Category Archives: Ultrasound

Bicuspid Aortic Valve – An important incidental PoCUS finding?

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Bicuspid Aortic Valve – An important incidental PoCUS finding?

Medical Student Pearl

 

Khoi Thien Dao

MD Candidate – Class of 2023

Dalhousie Medicine New Brunswick

Reviewed by: Dr. David Lewis

Case:

A 58-year-old male presents to Emergency Department with sudden onset of chest pain that is radiating to the back. He was also having shortness of breath at the same time of chest pain. The patient later reveals that his past medical history only consists of “bicuspid valve”, and he takes no medication. On examination, he was uncomfortable, but no signs of acute distress. His respiratory and cardiac exam were unremarkable for reduced air sound, adventitious sound, heart murmur, or extra heart sound. ECG was normal and initial cardiac markers were within normal range. His chest x-ray is normal.

You are aware that with his medical presentation and a history of bicuspid aortic valve, you need to consider associated concerning diagnosis (aortic root aneurysm and aortic dissection) within the differential (myocardial infarct, congestive heart failure, pneumonia, etc.).

Bicuspid Aortic Valve

Bicuspid aortic valve is one of the most common types of congenital heart disease that affects approximately one percent of population. There is a strong heritable component to the disease. Bicuspid aortic valve occurs when two leaflets fused (commonly right and left coronary leaflets) and form a raphe, a fibrous ridge1. The fusion of the leaflets can be partial, or complete, with the presence or absence of a raphe1. Bicuspid aortic valve disease is associated with increasing risks for valve calcification, which lead to aortic stenosis or regurgitation secondary to premature degeneration1. This congenital heart defect is also a well-known risks factor for aortic dissection and aortic dilatation. Reports have estimated prevalence of aortic dilation in patients with bicuspid aortic valve ranging between 20 to 80 percent, and that the risks of aortic dilation increase with age2. Increases risk of aortic dilatation in bicuspid valve disease also leads to a significantly greater risk for aortic dissection2.3.

The majority of patients with bicuspid aortic valve are asymptomatic with relatively normal valve function and therefore can remain undiagnosed for many years. However, most patients with bicuspid aortic valve will develop complications and eventually require valve surgery within their lifetime. Early diagnosis, while asymptomatic, can enable close follow-up for complications and early intervention with better outcomes. However, asymptomatic individuals are rarely referred for echocardiography.

With increasing use of cardiac PoCUS by Emergency Physicians, there are two scenarios where increased awareness of the appearance of bicuspid aortic valve and its complications may be of benefit.

  1. Known bicuspid aortic valve patients presenting with possible associated complications
  2. Undiagnosed bicuspid aortic valve patients presenting with unrelated symptoms undergoing routine cardiac PoCUS

This clinical pearl provides a review of the clinical approach to bicuspid aortic valve and its associated complications and provides guide to enhancing clinical assessment with PoCUS.

Clinical Approach:

Although bicuspid aortic valve commonly presents as asymptomatic, a detailed focused cardiac history can assess for clinical signs and symptoms related to valve dysfunction and its associated disease, such as reduced exercise capacity, angina, syncope, or exertional dizziness1. Information about family history with relation to cardiac disease is essential for a clinician’s suspicion of heritable cardiovascular disease. Red flag symptoms that shouldn’t be missed such as chest pain, back pain, hypertensive crisis, etc. should be specifically identified. They are indicators for possible emergent pathologies that should not be missed (for example: acute MI, aortic dissection, ruptured aortic aneurysm, etc.)

Physical examination findings in patients with bicuspid aortic valve include, but not limited to, ejection sound or click at cardiac apex/base, murmurs that have features of crescendo-decrescendo or holosystolic. Clinical signs of congestive heart failure such as dyspnea, abnormal JVP elevation, and peripheral edema may also be present.

Core Cardiac PoCUS:

With cardiac PoCUS, it is important to obtain images from different planes and windows to increase the complexity of the exam and to be able to be confidently interpreting the exam. There are four standard cardiac view that can be obtained: parasternal short axis (PSSA), parasternal long axis (PSLA), subxiphoid (sub-X), and apical 4-chamber view (A4C). Each cardiac view has specific benefits.

Parasternal Long Axis

With the PSLA, the phased-array transducer is placed to the left sternum at 3rd or 4th intercostal with transducer orientation pointing toward patient’s right shoulder. Key structures that should be seen are Aortic Valve (AV), Mitral Valve (MV), Left Ventricle (LV), pericardium, Right Ventricle (RV), Left Ventricular Outflow Tract (LVOT), and portion of ascending and descending aorta8. It is primarily used to assess left ventricular size and function, aortic and mitral valves, left atrial size8. Furthermore, pericardial effusions and left ventricular systolic function can be assessed.

Parasternal Long Axis

 

Parasternal Short Axis

Using the same transducer position as the PSLA the transducer can be centered to the mitral valve and rotated 90 degrees clockwise to a point where the transducer marker points to patient’s left shoulder to obtain the PSSA. With this orientation, one can assess for global LV function and LV wall motion8. Furthermore, with five different imaging planes that can be utilized with this view, aortic valve can be visualized in specific clinical contexts.

Parasternal Short Axis

 

Apical 4-Chamber

The apical 4-chamber view is generated by placing the transducer at the apex, which is landmarked just inferolateral to left nipple in men and underneath inferolateral of left breast in women. This view helps the clinician to assess RV systolic function and size relative to the LV8.

Apical 4-Chamber

 

Subxiphoid

The subxiphoid view can be visualized by placing a transducer (phased-array or curvilinear) immediately below the xiphoid process with the transducer marker points to patient’s right. The movements of rocking, tilting, and rotation are required to generate an optimal 4-chamber subcostal view. A “7” sign, which consists of visualizing the border between liver and pericardium, the septum, and the RV and LV that looks like number 7. This view allows user to assess RV functions, pericardial effusion, and valve functions8. In emergency setting, it can be used for rapid assessments in cardiac arrest, cardiac tamponade, and global LV dysfunction8.

From –  the PoCUS Atlas

Subxiphoid labelled

 

7 Sign

PoCUS Views for Aortic Valve Assessment

In assessing the aortic valve, the PSSA and PSLA can be best used to obtain different information, depending on clinical indications. Both views can be used to assess blood flows to assess stenosis or regurgitation. However, the PSLA view includes the aorta where clinician can look for aortic valve prolapse or doming as signs of stenosis and its complications, like aortic dilatation. On the other hand, PSSA are beneficial when assessing the aortic valve anatomy.

Parasternal Long Axis

From PoCUS 101

Parasternal Short Axis

From – the PoCUS Atlas

PoCUS Appearance of Normal Aortic Valve (Tricuspid) vs Bicuspid Aortic Valve

With PSSA view, the normal aortic valve will have three uniformly leaflets that open and form a circular orifice during most of systole. During diastole, it will form a three point stars with slight thickening at central closing point. The normal aortic valve is commonly referred to as the Mercedes Benz sign.

Parasternal Short Axis – Normal Tricuspid AV – Mercedes Benz Sign and 3 cusp opening

Pitfall

However, the Mercedes Benz Sign sign can be misleading bicuspid valve disease when three commissure lines are misinterpreted due to the presence of a raphe. A raphe is a fibrous band formed when two leaflets are fused together. It is therefore important to visualize the aortic valve when closed and during opening, to ensure all 3 cusps are mobile. Visualization of The Mercedes Benz sign is not enough on its own to exclude Bicuspid Aortic Valve.

Apparent Mercedes sign when AV closed due to presence of raphe. Fish mouth appearance of the same valve when open confirming bicuspid aortic valve

Bicuspid Aortic Valve

Identification requires optimal valve visualization during opening (systole). Appearance will depend on the degree of cusp fusion. In general a ‘fish mouth’ appearance is typical for bicuspid aortic valve.

Parasternal Short Axis – Fish Mouth Opening – Fusion L & R Coronary Cusps – Bicuspid Aortic Valve

In the parasternal long axis view the aortic valve can form a dome shape during systole, and prolapse during diastole, rather than opening parallel to the aorta. This is called systolic doming. Another sign that can be seen in PSLA view is valve prolapse, when either right or non-coronary aortic valve cusps showed backward bowing towards the left ventricle beyond the attachment of the aortic valve leaflets to the annulus. This can be estimated by drawing a line joining the points of the attachment.

Systolic doming

 

Diastolic prolapse and systolic doming

 

 

 

PoCUS Appearance of the Complications of Bicuspid Valve Disease

In patients presenting with chest/back pain, shock or severe dyspnea who have either known or newly diagnosed bicuspid valve disease, PoCUS assessment for potential complications can be helpful in guiding subsequent management.

Complications of bicuspid aortic valve include aortic dilatation at root or ascending (above 3.8cm) and aortic dissection 5-9.

Dilated aortic root, from – sonomojo.com

Aortic root dilatation – Normal maximum = 40mm

 

Aortic root dilatation with dissection

Valve vegetations or signs of infective endocarditis are among the complications of severe bicuspid valve5-9

Aortic valve vegetations

General Management of Patients with Bicuspid Valve in the Emergency Department

Management of bicuspid aortic valve disease is dependent on the severity of the disease and associated findings.

For a patient with suspicious diagnosis of bicuspid valve disease, a further evaluation of echocardiography should be arranged, and patient should be monitored for progressive aortic valve dysfunction as well as risk of aortic aneurysm and dissection. Surgical intervention is indicated with evidence of severe aortic stenosis, regurgitation, aneurysm that is > 5.5cm, or dissection1.

How accurate is PoCUS for Aortic Valve assessment?

Bicuspid aortic valve disease is usually diagnosed with transthoracic echocardiography, when physical examination has revealed cardiac murmurs that prompt for further investigation. However, patients with bicuspid valve disease frequently remain asymptomatic for a prolonged periods. Michelena et al. (2014) suggested that auscultatory abnormalities account for 60 to 70% diagnostic echocardiograms for BAV in community10.

While there are no published studies on the utility of PoCUS for the diagnosis of bicuspid aortic valve, there are studies on the use of PoCUS as part of the general cardiac exam. Kimura (2017) published a review that reported early detection of cardiac pathology when PoCUS was used as part of the physical exam 9. Abe et al. (2013) found that PoCUS operated by expert sonographer to screen for aortic stenosis has a sensitivity of 84% and a specificity of 90% in 130 patients 11. In another study by Kobal et al. (2004), they found that PoCUS has a specificity of 93% and sensitivity of 82% in diagnosing mild regurgitation12.

There are also limitations of using PoCUS to assess for bicuspid aortic valve disease, or valve disease in general. Obtaining images from ultrasound and interpretation are highly dependent on user’s experiences to assess for the valve9. Furthermore, research is needed to investigate the use of PoCUS in lesser valvular pathology.

 

When a new diagnosis of bicuspid aortic valve is suspected, a formal echocardiogram should be arranged, and follow-up is recommended.

Summary 

  • Bicuspid aortic valve is often asymptomatic and undiagnosed until later in life
  • Patients with known bicuspid aortic valve disease are closely followed and may require surgical intervention in the event of complications
  • Diagnosis of bicuspid aortic valve requires careful visualization of valve closing and opening during diastole and systole
  • The increased use of PoCUS by Emergency Physicians as an adjunct to cardiac examination may result in increased diagnosis of bicuspid  aortic valve. These may be related to the presentation or incidental findings
  • In patients presenting to the Emergency Department with known or newly diagnosed bicuspid aortic valve disease, consider if a complication is related to their presentation
  • In patient with incidental finding of bicuspid aortic valve disease refer for cardiology follow up

 

References

  1. Braverman, A. C., & Cheng, A. (2013). The bicuspid aortic valve and associated aortic disease. Valvular heart disease. Philadelphia: Elsevier, 179-218.
  2. Verma, S., & Siu, S. C. (2014). Aortic dilatation in patients with bicuspid aortic valve. N Engl J Med, 370, 1920-1929.
  3. Della Corte, A., Bancone, C., Quarto, C., Dialetto, G., Covino, F. E., Scardone, M., … & Cotrufo, M. (2007). Predictors of ascending aortic dilatation with bicuspid aortic valve: a wide spectrum of disease expression. European Journal of Cardio-Thoracic Surgery, 31(3), 397-405.
  4. Tirrito, S. J., & Kerut, E. K. (2005). How not to miss a bicuspid aortic valve in the echocardiography laboratory. Echocardiography: A Journal of Cardiovascular Ultrasound and Allied Techniques, 22(1), 53-55.
  5. Baumgartner, H., Donal, E., Orwat, S., Schmermund, A., Rosenhek, R., & Maintz, D. (2015). Chapter 10: Aortic valve stenosis. The ESC textbook of cardiovascular imaging. European Society of Cardiology.
  6. Fowles, R. E., Martin, R. P., Abrams, J. M., Schapira, J. N., French, J. W., & Popp, R. L. (1979). Two-dimensional echocardiographic features of bicuspid aortic valve. Chest, 75(4), 434-440.
  7. Shapiro, L. M., Thwaites, B., Westgate, C., & Donaldson, R. (1985). Prevalence and clinical significance of aortic valve prolapse. Heart, 54(2), 179-183.
  8. Gebhardt, C., Hegazy, A.F., Arntfield, R. (2015). Chapter 16: Valves. Point-of-Care Ultrasound. Philadelphia: Elsevier, 119-125.
  9. Kimura, B. J. (2017). Point-of-care cardiac ultrasound techniques in the physical examination: better at the bedside. Heart, 103(13), 987-994.
  10. Michelena, H. I., Prakash, S. K., Della Corte, A., Bissell, M. M., Anavekar, N., Mathieu, P., … & Body, S. C. (2014). Bicuspid aortic valve: identifying knowledge gaps and rising to the challenge from the International Bicuspid Aortic Valve Consortium (BAVCon). Circulation, 129(25), 2691-2704.
  11. Abe, Y., Ito, M., Tanaka, C., Ito, K., Naruko, T., Itoh, A., … & Yoshikawa, J. (2013). A novel and simple method using pocket-sized echocardiography to screen for aortic stenosis. Journal of the American Society of Echocardiography, 26(6), 589-596.
  12. Kobal, S. L., Tolstrup, K., Luo, H., Neuman, Y., Miyamoto, T., Mirocha, J., … & Siegel, R. J. (2004). Usefulness of a hand-carried cardiac ultrasound device to detect clinically significant valvular regurgitation in hospitalized patients. The American journal of cardiology, 93(8), 1069-1072.
  13. Le Polain De Waroux, J. B., Pouleur, A. C., Goffinet, C., Vancraeynest, D., Van Dyck, M., Robert, A., … & Vanoverschelde, J. L. J. (2007). Functional anatomy of aortic regurgitation: accuracy, prediction of surgical repairability, and outcome implications of transesophageal echocardiography. Circulation, 116(11_supplement), I-264.
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Resuscitative Transesophageal Echo

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Resuscitative TEE – the whats, the whys and the hows…. A brief review of the literature, examples of use and a proposed cardiac arrest protocol

Dr. David Lewis

Professor, Dalhousie Department of Emergency Medicine

Download Slides – PoCUS Rounds – TEE – Nov 2022

Further Reading

Introduction to Transesophageal Echo – Basic Technique

   http://pie.med.utoronto.ca/tee/

ACEP NOW – How to Perform Resuscitative Transesophageal Echocardiography in the Emergency Department

 

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Vascular Access In Children: Solve the Puzzle

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Dr. Rawan Alrashed (@rawalrashed)

PEM Physician

PoCUS Fellow

Reviewed and edited by: Dr. David Lewis

 

Background

Pediatric vascular access is one of the challenging skills in the medical field especially during an emergency, different guidelines have been established to facilitate the choice of the proper IV access one of which is the miniMAGIC that was published in 2020.1 Choosing the right access is crucial for success taking in consideration the urgency of access, patient safety, infused fluid characteristic  to determine the right one especially with a peripheral IV catheter failure rate of 77% in the first attempt.2 Difficult intravenous Access score (DIVA) is one of the tool that can be used to evaluate the feasibility of a peripheral IV and accordingly, the best next step for IV line insertion where Subjects with a DIVA score of 4 or more were more than 50% likely to have failed intravenous placement on first attempt.3

 

Figure-1: DIVA score.4

Types of vascular access

  • Peripheral IV catheters (PIVCS)
  • Intraosseous Access
  • Central Venous Catheters (CVCs) (Non-tunneled) 
  • US guided Access
  • Umbilical Catheter
  • Surgical cutdown

 

Figure 2: Vascular Access Locations.5

Consideration in pediatrics4

  • Pain management is a critical step for the success of IV cannulation

Multiple choices are available starting from non-pharmacological distraction technique and non-nutritive sucking to the utilization of local anesthetic such as EMLA and LMX as well the needle-free lidocaine jet-injection

  • Enhancing visualization of vein by using tourniquet, transilluminator with any available light source.
  • Ultrasound guided peripheral IV access is the recommended current practice in difficult access.
  • Ultrasound guided central IV access is the standard of care currently in comparison to anatomical landmark in critical care setting.

Indication of IV access

Patient resuscitation.

Delivering fluids, medication, Blood sampling.

Hemodynamics monitoring as well arterial blood gas.

Contraindications

Infection at the insertion site.

Thrombosis of the vein.

Bleeding diathesis in central line is a relative contraindication.

In IO Access, fracture on the same bone as well pathological disorder predisposing to fractures is a contraindication.

Peripheral IV catheter (PIVC)

Different veins can be used for PIVC starting with dorsal veins of the hand, then the feet and then proceeding to other choices including scalp vein in infants, external jugular vein, antecubital and the great saphenous vein as in Figure-2.5

Technique:5

  1. Prepare instruments: cleansing solution, tourniquet, catheter needle, connecting tube, flush, dressing, gauze, and stabilizer tape.
  2. Size of catheter as in the table: utilize the smallest gauge and shortest catheter as possible with exception in resuscitation where larger bore gauge is preferable or in case of midline cannulation where longer catheter is preferable.
  3. Apply tourniquet proximal to the site of insertion to enhance visualization
  4. Identify proper vein by visualization, palpation and utilizing the transilluminator or infrared light
  5. Clean the skin as per the facility protocol
  6. Hold the needle between the thumb and forefinger with the dominant hand and stretch the skin with the other hand
  7. Enter with an angle of 10-30 degree then if blood seen shallow your angle to advance 1-2 mm then advance the catheter and once in pull your needle or retract it.
  8. Flush to confirm patency and no swelling at the site then stabilize your catheter

 

 Neonate  Infant   Children Length
PIV 24-26G 22G 20G 2-6cm
Midline Access 22G 22G 20G 15-30cm

 

Table-1: Size of PIV catheter.

 

US guided peripheral vascular access

A recent RCT by Vinograd et.al. evaluated 167 children showed 85% success rate of first attempt with US guidance compared to 45% with traditional methods. Also US guidance resulted in shorter cannulation time, less redirection and fewer attempts.6 

Important consideration in US- guided PIV

  • The diameter and depth of the vein have been found determinate factors for success of cannulation in adult studies where very superficial (< 0.3 cm) and very deep (> 1.5 cm) veins are difficult to cannulate.7
  • The suggested veins are the cephalic vein in the forearm or the saphenous vein at the medial malleolus, while the antecubital vein might be an easy approach but the risk of brachial artery cannulation and the elbow bending make it less favorable. 7

Technique 7

  • Use a linear probe with 5-15 MHz ( Alternatively a hockey stick or MicroConvex might be useful)
  • Identify the vein and assess patency by being compressible and non pulsatile, for further confirmation utilize color or pulse wave doppler with augmentation to identify low status flow.

Longer catheter are preferable when using ultrasound guided insertion especially with a vein deeper then 0.5 cm to minimize the risk of dislodgment and infiltration (suggested to be longer than 2 cm). In a pilot study by Paladini, long catheter > 6 cm were associated with lower risk of failure in pediatric patients more than 10 years comparable to the short one <6 cm.8

  • Static or dynamic guidance are acceptable with preference of the latter. 
  • Two approach technique available with best outcome observed with out-of-plane in PIVC.

 

Out-of-plane (Short-Axis):
  • Consider using the middle point on the ultrasound machine to enhance alignment
  • The US wave perpendicular at right angle to the vessel.
  • The needle is inserted close to the probe at 20-30o angle then advance with meet and greet technique or dynamic needle tip positioning technique as in video

 

 

Pitfalls:

  • The needle shaft might be misidentified as the needle tip thus the importance of advancing the probe then the needle to maintain visualization of the tip only.  Also sweeping in the same plane can help to follow the needle proximal and distal to confirm the tip from the shaft.
  • Risk of posterior wall penetration and failure of cannulation.

 

In-Plane (Long-Axis):
  • The US beam is parallel to the vessel.
  • The whole needle shaft is visualized during insertion and advancement to the vein.
  • To facilitate visualization of needle “Ski left” technique can be used.

 

 

Pitfalls:

  • Maintaining the transducer static without any movement is difficult in small children as any movement would lead to loss of needle visualization, thus insertion will not be accurate (side lobe artifact)

No evidence of preferable technique in pediatrics but in adults out-of-plane proven to be superior for PIVC insertion.

 

How to Use US for PIVC:

https://www.coreultrasound.com/ultrasound-guided-peripheral-iv-access/

 

Intraosseous Access

It’s considered the best alternative IV access in emergencies (peri-arrest and arrest condition) after 2 failed attempts of PIVC within 60-90 seconds, AHA recommends IO catheter as first line access in cardiac arrest. Still the outcome of out of hospital cardiac arrest and best access need more delineation.4,5

Technique4

  • IO access can be accomplished using a manual needle or battery powered device such as EZ-IO or even a regular large bore needle.
  • Place the knee in slight flexion with padding.
  • Clean the skin and consider analgesia according to the urgency of the situation.
  • Insert the needle at 900 over the skin.
  • Remove the stylet and aspirate then infuse saline.
  • Confirmation of proper insertion by the needle standing still even if no backflow seen with lack of extravasation during fluid infusion.

Figure-2 (on green)  shows the possible site for IO insertion where the commonest one is the proximal tibial shaft about 1-2 cm from the tibial tuberosity avoiding the growth plate.

Complication4

  • IO needle is a temporary access that can not last for more than 24 hours
  • Longer use can predispose the child to complication including infection, thrombosis, fat embolism
  • Other complications of insertion include through-and-through penetration of the bone, physeal plate injury, pressure necrosis of the skin, compartment syndrome, osteomyelitis, subcutaneous abscess

 

Confirmation of IO by POCUS2

  • Use linear probe distal to the insertion site
  • Apply color doppler and observe for saline flush site
  • If above the bony cortical site or lateral or deep may indicate misplacement

 

Figure-3: POCUS confirmation of IO site.

 

 

Central IV Catheter (CIVC)

This an alternative longer duration route that can be utilized as an emergency line but less favorable compared to the IO during initial resuscitation. It is still considered a good choice in ill patients with difficulty of PIVC and failure of US guided peripheral access as well IO when fluid, high concentrated electrolytes and vasopressors are needed.4

The common site for insertion of non-tunneled CVC in pediatric is the internal jugular in critical care setting with higher success rate compared to femoral vein9 , but the femoral vein might be the first choice in PEM as it’s easily accessible and don’t interfere with resuscitation measures.10

Technique10

Always prepare your equipment and check them, also get consent when possible before attempting a central line

 

Age(years) weight (kg) Catheter gauge French gauge length (cm)
<1y 4-8 24 3 5-12
<1y 5-10 22 3-3.5 5-12
1-3y 10-15 20 4 5-15
3-8y 15-30 18-20 4-5 5-25
>8y 30-70 16-20 5-8 5-30

Table-2: CVC sizes.4

Anatomical Landmark5

Internal Jugular vein:

  • Under aseptic technique with proper draping, put the patient in Trendelenburg position and turn the head slightly to the other side.
  • Use the medial head of the sternocleidomastoid muscle or between the tow head at the level of the thyroid cartilage just lateral to the carotid artery guide your needle on a 45o  toward the ipsilateral nipple while aspirating during insertion until you feel loss of resistance and have a backflow.
  • follow with the guidewire into your needle and then dilator
  • Complete by  inserting the catheter line and fixing it.

Subclavian vein:

Directly below the clavicle at the junction of the lateral one third with the medial two third directing the needle toward the sternal notch

Femoral vein:

1-2 cm below the inguinal ligament medial to the femoral artery, guide the needle toward the umbilicus

 

US Guided CVC

The use of ultrasound guided insertion is considered the standard of care for central line insertion. Ultrasound use reduces the number of attempts and procedure duration, increases the successful insertion rate, and reduces complications compared to the skin surface anatomic landmarks technique.9

This can facilitate visualization, increase the success rate with 95% first attempt success rate of ultrasound-guided venous punctures compared to 34% of the anatomical landmark and decrease the rate of complication that would occur with the anatomical landmark.11

 

  • Always start by identifying the land mark on US before starting the procedure (vein is compressible and less pulsatile than the adjacent artery)
  • Probe position according to the site of insertion.  
  • Prepare the patient under aseptic technique as well the probe with sterile sheet and the ultrasound counsel unless you have assistance.
  • Infiltrate local anesthesia to the skin puncture site.
  • Utilize sterile gel on the outside of the sterile sheet or alternatively sterile water or saline
  • Use an out of plane technique to guide the needle into the vein (higher success rate).
  • Start by inserting the needle at 45 degree angle from the probe and the same distance away as the vein from the skin
  • Follow the dynamic needle tip positioning technique (meet &greet) to keep visualizing the needle tip while guiding it toward the vein
  • If confusing the needle tip with the shaft try to slide the probe proximal and distal until confirmation
  • Use the same steps in aspirating while inserting until having a backflow and confirming the needle is inside the vein lumen
  • Complete the steps as before and confirm the position of the guidewire by ultrasound.
  • Insert the central catheter and fix it with sutures and transparent dressing.

 

Internal jugular vein:

Subclavian vein

Femoral vein

 

Complication12

Confirm proper placement by US as well X-Ray

R/O complication as pneumothorax, hemothorax or hematoma, mis-displacement

Artery puncture, air embolism, thoracic duct injury, arrhythmia are possible complications.

 

Umbilical Catheter

  • Can be used in neonate up to 7 days old.
  • Apply tourniquet to umbilical stump then cut the upper dried part.
  • Identify the vein which is single and thin walled while arteries are two and thick wall.
  • Stent the vessel with a forceps then insert the catheter up to 3-4 cm until blood return (Do NOT advance further as the risk of complication and adverse events are high)

 

Venous Cutdown

It is uncommon access in pediatric patients with the availability of IO needle, if needed the classic site is the saphenous vein which is 2 cm superior and anterior to the medial malleolus.

 

 

Resources:

  1. Ullman AJ, Bernstein SJ, Brown E, et al. The Michigan Appropriateness Guide for Intravenous Catheters in Pediatrics: miniMAGIC. Pediatrics. 2020;145(Suppl 3):S269-S284. doi:10.1542/peds.2019-3474I.
  2. Delacruz N, Malia L, Dessie A. Point-of-Care Ultrasound for the Evaluation and Management of Febrile Infants. Pediatr Emerg Care. 2021;37(12):e886-e892. doi:10.1097/PEC.0000000000002300.
  3. Yen K, Riegert A, Gorelick MH. Derivation of the DIVA score: a clinical prediction rule for the identification of children with difficult intravenous access. Pediatr Emerg Care. 2008;24(3):143-147. doi:10.1097/PEC.0b013e3181666f32.
  4. Whitney R, Langhan M. Vascular Access in Pediatric Patients in the Emergency Department: Types of Access, Indications, and Complications. Pediatr Emerg Med Pract. 2017;14(6):1-20.
  5. Naik VM, Mantha SSP, Rayani BK. Vascular access in children. Indian J Anaesth. 2019;63(9):737-745. doi:10.4103/ija.IJA_489_19.
  6. Vinograd AM, Chen AE, Woodford AL, et al. Ultrasonographic guidance to improve first-attempt success in children with predicted difficult intravenous access in the emergency department: a randomized controlled trial. Ann Emerg Med. 2019;74:19–27.
  7. Nakayama Y, Takeshita J, Nakajima Y, Shime N. Ultrasound-guided peripheral vascular catheterization in pediatric patients: a narrative review. Crit Care. 2020;24(1):592. Published 2020 Sep 30. doi:10.1186/s13054-020-03305-7.
  8. Paladini A, Chiaretti A, Sellasie KW, Pittiruti M, Vento G. Ultrasound-guided placement of long peripheral cannulas in children over the age of 10 years admitted to the emergency department: a pilot study. BMJ Paediatr Open. 2018;2(1):e000244. Published 2018 Mar 28. doi:10.1136/bmjpo-2017-000244.
  9. Pellegrini S, Rodríguez R, Lenz M, et al. Experience with ultrasound use in central venous catheterization (jugular-femoral) in pediatric patients in an intensive care unit. Arch Argent Pediatr. 2022;120(3):167-173. doi:10.5546/aap.2022.eng.167.
  10. Skippen P, Kissoon N. Ultrasound guidance for central vascular access in the pediatric emergency department. Pediatr Emerg Care. 2007;23(3):203-207. doi:10.1097/PEC.0b013e3180467780.
  11. De Souza TH, Brandão MB, Santos TM, Pereira RM, Nogueira RJ. Ultrasound guidance for internal jugular vein cannulation in PICU: a randomised controlled trial. Arch Dis Child. 2018; 103(10):952-6.
  12. Georgeades C, Rothstein AE, Plunk MR, Arendonk KV. Iatrogenic vascular trauma and complications of vascular access in children. Semin Pediatr Surg. 2021;30(6):151122. doi:10.1016/j.sempedsurg.2021.151122

 

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CanPoCUS May 2022

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CanPoCUS May 2022

New to Point of Care Ultrasound (PoCUS)? Been scanning for a while but wanted some formal, hands on training? Join us for the CanPoCUS Core Course in Saint John, NB this upcoming May 2022. 

This introductory PoCUS course has been designed for doctors, nurse practitioners, physician assistants who work in acute care e.g Emergency Medicine, Family Medicine, Internal Medicine, Critical Care, Surgery.

It provides the core knowledge and hands-on training required to confidently add PoCUS to your practice.

Our course fills up quickly – what are you waiting for? Register today 

 

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Scrotal Pain – Scrotal PoCUS in a nutshell

Posted on by

Rawan Alrashed (@rawalrashed)

PEM Physician

PoCUS Fellow

Background

Acute Scrotal pain represent 0.5% of Emergency department visit, less than 25% of those are due to testicular torsion (1). Clinical history and physical examination don’t consist a definitive tool to diagnose the problem especially when presentation of different causes of scrotal pain can overlap. Testicular torsion doesn’t always present with the typical acute onset of pain as gradual onset was found in 25% of presentation which is described for the epididymo-orichitis (2-3). Scrotal pathology is divided into the 4 following groups: torsion, trauma, infection, and tumors, often described as the scrotum’s “4 T’s (4).

 

Review on how to approach Acute scrotal pain can be found on this post:

The Acute Scrotum

Anatomy

The testicles originate in the posterior abdominal wall in embryonic life then migrates to the scrotum, in case of failure of migration presentation of acute scrotum can be along the abdomen, inguinal canal.

 

       

 

Figure-1 Anatomy on Transverse and Longitudinal plane (Radiology Key)(5) 

 

The testicle is enveloped by a fibrous capsule called the tunica albuginea, which projects into the testis to form the mediastinum testis. The tunica vaginalis is a two-layered membrane that covers the tunica albuginea. Multiple testicular seminiferous tubules run toward the mediastinum and coalesce into a network of channels called the rete testis. These channels pass through the mediastinum and tunica albuginea to form the epididymal head, body, and tail ducts, which continue as the vas deferens. The spermatic cord contains the vas deferens, testicular vessels, pampiniform venous plexus, and nerve (6).

PoCUS Technique

  • Patient should be in supine position.
  • Use a towel under the scrotum for elevation and support and a second towel to cover and retract the penis of the scrotum.
  • Use a linear high-frequency (>7MHz) transducer with broad bandwidth.
  • Scan in transverse and sagittal planes.
  • Assess the size and texture of each testicle and look to the surroundings including the epididymis and tunica vaginalis for fluids.
  • Use comparison by visualizing both testicle in transverse plane.
  • Use Color and spectral Doppler imaging for the assessment of blood flow.
  • Images of the inguinal canal and spermatic cord can be obtained in the upright position during Valsalva maneuver to evaluate for inguinal hernias and varicoceles, respectively.

N.B. Doppler settings should be optimized to maximize detection of low-velocity flow. Color Doppler gain should be adjusted to eliminate artifacts. This can be done by adjusting the scale of flow on the normal testis then use it to visualize the abnormal one. (6)

 

Video on how to do the scan (7):

 

Normal Findings

Figure 2- Ultrasound Anatomy: a- Transverse view, b- sagittal view (6)

 

  • Scrotal wall is heterogeneous and the wall thickness ranges from 2 to 8mm.
  • The normal adult testicle is oval and measures approximately 5×3×2 cm, with a homogeneous echotexture and diffuse intermediate level echogenicity.
  • The tunica albuginea appears as a thin hyperechoic rim encasing the testicle, which invaginates in the central testicle as a hyperechoic band corresponding to the mediastinum testis.
  • The tunica vaginalis can be identified as a thin hyperechoic line, but this structure is not routinely visualized in the absence of hydrocele.
  • The epididymis is best visualized on longitudinal views and appears isoechoic to slightly hypoechoic relative to the adjacent testis.
  • The spermatic cord has a straight course from the external inguinal ring along the posterior border of the testicle, with a normal transverse diameter of less than 5mm. (6)

 

– Comparing testicular echogenicity bilaterally (Q-path)

– Comparing bilateral Testicular blood supply and notice the low flow scale (Q-path)

 

 

 

 

 

 

 

 

PATHOLOGY

1.VASCULAR 

 

Testicular Torsion (Torsion of the spermatic cord)

Testicular Torsion is a clinical diagnosis mainly affecting children with two age peaks at 1 year and adolescence (6). TWIST score can help in risk stratifying  the patients which was developed by urologist and validated in pediatric age group in emergency setting (8).

REMEMBER

Time is testicle, So once suspected involve surgical specialty for De-torsion. As the salvage rate is as high as 80%-100%  if it was repaired within 6 hours of symptom onset then drops to 20% after 12 hours (9).

If diagnosis couldn’t be made clinically, Scrotal ultrasound can help with the use of color and spectral doppler to rule in this diagnosis.

 

Findings:

It will depend on the timing of presentation

Early (within 6 hours):

  • Abnormal position.
  • Normal echogenicity could be seen early.
  • Twisting of the spermatic cord (most specific) (“whirlpool sign”)
  • Reduced venous flow.
  • Later testicular enlargement within the 6 hours due to tissue edema.
  • Scrotal wall thickening, and secondary hydrocele may also be observed. (6,9)

After 6 hours Reduced arterial blood supply with high resistance flow pattern compared to normal flow.

Late(After 24 h):

  • Testicular heterogeneity, hypo-echogenicity due to infarction and hemorrhage (at this stage salvageability is less likely (10).

 

Normal right testis (Q-path)

Abnormal echogenicity of left testis (Q-path)

Absence of color flow on this image (Q-path)

 

 

 

 

 

 

 

Whirlpool sign (11)

 

 

Important to keep in mind:

-In case of Partial torsion, the previous findings might not fully manifest and the scan could be falsely negative, still the abnormal spermatic cord can be seen as well on spectral doppler the arterial flow will be either absent or reversed diastolic flow.

-In Case of Torsion- De-torsion, rebound reperfusion with hyperemia may make the diagnosis difficult and confusing, so regular monitoring and re-scan could help in reaching the diagnosis (6,9).

 

Video explaining the findings on PoCUS and spectral doppler wave :

 

 

Torsion of testicular appendage

It’s the commonest presentation of pediatric testicular pain. This appendage is usually pedunculated and is present in more than 80% of children. It is located at the superior aspect of the testis in the groove between the testicle and the epidydimal head.

Findings:

  • Appendages are more readily apparent in the presence of a hydrocele.
  • Enlarged, rounded, extra-testicular masses, with mixed hyperechoic and heterogeneous echotexture depending on the degree of ischemia.
  • Absent flow on color Doppler, and hyperemia of the surrounding structures. (6)

 

normal appearing testicular appendix with hydrocele (11)

Hyperechoic torsion appendage (11)

Absent blood supply inside the appendage with hyperemia around it (11)

 

 

 

 

 

 

 

2. INFECTIOUS

 

Epididymitis and epididymo‑orchitis

Always try to scan the Epididymis from head to tail (some infection may be limited to the  tail) then compare the findings to the unaffected site.

Findings: 

  • Heterogenous echogenicity.
  • Enlargement in size.
  • Increase in color flow doppler.
  • Secondary findings includes Hydrocele and scrotal wall thickening.

The primary infection might get complicated and develop Abscess or Pyocele or end up with infarction and reversal arterial diastolic flow (6,9).

Enlarged epididymis (Q-path)

Increase flow on color doppler (Q-path)

 

 

 

 

 

 

 

 

 

Fournier gangrene

It’s a polymicrobial necrotizing fasciitis of the perineal, perianal, or genital areas. This diagnosis is clinical though the characteristic crepitus could only be found in 19-64% of cases. It’s critical that if this diagnosis is suspected, treatment should not be delayed for imaging confirmation. The modality of choice for diagnosis is CT scan (12).

Findings on US:

  • Diffuse subcutaneous tissue thickening.
  • Perifascial fluid accumulation.
  • Bright echogenic foci with dirty shadowing and reverberation artifacts corresponding to the underlying soft tissue gas. (12)

 

Thickening of scrotal wall with hydrocele and air reverberation artifact (13)

 

3. TRAUMA

The American Urological Association recommends surgical exploration in case of testicular trauma to delineate the extent of injury and should be within 72 hours as the rate of salvage up to 90% of blunt testicular rupture cases; But when surgery is delayed beyond this time point, the orchiectomy rate is 45%. (6,9)

 

Testicular Rupture: 

  • A tear in the tunica albuginea that results in extrusion of testicular contents.
  • Radiology US sensitivity 100% Specificity 93.5%.
  • Images will show heterogeneous testicle, contour abnormality, and disruption of the tunica albuginea.
  • Color Doppler imaging demonstrates focal or diffuse loss of vascularity.

Testes look heterogenous with irregular wall and abnormal blood supply (11)

Complete loss of the testicle contour (13)

 

 

 

 

 

 

 

 

 

 

 

 

Testicular fracture 

Disruption of the testicular parenchyma with preserved testicular shape and integrity of the hyperechoic tunica albuginea. The fracture plane appears as an avascular linear hypoechoic band extending across the parenchyma.

It’s critical to identify blood flow on color doppler to determine salvageability(9,10).

 

Scrotal hematoma

Depend on the chronicity of the evolving blood products; hematoceles and focal testicular, epididymal, and scrotal wall hematomas are acutely hyperechoic with decreasing echogenicity and increasing complexity (septa, loculations, and fluid levels) as they evolve to subacute and chronic phases. Hematomas have no internal flow on color and power Doppler images(9,10).

 

4. OTHERS

 

Testicular tumors:

  • Well-defined, hypoechoic or heterogeneous echogenicity intra-testicular lesion.
  • Might also see calcifications, micro-lithiasis, and necrosis.
  • Low level echoes with increased blood flow on color Doppler.(9)

 

multiple hypoechoic area with micro-lithiasis (11)

 

Varicocele:

  • Normal diameter of the pampiniform plexus veins range from 0.5 to 1.5 mm, the diameter of the main draining vein measuring up to 2 mm.
  • When this diameter increases, the collection of tortuous elongated veins seen posterior to testes.
  • Primary varicocele is almost always (98%) left sided due to venous drainage into the renal vein, contrary to direct drainage of the right vein into the inferior vena cava.
  • Secondary varicoceles are bilateral in up to 70%.

Dilated vein (worm like appearance) (14)

 

augmented vascularity with Valsalva (14)

 

 

 

 

 

 

 

 

 

The Evidence

  • Color and power Doppler ultrasonography reported sensitivity ranges between 86% and 98%, specificity up to 100%, and accuracy up to 97% by radiologist(9).
  • Friedman et.al. reported an agreement rate of  70% accuracy of all performed acute scrotum point-of-care ultrasound with final diagnosis(15).
  • Testicular torsion showed a sensitivity of 100% and Specificity of 99.1% with 73 minutes difference between the emergency physician and the radiologist acquiring the results(15).
  • For the other applications, still the evidence to be established but Blaivas et al. in a sample of 36 patients found the accuracy of emergency physician diagnosis compared to radiological studies was 95% sensitive and 94% specific(16).

 

Limitation and pitfalls

  • Normal variant
  • Overlapping of pathological findings might interfere with diagnosis, so clinical correlation is needed.
  • PoCUS in the emergency department is mainly a Rule In NOT out, So if no testicular torsion is identified it doesn’t mean that it’s ruled out.
  • Absence of scrotal pathology might signify an abdominal one especially if you identified undescended testes.

 

Bottom line:

  • Presentation of scrotal pathology could overlap greatly, and PoCUS can aid in delineating the diagnosis.
  • Most critical for emergency physician is to identify testicular torsion as time here is your enemy so PoCUS can assist in Ruling in this diagnosis with accuracy reaching 100%.

 

References

  1. Blaivas M, Sierzenski P, Lambert M. Emergency evaluation of patients presenting with acute scrotum using bedside ultrasonography. Acad Emerg Med. 2001;8(1):90-93.
  2. Cos LR, Rabinowitz R. Trauma-induced testicular torsion in children. J Trauma. 1982; 22:244–6.
  3. Melekos MD, Asbach HW, Markou SA. Etiology of acute scrotum in 100 boys with regard to age distribution. J Urol.1988; 139:1023–5.
  4. Wittenberg AF, Tobias T, Rzeszotarski M, et al. Sonography of the acute scrotum: The four T’s of testicular imaging. Curr Probl Diagn Radiol 2006;35:12-21.
  5. Testicular Ultrasound | Radiology Key.
  6. Sweet DE, Feldman MK, Remer EM. Imaging of the acute scrotum: keys to a rapid diagnosis of acute scrotal disorders. Abdom Radiol (NY). 2020;45(7):2063-2081.
  7. Badar Bin Bilal Shaf, 2018, Testicular Evaluation using Bedside Ultrasonography. (Testicular Evaluation using Bedside Ultrasonography: Practice Essentials, Indications, Positioning (medscape.com)
  8. Frohlich LC, Paydar-Darian N, Cilento BG Jr, Lee LK. Prospective Validation of Clinical Score for Males Presenting With an Acute Scrotum. Acad Emerg Med. 2017;24(12):1474-1482.
  9. Cokkinos DD, Antypa E, Tserotas P, et al. Emergency ultrasound of the scrotum: a review of the commonest pathologic conditions. Curr Probl Diagn Radiol. 2011;40(1):1-14.
  10. Rebik K, Wagner JM, Middleton W. Scrotal Ultrasound. Radiol Clin North Am. 2019;57(3):635-648.
  11. Radiopedia (Radiopaedia.org, the wiki-based collaborative Radiology resource).
  12. Levenson RB, Singh AK, Novelline RA (2008) Fournier gangrene: role of imaging. Radiographics 28:519-528.
  13. The Pocus Atlas (TPA (thepocusatlas.com)
  14. Liftl (Ultrasound Case 105 • LITFL • POCUS Top 100).
  15. Friedman N, Pancer Z, Savic R, et al. Accuracy of point-of-care ultrasound by pediatric emergency physicians for testicular torsion. J Pediatr Urol. 2019;15(6):608.e1-608.e6.
  16. Blaivas M, Sierzenski P, Lambert M. Emergency evaluation of patients presenting with acute scrotum using bedside ultrasonography. Acad Emerg Med. 2001;8(1):90-93.
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DVT PoCUS: When?, Where?, How? and What to do next?

Posted on by

 

Dr. Kyle Traboulsee

EM Physician, PoCUS Fellow

Reviewed by Dr. David Lewis

Copyedited by Dr. Rawan Alrashed 

 

Background

Lower extremity deep vein thrombosis (DVT) is a common, and potentially life-threatening vascular condition, with an annual incidence of 1 per 1000 adults. If left untreated, it may progress to pulmonary embolism, which is associated with a higher mortality. Therefore, accurate and timely diagnosis and treatment are incredibly important. (1,2,3)

An initial approach to the diagnosis of DVT involves risk stratification, often with the clinical risk score “Well’s score”, in conjunction with D-dimer assays. Based on the associated pre-test probability of the above risk stratification, further imaging may be required.

Although the gold standard for the diagnosis of DVT has traditionally been contrast venography, Duplex ultrasonography has become the standard of care due (in large part) to its lack of radiation and intravenous contrast, as well as widespread availability. This elective scan evaluates from groin to ankle and can take upwards of 1 hour depending on the difficulty of the individual exam. Studies have shown that a simplified ultrasound technique, limited to proximal segments of the femoral and popliteal veins using compression alone has a high sensitivity and specificity for proximal DVT detection. (2,4)

Point of care ultrasound (POCUS) has been increasingly used by emergency room physicians to assess for proximal lower extremity DVTs, with studies finding comparable diagnostic accuracy to radiology or vascular lab-performed duplex ultrasonography for detection of proximal DVT. (2)

 

Anatomy

 

Figure 1: Veins of the lower extremity (5)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

The venous anatomy of the lower limb is relatively simple. The most proximal vein of interest is the Common Femoral Vein (CFV), which gives off the great saphenous vein (a superficial branch). Distal to this, the Common Femoral Vein should bifurcate into the Deep Femoral Vein, and Femoral Vein.

 

       N.B: the Femoral Vein also known as the Superficial Femoral Vein, but because it is still considered a deep vein with respect to the diagnosis of deep vein thrombosis, it is usually referred to as simply the Femoral Vein.

 

As the femoral Vein travels distally, it enters the adductor canal, passing posterior to the knee, and becomes the popliteal vein. The popliteal vein gives rise to three deep veins at the level of the calf: the perineal vein, anterior tibial vein, and posterior tibial vein. (5)

 

DVT POCUS protocols

There are multiple POCUS protocols with respect to lower extremity DVT evaluation, ranging from a 2-point ultrasound scan to a whole leg protocol. The more commonly studied, and utilized, protocols in the emergency department are referred to as the 2-point compression study and 3-point compression study. (1,2,5)

(It should be noted that the “points” are regions being scanned, opposed to distinct, singular points).

 

Figure 2: DVT protocols (5)

 

 

2-point compression study

This study evaluates the:

  • common femoral vein
  • popliteal vein

The common femoral vein is evaluated from the inguinal ligament until it becomes the femoral vein, including the junction of the common femoral vein and greater saphenous vein (CFV-GSV). Ensure this scan includes at least 1-2cm above and below the CFV-GSV junction. (2)

The popliteal vein is assessed from the popliteal fossa until it trifurcates. (2)

 

3-point compression study

This technique evaluates the:

  • Common femoral vein
  • Femoral vein
  • Popliteal vein.

Like the “2-point” examination, the common femoral vein is evaluated from the inguinal ligament until it becomes the femoral vein (including the CFV-GSV junction). The femoral vein is then further evaluated at least 2 cm distal to the bifurcation of the femoral vein and deep femoral vein. Some variations on the 3-point protocol may suggest continued evaluation of the femoral vein distally as it transitions to the popliteal vein. (2,4,5)

 

PoCUS Technique (3-point compression technique)

The linear array is the probe of choice for this scan.

 

 Femoral Veins

 

  1. Position the patient by raising the head of the stretcher 30 degrees and placing the patient in reverse Trendelenburg (if able). This allows distension of the lower limb veins. Slightly flex the knee and externally rotate the hip. (4,5)
  2. Place the probe along the inguinal ligament in the transverse plane midway between the pubic symphysis and anterior superior iliac spine and identify the common femoral vein (CFV). The common femoral artery and vein should be side by side, with the artery lateral to the vein.
  3. Ensure that you are at the most proximal part by sliding the probe proximally towards the abdomen until the CFV become in the far field obscured by bowel gases (most proximal point) then slide the probe distally and  Apply firm pressure with the probe until the vein collapses completely, or the artery begins to collapse without full collapse of the vein (which could indicate a DVT). (4,5)

 

Fig 3: Common femoral vein (5)

CFA: Common femoral artery
CFV: Common femoral Vein (5)

CFV compression (5)

 

 

 

 

 

 

 

 

 

 

 

 

 

4. After that slowly slide the probe distally, stopping every centimeter (or every width of the probe head), to compress the vein, ensuring it flattens completely. The end point of the scan is 1-2 cm distal to the bifurcation of the common femoral vein into the deep femoral vein and femoral vein. (4,5)

a. Within the first 1-2 cm, the great saphenous vein will branch off from the common femoral vein, usually medially and near field. Monitor the compressibility of both the common femoral vein, as well as the first 1-2 cm of the great saphenous vein.

 

Fig. 4: Branching of great saphenous vein (5)

CFA: common femoral artery
CFV: common femoral vein
SV: Great Saphenous Vein (5)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

b. The common femoral vein should bifurcate into the deep femoral vein, and femoral vein 1-2 cm distal to the CFV-GSV junction.  Ensure compressibility is assessed at least 1-2 cm distal to the bifurcation if the common femoral vein. Consider continuing to scan distally until the femoral vein becomes the popliteal vein or are no longer able to assess.

 

Fig.5: Femoral vein (5)

FA: Femoral Artery
FV: Femoral Vein (5)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Popliteal vein

  1. If the posterior aspect of the knee (popliteal fossa) can be easily accessed in the patient’s current position (i.e., hip externally rotated, knee slightly flexed), no further positioning changes are needed. Other options include having the patient turn to a lateral decubitus position, with the leg of interest above the other, or, have the patient sit on the side of the stretcher, with their legs dangling. (4,5)
  2. Place the probe into the posterior crease of the knee (popliteal fossa), in a transverse plane and scan 2 cm above and below to locate the popliteal vein. If the structure is not immediately identified, slide the probe slightly medially and laterally to attempt to locate it. The vein should be near field, and directly over, the popliteal artery. Once located, assess compressibility of the vessel (4,5)

 

Fig. 6: Popliteal Vein (5)

PA: Popliteal Artery
PV: Popliteal Vein (5)

Popliteal Vein compression (5)

 

 

 

 

 

 

 

 

 

 

 

 

 

Continue scanning distally (assessing compressibility along the way), until the popliteal vein trifurcates into the anterior tibial, posterior tibial, and peroneal vein. This marks the end of the examination. (4,5)

 

Fig.7: Popliteal Vein trifurcation (5)

PA: Popliteal artery
V: Popliteal Vein Trifurcation (5)

 

 

 

 

 

 

 

 

 

 

 

 

 

Doppler flow augmentation

If the veins are difficult to identify or compress, color doppler can be applied. With the probe held stationary over the vessel in question, gently squeeze the calf distal to the probe. This should augment blood flow into the vein of interest and appear (briefly) as a brighter signal. If there is no increase in blood flow seen, a DVT could be present. (3,5)

Of note, normal venous flow will also change with the respiratory cycle. As the intrabdominal pressure increases with inspiration, venous return from the lower extremities will decrease, while with expiration, flow increases. This can be appreciated with spectral doppler. (3)

 

Positive Scan

Failure to completely collapse the vein (with enough pressure to partially compress the adjacent artery), at any level, is highly suggestive for the presence of a clot.

Depending on the chronicity of the clot, it may appear echogenic enough to directly visualize under ultrasound, but this is not always the case. (3,4,5)

 

Direct clot visualization (5)

Non-compressible popliteal vein (own image)

Doppler flow around a DVT, popliteal vein (own image)

 

The Evidence

A meta-analysis published in 2019, looked at 16 articles utilizing either 2-point compression or 3-point compression and found comparable sensitivities and specificities for proximal DVT, with no statistically significant difference (1):

 

2-point compression technique

Sensitivity 91%

Specificity 98%

 

3-point compression technique

Sensitivity 90%

Specificity 95%

 

Although there was no statistically significant difference between tests, many clinicians still recommend performing the 3-point compression, to include visualization of the femoral vein.

Other studies have quoted sensitivities ranging from 93% to as high as 100% (3).

It’s important to note that compression ultrasound alone is not accurate at picking up below-knee DVT. It is rare for below-knee DVT to progress to pulmonary embolism without first extending to an above-knee DVT. Therefore, although proximal DVT is of more clinical significance in the emergency department, a negative proximal PoCUS DVT scan should be followed by a repeat scan in 5-7 days to ensure a below-knee DVT was not missed. (3)

 

Pitfalls (false positives and negatives)

False negatives

  • Small, non-occlusive DVTs may near completely compress under applied probe pressure. Ensure complete vein occlusion when applying pressure during scan.
  • Excessive probe pressure. If enough pressure is applied to compress the adjacent artery, then a DVT may also be compressed.
  • A pelvic vein DVT may be missed either due to starting the scan to distally or being unable to compress the vein due to its location. Further imaging may be required if high clinical suspicion including venography, MRI, or extended ultrasound to include the iliac vessels and IVC (3,4).

 

False positives

  • Lymph nodes can appear as non-compressible vessels. If in doubt, rotating the probe in a longitudinal orientation will reveal the spherical nature of the lymph node.
  • Superficial thrombophlebitis. These non-compressible superficial veins may be mistaken for deep veins. The major difference is superficial veins should not accompany arteries.
  • Recanalized DVT. Old thrombi that have recanalized may not compress appropriately under probe pressure, but flow should be apparent on color doppler imaging. (3,4,5)

 

Approach to DVT Diagnosis/exclusion

One in three patients with untreated DVTs will progress to clinically significant pulmonary emboli, thus diagnosis and treatment of DVT is vitally important.

Although a positive scan is very helpful, a negative scan does not rule out a thrombus, specifically a below-knee DVT, which can propagate to an above-knee DVT, and eventually a PE given time.

Multiple diagnostic approaches have been described, incorporating the DVT PoCUS scan, well established risk stratification tools (Such as Well’s criteria), and repeat imaging. Below is one such approach, adapted from Mazzolai 2017. (5,6)

 

DVT diagnostic algorithm (5)

 

Bottom Line

DVT PoCUS is a (relatively) simple scan, that can be performed quickly and used to assess for proximal DVT. Its utility is well recognized, and it is considered one of the core ultrasound applications for emergency medicine physicians by the American College of Emergency Physicians.

When assessing for DVT, the PoCUS scan should be incorporated into a diagnostic algorithm along with other risk stratification tools, and due to its low sensitivity for below-knee DVT, repeat imaging in the context of a negative scan may be warranted.

 

References

  1. Lee, J. H., Lee, S. H., & Yun, S. J. (2019). Comparison of 2-point and 3-point point-of-care ultrasound techniques for deep vein thrombosis at the Emergency Department. Medicine, 98(22).
  2. Varrias, D., Palaiodimos, L., Balasubramanian, P., Barrera, C. A., Nauka, P., Melainis, A. A., Zamora, C., Zavras, P., Napolitano, M., Gulani, P., Ntaios, G., Faillace, R. T., & Galen, B. (2021). The use of point-of-care ultrasound (Pocus) in the diagnosis of deep vein thrombosis. Journal of Clinical Medicine, 10(17), 3903.
  3. Atkinson, P., Bowra, J., Harris, T., Jarman, B., & Lewis, D. (2019). Point-of-care ultrasound for Emergency Medicine and Resuscitation. Oxford University Press
  4. Socransky, S., & Wiss, R. (2016). Essentials of point-of-care ultrasound: The ede book. The EDE 2 Course, Inc.
  5. Dinh, V. (n.d.). DVT Ultrasound made easy: Step-by-step guide. POCUS 101. Retrieved November 26, 2021, from https://www.pocus101.com/dvt-ultrasound-made-easy-step-by-step-guide/.
  6. Mazzolai, L., Aboyans, V., Ageno, W., Agnelli, G., Alatri, A., Bauersachs, R., Brekelmans, M. P., Büller, H. R., Elias, A., Farge, D., Konstantinides, S., Palareti, G., Prandoni, P., Righini, M., Torbicki, A., Vlachopoulos, C., & Brodmann, M. (2017). Diagnosis and management of acute deep vein thrombosis: A joint consensus document from the European Society of cardiology working groups of aorta and peripheral vascular diseases and pulmonary circulation and right ventricular function. European Heart Journal, 39(47), 4208–4218.
  7. Deep vein thrombosis (DVT). ACEP Symbol. (n.d.). Retrieved November 29, 2021, from https://www.acep.org/sonoguide/basic/dvt/.

 

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