Diagnostic Medical Sonography Program Lecture 11: Duplex Scanning and Color Flow Imaging of the Upper Extremity Holdorf

Duplex/Color Flow Imaging of the Upper Extremity Capabilities Localize stenosis / occlusion; evaluate degree of stenosis Determine the presence / absence of aneurysm Post-op study: Hemodialysis access or arterial bypass graft Detect Arteriovenous (AV) fistulas or other unusual abnormality

Limitations Limited access to extremity (e.g., dressings, skin staples or sutures, open wounds, IV site). Pertaining to hemodialysis access grafts: Graft angulation Difficult to adequately evaluate the outflow vein in an obese patient

Patient Positioning Patient is supine with small pillow under h ead Extremity close to the examiner Arm is at a 45 degree angle from the body, and externally rotated (“pledge position”)

Physical Principles Duplex scanning: combination of real-time B-mode imaging (gray sale evaluation) and Doppler spectral analysis. Doppler Color Flow imaging: Doppler information is displayed on image after evaluated for phase (direction toward or away from transducer) and its frequency content (hue or shade of the color) Sample size for acquiring pulsed Doppler information is usually 1-1.5 mm. Size is increased incrementally if needed. Review your Physics book regarding Doppler sample size (will be on the RVT boards)

Technique for Native Arteries Utilize a 5 or 7 MHz linear array transducer Neck vessels identified, with attention given to innominate artery on the Right. The Left Common Carotid Artery branches off the Ao Arch. Color / duplex scanning is also used to evaluate the following: Subclavian Axillary Brachial Radial Ulnar Palmar arch (if needed)

Example of Upper Extremity Arterial Signal

NOTE: It is uncommon for arteries in the upper extremities to become stenotic. Main use is evaluation of dialysis access grafts.

What is a hemodialysis Access Graft? A vascular access is a surgically created vein used to remove and return blood during hemodialysis. An arteriovenous (AV) fistula is a connection, made by a vascular surgeon, of an artery to a vein.

Technique: Hemodialysis Access Grafts Auscultate the access for bruit and or palpate for “thrill” (vibration). A patent dialysis access, as well as a stenotic one, can produce a “thrill”. Utilize a 5 or 7 MHz linear array transducer

Evaluate dialysis access grafts as follows: Inflow artery Arterial anastomosis Continue through the body of the graft Observe for aneurysm, puncture sites, peri-graft fluid If color available, observe the image for flow changes, turbulence, flow channel changes Venous anastomosis Outflow vein Note: Dialysis access assessments sites include: inflow artery, anastomosis, outflow vein e.g., Brescia-Cimino Fistula.

Dialysis access examples include: Brescia-Cimino Fistula and Straight, looped synthetic grafts

Technique-General Observations Longitudinal / Transverse approaches used to evaluate gray scale for thrombus, stenosis, etc. Doppler peak systolic velocities (PSV) obtained at appropriate sites as needed. Volume flow may be evaluated. Documentation consists of video tape or prints

Interpretation: Native Arteries Stenosis Currently, no criteria for classifying disease as there is for Lower extremity 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 a “Stenosis Profile” on your waveform.

Occlusion: Observe for lack of Doppler signal (image and or waveform) and the proverbial “thump” which is obtained proximal to occlusion Aneurysm: Dilation of the vessel from degeneration and or weakening of the wall. Ulnar artery aneurysms can form in response to using the palm as a hammer Subclavian aneurysms often are associated with embolization to the digits

Interpretation: Hemodialysis Access Identify / document if present (location, extent, and type), any aneurysmal changes, puncture sites, peri-graft fluid, thrombus. Peak systolic velocities (PSV) and end diastolic velocities (EDV) vary as to the type of access: normally both are elevated Low PSV obtained in access graft could indicate arterial INFLOW problems.

Interpretation: Hemodialysis Access No standardized velocity criteria at this time. Follow-up studies provide specific comparison to previous studies on same patient Venous anastomosis and outflow vein are most common sites for stenosis (likely caused by increased arterial pressure introduced to the vein and or intimal hyperplasia).

Other hemodynamic complications include: Large blood volumes shunted from artery to lower resistant venous circulation, can increase venous return resulting in congestive heart failure. A “steal syndrome” can occur. The distal arterial blood flow is reversed into the lower resistant venous circulation and can cause pain in hand and fingers on exertion, pallor and coolness of the skin distal to the shunt.

Assessment of 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 If flow improves there is a steal If flow stays the same, there is probably not a steal

Additional Notes Lecture 11 Duplex/Color Flow Imaging (UE) Not looking for a lot of disease.

This section pertains to hemodialysis access grafts. A fistula is formed in the wrist area. One access site can take arterial flow to the dialysis machine, and one access site can bring the blood back (venous flow) to the body. (Easy and constant hooking up to the dialysis machine)   The Brescia Cimino dialysis access graft is an AV fistula. Another type is the loop dialysis just under the skin. Look to the digits. Is there a change? A steal syndrome? Assessment of possible steal- this is ok to do. Hard to convince the patient, thought.

Homework Chapter 12: Pages 119- 126 SDMS assignments