Techniques of Ultrasound Evaluation of Vascular Access by 4BogQKK

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									      Techniques of
Ultrasound Evaluation of
     Vascular Access

            Marko Malovrh
  University Medical Centre Ljubljana
      Department of Nephrology
          Ljubljana, Slovenia
 Vascular access (VA) is the “life
 line”of dialysis pts.

 VAis 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
Grey scale   Doppler




Power        Pulse
Doppler      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                    A



    distensibility (IID)
                                                                             50 mmHg
                                                                             2 minutes




                                                         B




                                              IID (%)= [Bx100/A] -100   12
                  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).
                                 SV
    Normal Doppler waveform is
    high resistance, triphasic        DV

    with RI ≥ 1.




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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 < 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 >50%
         >2 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

1.   Duplex ultrasonography is a useful tool to
     optimize vascular access care in
     hemodialysis patients.



2.   Appropriate equipment, local conditions
     and knowledge about haemodynamics
     before and after vascular access creation
     are obligatory.

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               CONCLUSION
3.   Routine preoperative ultrasound in addition
     to clinical assessment improves AVF
     outcomes in terms of patency and use for
     dialysis.

4.   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


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