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Focused Cardiac Ultrasound for the Regional Anesthesiologist and Pain Specialist

Haskins, Stephen C. MD*; Tanaka, Christopher Y. MD; Boublik, Jan MD, PhD; Wu, Christopher L. MD§; Sloth, Erik MD, PhD∥**

doi: 10.1097/AAP.0000000000000650
Regional Anesthesia and Acute Pain: Review Articles

Abstract: This article in our point-of-care ultrasound (PoCUS) series discusses the benefits of focused cardiac ultrasound (FoCUS) for the regional anesthesiologist and pain specialist. Focused cardiac US is an important tool for all anesthesiologists assessing patients with critical conditions such as shock and cardiac arrest. However, given that ultrasound-guided regional anesthesia is emerging as the new standard of care, there is an expanding role for ultrasound in the perioperative setting for regional anesthesiologists to help improve patient assessment and management. In addition to providing valuable insight into cardiac physiology (preload, afterload, and myocardial contractility), FoCUS can also be used either to assess patients at risk of complications related to regional anesthetic technique or to improve management of patients undergoing regional anesthesia care. Preoperatively, FoCUS can be used to assess patients for significant valvular disease, such as severe aortic stenosis or derangements in volume status before induction of neuraxial anesthesia. Intraoperatively, FoCUS can help differentiate among complications related to regional anesthesia, including high spinal or local anesthetic toxicity resulting in hemodynamic instability or cardiac arrest. Postoperatively, FoCUS can help diagnose and manage common yet life-threatening complications such as pulmonary embolism or derangements in volume status. In this article, we introduce to the regional anesthesiologist interested in learning FoCUS the basic views (subcostal 4-chamber, subcostal inferior vena cava, parasternal short axis, parasternal long axis, and apical 4-chamber), as well as the relevant sonoanatomy. We will also use the I-AIM (Indication, Acquisition, Interpretation, and Medical decision making) framework to describe the clinical circumstances where FoCUS can help identify and manage obvious pathology relevant to the regional anesthesiologist and pain specialist, specifically severe aortic stenosis, hypovolemia, local anesthetic systemic toxicity, and massive pulmonary embolism.

From the *Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York; †Department of Anesthesiology, Montefiore Medical Center; Albert Einstein College of Medicine, New York, NY; ‡Department of Anesthesiology, Stanford University School of Medicine, Stanford, CA; §Department of Anesthesiology, Johns Hopkins University, Baltimore, MD; ∥Department of Anesthesiology and Intensive Care, Aarhus University Hospital, Aarhus, Denmark; and **Department of Anesthesiology, University of Cape Town, Cape Town, South Africa.

Accepted for publication April 30, 2017.

Address correspondence to: Stephen C. Haskins, MD, Department of Anesthesiology, Hospital for Special Surgery, 535 E 70th St, New York, NY 10021 (e-mail: haskinss@hss.edu).

E.S. is the co-owner of USABCD.org and creator of the FATE (Focus Assessed Transthoracic Echocardiography) card. The other authors declare no conflict of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.rapm.org).

Ultrasound (US) use by the regional anesthesiology and pain management specialist has become almost ubiquitous. Many would argue that US-guided regional anesthesia is the standard of care because of the many benefits it has to offer over traditional techniques.1 Similar to the impact that US has had on regional practice, focused cardiac US (FoCUS) has been equally influential in the emergency medicine2 and critical care settings3 for both diagnosis and ongoing assessment of patients with complex and evolving pathology. Focused cardiac US has been used in critical care for approximately 25 years, with the earliest example being the Focus Assessed Transthoracic Echocardiography (FATE) protocol.4 Although originally described as a tool primarily for critical care clinicians, FoCUS protocols such as FATE have been shown to be fundamental to the entire perioperative setting with a clear benefit for the regional anesthesiologist and pain specialist.

Focused cardiac US allows for rapid assessment of cardiac physiology and pathology as a supplement to conventional hemodynamic parameters (clinical examination, electrocardiogram [ECG], heart rate, peripheral blood pressure, and surrogate markers of cardiac output). Specifically, FoCUS provides essential insight into the patient's preload, afterload, and myocardial contractility. Preload, often described as the ventricular end-diastolic volume, is the end volumetric pressure that stretches the right or left ventricle (LV) of the heart to its greatest geometric dimensions under variable physiological demands. Afterload is the tension developed in the myocardial wall of the LV during the ejection period. Myocardial contractility is the intrinsic ability of the myocardium to contract. For complete hemodynamic evaluation, it is essential to know the chamber dimensions of the heart, the thickness of the myocardial walls, and their function in the context of these physiological parameters.

In addition to being a powerful tool in the perioperative setting, FoCUS has been shown to be a skill that can be learned relatively quickly when it comes to identifying obvious yet clinically relevant pathology, such as aortic stenosis (AS).5 Even novices with limited training (50 examinations) can reliably diagnose important cardiac conditions such as pericardial effusions, left ventricular dilatation, hypertrophy and failure, and right ventricular dilatation.6

Ultrasound, in general, has become so widely used largely because of the reduced size and cost and the increased technical sophistication of US machines. The same improvements used to facilitate peripheral nerve blocks and neuraxial assessment have resulted in advancements in cardiac imaging. For example, pocket-sized, handheld point-of-care US (PoCUS) machines now can obtain similar resolution of the heart as larger machines (Fig. 1A). These handheld devices have been shown to be superior to bedside physical examination alone when identifying or ruling out cardiac pathology7 and thereby can alter perioperative management8,9 and potentially result in a reduction of overall cost of care.10

Cardiac US has traditionally been considered an exclusive skill for specially trained cardiologists and cardiac sonographers. However, growing interest and use by noncardiologists have led to increased acceptance of its use under certain circumstances. For example, the American Society of Echocardiography published a consensus statement in 2013 that acknowledged the clinical utility and legitimacy of FoCUS as an adjunct to traditional bedside assessments.11 Subsequently, WINFOCUS (World Interactive Network Focused on Critical UltraSound) conducted an extensive literature review and expert consensus conference that strongly recommended using FoCUS in a variety of specific clinical scenarios.3 In addition, a recent editorial presented evidence in support of the daily use of FoCUS by anesthesiologists, further promoting its potential as the “21st-century stethoscope.”12,13

In this review, we discuss the role FoCUS has for regional anesthesiologists and pain specialists. We will introduce the regionalist to the normal sonoanatomy of the basic FoCUS views and then use the Indication, Acquisition, Interpretation, and Medical decision making (I-AIM) framework to present the cardiac pathology most relevant to the regional anesthesiologist and pain specialist in the perioperative setting.

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FoCUS for the Regional Anesthesiologist in the Perioperative Setting

Preoperative Applications

The most relevant implication for FoCUS for the regional anesthesiologist is its role in improving patient assessment and clinical optimization and in guiding management of complications surrounding neuraxial anesthesia. There is a growing body of literature, especially in the orthopedic patient population, which demonstrates regional anesthesia, with a focus on neuraxial technique, decreases the risk of postoperative morbidity in high-risk patients.14,15 However, when complicated patients present for urgent or emergent surgery, there are often concerns with performing a neuraxial technique given the potential for undiagnosed, yet significant cardiac pathology. Focused cardiac US may be used preoperatively by the regional anesthesiologist and pain specialist prior to urgent or emergent surgery16 to screen high-risk patient populations for undiagnosed cardiac disease when formal echocardiography is not promptly available.11 The elderly patient presenting with a hip fracture is a familiar example in which FoCUS may improve the preanesthetic evaluation.17 In a prospective study of hip fracture, patients who underwent routine bedside echo screening found that 31% of patients with no audible murmur had AS.18 Diagnosis of significant AS should, in turn, alter anesthetic technique, monitoring, and postoperative care.19

Studies by Canty et al8,16 and Canty and Royse20 demonstrated that preoperative FoCUS often impacts perioperative decisions such as anesthetic technique, invasive monitoring, postoperative care settings, and further consultation. More specifically, these studies found preoperative FoCUS did not always lead to an escalation of care; rather, FoCUS findings frequently led to decisions to use less invasive monitoring and to not delay operations.

Current research suggests FoCUS could have utility in the preoperative examination prior to any anesthetic. Zhang and Critchley21 found that routine preoperative FoCUS volume assessments can predict hypotension after the induction of general anesthesia for elective surgery. Although not explicitly assessed within this study, it is possible that a similar principle applies to induction with a neuraxial technique. Further research is necessary to determine if changes in anesthetic management based on FoCUS volume assessments will improve patient outcomes. However, it is conceivable that preoperative FoCUS volume assessments will become the standard of care before every anesthetic in the future.

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Postblock/Intraoperative Applications

Given the increasing age and comorbidities of our patient population, FoCUS can be a powerful tool to differentiate between intraoperative complications related to regional anesthesia such as local anesthetic systemic toxicity (LAST) and inadvertent high spinal and other causes of cardiovascular collapse such as pulmonary embolism (PE), myocardial infarction (MI), and hypovolemia. Both LAST and high spinals can cause sudden hemodynamic changes such as hypotension and bradycardia. Intraoperative hypotension that responds to standard management (eg, fluid administration, vasopressors, or inotropes) does not necessitate FoCUS imaging. However, in the setting of refractory hypotension where the cause is unclear, FoCUS becomes an essential tool. Imaging of the heart can differentiate between poor cardiac filling and decreased preload as seen with a high spinal, poor contractility related to local anesthetic (LA) toxicity to the myocardium, or other complications associated with more complex cardiac pathologies (eg, MI, PE, undiagnosed pericardial effusion).22

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Postoperative Applications

Focused cardiac US can also be used by the regional anesthesiologist and pain specialist to assess their patients postoperatively in the postanesthesia care unit.20,23,24 Focused cardiac US can be performed in serial examinations to allow repeated evaluation of volume status and ventricular function, which is often not logistically feasible with formal echocardiography.11 It can also prompt further testing or consultation. In the example of PE, although FoCUS has a low sensitivity for PE,25,26 when there is a high level of clinical suspicion along with visualization of a dilated right ventricular via FoCUS, then a clinician might more urgently decide to pursue definitive imaging such as computed tomography angiography.11 Similarly, while FoCUS should not be used to detect wall motion abnormalities,3,11 global LV systolic dysfunction in a patient with ECG changes and other supportive symptoms may prompt more rapid cardiology consultation. In addition, the ability to continually assess the efficacy of ongoing interventions may be of importance in the postoperative period. Of note, negative findings with FoCUS in a clinical situation suggestive of the previously mentioned pathologies should not discourage pursuing more conclusive investigations, such as ordering advanced imaging (eg, computed tomography angiography or a complete transthoracic echocardiogram [TTE]).

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Cardiac Arrest

Focused cardiac US is emerging as a meaningful tool to assist with diagnosis and management of patients in cardiac arrest.27 There is a gaining momentum to incorporate FoCUS into the pulseless electrical activity (PEA) pathway in the advanced cardiac life support (ACLS) algorithm. Focused cardiac US can help diagnose treatable pathologies such as hypovolemia, PE, LV failure, and pericardial tamponade. Focused cardiac US can also provide insight into prognosis and survivability based on the presence or absence of LV wall motion. For example, Breitkreutz et al22 demonstrated that a pulseless patient with “true PEA” (defined by electrical activity on ECG with no LV wall motion) had an 8% chance of surviving to hospital admission versus a patient with “pseudo-PEA” (defined by coordinated electrical activity on ECG with LV motion), who had a 55% chance of surviving to hospital admission. The FEEL (focused echocardiographic evaluation in life) protocol describes the optimal timing and FoCUS views to assist in diagnosis and management during ACLS while avoiding interference with other essential treatments.22 Although the role of FoCUS in ACLS is an important one for all clinicians, it will not be covered in detail in this article, given our emphasis on pathology most relevant to the regional anesthesiologist and pain management clinician.

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Probe Selection

Probe selection is critical for a FoCUS examination. The cardiac US probe is a small-footprint, phased-array probe (Fig. 1B). When a phased-array transducer is not available, then a large-footprint curvilinear probe can be utilized to image the heart (Fig. 1C). The large-footprint curvilinear probe is routinely used to evaluate the pericardium during FAST (focused assessment with sonography for trauma) examination. Figure 1A represents several handheld devices available for bedside FoCUS assessment, each of which is equipped with a phased-array transducer.

Although most regional anesthesiologists are familiar with linear and curvilinear array transducers for US guided procedures, these probes are not ideal for FoCUS because of their high frequencies and large footprints. These transducers typically have 128 to 512 piezoelectric (PZE) crystal elements arranged in a row that are sequentially activated to emit individual US beams (Fig. 2A).28 Multiple parallel beams along the face of the probe then form a 2-dimensional image that features a wide imaging area and high resolution (Fig. 2B).29 Curvilinear probes are similar in design except the PZE crystal elements are arranged on a curved surface to create a wider imaging area for deeper structures.28

Whenever possible, cardiac US should be performed with a phased (or sector)–array transducer, which has a small surface footprint (approximately 20 × 15mm) and relatively lower frequencies (2–8 MHz) to allow greater penetration into the thoracic cavity.30 The footprint and frequency enable imaging between the ribs, but with a wide imaging sector. Unlike sequentially activated linear arrays, phased arrays use a small number (typically 64–128) of PZE crystal elements all activated simultaneously to generate US beams from a single point (Fig. 2C).30 By activating the elements at slightly different phases, beams can be steered across the sector to form a fan-shaped image (Fig. 2D).

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How to Obtain the Basic Cardiac Views

Table 1 provides a summary of the FoCUS views.

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Subcostal 4-Chamber View

The optimal patient positioning for the subcostal view is supine with the knees slightly bent to relax the abdominal muscles (Fig. 3A). Probe placement is directly under the xiphisternum (xiphoid process), with the orientation marker pointing toward the left shoulder. Inspiration improves imaging by bringing the heart closer to the abdomen as the diaphragm contracts.

The subcostal 4-chamber (4C) view requires scanning through the liver in order to visualize the heart; therefore, liver tissue is seen in the near field followed by the 4 chambers of the heart (right atrium [RA], right ventricle [RV], left atrium [LA], and LV) (Fig. 3B) (Video, Supplemental Digital Content 1, http://links.lww.com/AAP/A213). In addition, the tricuspid valve (TV) and the mitral valve (MV) are seen at the junction of the RA/RV and LA/LV. In this view, it is possible to note overall cardiac function, visualize signs of RV or LV dilation, assess for obvious TV or MV disease, and visualize pericardial effusions.

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Subcostal Inferior Vena Cava View

The subcostal inferior vena cava (IVC) view requires similar patient and probe positioning to the 4C view; however, optimal visualization involves sliding the probe slightly to the patient's right in order to center the RA on the screen and then slowly rotating the probe counterclockwise until the orientation marker is facing cephalad (Fig. 4A). Sonographically, the IVC is seen in long axis as a tubular vessel tracking into the RA (Fig. 4B) (Video, Supplemental Digital Content 2, http://links.lww.com/AAP/A214). Under normal circumstances, the IVC is collapsible with spontaneous inspiration and should not be mistaken for the aorta, which is pulsatile and noncollapsible. The IVC diameter and collapsibility give insight into the patient's volume status, the potential for hypotension upon induction,21 and fluid bolus responsiveness.

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Parasternal Long-Axis View

Optimal patient positioning for the parasternal long-axis view (PLAX) is left lateral decubitus (LLD) with the left arm out of the way—often placed behind the head (Fig. 5A). In this position, the heart falls anteriorly toward the chest wall, thereby increasing visibility through each intercostal window. Imaging improves during exhalation as deflation of the lungs brings the heart closer to the chest wall. Of note, LLD position is not always achievable with anesthetized or postoperative patients. In that scenario, the parasternal views are still quite obtainable from a supine position.

Probe placement is just lateral to the sternum on the left hemithorax between the second and fourth intercostal spaces, with the orientation marker pointing toward the right shoulder (Fig. 5A); however, depending on the patient's cardiac anatomy, the probe may need to be placed further caudad. (Note: This is the only basic FoCUS view where the orientation marker is directed toward the right side.) Anatomically, the right side of the heart is most anterior in the chest wall. Therefore, the sonoanatomy demonstrates the RV in the near field followed by the intraventricular septum, LV, and pericardium. The LV outflow tract (LVOT), aortic valve (AV), ascending aorta, MV, and LA are all visible (Fig. 5B) (Video, Supplemental Digital Content 3, http://links.lww.com/AAP/A215). This view can be used to qualitatively assess gross cardiac function and LV filling, dilation of the ascending aorta, and the presence of severe MV or AV disease. Of note, LA dilation may suggest valvular disease, as well as potential diastolic dysfunction due to impaired LV relaxation. Evaluation for a pericardial effusion is also possible from this view.

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Parasternal Short-Axis View

Optimal patient positioning and probe placement for the parasternal short-axis view (PSAX) are identical to those for the PLAX except that the orientation marker should be rotated 90 degrees clockwise such that it is pointing toward the left shoulder (Fig. 6A).

The sonoanatomy demonstrates the RV in the near field on the left side of the screen with the intraventricular septum separating it from the LV in the far field on the right. Visualization of the papillary muscles ensures you are accurately assessing the “midpapillary view” (Fig. 6B) (Video, Supplemental Digital Content 4, http://links.lww.com/AAP/A216). Of note, this view is the mirror image of the transgastric short-axis view with transesophageal echocardiography. In this view, it is possible to note overall cardiac function, visualize signs of RV or LV dilation, assess for volume status based on end-diastolic dimensions, assess for regional wall motion abnormalities, and visualize pericardial effusions. This view is also important for the assessment of pathology, such as massive PE.

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Apical 4C View

Optimal patient positioning for the apical 4C view is similar to the parasternal views; however, a “sloppy” LLD position facilitates probe placement on the lateral chest wall.31 (Fig. 7A) Exhalation improves visualization. Imaging in the supine position is achievable as is the case with the parasternal views; however, it is more challenging.

Probe placement is adjacent to the LV apex along the left anterior chest wall. Palpating the point of maximal impulse (generally at the fifth intercostal space) can aid in identifying the LV apex on the chest. The orientation marker should be pointed toward the patient's left back or axilla.

As suggested by the name, the apical 4C view visualizes the heart's 4 chambers through the LV apex. The LV apex should ideally be at the very top of the imaging sector, with the LV, MV, and LA situated immediately below on the right side of the screen. The RA, RV, and TV are located on the left side of the screen, although adequate visualization of these structures can often be challenging (Fig. 7B) (Video, Supplemental Digital Content 5, http://links.lww.com/AAP/A217). Minor probe adjustments in the form of rotation and tilting may be necessary to avoid the LVOT and AV coming into view, which is considered a 5-chamber view.

Qualitative assessment of LV size and function can be made in the apical 4C in a similar fashion to the PLAX view. Gross morphologic abnormalities of the MV and TV may be detected in this view. The pericardial space, which surrounds all 4 chambers, should also be inspected for potential effusions.

The American Society of Echocardiography recommends the apical 4C view for qualitative RV size evaluation, which normally appears less than two-thirds the size of the LV in this view.32 However, care must be taken to fully visualize the LV cavity to avoid foreshortening the LV and thus overestimating the relative RV size.11 An RV that appears larger than the LV in this view is considered significantly dilated.32

While RV systolic function is a complex topic, FoCUS practitioners can make reliable qualitative assessments using the apical 4C view. First, RV size should be considered, as RV dilation accompanies RV systolic failure.3 Next, the RV cavity size should decrease by at least roughly one-third during systole.32 Last, the motion of the lateral tricuspid annulus toward the apex during systole can be qualitatively assessed by a simple appreciation of normal versus abnormal tricuspid annular motion. Although it is beyond the scope of this article, this motion can be measured and quantified as the tricuspid annular plane systolic excursion.32

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The I-AIM Framework

Before implementing a new clinical skill, it is essential to understand the indications and subsequent steps required to both safely and correctly begin practicing this skill. The I-AIM framework is a standardized, step-by-step guide for clinicians learning a new PoCUS skill to identify the appropriate clinical scenarios where it can be utilized.33,34 The following section describes the role of FoCUS for the regional anesthesiologists in the perioperative setting using the I-AIM framework as a clinical guide. Table 2 summarizes the I-AIM framework for each of the following cardiac pathologies relevant to the regional anesthesiologist.

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Relevant Pathology for the Regional Anesthesiologist (AIM Framework)

Severe Aortic Stenosis

The indication for assessing a patient for AS involves a patient presenting for urgent or emergent surgery (eg, hip fracture surgery) without a recent medical workup and an audible systolic murmur on auscultation. Hip fracture patients have the potential to benefit greatly from neuraxial technique, depending on their comorbidities; however, a patient with AS is at risk of significant hemodynamic changes and potential complications following induction with neuraxial technique. The definitive diagnosis and grading of valvular AS require technical skill and knowledge beyond the scope of FoCUS and this review.3,11,35,36 However, FoCUS can detect morphologic signs that suggest AS and prompt additional diagnostic imaging.3,11 Acquisition of the AV using FoCUS is best obtained in the PLAX view. Qualitative interpretation of the AV cusps motion and degree of calcification (seen as bright echogenic areas on the valve) can be obtained with this view. Decreased mobility and increased thickness or calcification of the AV cusps correlate directly with the degree of AS37 (Fig. 8B) (Video, Supplemental Digital Content 6, http://links.lww.com/AAP/A218). The AV may also be viewed en face to better assess morphologic abnormalities by using the PSAX at the AV level. This view is obtained by rotating the probe 90 degrees clockwise from the PLAX view with the AV in the center of the sector. However, this is considered a more advanced view for FoCUS practitioners. It is also important to determine the degree of left ventricular hypertrophy by assessing myocardial thickness. In addition, assessment of LV contractility and function will provide insight into whether the AS has resulted in LV decompensation.

If the AV shows signs of moderate to severe AS, the suggested medical decision making depends on the clinical circumstances. Whenever possible, the patient should be referred for formal echocardiography and cardiology consultation; however, in emergent settings, appropriate precautions should be taken during induction of anesthesia to avoid significant alterations in cardiac preload and afterload. Placement of invasive monitors, specifically an arterial line, prior to induction will ensure close monitoring of hemodynamics throughout the induction. If arterial blood pressure is adequately monitored and maintained, then a neuraxial technique can be done in a safe manner; however, consider a gradual induction with either a continuous epidural or spinal catheter over a single-shot subarachnoid block that can result in significant hemodynamic swings. Aortic stenosis with preserved LV function requires titration of vasopressors to maintain adequate afterload, whereas AS with LV decompensation may require the use of both vasopressors and inotropes. Ultimately, postoperative management should be escalated from standard postanesthesia care unit to a step-down unit or intensive care unit.

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Hypovolemia

Another important indication for FoCUS for the regional anesthesiologist is the ability to identify patients who are hypovolemic prior to a neuraxial blockade, as neuraxial technique causes a reduction in the cardiac preload. For example, a trauma patient presenting for emergent surgery with an occult bleed or a patient with end-stage renal disease who has recently undergone dialysis may have inadequate preload at baseline, resulting in significant hemodynamic changes with the potential for cardiac arrest following induction with neuraxial technique. Alternatively, hypovolemia may be the result of low vascular resistance and reduced afterload, as seen in pathologies such as sepsis or septic shock. Whenever assessing a patient, it is essential to look at the entire clinical picture and not base clinical decision making on only 1 factor, such as FoCUS imaging. When assessing for hypovolemia, the highest-yield views for acquisition are the SC IVC and PSAX views (Figs. 3 and 5). Interpretation of these views that suggests hypovolemia is as follows. The SC IVC diameter will measure 1.5 cm or less with more than 50% collapse during inspiration. In the PSAX view, severe cases of hypovolemia with normal contractility cause the LV to be hyperdynamic, with underfilling during end-diastole with end-systolic “touching” of the myocardium. (Fig. 9B) (Video, Supplemental Digital Content 7, http://links.lww.com/AAP/A219). Imaging demonstrating an IVC “kissing wall” sign (Fig. 10B) with the complete collapse of the IVC with inspiration suggests severe hypovolemia. The appropriate medical decision making with FoCUS for a hypotensive patient (Figs. 9B and 10B) is fluid resuscitation with crystalloid, colloid, or blood prior to induction with any form of anesthesia, including neuraxial block. The optimal treatment goal is to achieve an increase in IVC diameter to more than 1.5 cm with a corresponding decrease in collapsibility of less than 50% for the IVC view. For the PSAX view, the goal is to increase the LV end-diastole and systolic diameters.

Of note, another indication is the assessment of volume overload, which can correspond with either RV or global myocardial dysfunction or from overly aggressive fluid resuscitation. This assessment also requires acquisition of the IVC view. Interpretation of an IVC view suggesting fluid overload presents as a dilated IVC (>3 cm), with the most concerning sign being a lack of collapsibility with inspiration (Fig. 10C). Of note, IVC dilation can be seen with highly trained elite athletes38; however, respiratory variation and collapsibility will still be present. It is meaningful to see the stark contrast between the kissing wall sign and a heart with either volume overload or myocardial dysfunction. Although hypervolemia may not necessarily change neuraxial technique, medical decision making depends on cardiac contractility. A patient who is hypotensive with a dilated IVC and poor cardiac contractility will not improve cardiac output in response to a fluid bolus. This patient instead requires ionotropic therapy and/or diuresis. Normal cardiac function, on the other hand, requires diuresis in order to decrease preload and optimize stroke volume.

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Local Anesthetic Systemic Toxicity

Although LAST is a rare complication for regional anesthesiologists and pain specialists, it is one of the most important complications to be able to assess and manage appropriately. Local anesthetic systemic toxicity (LAST) as a result of peripheral nerve blocks or neuraxial anesthesia can be devastating, causing severe ventricular arrhythmias, myocardial depression, and the potential for cardiovascular collapse. There is a complex algorithm for the assessment and management of LAST,39 which is particularly relevant when LAST is detected immediately following injection of an LA. However, an important indication for FoCUS is when LAST's presentation is delayed, which can mimic other cardiac pathologies. Although this presentation is rare, case reports have demonstrated that following minimal doses of bupivacaine (6 mg in the subarachnoid space40 and 25 mg in the epidural space,41 respectively), patients have presented with symptoms consistent with MI40 and cardiogenic shock.41 Given that LAs, and specifically bupivacaine, have a significant impact on myocardial contractility and conduction,42 FoCUS can be an important means to determine if even a low dose of LA is the cause of circulatory compromise and failure. For example, if an otherwise healthy patient presents with delayed hemodynamic instability following either neuraxial or peripheral nerve block, FoCUS can reveal the new onset of myocardial dysfunction that would suggest LAST as a potential cause, thereby, making it possible to rapidly diagnose and accurately manage this reversible condition.

When assessing for myocardial dysfunction as a result of hemodynamic instability, the optimal FoCUS view for acquisition is the PSAX. Interpretation of this view would present with a sluggish, poorly contracting, and potential dyssynchronous LV in a patient without known cardiac pathology (Video, Supplemental Digital Content 8, http://links.lww.com/AAP/A220). The medical decision making for such a patient would be to provide hemodynamic support (with inotropes and/or vasopressors) and following the LAST treatment guidelines, including the use of lipid emulsion.

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Massive Pulmonary Embolism

Pulmonary embolism is a relatively common complication following orthopedic procedures (~1.7%)43 and is a significant cause of death following trauma surgery (~1.6%).44 Regional anesthesiologists routinely manage patients at risk of this complication, and it should be high on our differential diagnosis in the perioperative setting of hemodynamic instability and cardiovascular collapse. Pulmonary embolism is a time-sensitive emergency that requires a rapid diagnosis to ensure adequate intervention and management, and FoCUS is indicated whenever massive PE is suspected. Although FoCUS has a low sensitivity for PE,25,26 it has been shown to have high specificity in the setting of massive PE, particularly in patients without any known preexisting cardiovascular disease.45,46 Occlusion of the pulmonary vasculature as seen with massive PE causes an acute elevation in RV pressure, resulting in RV dilation and failure. Although emboli are not typically visualized by FoCUS, there are multiple FoCUS findings that significantly increase suspicion for PE and should direct further evaluation and/or management.

Diagnosis of massive PE requires image acquisition of the PSAX, apical 4C, and/or subcostal 4C views. In the PSAX view, interpretation of massive PE presents as dilation of the RV, while LV size is diminished as a result of decreased preload. As the RV pressure surpasses that of the LV, the ventricular pressure gradient causes systolic movement of the intraventricular septum from the RV to the LV during systole. Therefore, the typical “doughnut” shape of the LV changes into a “D-shape” (Figs. 11A, B). This D-shaped septal shift is nearly pathognomonic for acute massive PE, and it should be high on the differential diagnosis of any patient in the perioperative setting who has recently had surgery or has been immobile because of trauma.

Interpretation of massive PE in the apical 4C and/or subcostal 4C views presents as RV dilation in comparison to the LV. Given that a normal RV should be two-thirds the size of the LV in the apical and subcostal 4C views, a massive PE will cause the RV to appear greater in size than the LV. In addition, increased RV pressure will enlarge the RA. The intraventricular septal shift can also be seen in the 4C views as the septum bowing toward the LV during systole (Figs. 11B, D).

Medical decision making depends on the severity of the hemodynamic instability; however, typically, a massive PE visualized on FoCUS will have a significant impact on cardiac output requiring cardiopulmonary resuscitation and initiation of thrombolytic therapy and/or emergent embolectomy.

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CONCLUSIONS

Focused cardiac US is a powerful and essential PoCUS tool for all anesthesiologists in the perioperative setting; however, there are several clinical scenarios where it can help improve management as well as aid in the diagnosis of complications related to regional anesthesia. Although FoCUS is a more challenging skill to learn and perform than other PoCUS examinations, with structured learning followed by a limited number of supervised examinations, clinicians have been shown to be proficient at recognizing clinically significant pathology such as pericardial effusions, LV and RV pathology, derangements in volume status, and severe valvular disease. The use of FoCUS can lead to changes in patient management and aid in the diagnosis of significant cardiac pathology in the preoperative, intraoperative, postoperative and settings and in cardiac arrest. The fundamental FoCUS views (PSAX, PLAX, apical 4C, subcostal 4C, and subcostal IVC) allow for rapid and ongoing assessment of cardiac function, morphology, and volume status. Table 1 summarizes the views, clinical indications, and relevant pathologies covered in this article for the regional anesthesiologist and pain specialist. Table 2 summarizes these pathologies using the I-AIM framework. Although there are many FoCUS protocols available, Figure 12 provides an example of the FATE card, the oldest of the FoCUS protocols.14 Resources such as the FATE card are a helpful way for novices to reinforce the content of this article.

Given the somewhat limited scope and target audience of this article, several of the most relevant pathologies to the regional anesthesiologist and pain specialist were highlighted, including severe AS, hypovolemia, and massive PE. However, FoCUS can also be used to assess for LV systolic and diastolic dysfunction, pericardial effusions, and RV dysfunction. Focused cardiac US utility in emergency settings is invaluable for identifying gross pathology; however, it must be emphasized that FoCUS is not to be performed in place of a formal TTE. Subtle pathology can be easily missed by an untrained eye, and severity of diseases such as AS and diastolic dysfunction cannot be formally assessed with a FoCUS examination. If pathology is present in a stabilized patient, then a formal TTE should be ordered.

For the regional anesthesiologist and pain specialist already familiar with bedside US, FoCUS is an essential tool to aid management of the increasingly complex patient while adding significant value to our growing role in the perioperative surgical home. The emergence of handheld US devices has led to the potential for FoCUS to truly become the “stethoscope of the future” for bedside cardiac assessment. The regional anesthesiologist and pain specialist have the training and the critical timing and positioning necessary to make use of this skill to innovate and improve patient safety, assessment, and management. As the perioperative role of the regional anesthesiology and pain specialists continues to broaden, FoCUS will become an increasingly meaningful tool to evaluate obvious cardiac pathology prior to surgery, to facilitate diagnosis and management of potential complications, and to help differentiate between and manage evolving pathologies in the postoperative setting.

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