Bedside Emergency Ultrasound For Deep Venous Thrombosis

Michael Blaivas, MD, MBA(candidate) FACEP, FAIUMProfessor of Medicine

University of South Carolina School of MedicineAIUM Third Vice President

Past President, Society of Ultrasound in Medical EducationEditorial Board Member, Critical Ultrasound Journal

Past Chair, AIUM Emergency and Critical Care Ultrasound Section Past Chair ACEP Ultrasound Section

Past President, WINFOCUS Sub-specialty Editor, Journal of Ultrasound in Medicine

Department of Emergency Medicine St Francis Hospital, Columbus Georgia

Disclosures

• GE

Objectives

• Understand regional anatomy

• Learn the POC DVT examination

• Understand DVT ultrasound criteria

• Understand how to identify DVT

• Understand potential pitfalls of ultrasound

• Understand Doppler adjunct use in POC US examination

Lower Extremity Thrombosis

• 260,000 cases per year

• Cause at least 50,000 deaths per year

• Imperative to diagnose DVT and prevent PE

• Most patients who die of PE die with in 30 minutes of having one

POC Settings and LE DVT

• Patients come in with painful and/or swollen legs

• Need to catch the ones with DVT

• Now rely on radiology or empirically treat patients

Radiology Evaluation for DVT

• Different means to diagnose LE DVT

• Most common is duplex ultrasound

• Average vascular laboratory ultrasound exam takes 37 minutes

• Life is harder after business hours if resources are limited

Clinician’s Dilemma

• What can Clinicians do?

• Clinical diagnosis unreliable

• We are very poor at finding DVT on exam

• No better than 50% in some studies

• Can use prediction rules that rank risks

– Improve results but still cannot rely upon

Clinician’s Dilemma

• In the real world may not be able to get vascular study at night or on weekend

• Perhaps need result now to plan care

• Why not just admit?

– Expensive

– Patients sit around, study could be false negative

• How about low molecular weight heparin?

Clinician Use Literature Date Back Decades

• Jolly et al. 1996

• Frazee et al. 1998 (2001)

• Blaivas et al. 2000

• Theodoro et al. 2004

• Bernardi et al. 2008 JAMA

Jolly et al. 1996

• Two attending EPs trained by vascular lab

• EPs had hands on training

• Each proctored for 25 to 30 scans

• No mention of scan time but average is about 37 minutes

• A great step forward for EM ultrasound but not practical in most clinical settings

Standard Approach

• Radiology technologist scans entire leg

• Looks at every inch of vein

– Blood flow

– Compressibility of vein

– Variations in blood flow with breathing and leg compression

Simplified Approach

• Look at common femoral vein

• Junction of femoral, deep femoral and superficial femoral veins

• Popliteal vein behind the knee

Simplified Approach

• Rationale behind cutting ultrasound corners?

• LE DVT locations

– Rare to find DVTs in isolated vein segments

– This has been well studied

– As DVTs form in large veins they tend to propagate

Simplified Approach

• Original validation of simplified approach

– Lensing et al. 1989, N Engl J med

– Poppiti et al. 1995, J Vasc Surg

– Birdwell et al. 1998, Ann intern med

What About Calf DVT?

• Not all vascular labs check for them now

– Why?

– Accuracy may be as low as 30-40%

– Some centers do not treat for calf DVTs

• This is why patients scanned for a DVT need a repeat examination if the first one is negative

• 20% of calf DVTs thought to propagate proximally, now know to be less

Frazee et al.

• EPs studied patients at bedside

• Looked for compressibility of veins in two locations. The simplified approach.

• The common femoral

• The popliteal

• 65 patients enrolled

• Sensitivity of 74%

• Specificity of 93%

• Negative predictive value 97%

• Indeterminate results in 19% of patients

• What does all this mean?

– If no DVT visualized on a good scan then ok to send home

Frazee et al. Comments

• 19% indeterminate scans is too high

• Sensitivity was not that great

• Limited equipment

• Would like to be able to say yes or no on most patients you encounter

• Also, how long do these test take?

Blaivas et al.

• 112 patients enrolled

• Proximal DVTs diagnosed in 34 patients

• ED and Radiology agreed in 110 out of 112

• One false positive

• Another “false positive” -but venogram dx DVT

• Two calf DVTs found by radiology without proximal DVT

• Median time for examination 3 minutes 28 seconds (95% CI, 2:45 to 4:02; IQR 3:08)

• High correlation between ED and Radiology results; % agreement 98% (95% CI 95.4% to 100%), Kappa coefficient of agreement K = .9

Additional Relevant Findings

• Augmentation and blood flow evaluation was not useful

• Doppler best for finding vascular structures in sonographically challenged

• 3 saphenous vein thrombi found

• 6 Baker’s cysts found, explaining presenting complaints

Theodoro et al.

• Prospective single blinded study

• 156 patients

• Had radiology US 24/7

• Ordered radiology US, then did our own

• Compared time to disposition and results

• 34 (22%) patients with DVT

• Triage to dispo for EM US 95 minutes

• Triage to dispo for rad US 220 minutes

• Difference of 125 minutes, P<0.0001

Clinician Use Literature Date Back Decades

• Jolly et al. 1996

• Frazee et al. 1998 (2001)

• Blaivas et al. 2000

• Theodoro et al. 2004

• Bernardi et al. 2008 JAMACONCLUSION: The 2 diagnostic strategies are equivalent when used for themanagement of symptomatic outpatients with suspected DVTof the lower extremities.

So How Do We Get Started?

POC DVT Examination

• Patient positioning

• Elevate head of bed to dilate veins

• Rotate leg out to access femoral region

• Access to popliteal fossa

Equipment Requirements

• US machine

• Linear transducer (typically)

• Color or Power Doppler

• Pulsed Wave Doppler

• Presets

Common Femoral VeinSuperficial Femoral

Deep Femoral Vein

All of these are deep veins!!!

Evaluating The Femoral Region

• Start just distal to inguinal crease

• Image above junction of greater saphenous and common femoral vein (CFV)

• Compress

• Make sure to collapse CFV completely

• Move down probe width and compress again, then repeat

• Walk through split of CFV into deep and femoral veins

Evaluating The Popliteal Region

• Start high in the popliteal fossa

• Identify popliteal vein proximal to take off of calf veins

• Compress

• Make sure to collapse CFV completely

Results of Compression

Common FemoralVein

Common FemoralArtery Common Femoral

Vein

Common FemoralArtery

Pre-Compression With Compression

Femoral Vein Compression

• Start high in the popliteal fossa

• Identify popliteal vein proximal to take off of calf veins

• Compress

• Make sure to collapse CFV completely

Identifying Anatomy

• Can scan up and down

• Identify anatomy

• If any doubt can use color Doppler

• More accuracy with pulsed wave Doppler

• We will focus on a slightly more distal area

Common Femoral VeinSuperficial Femoral

Deep Femoral Vein

All of these are deep veins!!!

Walking Down Femoral Vein

• Compress and walk down the vein

• Move about one probe width

• Want to make sure entire region has complete collapse

• Not just a spot check

• Important to include CFV, DFV and FV

Documenting Collapse

• Can use still images

• Sometimes helpful to generate video clip

• Can show side by side on video

• May document walking down, through region

• Critical for repeat examinations and later review

Augmentation

• Helps identify vessels

• Thought to rule out complete occlusion between point of compression and transducer

• Does not actually guarantee this (collaterals)

Augmentation Results

Augmentation

• Helps identify vessels

• Thought to rule out complete occlusion between point of compression and transducer

• Does not actually guarantee this (collaterals)

POC Augmentation Use

• Helps identify vessels

• This is a difficult patient

• Obese and large legs

• Did not see vessels initially

• Turned on color Doppler

• Helped identify key area

• Then turned off color and compressed

What is What

• Sometimes difficult to identify anatomy

• Specifically, what is vein and should collapse

• Everything that should collapse, must collapse

• Anything that does not collapse better be an artery

What is What

• Sometimes difficult to identify anatomy

• Specifically, what is vein and should collapse

• Everything that should collapse, must collapse

• Anything that does not collapse better be an artery

Compression Failure = DVT

Femoral Vein

Femoral Artery

Clot

Femoral Artery

Compression Failure = DVT

• Artery collapses partially, but vein does not

• Vein that is patent should collapse

• Can repeat compression a few times, no need to compress over and over

• Femoral vein DVT!

Coming Out of The Deep

• Great example of why we scan a region, on just one spot/point

• Appears to collapse initially

• However, some compressions appear to fail

• Turning to long axis, we see a thrombus

• Arises from deep femoral vein and has seeded CFV

Coming Out of The Deep

• Good example

• Tracing DVT from deep femoral vein

• Compression just at common femoral vein would have missed this

• Compression through bifurcation picked it up

A Thrombosis Surprise

• DVT suspected

• Scan appears to show DVT is present

• Something does not fit however

• Color Doppler shows strong pulsations

• Most superficial vessel

• Turns out to be a femoral artery thrombus

Freely Floating Thrombus

• Thrombus that is free floating is at a very high risk for embolization

• Should view in longitudinal axis and avoid further compression after discovery

• Anticoagulate quickly and monitor patient

• Not a good patient to send home on low molecular weight heparin

Popliteal Evaluation

Popliteal Fossa

• Start high in popliteal fossa and trace down

• Can scan down without compression first to identify anatomy and assure proximal location

• Then start compressing

Popliteal Fossa

• Start high in popliteal fossa and trace down

• Can scan down without compression first to identify anatomy and assure proximal location

• Then start compressing

Compression Through Popliteal

• Compress one probe width at a time

• Good to compress through trifurcation

• Might pick up calf DVT about to seed popliteal

Popliteal DVT

• Compress

• Spit screen can help illustrate and document

• Recall that vein is now more superficial since we are scanning from posterior approach

Distal Popliteal DVT

• Would have been missed with only proximal popliteal vein compression

• Found in distal portion of scan

• Long axis shows it arising from calf vein

• Distal popliteal has been seeded

Special Cases and Pitfalls

• Several areas to be careful in

• Mostly requires careful scanning

• Keep anatomy in mind

• Don’t be fooled by imposters

Pelvic Vein DVT

• Less common but not rare

• Difficult when isolated (not in femoral or distal)

• Can image directly in some patients

• Success decreases as soft tissue burden increases

• Must rely on respiratory variation in femoral vein to rule out pelvic DVT

Superficial Thrombosis

• Can be confusing clinically and sonographically

• Keep your anatomy and depth in mind as well as the depth on the screen

Superficial Thrombosis

• Sometimes see physiology at work

• Blood sludging and local inflammation

Superficial Thrombosis

• Still helpful to compress

• Image in short and long axis if confusing

Chronic DVT

• Some defer such scans, quite reasonable

• In time, realize not impossible to diagnose

• Typically higher echogenicity

• How do thrombi re-cannulate?

• Hug walls

• May be very irregular

Chronic DVT?

• Be careful out atypical appearance

• This looks like a chronic DVT, hugging wall

• But look at echogenicity: Looks fresh

• Turn to long axis, trace down

• Fresh, Fresh DVT!

Isolated DVT?

• In theory occur all the time – not true

• Studies suggesting this use semantic trick

• Proof is experience and literature

• First one after 15 year, another in last 5

Pitfalls: Look For Impostors

• This looks like a DVT

• Don’t be too hasty

• Interrogate it and see what is says

• Patience, even in POC setting is important

Femoral DVT or Not?

• Has finite end

• Not a tube so not a vessel

• Actual vessels nearby

• Called a DVT

• Fortunately, the vessels (never noted by resident) did not collapse either

Not Pressing Hard Enough or DVT?

• Compression is important

• Easy to discount a sliver of vein left over

• Eventually, it will get you

Not Pressing Hard Enough

• Compression is important

• Easy to discount a sliver of vein left over

• Eventually, it will get you

Femoral Vein

Femoral Artery

Not Pressing Hard Enough or DVT?

• Here is an example of where discounting lack of complete collapse would be a critical miss

• Think DVT seen

QUESTIONS?