Bedside Emergency Ultrasound For Deep Venous Thrombosis

Transcription

1 Bedside Emergency Ultrasound For Deep Venous Thrombosis Michael Blaivas, MD, MBA(candidate) FACEP, FAIUM Professor of Medicine University of South Carolina School of Medicine AIUM Third Vice President Past President, Society of Ultrasound in Medical Education Editorial 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

2 GE Disclosures

3 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

4 Lower Extremity 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 Thrombosis

5 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

6 Radiology Evaluation for 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 DVT

7 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

8 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?

9 Clinician Use Literature Date Back Decades Jolly et al Frazee et al (2001) Blaivas et al Theodoro et al Bernardi et al JAMA

10 Jolly et al 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

11 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

12 Simplified Approach Look at common femoral vein Junction of femoral, deep femoral and superficial femoral veins Popliteal vein behind the knee

13 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

14 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

15 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

16 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

17 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?

18 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

19 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

20 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

21 Clinician Use Literature Date Back Decades Jolly et al Frazee et al (2001) Blaivas et al Theodoro et al Bernardi et al JAMA CONCLUSION: The 2 diagnostic strategies are equivalent when used for the management of symptomatic outpatients with suspected DVT of the lower extremities.

22 So How Do We Get Started?

23 POC DVT Examination Patient positioning Elevate head of bed to dilate veins Rotate leg out to access femoral region Access to popliteal fossa

24 Equipment Requirements US machine Linear transducer (typically) Color or Power Doppler Pulsed Wave Doppler Presets

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26 Common Femoral Vein Superficial Femoral Deep Femoral Vein All of these are deep veins!!!

27 Evaluating The Femoral 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 Region

28 Evaluating The Popliteal Start high in the popliteal fossa Identify popliteal vein proximal to take off of calf veins Compress Make sure to collapse CFV completely Region

29 Results of Compression Pre-Compression With Compression Common Femoral Vein Common Femoral Artery Common Femoral Vein Common Femoral Artery

30 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

31 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

32 Common Femoral Vein Superficial Femoral Deep Femoral Vein All of these are deep veins!!!

33 Walking Down Femoral 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 Vein

34 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

35 Augmentation Helps identify vessels Thought to rule out complete occlusion between point of compression and transducer Does not actually guarantee this (collaterals)

36 Augmentation Results

37 Augmentation Helps identify vessels Thought to rule out complete occlusion between point of compression and transducer Does not actually guarantee this (collaterals)

38 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

39 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

40 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

41 Compression Failure = DVT Femoral Artery Femoral Artery Femoral Vein Clot

42 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!

43 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

44 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

45 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

46 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

47 Popliteal Evaluation

48 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

49 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

50 Compression Through Compress one probe width at a time Good to compress through trifurcation Might pick up calf DVT about to seed popliteal Popliteal

51 Popliteal DVT Compress Spit screen can help illustrate and document Recall that vein is now more superficial since we are scanning from posterior approach

52 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

53 Special Cases and Pitfalls Several areas to be careful in Mostly requires careful scanning Keep anatomy in mind Don t be fooled by imposters

54 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

55 Superficial Thrombosis Can be confusing clinically and sonographically Keep your anatomy and depth in mind as well as the depth on the screen

56 Superficial Thrombosis Sometimes see physiology at work Blood sludging and local inflammation

57 Superficial Thrombosis Still helpful to compress Image in short and long axis if confusing

58 Chronic DVT Some defer such scans, quite reasonable In time, realize not impossible to diagnose Typically higher echogenicity How do thrombi recannulate? Hug walls May be very irregular

59 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!

60 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

61 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

62 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

63 Not Pressing Hard Enough or Compression is important Easy to discount a sliver of vein left over Eventually, it will get you DVT?

64 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

65 Not Pressing Hard Enough or Here is an example of where discounting lack of complete collapse would be a critical miss Think DVT seen DVT?

66 QUESTIONS?