Hello, my name is Dr. Karla Venegas and I am the Director of Echocardiography and Ultrasound in the Department of Critical Care Medicine at Mayo Clinic Florida. I'm going to be speaking about evident POCUS diagnostic difficulties or common pitfalls in ultrasonography. POCUS refers to the use of portable ultrasound applications at the bedside. It is performed directly by the treating physician for either guidance in a diagnosis or a procedure. Its use is rapidly increasing, but unfortunately there are no standardized national or international guidelines for its implementation into clinical practice, and the curriculum and training to competency have not been well defined. Due to POCUS is increasingly incorporated into the care of critical ill patients, there are currently concerns regarding appropriate POCUS use and oversight, and a risk assessment should include the technology, the provider, and the context in which medical care is delivered. POCUS can decrease time to diagnosis and improve care efficiency. In one study in post-operative follow-ups, two hours of care were saved per patient on average when POCUS was used in comparison to traditional ultrasound. In medical patients, POCUS can significantly reduce time to diagnosis from 186 minutes to 24 minutes. In trauma patients, the use of eFAS has increased over the last decade, saving patients money by reducing unnecessary diagnostic intervention, provider's time, and reducing unnecessary radiation exposure. In the ICU, ultrasound is a great tool in the placement of peripheral, central, and arterial lines, which facilitate administration of medications and drawing blood samples, especially helpful in patients with difficult IV. Finally, POCUS is a very powerful diagnostic tool in the ICU. However, as I already mentioned, device security, patient's confidentiality, and patient safety are main points of concern, and we have significant concerns about the provider, about qualifications, for example, for the provider, about the software, for example, about where all the information is going to be saved or what is going to happen if there is a breach on the cloud, for example, about the patient, can the patient feel some discomfort during the study, what is the proper infection control for the devices, and how we are going to minimize the over- or under-diagnosis. So we understand that the greatest risk regarding ultrasound use is from the users themselves. The use of ultrasound has robust data supporting improved provider performance and patient safety for almost 20 years, so we consider the greatest risk is likely non-learning and employing the ultrasound, but we are concerned about what are the risks from the lack of use when the technology is available and the diagnosis and the management of the patients can have better results. It is unlikely that severe harm will occur in a failed ultrasound-guided peripheral LV catheter insertion, but imagine a focused evaluation of cardiac contractility interpreted as normal ejection fraction in a patient with severe systolic dysfunction, and the patient is diagnosed later with myocarditis. Maybe the provider was correct in the initial interpretation and the cardiac dysfunction evolved over time, or maybe the provider misinterpreted the images and the dysfunction was present at the time of focus assessment. So the risk of the patient is obvious, and therapists may not align with underlying pathology, increasing the risk of morbidity and mortality. So risk increases if the providers do not receive adequate training or supervision, if the provider does not document the findings, or if the provider documents an interpretation but images are not saved and incorporated into the medical record. So let's go and review some clinical examples of this situation that can occur. So for example, pericardial effusion is often found in critical ill patients as a diastolic fluid filled space located within the two layers of the pericardium. It is usually anechoic but sometimes can show as a complex echo texture when it contains clots, holes, or fibrin. Pericardial effusion can be circumferential or regional and is not always visualized or very easy to visualize. Several echo views are needed to demonstrate the presence of real amount. So the most important tips to evaluate the presence of pericardial effusion are, for example, tracking the descending aorta, and this you can do it in a long parasternal view, on the apical four chambers view. We can check the dependent segments of the posterior wall, lateral wall, inferior wall, checking the diastolic collapse of right heart chambers, that is a sign of hemodynamic significance of the pericardial effusion. Remember the right chambers will be resistant to collapse in severe pulmonary hypertension. We can check also the IVC which is usually dilated more than two centimeters in a long axis and will reduce or absence collapsibility less than 20% of collapsibility in spontaneously breathing patients. Now a very common a very common pitfall is in hypovolemic patients with a small underfield cardiac chambers when even a mild pericardial effusion may be overestimated because the hyperdynamic heart could simulate a diastolic collapse of the right chambers. In these cases, look for an empty IVC with more than 50% or complete collapse during respiration variation, which may explain the hemodynamic compromise. Now the most common problematic diagnosis or differential diagnosis for pericardial effusion are pleural effusion, ascites, or epicardial or mediastinal FAD. So in ascites, for example, this can appear always in subcostal views anterior to the right heart chambers and in this case the falciform ligament that you can see here is observed within the fluid. These are the the orange arrows where the diaphragms can also be appreciated. Performing a fast exam will also help you to confirm the diagnosis of ascites. Now in the cases of epicardial FAD, like you can see here, this is an adipose tissue accumulated between the visceral pericardium and the myocardium. It is slightly isoecogenic and it is best observed in systole because it obliterates completely in diastole and exclusively in anterior regions. It is commonly seen in long parasternal, short parasternal, and subcostal 4-chambers views. Now a pericardial effusion diagnosed by mistake in the unstable patient may lead to unnecessary pericardiosynthesis with a strong possibility of cardiac chambers perforation, pericardial tamponade, and eventually death. To avoid this error, it is important to integrate the findings of the ultrasound in the clinical context. In case of a doubt, it is recommended draining other effusions like a pleural effusion or an abdominal effusion if they are present and then reevaluate the hemodynamic impact of a pleural pericardial effusion. If pericardial effusion is still present but is not large and shows no hemodynamic consequences on the mortality of the right heart chambers, drainage should be avoided unless an infectious effusion is suspected. In cases of posterior or loculated pericardial effusion, lightly difficult to drain, a surgical consult should be considered. Now, the diagnosis of right ventricular failure is important at the bedside diagnosis of massive pulmonary embolism. However, not always the right ventricular dilation is clearly visible, and many possibilities of error should be considered. The diagnosis of right ventricular dilation basically relies on a comparison between the end diastolic diameter of the right ventricle and left ventricle. A wrong and incomplete visualization of the cardiac chambers may lead to misdiagnosis. It is important to consider the possibility of a chronic right ventricular dilation, like in patients with chronic pathologies, like chronic volume overload, chronic pressure overload, like pulmonary hypertension, or significant tricuspid or pulmonary regurgitation. A common pitfall in patients with cardiac arrest from any cause occurs when ventricular chambers tend to equalize in short time, and then applying right ventricular dilation criteria may not be accurate for right ventricular strain. A wrong diagnosis of right ventricular dilation may lead to erroneous diagnosis of acute right pressure overload, secondary to massive pulmonary embolism, and guide to the use of thrombolytic or thrombectomy. On the other hand, missing the visualization of the right ventricular dilation from an acute status may delay proper treatment or be harmful for the patient. To avoid this error, it is recommended to clearly visualize the two ventricles, ideally in the apical four chambers view that you can see in this video, and the two end diastolic diameters taken at the level of the atrioventricular plane, a valve plane. A ratio of at least 0.9 is indicative of right ventricular dilation. When this view is not obtained, a conclusion should not be drawn so quickly. In this table, you can see the difference cut off in other views that are used for this calculation. Other signs of right ventricular pressure overload may be considered, that may be considered, are the right ventricular D-shape or systolic interventricular septal flattening in the short axis view, impairment of the right ventricular systolic function, like a low type C or a right ventricular inferior wall hypokinesia, as well as the right atrium peak pressure gradient higher than 30 millimeters of mercury. Also consider the presence of signs of chronic dilation, like a thickening of the right ventricular wall, what is considered with a wall of more than five millimeters, and consider also the status of the left ventricle. Now, the evaluation of the IVC is a common practice to consider the bulimic status of fluid responsiveness of a patient. I want to focus on the pitfalls that alter this supposed linear relationship between the size of the vein and the actual volume status, which can be easily encountered in clinical practice. IVC measurement may fail in indicating the real volume status in patients with high left ventricular filling pressure, acute right ventricular infarction, pericardial tamponade, acute massive pulmonary embolism, intra-abdominal hypertension, patients with asthma or COPD exacerbations, and absolutely also can be failing mechanically ventilated patients. IVC dynamics can be highly variable in patients with core pulmonar, severe tracheal space regurgitation, and pericardial construction. And a common mistake that leads to misinterpretation is when the technique is not correctly applied. For a correct measure, the IVC should be visualized in long axis and the inner walls should be clearly seen. In M mode, the movement of the vessel under the probe may erroneously give the impression of a respiratory collapse that is not real. This must be checked observing simultaneously the M mode with the 2D image. These misinterpretations in the IVC measurement may lead to avoid fluid or give diuretics in patients who are volume depleted and potentially fluid responsive, like shock states like a right ventricular myocardial infarction and obstructive shock, or in the other hand, lead to erroneous administration of fluid challenges in patients with high left-sided cardiac pressures, sometimes inducing pulmonary congestion, worsening hemodynamic status, and delaying administration of vasopressors or inotropics. To avoid this error, it is essential to integrate the IVC analysis with a comprehensive multi-organ ultrasound approach that should include the evaluation of the right and the left ventricle, pulmonary congestion by assessing long ultrasound for B-lines, and of course, a full consideration of all the available clinical information. Remember to assess the absolute IVC size always combined with the respiratory variation. In mechanical ventilated patients, use the distensibility index. In spontaneously breathing patients, evaluate the IVC collapsibility, and remember that in patients with non-invasive ventilation and other conditions affecting the transmural pressures between the thorax and the abdomen, this may preclude the use of the IVC for volume assessment. Let's talk now about the long ultrasound. There is a good evidence to support the use of ultrasound in the diagnosis of both pleural and parenchymal diseases, as well as an undifferentiated respiratory failure. The most common errors in long ultrasonography happen when we choose an inappropriate probe, depth or gain. For example, when scanning the anterior views using excessive depth will not allow for an optimal visualization of the pleura. So a depth of 9 to 10 centimeters is usually adequate for the anterior chest and the anterior axillary line, allowing a good balance of pleural morphology, such as long sliding, as well as the visualization of non-artifacts like the A-lines. But in the dependent areas, we may need 20 centimeters to identify solid organs and the diaphragm. So the most important pearl in lung imaging is to scan perpendicular to the pleura to allow for optimal visualization of pleural morphology and non-artifacts using the appropriate depth. Little changes in the angles of the insonation of the angle may generate a non-A, non-B pattern, which may difficult diagnostic interpretation. This image can be optimized finding the probe until the angle of insulation is perpendicular to the pleural line, generating a bright hyperechoic pleural line and visualizing the A-lines. In the interpretation of B-lines, one common mistake is to confuse B-lines with C-lines, which are vertical artifacts that generate from the pleura but no travel the entire depth of the screen and which are not pathological fineness. To differentiate B-lines from C-lines, increase your To differentiate B-lines from C-lines, increase your depth and focus your attention on the bottom part of your image to see if the vertical artifacts do in fact extend to the whole depth of the screen. As per understanding the meaning of the B-lines, they commonly represent pulmonary edema in the setting of congestive heart failure, but they can also represent infectious or inflammatory etiologies. Visualization of the pleural morphology can help us make this distinction as we can see a smooth pleural line with B-lines generating from A, which is consistent with hydrostatic pulmonary edema. And in contrast, when we see an irregular pleural line, we suspect an inflammatory or infectious etiology like atypical or viral pneumonitis, interstitial lung disease, pulmonary hemorrhage, ARDS, or COVID. Using ultrasonography signs in the diagnosis of pneumothorax include the long point, absence of lung sliding, and absence of B-lines or consolidations. A complex situation can happen in patients with pulmonary blebs, secondary to severe COPD, who also have a high risk to develop a secondary pneumothorax. In these cases, sometimes irregular lung sliding can be demonstrated in the end mode and help you to make the correct diagnosis. However, sometimes the presence of pleural additions precludes the visualization of the respiratory movements and induces error in the interpretation. So, in stable patients, absence of a sliding lung should never be considered enough to finalize the diagnosis of pneumothorax, especially in patients with complex pulmonary disorders. The misdiagnosis of the absence of sliding or a false lung point may lead to an unnecessary pleural drainage. On the other hand, a false sliding, false pulse, or multiple septa in the diagnosis of pneumothorax may be dangerously delayed or even missed. To avoid these errors, use a set of criteria to define pneumothorax by combining the four basic signs. Absence of lung sliding, absence of parenchymal signs like B-lines and consolidations, absence of lung pulse, and look for the lung point for final confirmation in the stable patient. Eventually, rule in a pneumothorax by chest CT scan if the patient is stable or correlate the ultrasound pattern with prior images when available, especially in cases of history of blebs or pleurodesis. Another common artifact is the mirror artifact, which consists in the repetition, look at this one here, look at the repetition of a false image resulting from the ultrasound beam hitting against a highly reflective surface like the diaphragm. This is seen often in the right side and this artifact can simulate a lung consolidation. This misdiagnosis may lead to initiation of antibiotics as well as a needed chest x-ray or CT scan. To avoid this error, along with integration into the clinical picture, observing the same tissue pattern, you can see the same tissue pattern. Like in this case, you have the same pattern from the liver or the spleen is usually enough to rule in this artifact. The presence of pleural effusion, like in this picture, and associated with lung consolidation or fluid bronchogram is never observed in mirror image artifacts and help in differentiating real lung disease. Now let's go move to the abdominal ultrasound where the peritoneal fluid recognition is a very important part of the FAST exam. When the abdomen is evaluated in left coronal views, a full stomach appearing below the diaphragm may mimic peritoneal fluid. In other situations, the stomach may appear in epigastric subcostal views and also simulate an abdominal collection. In other situations, the stomach, depending on the gastric content, for example, if it's fluid or if there is a food, the appearance of the stomach may vary, ranging from simple and echoic, like in this picture, or a very heterogeneous pattern. And in some cases, like in this case, you even can see the presence of a nasogastric tube, so sorry, you can see the presence of the nasogastric tube inside of the stomach cavity. So the diagnosis of a false peritoneal fluid may lead to unnecessary paracentesis and subsequent intra-abdominal organ trauma, but also may trigger unnecessary radiation and cause from CT scan status. But worst case scenario, this misinterpretation may lead to a laparotomy when increasing the surgical risk. So to avoid this error, consider the possibility of a full stomach since it is visible and most known FAST patients are, as well as in patients with delayed gastrointestinal emptying, which is a common situation in critical ill patients. When we have a doubt and the patient is able to take oral fluid, you can ask the patient to drink water and then observe the bubbles appearing in the stomach. If the patient is NPO, you can use, again, a nasogastric or orogastric tube and evaluate if you can see the image after you drain that fluid from the stomach. So those are some tips that may help you to differentiate a full stomach versus ascites. So last, I'm going to talk about the vascular ultrasound and, you know, most cases of DVT are found in the lower extremity limbs and it's a common differential diagnosis is this one, when we can see this congestion on the vein, but it's not a clot, this is called relapsed formation. And this is just accumulation of red blood cells around the venous valve and it's, again, this echogenic blood flow inside of the vassal. If you are confused, you are not sure if this is a clot, you just need to make some pressure on the vassal and then, like here, you can see that the flow gets clear after that. So the problem of misdiagnosis of DVT only based on relapse may lead to unnecessary anticoagulation, which increases the cost and the risk of bleeding. So, as I mentioned, just the way to differentiate these two diagnoses is making some pressure at the vassal and evaluating after the pressure, or you can also, of course, order a spectral Doppler and compare the findings in both extremities. So, as a conclusion, POCUS is a fast, affordable, portable, and accurate diagnostic test. It can improve patient's care through multiple specialties, but we know, we are aware that there are unsolved safety concerns which must be addressed, and absolutely POCUS does not replace the clinical judgment, physical examination, or common sense. Thank you, and I hope you are enjoying the conference.

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