Name: rapid point-of-care assay of enoxaparin anticoagulant efficacy in whole blood
Uploaded: 2012-10-12T12:00:00
Duration: 11 min 17 s
Description: Watch this Scientific Journal Video about Rapid Point-of-Care Assay of Enoxaparin Anticoagulant Efficacy in Whole Blood at JoVE.com

The investigations were carried out solely with support from departmental and institutional resources. The coagulation apparatus (Hemochron 801) was loaned without obligation from the manufacturer. The assay cartridges were purchased at their retail costs. The introductory figure in the video was modified from Sanderink, et al.12 The second figure in the video (heparinase digestion time course) was reproduced with permission from Inchiosa et al.1

1. Heparinase Reconstitution
<ol>
 <li>Lyophilized heparinase I is obtained commercially (Siemens, Newark Delaware, DadeHepzyme REF B4240-10) in vials containing 1 &mu;g of the purified protein. The protein is dissolved in 0.25 ml of saline (0.9% NaCl). </li>
</ol>
2. Collection of Blood Samples
<ol>
 <li>Two blood samples are drawn by vacuum into sodium citrate (0.3 ml 0.109M; 3.2%) buffered Vacutainer tubes (Becton-Dickinson; Franklin Lakes, NJ); the tubes are both pre-spiked with a known concentration of enoxaparin; the blood volume that is drawn is 2.7 ml. The total content is then 3.0 ml. </li>
</ol>
3. Heparinase Digestion
<ol>
 <li>The entire contents of the heparinase vial that can be aspirated into a syringe (approximately 0.2 ml; 80% of the vial; 0.8 &mu;g of protein), is transferred to one Vacutainer tube; 0.2 ml of saline (0.9% NaCl) is added to the second tube, which serves as the baseline state before elimination of the enoxaparin effect. </li>
 <li>Both Vacutainer tubes are placed in the thermostated wells of the Hemochron apparatus for a period of 5 min. (The adequacy of a 5 min digestion time with heparinase was established in our previously published work.1) </li>
</ol>
4. Clotting Assays
<ol>
 <li>At the end of the heparinase incubation, 2.0 ml of blood is transferred to the assay cartridge. In the case of the MAA tube, it is pre-filled with 0.1 ml of 250 mM CaCl2 to initiate coagulation. The commercial aPTT assay cartridge (A104) is designed to initiate clotting in whole blood that has been drawn into Vacutainer tubes containing sodium citrate as anticoagulant. </li>
 <li>The Hemochron apparatus signals the completion of blood coagulation and preserves the clotting times in seconds. The difference in clotting times between the heparinase-treated sample and the baseline sample, divided by the clotting time for the baseline sample, yields the percent decrease resulting from elimination of enoxaparin. As discussed below, strong linear correlations have been obtained for the relationship between percent decrease in clotting time and the concentration of enoxaparin in spiked samples of whole blood, as well as for the correlation with measured concentrations of enoxaparin by the chromgenic assay of anti-Xa activity. Anti-Xa assays of enoxaparin concentration were conducted with a commercial kit for a two-stage chromogenic assay (BIOPHEN; Aniara, Mason, OH). </li>
</ol>

<ol>
	<li>Inchiosa, M. A. J. r., Pothula, S., Kubal, K., Sanchala, V. T., Navarro, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Toward+development+of+a+point-of-care+assay+of+enoxaparin+anticoagulant+activity+in+whole+blood.">Toward development of a point-of-care assay of enoxaparin anticoagulant activity in whole blood.</a> J. Thromb. Thrombolysis. 32, 47-53 (2011).</li><li>Despotis, G. J., Filos, K. S., Levine, V., Alsoufiev, A., Spitznagel, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aprotinin+prolongs+activated+and+nonactivated+whole+blood+clotting+time+and+potentiates+the+effect+of+heparin+in+vitro.">Aprotinin prolongs activated and nonactivated whole blood clotting time and potentiates the effect of heparin in vitro.</a> Anesth. Analg. 82, 1126-1131 (1996).</li><li>Pothula, S., Inchiosa, M. A., Sanchala, V. T., Sarabu, M., Inchiosa, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+effect+of+protamine+excess+on+blood+coagulation+assays.">In vitro effect of protamine excess on blood coagulation assays.</a> Anesth Analg. 96, SCA39 (2010).</li><li>Inchiosa, M., Pothula, S., Sanchala, V., Kubal, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Detection+of+low+plasma+levels+of+low+molecular+weight+heparin.">Detection of low plasma levels of low molecular weight heparin.</a> Anesth Analg. 102, SCA10 (2010).</li><li>Gogarten, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+influence+of+new+antithrombotic+drugs+on+regional+anesthesia.">The influence of new antithrombotic drugs on regional anesthesia.</a> Curr. Opin. Anaesthesiol. 19, 545-550 (2006).</li><li>Gouin-Thibault, I., Pautas, E., Siguret, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safety+profile+of+different+low-molecular+weight+heparins+used+at+therapeutic+dose.">Safety profile of different low-molecular weight heparins used at therapeutic dose.</a> Drug Saf. 28, 333-349 (2005).</li><li>Bazinet, A., Almanric, K., Brunet, C., Turcotte, I., Martineau, J., Caron, S., Blais, N., Lalonde, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dosage+of+enoxaparin+among+obese+and+renal+impairment+patients.">Dosage of enoxaparin among obese and renal impairment patients.</a> Thromb. Res. 116, 41-50 (2005).</li><li>El Rouby, S., Cohen, M., Gonzales, A., Hoppensteadt, D., Lee, T., Zucker, M. L., Khalid, K., LaDuca, F. M., Fareed, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+use+of+a+HEMOCHRON+JR.+HEMONOXTM+point+of+care+test+in+monitoring+the+anticoagulant+effect+of+enoxaparin+during+interventional+coronary+procedures.">The use of a HEMOCHRON JR. HEMONOXTM point of care test in monitoring the anticoagulant effect of enoxaparin during interventional coronary procedures.</a> J. Thromb. Thrombolysis. 21, 137-145 (2006).</li><li>Yang, V. C., Bernstein, H., Cooney, C. L., Kadam, J. C., Langer, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Removal+of+the+anticoagulant+activities+of+the+low+molecular+weight+heparin+fractions+and+fragments+with+flavobacterial+heparinase.">Removal of the anticoagulant activities of the low molecular weight heparin fractions and fragments with flavobacterial heparinase.</a> Thromb Res. 44, 599-610 (1986).</li><li>Maddineni, J., Walenga, J. M., Jeske, W. P., Hoppensteadt, D. A., Fareed, J., Wahi, R., Bick, 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=Product+individuality+of+commercially+available+low-molecular-weight+heparins+and+their+generic+versions:+therapeutic+implications.">Product individuality of commercially available low-molecular-weight heparins and their generic versions: therapeutic implications.</a> Clinical and Applied Thrombosis/Hemostasis. 12, 267-276 (2006).</li><li>Wijnhoven, T. J., van de Westerlo, E. M., Smits, N. C., Lensen, J. F., Rops, A. L., vander Vlag, J., Berden, J. H., vanden Heuvel, L. P., van Kuppevelt, T. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+anticoagulant+heparinoids+by+immunoprofiling.">Characterization of anticoagulant heparinoids by immunoprofiling.</a> Glycoconj. J. 25, 177-185 (2008).</li><li>Sanderink, G. -. J. C. M., Guimart, C. G., Ozoux, M. -. L., Jariwala, N. U., Shukla, U. A., Boutouyrie, B. X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Pharmacokinetics+and+pharmacodynamics+of+the+prophylactic+dose+of+enoxaparin+once+daily+over+4+days+in+patients+with+renal+impairment.">Pharmacokinetics and pharmacodynamics of the prophylactic dose of enoxaparin once daily over 4 days in patients with renal impairment.</a> Thromb. Res. 105, 225-231 (2002).</li></ol>

The authors have nothing to disclose.

This assay of enoxaparin efficacy may serve as an important option to determine the relative safety of performing an invasive procedure that has an attendant risk of bleeding or development of a hematoma. This would be of particular importance when an epidural injection is being considered. The majority of guidelines recommend a waiting period of 12 hours between injection of enoxaparin and initiation of an invasive procedure.5 Renal impairment, obesity and pregnancy may influence the dosing requirements of enoxaparin.6,7 Since the assay can be completed within a 10-min period, it could also be used in a clinic or physician's office, where it would provide information on the adequacy of anticoagulation in patients who are at a risk of development of venous thromboembolism. Immediate dosage adjustments could be instituted, as needed. 
The enoxaparin concentration in plasma can be measured by a chromogenic assay of the extent of inhibition of the coagulation factor, Xa. However, this only yields its concentration, not specifically its anticoagulant efficacy, which varies widely among individual patients.6-8
Our studies were carried out only with enoxaparin. However, it can be anticipated that the assay could be applied to any LMWH that is degraded by heparinase I. This is already known to be the case for dalteparin, nadroparin and tinzaparin.9-11 We designed the assay in relation to the features of the Hemochron clotting time instrument. The instrument is relatively inexpensive; also, the disposable blood collection tubes, heparinase ampoule, and assay cartridges to complete an analysis for one patient is approximately 15 U.S. dollars. Thus, it would be expected to be suitable to monitor anticoagulant status in various clinical settings.

<table border="1">
<tbody>
 <tr>
 <td>Name of reagent </td>
 <td>Company</td>
 <td>Catalogue number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>Hepzyme</td>
 <td>Siemens</td>
 <td>B4240</td>
 <td>heparinase I</td>
 </tr>
 <tr>
 <td>"MAA" cartridge</td>
 <td>Technidyne</td>
 <td>FTK-ACT</td>
 <td>modified by kaolin removal</td>
 </tr>
 <tr>
 <td>aPTT cartridge</td>
 <td>Technidyne</td>
 <td>A104</td>
 <td>&nbsp; </td>
 </tr>
</tbody>
</table>

rapid point-of-care assay of enoxaparin anticoagulant efficacy in whole blood

There is the need for a clinical assay to determine the extent to which a patient's blood is effectively anticoagulated by the low-molecular-weight-heparin (LMWH), enoxaparin. There are also urgent clinical situations where it would be important if this could be determined rapidly. The present assay is designed to accomplish this. We only assayed human blood samples that were spiked with known concentrations of enoxaparin. The essential feature of the present assay is the quantification of the efficacy of enoxaparin in a patient's blood sample by degrading it to complete inactivity with heparinase. Two blood samples were drawn into Vacutainer tubes (Becton-Dickenson; Franklin Lakes, NJ) that were spiked with enoxaparin; one sample was digested with heparinase for 5 min at 37 &deg;C, the other sample represented the patient's baseline anticoagulated status. The percent shortening of clotting time in the heparinase-treated sample, as compared to the baseline state, yielded the anticoagulant contribution of enoxaparin. We used the portable, battery operated Hemochron 801 apparatus for measurements of clotting times (International Technidyne Corp., Edison, NJ). The apparatus has 2 thermostatically controlled (37 &deg;C) assay tube wells. We conducted the assays in two types of assay cartridges that are available from the manufacturer of the instrument. One cartridge was modified to increase its sensitivity. We removed the kaolin from the FTK-ACT cartridge by extensive rinsing with distilled water, leaving only the glass surface of the tube, and perhaps the detection magnet, as activators. We called this our minimally activated assay (MAA). The use of a minimally activated assay has been studied by us and others. 2-4 The second cartridge that was studied was an activated partial thromboplastin time (aPTT) assay (A104). This was used as supplied from the manufacturer. The thermostated wells of the instrument were used for both the heparinase digestion and coagulation assays. The assay can be completed within 10 min. The MAA assay showed robust changes in clotting time after heparinase digestion of enoxaparin over a typical clinical concentration range. At 0.2 anti-Xa I.U. of enoxaparin per ml of blood sample, heparinase digestion caused an average decrease of 9.8% (20.4 sec) in clotting time; at 1.0 I.U. per ml of enoxaparin there was a 41.4% decrease (148.8 sec). This report only presents the experimental application of the assay; its value in a clinical setting must still be established.

Figure 1 presents the results for the relationships between the percent decrease in clotting time following the elimination of enoxaparin with heparinase for a series of spiked concentrations of enoxaparin (0.2, 0.4 and 1.0 anti-Xa IU per ml). Results are presented for both the MAA and aPTT assay cartridges. The measured concentrations of enoxaparin from chromogenic assay of anti-Xa activity are also included in the abscissa of each plot.
Figure 2 presents plots of the same data as percent decrease in clotting time vs chromogenic measure of anti-Xa activity.
Strong linear correlations, with high statistical significances, were found for all four relationships.
<img src="/files/ftp_upload/3852/3852fig1.jpg" alt="Figure 1" /> 
 Figure 1. Point-of care determinations of enoxaparin contribution to clotting times of spiked whole blood based on percent change (shortening) of clotting time after incubation with heparinase. The spiked enoxaparin concentrations added to whole blood and the measured anti-Xa plasma concentrations (mean &plusmn; S.E., in parentheses) are placed in the abscissa of each graph. All percent changes in clotting times are presented as means and S.E., together with the average shortening of clotting time in seconds. Data from the same patient are connected by dashed lines. The data for the four patients identified with asterisks in plot A (MAA results) are the same as the four patients in plot B (aPTT assays). All of the results represent single determinations. The Pearson correlation coefficients were r = 0.869 (p = 1.9 x 10-5) and r = 0.916 (p = 2.8 x 10-5) for the relationships with the MAA and aPTTassay, respectively. Reproduced with permission from Inchiosa et al.1 
<img src="/files/ftp_upload/3852/3852fig2.jpg" alt="Figure 2" /> 
 Figure 2. The results for the percent changes in clotting times in the point-of-care assays shown in Figures 1A &amp; B are plotted against plasma anti-factor Xa concentrations. A, MAA results; B, aPTT assays. All of the results are from single clotting time assays and single determinations of anti-factor Xa concentrations. The Pearson correlation coefficients were r = 0.910 (p = 2.5 x 10-6) and r = 0.922 (p = 2.0 x 10-5) for the relationships with the MAA and aPTT assay, respectively Reproduced with permission from Inchiosa et al.1

Watch this Scientific Journal Video about Rapid Point-of-Care Assay of Enoxaparin Anticoagulant Efficacy in Whole Blood at JoVE.com

Rapid Point-of-Care Assay of Enoxaparin Anticoagulant Efficacy in Whole Blood

Demonstration of a rapid quantitative assay of the inhibition of blood coagulation by the low-molecular-weight-heparin, enoxaparin. The contribution of enoxaparin is assessed by removing its influence through digestion with heparinase. A fuller description of the assay is detailed in our published paper.1 The assay still requires clinical confirmation.

There is the need for a clinical assay to determine the extent to which a patient's blood is effectively anticoagulated by the ...

rapid-point-care-assay-enoxaparin-anticoagulant-efficacy-whole

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Cardiovascular Drugs: Anticoagulants and Antianginal Agents

SCIENTISTS IN ACTION

Rapid Fractionation and Isolation of Whole Blood Components in Samples Obtained from a Community-based Setting

Collection and processing of whole blood samples in a non-clinical setting offers a unique opportunity to evaluate community-dwelling individuals both with and without preexisting conditions. Rapid processing of these samples is essential to avoid degradation of key cellular components. Included here are methods for simultaneous peripheral blood mononuclear cell (PBMC), DNA, RNA and serum isolation from a single blood draw performed in the homes of consenting participants across a metropolitan area, with processing initiated within 2 hr of collection. We have used these techniques to process over 1,600 blood specimens yielding consistent, high quality material, which has subsequently been used in successful DNA methylation, genotyping, gene expression and flow cytometry analyses. Some of the methods employed are standard; however, when combined in the described manner, they enable efficient processing of samples from participants of population- and/or community-based studies who would not normally be evaluated in a clinical setting. Therefore, this protocol has the potential to obtain samples (and subsequently data) that are more representative of the general population.

We outline a methodology for the processing of whole blood to obtain a variety of components for further analysis. We have optimized a streamlined protocol that enables rapid, high-throughput simultaneous processing of whole blood samples in a non-clinical setting.

Collection and processing of whole blood samples in a non-clinical setting offers a unique opportunity to evaluate community-dwelling individuals both ...

Assessment of the Anticoagulant and Anti-inflammatory Properties of Endothelial Cells Using 3D Cell Culture and Non-anticoagulated Whole Blood

In vivo, endothelial cells are crucial for the natural anticoagulation of circulating blood. Consequently, endothelial cell activation leads to blood coagulation. This phenomenon is observed in many clinical situations, like organ transplantation in the presence of pre-formed anti-donor antibodies, including xenotransplantation, as well as in ischemia/reperfusion injury. In order to reduce animal experimentation according to the 3R standards (reduction, replacement and refinement), in vitro models to study the effect of endothelial cell activation on blood coagulation would be highly desirable. However, common flatbed systems of endothelial cell culture provide a surface-to-volume ratio of 1 - 5 cm2 of endothelium per mL of blood, which is not sufficient for natural, endothelial-mediated anticoagulation. Culturing endothelial cells on microcarrier beads may increase the surface-to-volume ratio to 40 - 160 cm2/mL. This increased ratio is sufficient to ensure the &#34;natural&#34; anticoagulation of whole blood, so that the use of anticoagulants can be avoided. Here an in vitro microcarrier-based system is described to study the effects of genetic modification of porcine endothelial cells on coagulation of whole, non-anticoagulated human blood. In the described assay, primary porcine aortic endothelial cells, either wild type (WT) or transgenic for human CD46 and thrombomodulin, were grown on microcarrier beads and then exposed to freshly drawn non-anticoagulated human blood. This model allows for the measurement and quantification of cytokine release as well as activation markers of complement and coagulation in the blood plasma. In addition, imaging of activated endothelial cell and deposition of immunoglobulins, complement- and coagulation proteins on the endothelialized beads were performed by confocal microscopy. This assay can also be used to test drugs which are supposed to prevent endothelial cell activation and, thus, coagulation. On top of its potential to reduce the number of animals used for such investigations, the described assay is easy to perform and consistently reproducible.

We present an in vitro model which allows the study and analysis of coagulation in whole, non-anticoagulated blood. Anticoagulation in the system depends on the natural anticoagulation effect of healthy endothelial cells and endothelial cell activation will result in clotting.

In vivo, endothelial cells are crucial for the natural anticoagulation of circulating blood. Consequently, endothelial cell activation leads to blood ...

Endotoxin Activity Assay for the Detection of Whole Blood Endotoxemia in Critically Ill Patients

Lipopolysaccharide, also known as endotoxin, is a fundamental component of gram-negative bacteria and plays a crucial role in the development of sepsis and septic shock. The early identification of an infectious process that is rapidly evolving to a critical illness might prompt a quicker and more intensive treatment, thereby potentially leading to better patient outcomes. The Endotoxin Activity (EA) assay can be used at the bedside as a reliable biomarker of systemic endotoxemia. The detection of elevated endotoxin activity levels has been repeatedly shown to be associated with an increased disease severity in patients with sepsis and septic shock. The assay is quick and easy to perform. Briefly, after sampling, an aliquot of whole blood is mixed with an anti-endotoxin antibody and with added LPS. Endotoxin activity is measured as the relative oxidative burst of primed neutrophils as detected by chemioluminescence. The assay&#39;s output is expressed on a scale from 0 (absent) to 1 (maximal) and categorized as &#8220;low&#8221; (&#60;0.4 units), &#8220;intermediate&#8221; (0.4&#8211;0.59 units), or &#8220;high&#8221; (&#8805;0.6 units). The detailed methodology and rationale for the implementation of the EA assay are reported in this manuscript.

We hereby present a protocol to measure at the bedside the endotoxin activity of human whole blood samples. The Endotoxin Activity assay is a simple test to perform and may be a useful biomarker in critically ill patients with sepsis.

Lipopolysaccharide, also known as endotoxin, is a fundamental component of gram-negative bacteria and plays a crucial role in the development of sepsis ...

Evaluation of a Point-of-Care Testing Analyzer for Measuring Peripheral Blood Leukocytes

White blood cell (WBC) is an important indicator of inflammation in the body, and it can help distinguish between bacterial and viral infections. At present, most primary medical institutions in China have a poor percentage of adoption of blood-testing technology, and a hematology detection system with a high price to performance ratio and easy operation is urgently needed in primary healthcare centers. This paper introduces the principle and operation procedures of a point-of-care testing (POCT) card-based leukocyte analyzer (evaluated system), which was used to detect WBC indexes such as neutrophils, lymphocytes, and intermediate group cells (including eosinophils, basophils, and monocytes) in whole blood. The results from the evaluated system were compared to those from two commercial automatic hematology analyzers (reference system). The correlation and consistency between the evaluated system and the commercial reference systems were analyzed. The results showed that WBC count and number of granulocytes detected by the evaluated and reference systems showed a strong positive correlation (rs = 0.972 and 0.973, respectively), while the number of lymphocytes showed a relatively low correlation (rs = 0.851). A Bland-Altman plot showed that the major difference between the values detected by the evaluated system and the reference systems is within 95% limits of agreement (LoA), indicating that the two systems are in good agreement. In conclusion, the evaluated system has an excellent correlation, robust consistency, and a reliable comparison with the results of the widely used automatic hematology analyzers. It is ideal for WBC detection in primary medical institutions where a full-automatic five-category hematology analyzer is unavailable, especially during the COVID-19 normalized prevention and control period.

A protocol to measure peripheral blood leukocytes using a POCT card-based leukocyte analyzer is presented here. Same blood samples were tested by two automated hematology analyzers to evaluate the consistency and accuracy of the results. The results showed that the evaluated analyzer had a good correlation with the reference system.

White blood cell (WBC) is an important indicator of inflammation in the body, and it can help distinguish between bacterial and viral infections. At ...

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.

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 ...

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 ...