The Role of the Technologist in
Pre-Op Surgical Planning for
AVF/AVG
David Lorelli, MD, RVT, FACS
Medical Director Vascular Lab
St John Hospital and Medical Center
Detroit, Michigan
Table of Contents
•
•
•
•
•
•
•
•
•
Upper Extremity Anatomy
Basics of an Arteriovenous Fistula
Arteriovenous Graft (AVG)
Access Performance
Upper Extremity Duplex
Information for the Physician
Vein Mapping
Limitations
Helpful Scanning Techniques
Upper Extremity Anatomy
• Deep Veins
- Jugular
- Subclavian
- Axillary
- Brachial
- Radial
- Ulnar
• Superficial Veins
- Cephalic
- Basilic
- Medial cubital vein
What is an Arteriovenous Fistula
(AVF)
• Patients who are in kidney failure need hemodialysis to
supplement their kidney function.
• An arteriovenous fistula is the connection of a vein and an
artery to allow access to the vascular system for hemodialysis.
• The surgical creation of an AVF provides a long-lasting site
through which blood can be removed and returned to the
body during a hemodialysis treatment.
• The fistula, which allows the person to be connected to a
dialysis machine, must be prepared by a surgeon weeks or
months before dialysis is started.
• It takes approximatley 4-12 weeks for an AVF to fully mature.
Basics of an Arteriovenous Fistula
• The venous system contains Deep and Superficial
veins. The Superficial system is most important for
AVF creation.
• Cephalic vein is most commonly utilized.
- radiocephalic and brachiocephalic
• All Cephalic options are considered before the
proximal Basilic vein.
• Basilic vein is second choice because it lies beneath
the deep fascia and must be brought more superficial.
This is known as a Transposed Basilic vein AVF.
• Brachial veins can also be used for access.
Arteriovenous Graft (AVG)
• If all native vessels are not suitable for creating
an AVF then a graft made of synthetic material
is utilized.
• Common material is Polytetrafluoroethylene
(PTFE)
• Types of loops include: Forearm loop, upper
arm straight or loop, and thigh loop.
Access Performance
• Rate of blood flow varies depending on the
anatomy of the access:
AVF with radial artery 600-700 ml/min
AVF with brachial artery 13001500 ml/min
AVG 800-1200 ml/min
Factors Affecting Blood Flow Rates
• Performance of the blood pump (heart)
Blood pressure, ejection fraction, cardiac
rhythm
• Cardiac output also affected by
Fluid volume status, BP medications,
cardiac disease
• Atherosclerosis causing flow limiting stenosis
Blood Flow Rates
• Any factor which decreases the rate of
intra access blood flow can lead to
suboptimal hemodialysis treatments and
may eventually increase patient morbidity
and mortality.
Upper Extremity Duplex
• An ultrasound is done to determine
the patency, size and condition of the
veins.
• Generally a full evaluation of the
venous system is completed to rule out
DVT.
• Diameter measurements are taken of
the superficial veins .
- Proximal, mid, distal upper and
lower Cephalic.
-Proximal, mid, distal upper and lower
Basilic.
- If visualized, measure the medial
cubital vein.
• Depending on the physician, diameter
measurements are taken of specific
arteries.
Diameter measurement of the
Cephalic Vein.
Information for the Physician
• Dominant arm of the patient
• Any branches that come off the superficial
veins
• Any dilations in the veins
• Thickening of the vessel walls
• If DVT or SVT is visualized
• Any areas of stenosis.
• Any limitations
Information for the Physician
• Once the duplex is finished, the physician
makes the decision of which fistula or graft is
best for the patient.
• 2-2.5 mm and above are acceptable diameter
measurements for a fistula.
• The non-dominant hand is preferable.
Vein Mapping
• The day of the surgery the technologist needs to
mark the exact location and where the vein courses
down the arm.
• With a permanent marker, the tech keeps the vein in
the middle of the screen and writes on the patients
arm at the center of the probe to ensure the right
area is being mapped.
• Follow the vein as far proximal and distal as
possible.
• Also mark any branches that might be coming off the
vein.
• The physician may also need to know how far the
vein is from the skin. Measure from the top of the
vein to the top of the screen.
Limitations
•
•
•
•
•
Obese patients with deep vessels
A cast that limits the scanning area
Trauma or open wounds
Severe edema
Central venous line or dialysis access
Helpful Scanning Techniques
• If the vein is very superficial and the weight of the
probe is collapsing the vein, stabilize your hand on
the patients arm to release some pressure from the
probe.
• Switch to a higher frequency probe to visualize the
superficial veins better.
• When mapping for surgery, a tourniquet can be used
to better visualize the veins.
• Do not leave the tourniquet on for too long or have it
too tight, just enough to help the veins be more
visible.
New Alternatives
• HeRO catheter/graft
Allows upper extremity access even with
peripheral venous outflow obstruction.
The HeRO Graft
(Hemodialysis Reliable Outflow)
HeRO Graft is the only
fully subcutaneous
HeRO bypasses central
venous stenosis
AV access solution
clinically proven
to maintain long-term
access for catheterdependent patients
with central venous
stenosis.
New Alternatives
• TEVG (Tissue Engineered Vascular Graft)
Built to tolerate hemodynamic loads, heal
and remodel in response to needle sticks,
resist infection, no post op maturation period.
Currently the major draw back is cost
effectiveness.
References
ACR–AIUM–SRU Practice Guideline for the Performance of Peripheral Venous Ultrasound
Examination. 2010. American College of Radiology.
http://www.acr.org/SecondaryMainMenuCategories/qualitysafety/guidelines/us/us_peripher
al_venous.asp
Atlas of Dialysis Vascular Access. Tushar J. Vacharajani. 2010.
Mayo Foundation for Medical Education and Research (MFMER).March 2010.
http://www.mayoclinic.com/health/arteriovenous-fistula/DS01171
Upper Extremity Venous Duplex Evaluation R/O Deep/Superficial Vein Thrombosis. Society for
Vascular Ultrasound. January 2010.
http://www.svunet.org/files/positions/Upper_Extremity_Venous_ Duplex_Eval_2010.pdf
Vascular Access to Hemodialysis. National Kidney and Urologic Disease Information
Clearinghouse, Home Health Information. December 1999. http://www.niddk.nih.gov
Questions