Assessment of Av Fistula

7/30/2019 Assessment of Av Fistula

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ASSESSMENT OF

AV FISTULA


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AV access types

Fistula:

Formed by subcutaneous anastomosis of an

artery to an adjacent vein, allowing flow directlyfrom artery to vein.

Graft :

a tube made of prosthetic material bridges thegap between the feeding artery and vein


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AV fistula over Grafts : Why?

Lesser stenosis rates.

Lesser infection rates.

Simple surgical procedure, done on OPD

basis.

Thus avoiding/ markedly reducing

hospitalization and emergency

operations for complications


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Comparison of graft and fistula

outcomes in HD patients


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Comparison of graft and fistula

outcomes in HD patients


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GUIDELINES

KDOQI, & Fistula First initiative: Targeting

60 % use of AV fistulas in patients

beginning on HD, and 50 % fistula use inprevalent patients.


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HURDLES: Fistula Hurdle


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Hurdles OVERCOME by:

Early referral to nephrologist

Early access evaluation and construction of

access avoid central vein cannulation. Use of preop imaging of arterial & venous

system to maximize successful creation of

functioning fistula

Dedicated and trained vascular surgeon as part

of vascular access team.


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ANTICIPATE NEED FOR AV

access. In pts with progressive renal failure protect the veins

minimize venipunctures and catheter placement inforearm veins.

Avoid subclavian vein catherterization.

Avoid PICC.

Create AVF atleast 6 months prior to initiating HD.


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EVALUATION

Preop evaluation

For Maturation

For complication


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EVALUATION

PREOP Evaluation:

history

physical examination

imaging studies.


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Pt HISTORY

Dominant arm: To minimize negative

impact on quality of life, use of the

nondominant arm is preferred. History of previous central venous

catheter, History of pacemaker use :

associated with central venous stenosis


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Pt HISTORY

History of severe congestive heart failure:Accesses may alter hemodynamics and cardiacoutput.

History of arterial or venous peripheral catheter:Previous placement of an arterial or venousperipheral catheter may have damaged targetvasculature

History of diabetes mellitus: Diabetes mellitus isassociated with damage to vasculaturenecessary for internal accesses.


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Pt HISTORY

History of anticoagulant therapy or any coagulationdisorder: Abnormal coagulation may cause clotting orproblems with hemostasis of accesses.

Presence of comorbid conditions, such as malignancy orcoronary artery disease, that limit patients lifeexpectancy. Morbidity associated with placement andmaintenance of certain accesses may not justify theiruse in some patients.

History of vascular access: Previously failed vascularaccesses will limit available sites for accesses.


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EXAMINATION

Bp, arm girth, Allens test in both arms.

Arm edema, presence of collterals,

differential exterimity size central veinstenosis.

Look for evidence of central or venous

catheterization, trauma to arm, chest neck.


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Imaging studies

Routinely used

To select appropriate vessel and location


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Imaging studies

Doppler ultrasonography

Venography

Arteriography

Magnetic resonance


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DOPPLER ULTRASONOGRAPHY

To check arterial inflow.

To assess venous anatomy and patency prior to

AV fistula formation or graft insertion. To identify the presence of cephalic vein

branches needing ligation to prevent diversion of

flow from the fistula.

To study subclavian vein patency as stenosis

there leads to early failure of the fistula


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SIZE: lumen diameter:

feeding artery 2 mm

target vein 2.5 mm

NORMAL VEIN : lumen is echo free.

thin wall. Wall thickeningpathology.

valves may be seen

comprssible with min externalpressure.


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VEIN DILATION TEST: 50% increase in

internal diameter of vein after proximal

occlusion is associated with a good fistulaoutcome.


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ARTERIAL DILATION

TEST: Pulse contour of

artery is normally

triphasic.

Clench fist for 2 mins and

then open it during

hyperemic phase the

pulse contour will bebiphasic - adequate

arterial dilatation.


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VENOGRAHY: Indications

Extremity edema

Presence of collaterals

Differential extremity size

Current or previous subclavian catheter

placement of any type in venous drainage

of planned access


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VENOGRAHY: Indications

Current or previous transvenouspacemaker in venous drainage of planned

access Previous arm, neck, or chest trauma or

surgery in venous drainage of plannedaccess

Multiple previous accesses in an extremityplanned as an access site


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Arteriography: indications

Diminished pulses in desired extremity

BP difference of > 20 mm Hg between

arms.


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Assessment of the New

AVF for Maturity


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Fistula Maturation

Definition: Process by which a fistula becomes

suitable for cannulation (ie, develops adequate

flow, wall thickness, and diameter) Rule of 6s: In general, a mature fistula should:

Be a minimum of 6 mm in diameter with discernible

margins when a tourniquet is in place

Be less than 6 mm deep Have a blood flow greater than 600 mL/min

Be evaluated for nonmaturation 46 weeks after

surgical creation if it does not meet the above criteria

National Kidney Foundation.Am J Kidney Dis.2006;48(suppl 1):S1-S322.


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During AVF Maturation Process

Look, listen, and feel the new AVF atevery dialysis treatment

After the scar heals, begin assessing AVFusing a gentle tourniquet placed high inthe axilla area

Instruct patient to start access exercises

after healing (check with surgeon first) Document patient education as well as

condition and maturation of the AVF


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During Maturation

Feel for strong thrill at arterial anastomosis

Listen for continuous low-pitched bruit


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During Physical Examination

Assess AVF for complications

Thrombosis

Stenosis

Infection

Steal syndrome

Aneurysms

Select cannulation sites


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Fistula Maturation

What diagnostic tools or techniques can

be used to determine if an AVF is ready

for cannulation?


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Diagnostic Tools/Techniques toDetermine If an AVF Is Ready

Duplex Doppler study

Physical exam by the:

Nephrologist

Nephrology nurse

Surgeon

Angiogram (fistulogram)


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Best Tool/Technique?

Physical Exam!

Look, Listen, and Feel

Use Your:

Eyes

Ears

Fingertips


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Assessment of the AVF

for Complications


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Look for Complications

Changes in Access

Redness

Drainage Infection Abscess

Cannulation sites

Aneurysms

Changes in Access

Extremity

Skin color

Edema Small blue

or purple

veins

Hematoma

Bruising

Distal Areas of Access

Extremity Hands/Feet:

Cold

Painful StealNumb syndrome

Fingers/Toes:

Discolored

Central

oroutflow

vein

stenosis


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Stenosis

Harbinger of

thrombosis.

Reduces blood flowrate underdialysis.

Cause: fibrosis

following needle stick

injuries, abscess,pseudoaneurysm.

Stenosis


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Observe Access Extremityfor Stenosis Before the patient has needles inserted

Make a fist with access arm dependent;

observe vein filling

Raise access arm; entire AVF should flatten/

collapse if no stenosis/obstruction

If a segment of the AVF has not collapsed,

stenosis is located at junction betweencollapsed and noncollapsed segment

Instruct patient to perform this at home


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Stenosis

An increase in the intensity of the thrill, or

the pitch of the bruit as one moves the

finger/ stethescope along the midportion ofthe draining vein implies stenosis.


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Other methods of predicting

stenosis: MEAURING ACCESS

FLOW

DIRECT: Indicator dilution method

DopplerMRA

INDIRECT: serial measurement of intra

access pressure.


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Access flow measurements.

Flow through AV fistula averages 500-800

ml per min.

KDOQI reccomends to intervene if flowrate is < 600 ml/min, or there is decrease

in flow rate by > 25% over the preceding 4

months.


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INTERVENTION FOR STENOSIS

PTCA or revision surgery in a pt with >50% stenosis with 1 or more of following:

abnormal physical examination previous h/o thrombosis

decreasing access flow.

elevated or increasing intra accesspresure.


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Ischemia in a limb bearing AV

acess Ischemia distal to AVF can occur any time.

Incidence 2-5 %

Common in : DM, elderly, H/o CAD/PAD.

Arm fistulas.


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Vascular AccessInduced

Ischemia C/F: numbness, tingling, pain, motor

weakness

Signs: changes in skin color, temperature,loss of sensation, loss of motor fumction,

or loss of distal arterial pulses, and

development of arm edema whencompared to other side.


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Vascular AccessInduced

Ischemia Grade 1: pale/blue or cold hand without

pain

Grade 2: pain during exercise or HD

Grade 3: ischemic pain at rest

Grade 4: ulceration, necrosis, and

gangrene


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DIAGNOSING ISCHEMIA

Physical examination alone is inadequate.

Additional noninvasive testing with

measurement of digital pressures andcalculation of the digit to brachial index,transcutaneous oximetry, ultrasound offorearm arteries, and access blood flow

measurement are important steps in thediagnosis and decision-making process.


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TO CONCLUDE:

Vascular access created with minimal delay.

Have a functional fistula prior to initiate HD.

Minimize CV catheter usage. A multidisciplinary approach to access creation

and maintenance, involving nephrologists,interventional radiologists, access surgeons, and

dialysis nurses, is mandatory to meet the burdenof HD vascular access on health care facilitiesand costs


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THANK YOU


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REFERENCES

Dialysis access: current practice

Comprehensive Clinical Nephrology

Hand Book of Dialysis

Current Management of Vascular Access: Review article-Clin J AmSoc Nephrol2: 786800, 2007.

KDOQI 2006 guidelines

Fistula first initiative guidelines.

Assessment of Av Fistula

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