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DVT Ultrasound

Background

Surgery is a risk factor for deep vein thrombosis and pulmonary emboli. As Anesthesiologists become increasingly involved in the perioperative management of patients beyond the intraoperative period, it is imperative that they possess the skills and knowledge to assess and treat patients with thromboemboli. DVT ultrasound is a rapid, noninvasive imaging modality that can be easily applied to patients at the bedside.

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Indication

  • Suspicion of pulmonary embolism 

    • Shock

    • RV Strain

    • Hypoxemia 

    • Chest pain

  • Suspicion of DVT

    • Calf tenderness

    • Unilateral swelling or redness

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Acquisition

Transducer: Linear high frequency

 

Patient Position:

  • Supine - can raise head of bed to assist with venous pooling and visualization

  • Frog leg position - hip externally rotated, knee flexed

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Operator Mechanics

  • Operate probe with dominant hand 

  • Place ultrasound machine on same side as operator to manipulate controls with non-dominant hand

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Scanning Technique

  • Probe is oriented in transverse plane 

  • There is a theoretical risk of dislodging a clot by compressing a thrombus within a vein, so it may be beneficial to complete a comprehensive examination without compression, then proceed to an exam with compression if no clot is directly visualized

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Common Femoral Vein

  • Place probe at medial inguinal crease and look for the “peanut sign”

  • Locate CFV - often medial to common femoral artery

  • Apply downward force until slight compression of artery is achieved

Saphenofemoral junction (SFJ)

  • Slide probe down 1-2 cm until “Mickey Mouse” is visualized

    • The saphenous vein should branch off medially

      • Dont get confused with the lateral perforator 

    • CFA will typically bifurcate prior to the SFJ

  • Compress at this site

Superficial femoral vein (SFV)

  • Slide probe down 1-2 cm until CFV bifurcates into superficial femoral vein and deep femoral vein

    • SFV travels alongside (typically medial) the femoral artery

  • Compress immediately distal to bifurcation

  • Can optionally compress every 1-2 cm as you scan down towards the popliteal vein

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Popliteal vein (PV)

  • Slide probe to posterior crease of knee between hamstring tendons

    • PV is superficial to popliteal artery

  • Can pronate patient for better visualization

  • Compress at this site

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Trifurcation of popliteal vein (TPV)

  • Slide probe down 1-2 cm until PV trifurcates into anterior and posterior tibial veins and peroneal vein

  • Veins are superficial to popliteal artery

  • Compress at this site

Pearls

  • Scan veins in long axis to ensure visualized structure is in fact a vein

  • Ensure veins are accompanied by an artery

    • This may help differentiate between superficial and deep veins

  • An adequate amount of pressure will slightly deform the walls of adjacent arteries

Interpretation

  • Direct clot visualization

    • As thrombus ages, it becomes more echogenic 

  • Non-compressibility 

    • If vein does not collapse despite evidence of arterial compression, the vein is considered non-compressible and clot is likely

  • Absent colour doppler flow

Medical Decision Making

  • Assess patient with formal DVT ultrasound or CT Chest

Pitfalls and Modifications

  • Baker’s cysts

    • Common painful fluid filled sacs in the popliteal fossa

    • Do not appear cylindrical in long axis

    • Do not have any flow with colour doppler

    • Sharper borders compared to veins

  • Lymph nodes

    • Do not appear cylindrical in long axis and are not continuous

    • If the structure disappears when scanning proximal and distal, it is unlikely to be vascular

  • Pseudoaneurysms

  • Groin hematoma

Comprehension Questions

1. How should you position patient for DVT ultrasound?

     A. Frog leg and head up

     B. Straight leg and head up

     C. Frog leg and head down

     D. Straight leg and head down

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2. Which veins are examined in the 5-point DVT ultrasound?

     A. ​Common femoral, popliteal, tibial

     B. Common femoral, superficial femoral, popliteal

     C. Varicose veins, popliteal, tibial

     D. Brachial, brachiocephalic, common femoral​
 

3. What are two sonographic features that may suggest the presence of a DVT?

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4. What are four common false positives for DVT?​​

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Answers

1. A

2. B

3. Non-compressibility, echogenic thrombus, lack of colour doppler flow

4. Baker’s cysts, lymph nodes, hematoma, pseudoaneurysms

References

Baker, M., Anjum, F., & dela Cruz, J. (2021). Deep Venous Thrombosis Ultrasound Evaluation. In StatPearls. essay. Retrieved May 1, 2022, from https://www.ncbi.nlm.nih.gov/books/NBK470453/. 

 

Dinh, V., & Ahn, J., DVT Ultrasound Made Easy: Step-By-Step Guide. Retrieved May 1, 2022, from https://www.pocus101.com/dvt-ultrasound-made-easy-step-by-step-guide/

 

Knipe, H. (2021, September 9). Deep vein thrombosis: Radiology reference article. Radiopaedia Blog RSS. Retrieved May 1, 2022, from https://radiopaedia.org/articles/deep-vein-thrombosis 

 

Needleman, L., Cronan, J. J., Lilly, M. P., Merli, G. J., Adhikari, S., Hertzberg, B. S., DeJong, M. R., Streiff, M. B., & Meissner, M. H. (2018). Ultrasound for Lower Extremity Deep Venous Thrombosis: Multidisciplinary Recommendations From the Society of Radiologists in Ultrasound Consensus Conference. Circulation, 137(14), 1505–1515. https://doi.org/10.1161/CIRCULATIONAHA.117.030687

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