38051565 Hemodialysis Access

8/7/2019 38051565 Hemodialysis Access

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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

38051565 Hemodialysis Access

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