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Hemodialysis Access
Ultrasound Evaluation Before
& After Creation
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Basic Concepts
Hemodialysis is for patients with end-stage renal disease
~ 8,000 new dialysis patients per year
Blood is cleansed by diffusion across a semipermeable
membrane Dialysis is accomplished by AVF creation (preferred
method), graft or central venous catheter placement
AVF or graft
Two 15 gauge needles are placed One distal, which takes blood from the patient to the dialyzer
One proximal, which returns blood from the dialyzer to the patient
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AVF Anastomoses Most Common
AVF Types Artery Vein
Forearm cephalic
vein
Radial Cephalic
Forearm vein
transposition
Radial Ulnar, dorsal or volar
vein transposition
Upper arm
cephalic vein
Brachial Cephalic
Basilic vein
transposition
Brachial Basilic
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Basic Considerations - continued
AVF creation or graft placement
Preferable placement is in the nondominant arm
First access is generally in the forearm
Saving the upper arm for future access
Forearm graft is preferable for patients without suitable anatomy for
AVF creation
Thigh graft is generally a last choice
AVF creation in the dominant arm may be preferable to
placement of a graft in the nondominant arm
Central venous catheter
Higher infection rate
Lower flow rates
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Preferred Order of Access Placement
Order Type of Placement
1 Nondominant forearm cephalic vein fistula
2 Dominant forearm cephalic vein fistula3 Nondominant or dominant upper arm cephalic vein fistula
4 Nondominant or dominant upper arm basilic vein transposition
fistula
5 Forearm loop graft
6 Upper arm straight graft
7 Upper arm loop graft (axillary artery to axillary vein)
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Forearm AVF
Brescia-Cimino Fistula
Radiocephalic fistula
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Brachiocephalic Fistula
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Brachiobasilic Fistula
Vein transposition
fistula
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Forearm Loop Graft
Brachial artery to
cephalic vein
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Upper Arm Straight Graft
Brachial artery to axillary
vein
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Axillary-Axillary Loop Graft
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Thigh Graft
Common femoral
artery to greater
saphenous vein
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Preoperative Vascular Mapping
Preoperative evaluation may include
Physiologic upper extremity arterial evaluation
Ultrasound imaging
Ultrasound imaging
Linear ultrasound transducer
> 7 MHz
Identify vessels
Transverse imaging plane
Evaluate vessel diameter and wall thickness Assess venous compressibility
Depth from skin surface to anterior vessel wall
Longitudinal imaging plane
Color flow and spectral Doppler waveforms
Assess arteries for intimal thickening, calcification and stenosis
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Forearm Assessment
Assess nondominant arm first Assess the radial artery in lower third of forearm
At least 2 mm internal diameter
Assess the ulnar artery if the radial artery is not suitable
If no suitable artery is found in the nondominant forearm,assess the arteries in the dominant forearm
If suitable artery is found in the nondominant forearm Assess the forearm veins
Place a tourniquet below at or just below mid forearm
The cephalic vein is the preferable vein for creation of a forearm
fistula
Adequate sized veins will be at least 2.5 mm in its internal diameter
Assess for vessel continuity, branch points, compressibility
Sequentially move the tourniquet to assess over its length and itsinsertion into the deep veins
Assess the dominant arm is indicated
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Minimum Diameter Criteria for AVF &
Graft Creation
Vessel Minimum Diameter (cm)
AVF vein 0.25 (2.5 mm)
Graft vein 0.40 (4.0 mm)
Artery (graft or AVF) 0.20 (2.0 mm)
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Scanning Position
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Radial Artery - Normal
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Cephalic Vein - Wrist
Diameter = 2.9 mm; Depth = 3.4 mm
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Upper Arm Assessment
Assess the following vessels Brachial artery diameter at the antecubital fossa
Cephalic vein from the antecubital fossa to its termination
Need ~2 cm of vein below AC fossa to create AVF anastomosis
Median cubital vein Basilic vein if indicated
Need ~2 cm of vein below elbow for AVF creation
If does not extend below elbow may still be used for graft
Needs to have internal diameter or 4.0 mm
Axillary vein and artery if indicated For possible creation of upper arm loop graft
Subclavian, internal jugular and central vein assessment
Luminal filling defects
Doppler flow characteristics
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Cephalic Vein - Abnormal
Upper arm cephalic vein measuring with internal
diameter of 1.4 mm
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Upper Arm Assessment
Brachial artery - normal Basilic vein - normal
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Subclavian Vein Normal / Abnormal
Venogram Occluded
brachiocephalic vein
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Key Points - Preoperative
1. If upper arm cephalic vein is unsuitable, a forearm AVFmay still be possible depending on its eventual point ofdrainage, i.e. with the brachial, basilic or mediancubital vein
2. Carefully assess branch points for focal stenosis3. Cephalic vein diameter may be adequate but toodeeply situated, i.e. >0.5 cm, to be palpated
4. High origin of the radial artery may make it unsuitablefor use as there is increased likelihood of a stealsyndrome
5. It is important to assess brachial and radial arterieswith Doppler spectral analysis to identify proximal ordistal obstruction
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Cephalic Vein
Adequate size, but too deep
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AVF Maturity Assessment
General Principles Large, dilated, easily palpated vein
Sonographic evaluation
Evaluate Feeding artery Above (cephalad) from the fistula
Immediately below (caudal) to the fistula
Fistula itself (arteriovenous anastomosis)
Draining vein Diameter
Depth
Entire length
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Sonographic Evaluation
Evaluate utilizing:
B-mode, color Doppler flow & spectral Doppler
Spectral Doppler criteria
Volume/Flow
Should be at least 350 cc/minute
In general a volume/flow of 2.0 = 50%
>3.0 = time to do something Mid graft flow velocity of
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AVF Occlusion
Absence of flow in the arteriovenous
anastomosis
Triphasic flow in the artery above theanastomotic site
Phasic flow with respiration in the veins
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AVF Anastomotic Stenosis
Feeding artery 2 cm upstream from AVF
with normal low resistance Doppler
waveform but abnormally low flow velocity
AVF anastomosis with elevated velocity
and systolic velocity ratio of 31
consistent with stenosis
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AVF Evaluation Key Points
1. Assess for presence of large vein branches
- May divert flow from the primary draining vein
- Frequently inhibits maturing of draining vein
- May need to be ligated
2. Assess subclavian, internal jugular and brachial veins
as indicated
3. Evaluate the feeding artery distal to the fistula for
possible steal syndrome
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Large Draining Vein Branch
Draining Vein
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Central Venous Thrombosis
Internal Jugular - Thrombosed
Subclavian vein Laterally
MRV with left brachiocephalic vein
and central internal jugular vein and
central subclavian vein thrombosis
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Graft Evaluation General Principles
Greater incidence of: Stenosis
Infection
Pseudoaneurysm
Graft stenosis occurs due to intimal hyperplasia Most commonly at the venous anastomosis
Surveillance methods vary institution to institution
Ultrasound utilized for:
Evaluation of palpable focal mass Differentiate hematoma from pseudoaneurysm
Intermediate likelihood of graft stenosis
Arterial steal
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Access Graft Sonographic Evaluation
High resolution, > 7 MHz transducer
Evaluate with B-mode, color Doppler flow & spectral Doppler
Evaluate with Doppler spectral analysis:
Afferent artery
~2 cm cephalad to arterial anastomosis
Arterial anastomosis
Graft body
Arterial anastomosis
Mid graft
Venous anastomosis
Any other point of interest
Venous anastomosis
~2 cm caudal to venous anastomosis
Efferent vein
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Access Graft Sonographic Evaluation
Doppler criteria
Systolic velocities
PSVs generally range from 100 400 cm/s
EDVs generally range from 60 200 cm/s
Volume/Flow
Will generally be >300 ml/minute
2.0 = >50% diameter reduction
>3.0 = >75% diameter reduction
Some authors suggest a ratio of >4.0 = >75% diameter reduction
Must also see visual confirmation of stenosis with the presence of poststenoticturbulence and low flow distal
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General Classification Scheme
Normal Arterial anastomosis velocity >300 cm/s
Mid graft velocity >150 cm/s
No visible narrowing
Distended outflow veins
Moderate stenosis Arterial anastomosis velocity >400 cm/s
Mid graft velocity 100-150 cm/s
Decrease in lumen diameter
Echogenic material within the graft lumen
Wall abnormalities
Severe stenosis
Mid graft velocity 100% increase in PSV
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General Classification Scheme
Inflow stenosis
Inflow anastomotic site >400 cm/s with turbulence
Monophasic spectra with graft compression
Mid graft velocity
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Graft Stenosis
Stenosis at venous anastomosisDoppler flow 2 cm upstream from
venous anastomosis
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Graft Stenosis
Spectral Doppler at venous
anastomosis
Angiography with >50%
narrowing
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