Techniques of Ultrasound Evaluation of Vascular Access

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Techniques of Ultrasound Evaluation of Vascular
Access

• Marko Malovrh
• University Medical Centre Ljubljana
• Department of Nephrology
• Ljubljana, Slovenia

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• Vascular access (VA) is the life lineof
  dialysis pts.
• VA is prone to frequent complications before and
  after creation.

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• Native arteriovenous fistula (AVF) is superior to
  an AV graft and a catheter, due to its lower
  complication and higher patency rates.
• Number of elderly, with co-morbid conditions
  (diabetes, vascular disease) is increasing the
  creation and maintenance of functional VA is not
  an easy task.

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• To establishing reliable VA for haemodialysis
• Careful planning
• Preoperative evaluation
• Medical history
• Physical examination
• Ultrasonography

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• US is non-invasive, low cost and there is no need
  for radiocontrast.
• The main disadvantage of US is
• Operator dependency
• Additional knowledge to interpret DU
• Changes in local vascular haemodynamic after VA
  creation
• Patophysiological mechanisms behind VA
  complications

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• Ultrasound is sound above the audible range
  frequency above 20.000 Hz.
• B mode real time ultrasound scanning
• Allows visualization of structures as being
• black (blood, fluid..)
• grey (solid organs..)
• white (vessels, calcifications..)
• Rapid rate of changes provide a real time B mode
  ultrasound scan

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• By Doppler ( color D, pulsed wave D, power mode
  D) we can obtain information
• On the direction ob blood flow
• On the velocity of blood flow
• Combination of B mode US and DU- Duplex
  Ultrasound - linear high frequency transducer
  (8-12 MHz)

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Color Doppler
Grey scale
Pulse Doppler
Power Doppler
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HEMODIALYSIS VASCULAR ACCESS ULTRASONOGRAPHY

• Preoperative vascular ultrasound
• In addition to clinical assessment improves AVF
  outcomes in terms of patency
• Improves maturation and use of AVF for dialysis
• Intraoperative examination
• Confirm pre-op studies
• Assess the impact of fistula flow on the artery
  inflow
• Assess the flow in the fistula vein
• Evaluation of VA
• Measurement of access flow
• Detection of complications (stenosis, steal,
  thrombosis)

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Preoperative vascular ultrasound

• Clinical examination first!
• Patient is in supine position
• Non-dominant arm first
• Stable local conditions
• Start with vein mapping
• Continue with arteries

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VEIN MAPPING

• Apperance of the vein
• At the upper part of upper arm put tourniquet or
  cuff for blood pressure measurement inflated 70
  to 80 mmHg
• Trace cephalic vein from distal part of forearm
  toward cubital fossa
• Assess anatomy, size and suitability of upper arm
  cephalic vein
• Trace basilic vein from the wrist to its
  insertion to brachial or axillary vein
• Not useful for central veins

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VEIN MAPPING

• Examine all the veins for continuity, including
  major accessory branches, evidence of intramural
  or intraluminal thrombus or stenosis
• Measure internal diameter at different parts of
  veins and wall thickness
• After releasing tourniquet/cuff measure internal
  diameter - difference is distensibility (IID)

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VEIN MAPPING

• Measure the depth of the vein.
• Test changes of venous Doppler signal during
  deep respiration increasing of venous flow
  during inspiration - indirect sign for no venous
  outflow stenosis.
• Choose the most distal part of suitable vein.

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ARTERIAL EVALUATION

• Start artery assessment at the nearest place of
  suitable vein.
• Assess anatomy, quality of artery (radial,
  brachial or ulnar), luminal diameter, wall
  thickness and amount of calcification.
• ID 2 mm

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ARTERIAL EVALUATION

• Assess Doppler waveform, systolic velocity (SV),
  diastolic velocity (DV). Normal Doppler waveform
  is high resistance, triphasic with RI 1.

SV
DV
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ARTERIAL EVALUATION

• Consider reactive hyperaemia test with clenching
  the fist for 2 minutes or by pneumatic cuff
  inflator 20-30 mmHg above systolic pressure for 2
  minutes and calculate RI after releasing the
  fist.
• RI 0.7 or at least change HRF to LRF.

• Normal Doppler waveform of feeding artery for
  arteriovenous fistula or graft is low resistance
  with RI lt 1.

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POSTOPERATIVE USE OF ULTRASOUND

• To evaluate maturation or non-matured AVF
• To evaluate early or late AVF and AVG
  complications

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POSTOPERATIVE USE OF ULTRASOUND nonmatured AVF

• Test should be done 4-6 weeks after AVF creation
  if AVF is clinically non-matured
• B mode ultrasound provide diameter, depth and
  length of fistula vein and internal diameter of
  the feeding artery (should be increased.
• Brachial artery as inflow artery for upper arm
  vascular access flow measurement provides
  indirect measure of fistula flow (ID and TAV).

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POSTOPERATIVE USE OF ULTRASOUND nonmatured AVF

• Measurement of access flow
• It should be measured in a straight vascular
  segment (venous outflow not to very wide less
  than 7 mm)
• Segment should be at least 5 cm away from
  anastomosis
• Brachial artery is recommended 20 have high
  bracial artery bifurcation !!)
• Longitudinal axis of blood vessel (diameter) and
  TAV
• Modern US devices have special software for
  calculatinfg blood flow from ID and TAV

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POSTOPERATIVE USE OF ULTRASOUND nonmatured AVF

• The most common reason for low arterial inflow is
  juxta anastomotic stenosis or proximal stenosis
  of the feeding artery or outflow stenosis.

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POSTOPERATIVE USE OF ULTRASOUND nonmatured AVF

• Diagnostic criteria for hemodinamiucally
  significant stenosisi
• Increasing of RI in feeding artery
• Diameter narrowing (B-mode) by gt50
• gt2 fold increase of peak systolic velocity
• Post stenotic turbulence

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POSTOPERATIVE USE OF ULTRASOUND nonmatured AVF

• Ultrasound provides a good visualization of
  haematoma or seroma around fistula vein or graft,
  depth of graft and graft tissue incorporation.

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POSTOPERATIVE USE OF ULTRASOUND access
complications evaluation

• Should be used in conjunction with clinical
  examination to evaluate access dysfunction.
• The most common complication is outflow stenosis.
• Ultrasound provides visualisation of chronic
  thrombus within large aneurismal dilation when
  problems with needling are present.

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POSTOPERATIVE USE OF ULTRASOUND access
complications evaluation

• Steal phenomenon is more and more frequent,
  particularly in patients with forearm and upper
  arm AVFs and in patients with prosthetic straight
  or loop grafts.
• Assessment of the access-feeding artery by
  investigating the parts proximal and distal to
  the anastomosis.
• US sign for steal syndrome is change in flow
  direction.

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CONCLUSION

• Duplex ultrasonography is a useful tool to
  optimize vascular access care in hemodialysis
  patients.
• Appropriate equipment, local conditions and
  knowledge about haemodynamics before and after
  vascular access creation are obligatory.

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CONCLUSION

• Routine preoperative ultrasound in addition to
  clinical assessment improves AVF outcomes in
  terms of patency and use for dialysis.
• In case of access complications, after clinical
  evaluation, initial anatomic and functional
  assessment may be best performed by non-invasive
  duplex sonography, followed by other imaging
  methods, including intervention.

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THANK YOU FOR YOUR ATTENTION