Name: point-of-care ultrasound screening for proximal lower extremity deep venous thrombosis
Uploaded: 2023-02-10T13:13:00
Description: Watch this Scientific Journal Video about Point-Of-Care Ultrasound Screening for Proximal Lower Extremity Deep Venous Thrombosis at JoVE.com

The authors have no acknowledgments.

All procedures performed in studies involving human participants were in accordance with the ethical standards of the Duke University Health System institutional research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The protocol was performed using inputs from the following publications3,10. Images were performed on the authors themselves for normal images and as part of routine educational ultrasound ...

<ol>
	<li>Beckman, M. G., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Venous+thromboembolism:+A+public+health+concern.">Venous thromboembolism: A public health concern.</a> American Journal of Preventive Medicine. 38, 495-501 (2010).</li><li>Kearon, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Natural+history+of+venous+thromboembolism.">Natural history of venous thromboembolism.</a> Circulation. 107 (23), 22-30 (2003).</li><li>Schafer, J. M., Stickles, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sonoguide:+Ultrasound+guide+for+emergency+physicians.">Sonoguide: Ultrasound guide for emergency physicians.</a> American College of Emergency Physicians. , (2020).</li><li>Pomero, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+emergency+physician-performed+ultrasonography+in+the+diagnosis+of+deep-vein+thrombosis:+A+systematic+review+and+meta-analysis.">Accuracy of emergency physician-performed ultrasonography in the diagnosis of deep-vein thrombosis: A systematic review and meta-analysis.</a> Thrombosis and Haemostasis. 109 (1), 137-145 (2013).</li><li>Theodoro, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Real-time+B-mode+ultrasound+in+the+ED+saves+time+in+the+diagnosis+of+deep+vein+thrombosis+(DVT).">Real-time B-mode ultrasound in the ED saves time in the diagnosis of deep vein thrombosis (DVT).</a> American Journal of Emergency Medicine. 22 (3), 197-200 (2004).</li><li>Burnside, P. R., Brown, M. D., Kline, J. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Systematic+review+of+emergency+physician-performed+ultrasonography+for+lower-extremity+deep+vein+thrombosis.">Systematic review of emergency physician-performed ultrasonography for lower-extremity deep vein thrombosis.</a> Academic Emergency Medicine. 15 (6), 493-498 (2008).</li><li>Adhikari, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolated+deep+venous+thrombosis:+Implications+for+2-point+compression+ultrasonography+of+the+lower+extremity.">Isolated deep venous thrombosis: Implications for 2-point compression ultrasonography of the lower extremity.</a> Annals of Emergency Medicine. 66 (3), 262-266 (2015).</li><li>Cogo, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Distribution+of+thrombosis+in+patients+with+symptomatic+deep+vein+thrombosis.+Implications+for+simplifying+the+diagnostic+process+with+compression+ultrasound.">Distribution of thrombosis in patients with symptomatic deep vein thrombosis. Implications for simplifying the diagnostic process with compression ultrasound.</a> Archives of Internal Medicine. 153 (24), 2777-2780 (1993).</li><li>Badgett, D. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Duplex+venous+imaging:+Role+for+a+comprehensive+lower+extremity+examination.">Duplex venous imaging: Role for a comprehensive lower extremity examination.</a> Annals of Vascular Surgery. 14 (1), 73-76 (2000).</li><li>Kory, P. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Accuracy+of+ultrasonography+performed+by+critical+care+physicians+for+the+diagnosis+of+DVT.">Accuracy of ultrasonography performed by critical care physicians for the diagnosis of DVT.</a> Chest. 139 (3), 538-542 (2011).</li><li>Bates, S. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnosis+of+DVT:+Antithrombotic+therapy+and+prevention+of+thrombosis,+9th+ed:+American+College+of+Chest+Physicians+Evidence-Based+Clinical+Practice+Guidelines.">Diagnosis of DVT: Antithrombotic therapy and prevention of thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.</a> Chest. 141 (2), 3512 (2012).</li><li>Wolf, S. J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=American+College+of+Emergency+Physicians+Clinical+Policies+Subcommittee+(Writing+Committee)+on+Thromboembolic+Disease.+Clinical+policy:+Critical+issues+in+the+evaluation+and+management+of+adult+patients+presenting+to+the+emergency+department+with+suspected+acute+venous+thromboembolic+disease.">American College of Emergency Physicians Clinical Policies Subcommittee (Writing Committee) on Thromboembolic Disease. Clinical policy: Critical issues in the evaluation and management of adult patients presenting to the emergency department with suspected acute venous thromboembolic disease.</a> Annals of Emergency Medicine. 71 (5), 59-109 (2018).</li><li>Elliott, C. G., Goldhaber, S. Z., Jensen, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delays+in+diagnosis+of+deep+vein+thrombosis+and+pulmonary+embolism.">Delays in diagnosis of deep vein thrombosis and pulmonary embolism.</a> Chest. 128 (5), 3372-3376 (2005).</li><li>Musil, D., Kovacik, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Delay+between+clinical+presentation+and+treatment+of+deep+venous+thrombosis+in+the+lower+limbs+and+regression+of+thrombosis.">Delay between clinical presentation and treatment of deep venous thrombosis in the lower limbs and regression of thrombosis.</a> Phlebology. 37 (2), 120-124 (2022).</li><li>Laursen, C. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Focused+sonography+of+the+heart,+lungs,+and+deep+veins+identifies+missed+life-threatening+conditions+in+admitted+patients+with+acute+respiratory+symptoms.">Focused sonography of the heart, lungs, and deep veins identifies missed life-threatening conditions in admitted patients with acute respiratory symptoms.</a> Chest. 144 (6), 1868-1875 (2013).</li><li>Barosse-Antle, M. E., Patel, K. H., Kramer, J. A., Baston, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Point-of-care+ultrasound+for+bedside+diagnosis+of+lower+extremity+DVT.">Point-of-care ultrasound for bedside diagnosis of lower extremity DVT.</a> Chest. 160 (5), 1853-1863 (2021).</li><li>Frankel, H. L., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Guidelines+for+the+appropriate+use+of+bedside+general+and+cardiac+ultrasonography+in+the+evaluation+of+critically+ill+patients-Part+I:+General+ultrasonography.">Guidelines for the appropriate use of bedside general and cardiac ultrasonography in the evaluation of critically ill patients-Part I: General ultrasonography.</a> Critical Care Medicine. 43 (11), 2479-2502 (2015).</li><li>Bernardi, E., Camporese, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Diagnosis+of+deep-vein+thrombosis.">Diagnosis of deep-vein thrombosis.</a> Thrombosis Research. 163, 201-206 (2018).</li><li>Caronia, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Resident+performed+two-point+compression+ultrasound+is+inadequate+for+diagnosis+of+deep+vein+thrombosis+in+the+critically+ill.">Resident performed two-point compression ultrasound is inadequate for diagnosis of deep vein thrombosis in the critically ill.</a> Journal of Thrombosis and Thrombolysis. 37 (3), 298-302 (2014).</li></ol>

Venous thromboembolism is a common disease, affecting approximately 300,000-600,000 people in the United States annually, with serious complications including pulmonary embolism. Mortality rates in these patients range from 10%-30%2,3,4. Studies have consistently found significant delays in the diagnosis of DVT, with one prospective study of 1,152 patients across 70 medical centers identifying a delay of greater than 1 week in 2...

Deep venous thrombosis (DVT) is the formation of a thrombus in the deep peripheral veins of the extremities. It is a common and important finding, affecting about 300,000-600,000 people in the United States annually1. The propagation of DVT into a pulmonary embolism can occur in 10%-50% of patients and can be deadly, with a mortality rate of 10%-30%, which is higher than the in-hospital mortality for myocardial infarction1,2,3. The risk factors for thrombus formation include hypercoagulable states from genetic factors (family history of DVT, factor V Leiden, protein C or S deficiency), acquired factors (older age, malignancy, obesity, antiphospholipid antibodies, and others), and situational factors (pregnancy, oral contraceptives, recent surgery, travel, trauma, or prolonged immobilization, including from hospitalizations)1.
Early diagnosis of DVT in critically ill patients can expedite patient care and potentially prevent life-threatening complications such as pulmonary embolism, pulmonary infarct, and cardiac involvement1,2,3. A systematic review by Pomero et al. showed a pooled prevalence of 23.1% for DVT in critically ill patients4. Screening for lower extremity DVT has traditionally been performed by radiology ultrasound technicians conducting comprehensive whole-leg duplex exams including both grayscale compression ultrasound and color/spectral Doppler. However, several smaller or community clinical sites lack the direct availability of a sonographer during certain times of the day, such as on nights or weekends, thus creating a delay in patient care5. More recently, acute care providers have devised methods of screening for proximal lower extremity DVTs using point-of-care ultrasound (POCUS)-focused imaging protocols, which demonstrate similarly high sensitivity and specificity in critically ill patients3,4,6. Proximal lower extremity DVTs are defined as DVTs occurring anywhere in the groin, thigh, or knee within the femoral or popliteal venous system. Falling outside of this category are DVTs in the following locations: calf veins (where DVTs are of uncertain clinical significance) and pelvic veins (i.e., the common, external, and internal iliac veins), which are only detectable indirectly using the color and spectral Doppler portion of consultative lower extremity venous ultrasound exams2,3.
Understanding the typical anatomic distribution of DVTs makes performing these bedside exams rapid and easy. First, 70%-99% of proximal lower extremity DVTs involve the femoral or popliteal regions7,8,9. Second, grayscale compression ultrasound is a simple and accurate method for evaluating DVTs; when enough pressure is applied to indent an adjacent artery, normal veins should collapse fully, whereas veins harboring a DVT will not. Combining these principles, the two-zone or three-zone lower extremity DVT POCUS examinations center on compression ultrasound of veins in the inguinal, thigh, and popliteal areas. These techniques have been clinically validated in prior intensive care and emergency medicine studies, demonstrating high sensitivity (96.1%, with a 95% confidence interval (CI) of 90.6%-98.5%) and specificity (96.8%, with a 95% CI of 94.6%-98.1%), with high overall diagnostic accuracy (95%)3,4,6. However, in the experience of the authors, the DVT POCUS exam remains grossly underutilized in the care of critically ill patients, possibly because clinicians are not familiar with the image acquisition sequence. This narrative review with associated visual aids describes an image acquisition protocol for performing a POCUS exam to screen for proximal lower extremity DVTs to assist providers in proper expedited image acquisition during clinical care.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Edge 1 ultrasound machine</td>
			<td>SonoSite</td>
			<td>n/a</td>
			<td>Used to obtain normal images/clips</td>
		</tr>
		<tr>
			<td>SPARQ ultrasound machine</td>
			<td>Philips</td>
			<td>n/a</td>
			<td>Used to obtain abnormal images/clips</td>
		</tr>
	</tbody>
</table>

point-of-care ultrasound screening for proximal lower extremity deep venous thrombosis

Acute lower extremity deep venous thrombosis (DVT) is a serious vascular disorder that requires accurate and early diagnosis to prevent life-threatening sequelae. While whole leg compression ultrasound with color and spectral Doppler is commonly performed in radiology and vascular labs, point-of-care ultrasound (POCUS) is becoming more common in the acute care setting. Providers appropriately trained in focused POCUS can perform a rapid bedside examination with high sensitivity and specificity in critically ill patients. This paper describes a simplified yet validated approach to POCUS by describing a three-zone protocol for lower extremity DVT POCUS image acquisition. The protocol explains the steps in obtaining vascular images at six compression points in the lower extremity. Beginning at the level of the proximal thigh and moving distally to the popliteal space, the protocol guides the user through each of the compression points in a stepwise manner: from the common femoral vein to the femoral and deep femoral vein bifurcation, and, finally, to the popliteal vein. Further, a visual aid is provided that may assist providers during real-time image acquisition. The goal in presenting this protocol is to help make proximal lower extremity DVT exams more accessible and efficient for POCUS users at the patient&#39;s bedside.

We describe the interpretation of proximal lower extremity DVT POCUS in patients with an initial suspected DVT.
The attached Figure 2 demonstrates negative POCUS ultrasound images for DVT in the left and right lower extremities, with multi-point compression from the proximal to distal veins as demonstrated in Figure 1 (from thigh to knee). In a negative DVT study, the veins are completely collapsible, with the anterior wall touching t...

Watch this Scientific Journal Video about Point-Of-Care Ultrasound Screening for Proximal Lower Extremity Deep Venous Thrombosis at JoVE.com

Point-Of-Care Ultrasound Screening for Proximal Lower Extremity Deep Venous Thrombosis

Traditionally, lower extremity deep venous thrombosis (DVT) is diagnosed by radiology-performed venous duplex ultrasound. Providers appropriately trained in focused point-of-care ultrasound (POCUS) can perform a rapid bedside examination with high sensitivity and specificity in critically ill patients. We describe the scanning technique for focused POCUS DVT lower extremity examination.

Acute lower extremity deep venous thrombosis (DVT) is a serious vascular disorder that requires accurate and early diagnosis to prevent life-threatening ...

Our protocol describes a simplified yet validated approach to diagnostic point-of-care ultrasound by describing a three-zone protocol for lower extremity DVT image acquisition. Providers appropriately trained in focused point-of-care ultrasound can perform a rapid bedside DVT examination with high sensitivity and specificity in critically ill patients. Diagnostic POCUS exams can expedite the diagnosis of DVT and thereby initiate earlier treatment with potentially decreased complication rates and improved patient clinical outcomes.Key steps for appropriate DVT image acquisition include proper patient positioning, adequate gain and depth, and complete compression of the veins'vessel walls to ensure no thrombus is present. Select the high frequency linear transducer for the deep venous thrombosis or DVT scan to ensure a high resolution image of the veins. Next, set the depth, gain, and focus.Set the depth so that the target vessels appear in the middle one-third of the ultrasound screen by pressing the up or down depth button. Then set the gain so that the vessels contain a few spots of gray but are otherwise black by pressing the right or left gain button and turning the dial. If the machine has the capability, aim the focus beam at or slightly below the level of the target vessels by clicking the box on the screen and moving it while holding down the button and then release.Set the machine mode. Click on B-mode, which is a two-dimensional gray scale ultrasound exam, to obtain both the non-compressed and compressed images. For optimal scanning ergonomics, place the machine with the ultrasound in a direct line of sight with the ultrasound probe.Before scanning, expose the patient's entire leg from the groin to the knee. Place the patient supine for DVT examination of the common femoral and femoral veins. Place the patient in the frog-leg position to enable better visualization and scanning of the distal veins.For B-mode scanning of the groin and thigh, apply gel to the patient's skin in a linear path that traces out the expected path of the ultrasound transducer to increase the efficiency of motion. For B-mode scanning of the knee, apply gel to the transducer itself, as a generous gel application will facilitate the scanning efficiency. Next, for transducer orientation, place the transducer in a transverse position with the orientation marker directed toward the patient's right side to ensure that images captured during scanning correspond to the anatomical direction of the structures.Place the probe perpendicular to the path of the vein to visualize the vein in a short axis view. Center the venous structure on the screen. Add long axis imaging in ambiguous cases by rotating the probe 90 degrees so the marker points towards the patient's head.For compression sequence, begin scanning immediately coddle to the inguinal crease. Progress distally sequentially with downward compression and then release at each point. Compress such that the entire vein collapses with the anterior wall touching the posterior wall while the artery remains pulsatile.Do not apply resting surface pressure between each compression, as it can obscure the visualization of the veins. The vein should collapse fully when enough pressure is applied with the transducer to indent an adjacent artery. Click save clip and compress.Then release the common femoral vein or CFV and femoral artery or FA just below the inguinal ligament. Slide the probe distally about one centimeter and record the same compression and release technique at the CFV and FA at the intake of the great saphenous vein or GSV. Click save clip, then compress and release the probe at the CFV at the bifurcation of the FA into the superficial femoral artery or SFA and deep femoral artery or DFA.Between the SFA and DFA, there will be a lateral perforator vein draining from the lateral to medial into the CFV. Ensure that both the lateral perforator vein and GSV are compressible. Click save clip, then compress and release the probe at the CFV at the bifurcation of the CFV into the femoral vein or FV and deep femoral vein or DFV.Again, click save clip, compress, and release the probe at the popliteal vein behind the knee. Once points one to five are fully compressible, scan the FV along the thigh from proximal to distal until the vein disappears into the adductor canal. During this scanning process, attempt to compress the vein approximately every one to two centimeters.In this study, left leg vascular anatomy with negative and positive lower extremity DVT examples in transverse views, are shown here. In a negative DVT study, the veins are completely collapsible with the interior wall touching the posterior wall during compression ultrasound in all the zones. In a positive DVT study, proximal vein POCUS can both directly visualize a thrombus or detect non-compressibility of the proximal veins, which is diagnostic of a non-occlusive thrombus.The protocol explains the steps in obtaining DVT images at six compression points in the lower extremity from the proximal thigh, moving distally, to the popliteal space.

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Research

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Medicine

Electrolytic Inferior Vena Cava Model (EIM) of Venous Thrombosis

Animal models serve a vital role in deep venous thrombosis (DVT) research in order to study thrombus formation, thrombus resolution and to test potential therapeutic compounds (1). New compounds to be utilized in the treatment and prevention of DVT are currently being developed. The delivery of potential therapeutic antagonist compounds to an affected thrombosed vein has been problematic. In the context of therapeutic applications, a model that uses partial stasis and consistently generates thrombi within a major vein has been recently established. The Electrolytic Inferior vena cava Model (EIM) is mouse model of DVT that permits thrombus formation in the presence of continuous blood flow. This model allows therapeutic agents to be in contact with the thrombus in a dynamic fashion, and is more sensitive than other models of DVT (1). In addition, this thrombosis model closely simulates clinical situations of thrombus formation and is ideal to study venous endothelial cell activation, leukocyte migration, venous thrombogenesis, and to test therapeutic applications (1). The EIM model is technically simple, easily reproducible, creates consistent thrombi sizes and allows for a large sample (i.e. thrombus and vein wall) which is required for analytical purposes.

Electrolytic Inferior Vena Cava Model EIM of Venous Thrombosis

The electrolytic induction of endothelial activation to the internal surface of the Inferior Vena Cava results in venous type thrombus formation due to endothelial activation and partial blood stasis, two components of Virchow's triad.

Animal models serve a vital role in deep venous thrombosis (DVT) research in order to study thrombus formation, thrombus resolution and to test potential ...

Protocol and Guidelines for Point-of-Care Lung Ultrasound in Diagnosing Neonatal Pulmonary Diseases Based on International Expert Consensus

Ultrasound is a safe bedside imaging tool that obviates the use of ionizing radiation diagnostic procedures. Due to its convenience, the lung ultrasound has received increasing attention from neonatal physicians. Nevertheless, clear reference standards and guideline limits are needed for accurate application of this diagnostic modality. This document aims to summarize expert opinions and to provide precise guidance to help facilitate the use of the lung ultrasound in the diagnosis of neonatal lung diseases.

Lung ultrasound is a noninvasive and valuable tool for bedside evaluation of neonatal lung diseases. However, a relative lack of reference standards, protocols and guidelines may limit its application. Here, we aim to develop a standardized neonatal lung ultrasound diagnostic protocol to be used in clinical decision-making.

Ultrasound is a safe bedside imaging tool that obviates the use of ionizing radiation diagnostic procedures. Due to its convenience, the lung ultrasound ...

Point-of-Care Lung Ultrasound in Adults: Image Acquisition

Consultative ultrasound performed by radiologists has traditionally not been used for imaging the lungs, as the lungs&#39; air-filled nature normally prevents direct visualization of the lung parenchyma. When showing the lung parenchyma, ultrasound typically generates a number of non-anatomic artifacts. However, over the past several decades, these artifacts have been studied by diagnostic point-of-care ultrasound (POCUS) practitioners, who have identified findings that have value in narrowing the differential diagnoses of cardiopulmonary dysfunction. For instance, in patients presenting with dyspnea, lung POCUS is superior to chest radiography (CXR) for the diagnosis of pneumothorax, pulmonary edema, lung consolidations, and pleural effusions. Despite its known diagnostic value, the utilization of lung POCUS in clinical medicine remains variable, in part because training in this modality across hospitals remains inconsistent. To address this educational gap, this narrative review describes lung POCUS image acquisition in adults, including patient positioning, transducer selection, probe placement, acquisition sequence, and image optimization.

Point-of-care ultrasound (POCUS) of the lungs provides quick answers in rapidly changing clinical scenarios. We present an efficient and informative protocol for image acquisition for use in acute care settings.

Consultative ultrasound performed by radiologists has traditionally not been used for imaging the lungs, as the lungs&#39; air-filled nature normally ...

Point-of-Care Ultrasound: A Review of Ultrasound Parameters for Predicting Difficult Airways

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON method, which looks for and evaluates the Mallampati classification, signs of obstruction, and neck mobility. Clinical findings help predict a higher likelihood of difficult tracheal intubation, but no clinical result reliably excludes difficult intubation. Ultrasound as an adjunct to clinical examination can provide the clinician with a dynamic anatomical airway assessment, which is impossible with clinical examination alone. In the hands of anesthesiologists, ultrasound is becoming more popular in the perioperative period. This method is particularly applicable for identifying proper endotracheal tube positioning in specific patient populations, such as those who are morbidly obese and patients with head and neck cancer or trauma. The focus is on identifying the normal anatomy, correctly positioning the endotracheal tube, and refining the parameters that predict difficult intubation. Several ultrasound measurements are clinical indicators of difficult direct laryngoscopy in the literature. A meta-analysis revealed that the distance from the skin to the epiglottis (DSE) is most associated with a difficult laryngoscopy. An ultrasound of the airway could be applied in routine practice as an adjunct to the clinical examination. A full stomach, rapid sequence intubation, gross visual anatomical abnormalities, and restricted neck flexibility prevent using ultrasound to assess the airway. The airway evaluation is performed with a linear array transducer of 12-4 MHz, with the patient in the supine position, with no pillow, and with the head and neck in a neutral position. The central axis of the neck is where the ultrasound parameters are measured. These image acquisitions guide the standard ultrasound examination of the airway.

A point-of-care ultrasound (POCUS) is a simple, non-invasive, and portable tool that enables dynamic airway assessment. Several studies have attempted to determine the role of ultrasound parameters as an adjunct to clinical examination in predicting difficult laryngoscopies.

Airway management remains a crucial part of perioperative care. The conventional approach to assessing potentially difficult airways emphasizes the LEMON ...

Optic Nerve Sheath Point of Care Ultrasound: Image Acquisition

The goal of this protocol is to develop a standardized method for acquiring images of the optic nerve sheath and measuring the optic nerve sheath diameter (ONSD). Diagnostic ultrasound of the ONSD to detect intracranial hypertension has traditionally faced many problems because of methodologic discrepancies. Due to inconsistencies in the measuring techniques, the potential for ONSD to become a non-invasive bedside monitoring tool for ICP has been hampered. However, establishing a transparent, consistent methodology for measuring the ONSD would support its use as a valid and reliable method of identifying intracranial hypertension. This is important as it has both high sensitivity and specificity in acute care settings. This narrative review describes ONSD POCUS image acquisition, including patient positioning, transducer selection, probe placement, the acquisition sequence, and image optimization. Further, visual aids are provided to assist in real-time during image acquisition. This method should be considered for patients for whom there are concerns regarding intracranial hypertension but who do not have an intracranial monitor in place.

Point-of-care ultrasound (POCUS) of the optic nerve sheath diameter (ONSD) has been shown to be useful in identifying patients with increased intracranial pressure (ICP). However, the non-standardized technique for this POCUS has hampered its use. We present a standardized image acquisition protocol for use in the acute care setting.

The goal of this protocol is to develop a standardized method for acquiring images of the optic nerve sheath and measuring the optic nerve sheath diameter ...

Imaging the Abdominal Aorta with Point-of-Care Ultrasound

An Approach to Point-Of-Care Ultrasound Evaluation of the Abdominal Aorta

Disorders of the abdominal aorta, including aneurysms and dissection, have potentially high rates of morbidity and mortality. While computed tomography (CT) is the current gold standard to image the abdominal aorta, the process of obtaining a CT may be time-consuming, requires the use of intravenous contrast dye, and involves exposure to ionizing radiation. Point-of-care Ultrasound (POCUS) can be performed at the bedside and has excellent sensitivity and specificity for the diagnosis of abdominal aortic aneurysm and excellent specificity for the diagnosis of abdominal aortic dissection. Additionally, POCUS is non-invasive, cost-effective, lacks ionizing radiation, requires no intravenous contrast dye, and can be performed without taking the patient from a critical care area. Screening for abdominal aortic aneurysm (AAA) can be done in primary care settings as well. 
This article will review the approach to POCUS of the abdominal aorta to evaluate such critical pathology. In this paper, we will review the sonographic anatomy of the abdominal aorta as well as the choice of the ultrasound probe, description of POCUS image acquisition, and some pearls and pitfalls of using POCUS to aid in the diagnosis of potentially life-threatening abdominal aortic pathology.

Author Spotlight: Using Point-of-Care Ultrasound for Comprehensive Evaluation of the Abdominal Aorta

This protocol reviews the steps to image the abdominal aorta with point-of-care ultrasound. We discuss image acquisition, troubleshooting imaging pitfalls and artifacts, and the recognition of life-threatening abdominal aortic pathology.

Disorders of the abdominal aorta, including aneurysms and dissection, have potentially high rates of morbidity and mortality. While computed tomography ...

Gastric Ultrasound Technique for Mitigating Peri-Procedural Aspiration Risk

Gastric Point of Care Ultrasound in Adults: Image Acquisition and Interpretation

Over the past two decades, diagnostic point-of-care ultrasound (POCUS) has emerged as a rapid and non-invasive bedside tool for addressing clinical inquiries related to gastric content. One emerging concern pertains to patients about to undergo sedation and/or endotracheal intubation: the elevated risk of aspiration from the patient&#39;s stomach contents. Aspiration of gastric contents into the lungs poses a serious and potentially life-threatening complication. This occurs more frequently when the stomach is considered &#34;full&#34; and can be affected by the techniques employed for airway management, making it potentially preventable. To mitigate the risk of peri-procedural aspiration, two distinct medical specialties (anesthesiology and critical care medicine) have independently developed techniques to utilize ultrasonography for identifying patients requiring &#34;full stomach&#34; precautions. Due to these separate specialties, the work of each group remains relatively unfamiliar outside its respective field. This article presents descriptions of both techniques for gastric ultrasound. Furthermore, it explains how these approaches can complement each other when one of them falls short. Regarding image acquisition, the article covers the following topics: indications and contraindications, selection of the appropriate probe, patient positioning, and troubleshooting. The article also delves into image interpretation, complete with example images. Additionally, it demonstrates how one of the two techniques can be employed to estimate gastric fluid volume. Lastly, the article briefly discusses medical decision-making based on the findings of this examination.

Author Spotlight: Point-of-Care Ultrasound for Gastric Content Assessment and Risk Stratification in Perioperative Care 

This protocol introduces two methods for image acquisition in gastric ultrasonography. Additionally, tips are provided for interpreting this information to assist in medical decision-making.

Over the past two decades, diagnostic point-of-care ultrasound (POCUS) has emerged as a rapid and non-invasive bedside tool for addressing clinical ...

Ultrasound in Evaluating Diaphragm Dysfunction and Monitoring Treatment

Measuring Diaphragm Thickness and Function Using Point-of-Care Ultrasound

The diaphragm is the main component of the respiratory muscle pump. Diaphragm dysfunction can cause dyspnea and exercise intolerance, and predisposes affected individuals to respiratory failure. In mechanically ventilated patients, the diaphragm is susceptible to atrophy and dysfunction through disuse and other mechanisms. This contributes to failure to wean and poor long-term clinical outcomes. Point-of-care ultrasound provides a valid and reproducible method for evaluating diaphragm thickness and contractile activity (thickening fraction during inspiration) that can be readily employed by clinicians and researchers alike. This article presents best practices for measuring diaphragm thickness and quantifying diaphragm thickening during tidal breathing or maximal inspiration. Once mastered, this technique can be used to diagnose and prognosticate diaphragm dysfunction, and guide and monitor response to treatment over time in both healthy individuals and acute or chronically ill patients.

Author Spotlight: Unraveling the Impact of Mechanical Ventilation on Diaphragm Function and Patient Outcomes 

Diaphragm thickness and function can be assessed in healthy individuals and critically ill patients using point-of-care ultrasound. This technique offers an accurate, reproducible, feasible, and well-tolerated method for evaluating diaphragm structure and function.

The diaphragm is the main component of the respiratory muscle pump. Diaphragm dysfunction can cause dyspnea and exercise intolerance, and predisposes ...

Probe Selection and Machine Presets for Point-of-Care Ultrasound of the Abdominal Aorta

To perform a point of care ultrasound evaluation of the abdominal aorta, select a 2.5 to 3.5 megahertz curvilinear probe, which provides the best visualization for most adults. Alternatively, use the phased array probe of 1 to 5 megahertz, commonly called cardiac probe, which is typically used for echocardiography. Use the abdominal preset on the machine regardless of the probe used.Set the mode to B mode or two-dimensional gray scale and the depth to 20 centimeters. Adjust the depth once the aorta is visualized to keep the aorta in the midfield of the screen. Choose a lower frequency range for patients with a high body mass index to improve image acquisition.

Imaging the Abdominal Aorta in the Transverse Plane Using Point-of-Care Ultrasound

To begin scanning, position the patient's supine with the abdomen exposed. Hip flexion, if tolerated by the patient, relaxes the abdominal muscles and may improve image acquisition. Apply ultrasound gel to the transducer.Orient the transducer and the transverse plane with the indicator toward the patient's right. Ensure that the indicator position matches the one displayed on the screen. Place the transducer just distal to the patient's xiphoid process and apply light pressure to visualize the anterior aspect of the vertebra with its hyperechoic shadow casting arch.Slide the transducer coddly until the celiac trunk is visualized. The celiac trunk is short and quickly bifurcates into the hepatic artery and splenic artery, which together form the seagull sign. Capture these images for later review by clicking the button on the system that records clips.Slide the transducer coddly to view the superior mesenteric artery or SMA. Coming off the anterior aorta, SMA follows a path parallel to the aorta to course inferiorly. The splenic vein courses anterior to the SMA and the left renal vein courses between the SMA and the aorta.Measure the AP diameter of the suprarenal aorta by optimizing a live image of the aorta in this location, and then pressing the system's freeze button. Press caliper or measure and move the track ball or touch pad of the system to the outer edge of the anterior wall, the adventitia and click select. Next, move the track ball or touch pad again to the outer edge of the posterior wall and click select.Wait for the system to generate a measurement. Click the button on the system that saves still images to save this image as a still image containing the measurement. Continue scanning in a transverse plane to visualize the entirety of the aorta through the bifurcation and capture the images.When a live image of the distal aorta is optimized, measure the AP diameter of the infrarenal aorta. Press caliper or measure and move the track ball or touch pad of the system to the outer edge of the anterior wall, the adventitia and click select. Move the track ball or touch pad again to the outer edge of the posterior wall and click select.Wait for the system to generate a measurement. Save the still image as demonstrated previously. Adjust the depth as the abdominal aorta courses coddly through the abdomen becoming more superficial and tapering slightly.Continue scanning coddly through the aortic bifurcation into the left and right iliac arteries. Adjusting the depth to maintain the aorta in vertebral body in the middle of the screen. Capture images while scanning through the bifurcation.When imaging the abdominal aorta in the transverse plane, an aorta measuring greater than 3 centimeters was considered aneurysmal. Such aneurysms also showed the presence of a hematoma filling most of the lumen. The presence of an intimal flap within the lumen of the aorta indicated aortic dissection.Depending on the chronicity of the dissection, the flap was either thin and moved with the pulsations of the aorta or thickened and had an adjacent hematoma. An acute thoracic aortic dissection was found to extend through the abdominal aorta and into the right iliac artery.