The CORE Scan

The CORE Scan Concentrated Overview of Resuscitative Efforts The use of bedside ultrasonography has been successfully integrated universally into the assessment of patients presenting with acute traumatic injury.1,2 Various protocols are also being studied regarding the use of bedside ultrasonography in the evaluation of patients presenting with shock and undifferentiated hypotension, and during volume resuscitation.3–6 This article describes a compendium of bedside scans that should be performed during the assessment and management of critically ill patients. The CORE (Concentrated Overview of Resuscitative Efforts) scan can be used to help make critical diagnoses and guide resuscitation efforts in patients with undifferentiated deterioration. ENDOTRACHEAL TUBE ASSESSMENT The first part of the CORE scan addresses the patient’s airway. Traditionally, assess- ngmethods such EM Residency Program, Department of Emergency Medicine, Maricopa Medical Center, University of Arizona, College of Medicine-Phoenix, 2601 East Roosevelt Street, Phoenix, AZ 85008, USA E-mail address: teresawumd@gmail.com Crit Care Clin 30 (2014) 151–175 ment of proper endotracheal tube placement has been performed usi decompensation is not readily apparent based solely on history and physical exami- Teresa S. Wu, MD INTRODUCTION Critically ill patients require rapid, accurate assessments and appropriate therapeutic interventions to maximize their chances of recovery. Often, the cause of a patient’s nation findings. Furthermore, the evaluation of resuscitation efforts is often difficult because of the time-intensive and invasive nature of most monitoring techniques. KEYWORDS � Resuscitation ultrasound � CORE scan � Emergency bedside ultrasonography KEY POINTS � Ultrasound can be used at the patient’s bedside to make critical diagnoses that can help expedite and improve patient care. � During a critical resuscitation, the CORE scan can be used to identify life-threatening causes for a patient’s deterioration and help guide management options. � Emergent procedures can be performed under ultrasound guidance during resuscitation attempts. � The CORE scan can be repeated if serial exams are required. http://dx.doi.org/10.1016/j.ccc.2013.08.001 criticalcare.theclinics.com 0749-0704/14/$ – see front matter � 2014 Elsevier Inc. All rights reserved. as direct laryngoscopy, auscultation of breath sounds, end-tidal CO2 detection, and chest radiography. Ultrasonography has been shown to be useful in determining proper endotracheal tube positioning at the bedside.7 During intubation attempts, a linear-array transducer can be placed in a horizontal fashion across the patient’s neck, at the level of the cricothyroid membrane. The orientation marker on the probe is typically oriented toward the patient’s right (Fig. 1). With the probe in this position, the patient’s thyroid can be visualized nearfield on the screen, with the bright white hyperechoic rings of the trachea just farfield to it (Fig. 2). As the endotracheal tube is being passed down through the trachea, the bright white hyperechoic tube can be visualized entering the tracheal lumen. The tube will cast a white acoustic shadow farfield on the screen once it is in the lumen of the trachea (Fig. 3). On ultrasonography, the esophagus can be seen as a muscular ring just postero- lateral to the trachea. During the intubation, applying color Doppler over the trachea can help visualize movement of the endotracheal tube as it is advanced into the patient transfer, repositioning, or changes in a patient’s respiratory status. Performing Wu152 bedside ultrasonography to determine tube positioning is faster than performing a direct laryngoscopy, and carries less risk of accidentally dislodging the endotracheal tube. Once the endotracheal tube has been confirmed to be properly in the trachea, it is useful to evaluate the lungs for symmetric, bilateral lung inflation and lung sliding during ventilation and oxygenation attempts. BEDSIDE PULMONARY ULTRASONOGRAPHY The CORE scan can be modified based on the clinical suspicion of what is likely contributing to a patient’s deterioration. In most situations, once the endotracheal tube position has been confirmed within the trachea, it is useful to evaluate the lungs as the next step. A thoracic ultrasonographic scan can be completed quickly at the trachea (Fig. 4). If the endotracheal tube is accidentally passed into the esophagus, the comet tails from the tube will be seen in the esophagus, and a flash of color will be seen on color Doppler imaging of the esophagus during the failed intubation attempt (Fig. 5). Endotracheal ultrasonography can be useful in guiding proper tube placement during the initial intubation attempt, or for reassessment of tube placement following Fig. 1. Ultrasonographic evaluation of endotracheal tube placement. Note that the indica- tor marker should be directed toward the patient’s right side. bedside to determine whether the patient has ventilation of both lungs and to assess Fig. 2. Ultrasonographic visualization of the hyperechoic tracheal rings and empty trachea behind the thyroid tissue. The CORE Scan 153 whether the patient has a pneumothorax or pleural effusion that needs to be emer- gently addressed. The lungs can be visualized by placing either a high-frequency linear-array trans- ducer or a lower-frequency curvilinear transducer in a horizontal fashion in the second or third intercostal space (Fig. 6). With the probe in this position, the parietal and visceral pleural interface can be seen as a bright white hyperechoic line coursing horizontally across the ultrasound screen. Fig. 3. Endotracheal tube within the tracheal lumen producing a hyperechoic comet-tail farfield. Wu154 For patients in whom it is difficult to identify the pleural line, begin the scan with the probe in a longitudinal fashion, at the third intercostal space, along the midclavicular line; this will provide a view of the ribs and underlying structures. To ensure proper visualization of the parietal-visceral pleural interface, locate an anechoic rib and focus on the hyperechoic line just farfield to the rib (Fig. 7). During the normal inspiratory and expiratory cycle, the visceral pleura can be seen gliding along the parietal pleura. On ultrasonography, this horizontal to-and-fro move- ment across the screen has been termed lung sliding.8 If a patient is intubated with Fig. 4. Improving visualization of the endotracheal tube entering the trachea using color Doppler. the endotracheal tube in the proper position, bagging the patient should produce bilateral lung sliding with each ventilation. If the endotracheal tube is in the right main- stem bronchus, there will be an absence of lung sliding on the left. Similarly, with Fig. 5. Comparison of color Doppler imaging of the endotracheal tube entering the trachea (left) versus the esophagus (right). A, carotid artery; Es, esophagus; Tr, tracheal rings. an endobronchial intubation on the left, lung sliding will not be seen over the right hemithorax. If lung sliding is difficult to visualize, or if a unilateral pneumothorax is suspected, the next step is to evaluate the diaphragm for bilateral, symmetric excursion. The dia- phragm is best visualized by placing a lower-frequency curvilinear or phased-array transducer in a longitudinal fashion along the midaxillary line at the T7-T9 intercostal space (Fig. 8). With the indicator pointing toward the patient’s head, the diaphragm will appear as a bright white hyperechoic line just to the left of the liver or the spleen (Fig. 9). Compare the excursion of the diaphragm on both the left and right sides of the chest. Fig. 6. Linear array transducer and probe placement for a thoracic ultrasound. The CORE Scan 155 If there is no lung sliding and no diaphragmatic excursion, the patient has an endo- bronchial mainstem intubation, a large unilateral airway obstruction, or a very large pneumothorax. Fig. 7. Bedside ultrasound of the parietal-visceral pleural interface in between 2 anechoic ribs. Wu156 Fig. 8. Probe placement to evaluate the diaphragm for proper excursion during ventilation. On ultrasonography, a normal lung typically demonstrates lung sliding and artifacts called comet tails. Comet tails are bright white hyperechoic artifacts that shoot farfield off the pleural interface when the parietal and visceral pleura appose one another dur- ing the respiratory cycle (Fig. 10). If there is air trapped in between the parietal and visceral pleura, comet tails and lung sliding will not be visualized. When normal lung is visualized on M-mode, a characteristic pattern termed the seashore sign is seen (Fig. 11). The seashore sign depicts a normal interface between the lung and chest wall, where the static thoracic wall and soft tissue produces parallel lines across the screen. The pleural line is seen as a bright white horizontal line Fig. 9. Bedside ultrasonographic evaluation of the diaphragm and the inferior thoracic cavity. Fig. 10. Comet tails from a normal parietal-visceral pleural interface. The CORE Scan 157 separating the soft tissue nearfield and the dynamic lung parenchyma farfield. If the patient has a pneumothorax, the M-mode imaging of the lung will produce a pattern called the stratosphere sign or bar-code sign (Fig. 12). This pattern is seen on M- mode because the air trapped in between the parietal and visceral pleura produces horizontal hyperechoic artifacts in the farfield. If there is concern that there may be a pneumothorax instead of just an endobron- chial mainstem intubation, scan along the chest until the edge of the pneumothorax is visualized. The transition point between normal lung and a pneumothorax is called the lung point.9 At the lung point, normal lung sliding and comet tails will be seen abut- ting a region of the pleura where there is a distinct absence of lung sliding or comet tails. With B-mode scanning, it is easy to see the transition between the normal lung sliding across the screen and the stationary pneumothorax in real time (Fig. 13). On M-mode, if the cursor is placed directly over the lung point, a clear transition be- tween the seashore sign and the bar-code sign will be observed (Fig. 14). If thoracic ultrasonography does not demonstrate lung sliding and the lung point cannot be clearly visualized, it may be difficult to determine whether the patient has a pneumothorax or an endobronchial intubation. To help distinguish between the two entities, scan the lung for a lung pulse. The lung pulse is the detection of cardiac Fig. 11. The seashore sign: normal lung in M-mode. Fig. 12. The stratosphere sign or bar-code sign of a pneumothorax in M-mode. Fig. 13. A static image of the transition between normal lung and a pneumothorax at the lung point. In real-time B-mode scanning, the movement of the normal lung will be in distinct contrast to the stationary pneumothorax. Fig. 14. Lung point on M-mode. Note the transition between the bar-code sign of a pneu- mothorax and the seashore sign of normal lung. Wu158 pulsations transmitted to the parietal pleura in a lung that is not being actively venti- lated, and is best visualized on M-mode. A lung pulse should not be visualized with a large pneumothorax. It is important to remember that lung sliding can be absent in patients who have had a pleurodesis, or who have pleural adhesions, pulmonary con- tusions, pulmonary infiltrates, acute respiratory distress syndrome, atelectasis, bullae, blebs, large pulmonary contusions, or pulmonary masses abutting the pleural line. Further research is being undertaken to help distinguish between these entities on bedside ultrasonography. During the thoracic portion of the CORE scan, it is useful to know if the patient has a large pleural effusion that may require immediate intervention. Pleural effusions are best visualized by placing the probe in the mid- to posterior-axillary line between T7 and T10. Attempt to visualize the interface between the inferior lung and the dia- phragm. A pleural effusion will appear as a dark anechoic layer of fluid just cranial to the diaphragm. Lung may be seen floating in the effusion during the respiratory ically significant pulmonary edema will demonstrate large “B-lines” or “lung rockets” The CORE Scan 159 (Fig. 16). Lung rockets are bright white hyperechoic comet tails that move with sliding of the lung, and are the result of interlobular septa filled with water. These features are wider than the comet tails seen in normal lung, and should extend to the farfield depths of the ultrasound image. Patients with pulmonary edema should demonstrate more than two lung rockets in at least two areas of the thoracic cavity. Current research is under way to determine whether the number of lung rockets correlates with the degree of pulmonary edema. If lung rockets are visualized during the CORE scan, resuscitation and management options for alveolar-interstitial syndrome should be instituted accordingly. BEDSIDE CARDIAC ULTRASONOGRAPHY During the CORE scan, it is imperative to evaluate the heart to establish that the pa- tient still has cardiac activity; to note if there is a pericardial effusion and cardiac tam- ponade; to assess for any right ventricular strain that may indicate the presence of a cycle (Fig. 15). If the pleural effusion is thought to be contributing to the patient’s deterioration, an emergent thoracostomy tube should be placed to drain the fluid noted on ultrasonography. The CORE scan may demonstrate findings of pulmonary edema. Patients with clin- Fig. 15. Pleural effusion over the liver. Wu160 large pulmonary embolism; to determine whether the patient requires more intravas- cular volume; and to evaluate the estimated ejection fraction of the heart. To perform a rapid assessment of the heart during resuscitation attempts, it is ideal to start with a parasternal long-axis view of the heart. First, identify that the patient still has cardiac activity and that chest compressions are not warranted. Once cardiac activity has been visualized, assess for the presence of a pericardial effusion and cardiac tamponade. Pericardial fluid will appear as a dark anechoic stripe of fluid sur- rounding the heart. If the effusion is small, it may only be seen as a small black stripe of fluid along the posterior, dependent portion of the pericardial sac (Table 1). Larger effusions will be seen circumferentially around the heart and are typically more than 15 mm in diameter (Fig. 17). The presence of a moderate or large pericardial effusion does not necessarily mean that the patient has cardiac tamponade. Ultrasonographic findings of cardiac tampo- nade include end-diastolic right ventricular collapse (Fig. 18), right atrial collapse, respiratory variation of blood flow across the tricuspid or mitral valve of more than 40%, and a dilated inferior vena cava (IVC) that does not change with inspiration or “sniffing” (Fig. 19).10,11 If tamponade physiology is noted clinically or on bedside ultra- Fig. 16. “Lung rockets” from a patient with acute pulmonary edema. sonography of the heart, a pericardiocentesis should be performed immediately under ultrasound guidance.12 If there is clinical suspicion for a large pulmonary embolism causing hemodynamic compromise, bedside cardiac ultrasonography can be performed to assess for right ventricular dilation (>1:1 right ventricular/left ventricular diameter) (Fig. 20), right ven- tricular systolic dysfunction, paradoxic septal bowing into the left ventricle (Fig. 21), IVC dilation without inspiratory collapse (Fig. 22), or presence of thrombus visualized in the right ventricle.13 On a parasternal short-axis view of the heart, the septum may be seen bowing into the left ventricle, thereby creating the so-called D-sign from right Table 1 Categories of pericardial effusion Effusion Size Location Diameter (mm) Small Localized, dependent region <10 Medium Localized or circumferential 10–15 Large Circumferential >15 Fig. 17. Large pericardial effusion surrounding the heart. Ao, aortic outflow tract; LA, left atrium; LV, left ventricle; RV, right ventricle. Fig. 18. End-diastolic collapse of right ventricle (RV) from a pericardial effusion causing cardiac tamponade. Fig. 19. Dilated inferior vena cava (IVC) from a pericardial effusion causing cardiac tamponade. The CORE Scan 161 Fig. 20. Right ventricular (RV) dilation from a massive pulmonary embolism. RA, right atrium; RV, right ventricle; LA, left atrium; LV, left ventricle. Fig. 21. Septal bowing into the LV, otherwise known as the D-sign, on parasternal short-axis view of the heart. Fig. 22. Dilated IVC from a large pulmonary embolus (26.5 mm). Wu162 ventricular dilation. In this view, instead of its typical circular appearance, the left ventricle appears more like the letter D (see Fig. 21). It is important to bear in mind that these sonographic findings must be taken in the context of the entire clinical picture, as many of these findings can also be seen with long-standing chronic obstructive pulmonary disease, obstructive sleep apnea, pulmonary hypertension, and right-sided myocardial infarction. Evaluation of the diameter of the right ventricular wall can help distinguish between acute and chronic right ventricular dilation and right ventricular dysfunction. Patients with chronic right ventricular strain will typically have a right ventricular wall thickness greater than 6 mm.14 In addition, most patients with chronic right ventricular dysfunction will demonstrate global hypokinesis, whereas patients with a large, acute pulmonary The CORE Scan 163 embolism may exhibit hypokinesis of the right ventricular free wall and base, but normal contractility of the right ventricular apex. This apical sparing is known as the McConnell sign, and has been shown to have specificity of 94% and sensitivity of 77% for diagnosing an acute pulmonary embolism.15 These findings on the CORE scan in a hemodynamically unstable patient or in a patient in cardiac arrest should prompt the clinician to consider a large pulmonary embolism, and to contemplate initiation of thrombolytic therapy immediately.16 During the CORE scan, the heart should also be assessed to evaluate global contractility and estimate the ejection fraction. This information can be very useful in guiding fluid resuscitation and titrating doses of vasopressor agents. To evaluate global function, obtain a parasternal long-axis view of the heart and examine the diameter of the left ventricle during systole and diastole. On global assessment, the heart’s contractility can be generally categorized as either hyperdy- namic, normal, mild to moderately decreased, or severely dysfunctional. To obtain a quantitative evaluation of the contractility of the left ventricle, use M-mode to evaluate the fractional shortening of the left ventricular diameter during systole and diastole. Fractional shortening can be calculated using the following formula: Fractional shortening (%) 5 [(EDD � ESD)/EDD] � 100 where ESD is the end-systolic diameter measured between the ventricular walls just distal to the tips of the mitral valve leaflets, and EDD is the end-diastolic diameter measured between the ventricular walls at the same distance distal to the mitral valve leaflets (Fig. 23). Studies have shown that a fractional shortening of 30% to 45% correlates with a normal ejection fraction.17 Note that an M-mode tracing in a normal heart will show the left ventricular walls almost touching completely during systole with a high frac- tional shortening (Fig. 24). Fig. 23. End-diastolic diameter (EDD) and end-systolic diameter (ESD) on B-mode in a normal heart. Wu164 In a poorly contracting heart, the M-mode tracing demonstrates wide systolic sep- aration between the ventricular walls and a low fractional shortening (Fig. 25