effect on patient management. Moreover, it aids in dynamic monitoring of the constantly changing clinical status of ICU patients because of its bedside availability and repeatability. This dynamic monitoring capability is a distinct CCU feature that radiology routines can never adopt (e.g., recognize interstitial pulmonary edema and assess the effect of diuresis every 10 minutes). Most CCU techniques promise better outcomes only if used within the clinically driven time frame. Typically, still image–based, technician-performed studies are associated with delayed radiologist interpretation and serve different purposes.

Thus, CCU satisfies a need that is not currently met and is a highly rational opportunity to improve patient care that has no alternatives at this time. In this sense, CCU is rather similar to physician-performed focused emergency ultrasound—a similarity that at superficial glance makes the two methods appear identical. There are, however, major differences in principle. As part of initial patient assessment, emergency ultrasound usually answers binary (yes-no, either-or) questions. CCU answers binary questions too, but does not stop there because ICU patients rarely have a single problem to identify and monitor, and many new questions are often posed in the course of their stay. Following the clinical logic of intensivists, CCU in their hands seeks answers to questions that are not necessarily binary and often proceeds, as time and physician imaging experience permit, onto secondary questions and broader organ or system assessment. Another essential role of CCU is monitoring known problems and following the results of treatment measures or recovery from known states. Assessing and monitoring volume status, identifying return of peristaltic activity after major abdominal surgery, and evaluating the effectiveness of respiratory therapy are typical examples of CCU applications. Finally, a very important group of CCU applications are related to procedure support, and examples of such are numerous.

In the following section HOLA is explained as a concept that justifies and rationalizes the initial efforts (e.g., equipment procurement, training, planning, credentialing) at implementation of CCU and serves as a basis for planning a phased introduction of ultrasound into the ICU.

The HOLA concept of critical care ultrasound imaging

The HOLA concept of CCU imaging was introduced in Chapter 1. This textbook in its entirety is, in essence, a detailed description of HOLA. In all fairness, adoption of HOLA is a major, understandably difficult conversion of a physician’s mindset and attitude toward changing the established routine of clinical practice. It takes effort to reconsider the notion that scanning is a prerogative of equipment-savvy technicians and image interpretation is a separate “darkroom magic” by radiologists. Such conversion requires realization and acceptance of the unity and synchrony of scanning and interpretation when performed by a clinician to see or rule out pathologies in real-time by using somewhat unconventional techniques and implementing complex monitoring protocols.³

Applying all possible CCU techniques in imaging a single patient is an obvious exaggeration. However, to explain the HOLA concept, let us consider a fictional scenario in which all CCU techniques are conducted in a single “head-to-toe” examination, like an ultrasound “cocoon” wrapping the entire body surface. For example, encountering a septic patient with acute respiratory distress syndrome and other comorbid conditions is not rare in the ICU. The standard approach is to focus on pulmonary function, acid-base status, and blood gases, but lung ultrasound offers additional means of monitoring trends in lung aeration and edema. These patients may have severely compromised cardiovascular function, and effusions or diffuse cerebral edema may develop by various mechanisms. Foci of possible infection could be located “outside the lung” (e.g., abdominal source). Rapid progression toward multiple organ failure syndrome may be the dominant clinical picture and requires monitoring of renal function as well. Numerous, even more complex clinical scenarios are encountered in routine ICU practice.

From the facility perspective, acceptance of HOLA means that all known specialized diagnostic, monitoring, and procedure support CCU techniques are either operationally available or awaiting implementation, and moreover, every part of the human body is a potential target of generic scanning. In a short diversion, let us parse the generic scanning principle. Besides the special techniques that are usually based on published evidence, HOLA includes generic scanning based on recognition of tissues and organs by the physician. After specific training and initial practice, the real-time gray-scale image on the screen is correctly perceived as a live cross section underneath the transducer. Once physicians start recognizing the live anatomy on the screen, their medical knowledge becomes a strong quality assurance mechanism. The HOLA concept perceives generic anatomic assessment by CCU as another visual source of structural information from deeper tissues underneath the skin that are hidden from human vision and other senses. Surely, excellent knowledge of normal and pathologic anatomy is an essential prerequisite for successful interpretation of such information. Diagnostic dilemmas occur daily in the ICU, and expert consultation is necessary on many occasions. For example, echocardiography requires expert input to correctly assess anomalies that an intensivist cannot adequately clarify. The recent implementation of advanced echocardiographic techniques such as tissue Doppler and three-dimensional imaging into routine practice further underlines the importance of such input. Other techniques (e.g., abdominal or vascular ultrasound) may require additional review or a second opinion when the initial assessment is inconclusive. The introduction of invasive techniques such as intravascular and endobronchial ultrasound suggests the creation of on-site suites technically capable of supporting these applications. Moreover, new methods such as ultrasound molecular imaging and image-guided interventional procedures will continue their growth. Experimental studies targeting pathologic processes with contrast-enhanced ultrasound, such as angiogenesis, inflammation, thrombi, and plaque formation, have shown promising results and require special expertise and conditions.4–8 Notably, therapeutic agents can be attached to the particles of contrast agents to enhance drug delivery and effect (e.g., continuous transcranial Doppler was suggested to augment tissue plasminogen activator–induced arterial recanalization in stroke).^8,9 Future studies are needed to validate the safety profiles, as well as the diagnostic and therapeutic indications, of the aforementioned and other highly specialized techniques. Assimilation of all established and realistically anticipated ultrasound techniques into the HOLA implementation goals appears to be an essential step-up for ICU services that will remain competitive for a reasonable number of years.

The HOLA concept and the set of overarching principles for its implementation outlined in the beginning of this chapter foresee basic and specific batteries of CCU techniques and generic scanning areas. Even though these batteries will probably differ between facilities and evolve in time, we suggest a number of illustrative examples (Table 57-1). Analyzing all goal-directed HOLA examination profiles is beyond our scope. Mastery of all techniques by the ICU team requires considerable education, training, and experience. Limitations do exist regarding the applicability of several CCU techniques, as analyzed in detail throughout this edition.

Physician education, training, and competence

In 2001 the American College of Emergency Physicians issued guidelines that defined the use of emergency ultrasound. Indications recommended for emergency ultrasound were trauma, pregnancy, emergency echocardiography, abdominal aorta imaging, and biliary, renal, and procedural ultrasound. The guideline was updated in 2008 to include new core applications such as ultrasound for deep venous thrombosis, soft tissue and musculoskeletal imaging, and thoracic and ocular imaging.^10,11 Recently, the American College of Chest Physicians and La Société de Réanimation de Langue Française published their recommendations after a consensus meeting to define the use of ultrasound in the ICU. This consensus suggested that all intensivists should achieve competency in basic CCU techniques such as pleural, lung, abdominal, diagnostic, and procedural vascular ultrasound and basic critical care echocardiography.¹² Notwithstanding the existence of recommendations as a basis for the future training of intensivists in ultrasound techniques, there is still a significant gap in ultrasound education, training, and accreditation. We wish to underline, however, that a tactical approach to CCU implementation based on a solid HOLA concept is a high-level demand that should no longer be overlooked by health authorities at all levels.

With adoption of the HOLA concept of ultrasound imaging by an ICU facility, ultrasound machines are placed in each unit (one machine for every two beds at the bedside) for use by all intensivists and for all patients. In such a setting, implementation of all known CCU techniques is significantly enabled. However, the array of special CCU techniques available depends on the combined CCU knowledge and experience of the intensivists present on a given shift. Moreover, thorough review of ambiguous results may require an expert such as a cardiologist or a radiologist (see Table 57-1). As in other ultrasound settings, CCU remains highly operator dependent, and the level of competency varies among operators and depends on training programs, background, and experience. In most European countries and in the United States, educational programs are gradually being introduced with specific requirements for various levels of competency in ultrasound applications.^1,2 However, additional programs are clearly required to meet the growing demand for CCU education and training in most countries around the globe.

The critical care ultrasound laboratory

Clinicians often favor the use of ultrasound to avoid delays in patient assessment, thus exploiting the fast nature of the method and its immediate effect on patient management. However, the effect of a specific examination on a particular patient may produce results that are anywhere in the continuum from highly specific and confident to indeterminate or nondiagnostic. For purposes of integrity of the patient management record, documentation of each examination is essential, and so are trend monitoring across multiple repeated examinations, self- and cross-training of ICU team members, and quality assurance and analysis. Storage of the imaging data is also necessary for secondary review by experts and for reference and development of new techniques.

These considerations have led to a search for mechanisms to integrate CCU data and optimize the application of both diagnostic and procedural ultrasound. Hence, the idea of a CCU laboratory (CCUL) was formulated as a rational consequence of the suggested ultrasound model using a HOLA concept (Figure 57-1). A CCUL is, first of all, a data capture and archival capability unit within the ICU that uses in-hospital servers and can therefore be integrated into the well-established picture archiving and communication system (PACS). Application of a PACS minimizes consultation responding time and facilitates image interpretation and quality control (Chapter 56). Moreover, the growing availability of telemedicine options further enhances the expert consultation potential. Notably, in facilities with existing electronic medical record systems, the CCU imaging data could be integrated with other clinical, imaging, and laboratory data in the same platform or on the distributed network. Advocates of simple and stand-alone use of ultrasound may consider this centralized archival concept complicated and redundant. As the HOLA ultrasound concept is adopted and implemented, use of CCU and its effects on patient outcomes grow dramatically, and thus it becomes necessary to keep the imaging data well organized and functional as part of an overall approach to patient management. Another important feature of a CCUL is an actual physical suite within the unit that includes a central station with optimal features for specialized procedures such as relatively invasive diagnostics and ultrasound-guided interventions on a cart-based full-featured machine.

In large multivalent units, a CCUL as a physical space must also have a dedicated area for cleaning and maintenance of the portable machines, storage of transducers and accessories, and minor testing and upgrades. A CCUL must have one or more image review workstations with professional-grade monitors for self- and cross-training of ICU staff and consultations. This area, as well as a conference room, can be separate or shared for all similar staff activities. Training plus practice for invasive procedures on phantoms and models justifies a separate multifunctional nonpatient area.

The operational cost of a CCUL should be properly evaluated, but no studies are available at this time to offer reference estimates. In view of the availability of portable ultrasound devices, along with the rapidly spreading integration of PACSs into hospital practice, we speculate that this cost may in fact be reasonable. Intensivists could enrich their knowledge and experience by continuous interaction with experts, and the training capabilities and benefits for residents, medical students, and operators are endless. Research activities could be strengthened and interactive clinical practice would flourish.

The benefits of adopting a HOLA ultrasound concept for critical care patients cannot be overstated, and the cost of equipment, training, physician credentialing, and other measures appears to be justified. Although current implementation of CCU is sporadic and usually initiated by one or two occasional ultrasound enthusiasts on the ICU team, sufficient evidence is already available not only to support such initiatives but also to integrate implementation of CCU into long-term plans of service or facility development.

Further studies are required to validate methodology issues and document the benefits of running a CCUL. The need for specific functions of the CCUL concept, however, will eventually become evident. Future policies and planning by health authorities and institutional boards are essential as well. Key issues such as cost-efficiency, accreditation, requirements, and regulations to ensure safe function of CCULs should equally be addressed.

In the second half of the 20th century there was a general public notion that everything is achievable through technology. This notion remains very strong in modern hospital settings. However, technology should serve and not guide and usurp medical practice, which should be driven by opportunities to improve the standard of care. In that sense, advances in critical care patient management and ICU organization are steps in the right direction, and ultrasound technology has a great potential to support such developments. The primary anticipated benefits of adopting the HOLA concept of CCU imaging are improvement in patient care and outcomes and ICU bed efficiency. Secondary benefits are also numerous and spread beyond the hospital setting since many CCU solutions could be applicable to emergency fields and environments with limited resources. We highlighted in Chapter 50 the perspective of a very unique medical field, space medicine, as a user of yet another “flavor” of ultrasound diagnostics that combines many features of HOLA ultrasound imaging with telemedicine as it seeks new options to optimize safeguarding of the health of crew members during long-duration space missions.¹³

Pearls and highlights

References