Duplex/Color Flow imaging (UE) Flashcards
Capabilities of duplex/color flow imaging?
- localize stenosis / occlusion; evaluate degree of stenosis
- determine the presence/absence of aneurysm
- post-op study: hemodialysis access or arterial bypass graft
- detect AVF’s or other unusual abnormality
Limitations of duplex/color flow imaging?
- limited access to extremity
Limitations pertaining to hemodialysis access grafts:
- graft angulation
- difficult to adequately evaluate the outflow vein in an obese patient
Patient positioning for duplex/color flow imaging:
- supine with small pillow under head
- extremity close to the examiner
- arm is at a 45 degree angle from the body and externally rotated
What is a “pledged positition”
arm is at a 45 degree angle from the body and externally rotated
Duplex scanning physical principles:
- combination of real-time B-mode imaging and doppler spectral analysis
Doppler color flow imaging physical principles:
- doppler information is displayed on image after evaluated for phase (direction toward or away from transducer) and its frequency content (hue or shade of color)
What is the sample size for acquiring pulsed Doppler information?
1-1.5 mm
- size can be increased if needed
What transducer is used for duplex/color flow imaging?
7 or 5 MHz linear array transducer
Color/duplex scanning is also used to evaluate what arteries?
- Subclavian
- Axillary
- Brachial
- Radial
- Ulnar
- Palmar arch (if needed)
What is the main use for evaluation of duplex/color flow imaging in the upper extremity?
evaluate dialysis access grafts
Is it common for upper extremity arteries to become stenotic?
no
A patent dialysis access, as well as a stenotic one can produce what?
a “thrill”
How do you evaluate dialysis access grafts?
- Inflow artery
- Arterial anastomosis
- Continue through the body of the graft
- Observe for aneurysm, puncture sites, peri-graft fluid
- If color is available, observe flow changes, turbulence, flow channel changes
- Venous anastomosis
- Outflow veing
Dialysis access assessment sites include:
inflow artery, anastomosis, outflow artery
What is a Brescia-Cimino fistula used for?
Dialysis access
Dialysis access examples include:
Brescia-Cimino fistula, straight, looped, synthetic grafts
Interpretation of stenosis:
- currently, no criteria for classifying disease as there is for LE
- Normal peak systolic velocities vary widely with skin temperature changes. Doppler signal quality is usually triphasic
- If a >50% diameter reduction is present, observe for characteristics of the “stenosis profile”
Interpretation of occlusion:
- Observe the lack of Doppler signals and the proverbial “thump” which is obtained proximal to occlusion
Interpretation of aneurysm:
- Dilation of the vessel from degeneration and/or weakening of the wall
Where can an aneurysm form in response to using the palm as a hammer?
Ulnar
What aneurysm is associated with embolization to the digits?
Subclavian
What is a normal PSV and DSV with hemodialysis access?
elevated
What could low PSV in access graft indicate?
arterial inflow problems
Where is the most common site for stenosis with hemodialysis access?
Venous anastomosis and outflow vein
How do you assess a possible “steal”?
-With dialysis access open/functioning use PPG to evaluate flow in at least 2 digits, one at a time
- Apply manual pressure to dialysis access and retake digit PPG tracings and/or pressures
What happens if flow improves with pressure to dialysis access?
there is a steal
What happens if flow stays the same without pressure to dialysis access?
there is probably not a steal
What results in large blood volumes shunted from artery to lower resistant venous circulations and will increase venous return?
congestive heart failure
