Chapter 30: Hemodialysis Access Grafts and Fistulae Flashcards
The location where the artery and vein are connected or where the graft is connected to the artery or vein
anastamosis
A balloon-like dilation of the blood vessel of the artery or vein
aneurysm
a deliberate connection between a native artery and vein constructed with an end-to-end anastamosis, created to allow for hemodialysis acccess
arteriovenous fistula
a type of hemodialysis access that uses an interposing bicompatible synthetic tube connecting an artery to a vein to allow for hemodialysis access
arteriovenous graft
the audible sound caused by the high pressure pressure arterial flow of blood passing through a low-resistance venous structure such as an arteriovenous fistula or graft
bruit
a means to artificially cleanse the blood by removing by-products, waste, and fluid in patients with end-stage renal disease via a dialyzer machine
hemodialysis
also known as vascular access, is a surgically created connection between an artery and a vein to allow for the removal of toxic by-products from the blood via hemodialysis
hemodialysis access
a minimally invasive method for arteriovenous fistula created by means of readiofrequency energy that combines heat and pressure
percuteaneous fistula
a balloon-like outpuching of the access, often associated with repeated needle puncture, leading to loss of structural integrity
pseudoaneurysm
the palpable sensation of an arteriovenous fistula or graft caused by the high pressure arterial flow of blood passing through a low-resistance venous structure
thrill
posterior radial artery to cephalic vein
snuff box fistula
radial artery to cephalic vein
Brescia-Cimino fistula
Normal AVF characteristics
anechoic flow lumen free of intraluminal echoes
lumen fills wall to wall with color flow
low-resistive pulsatile flow without focal velocity elevation
Stenotic AVF characteristics
intraluminal echos
thickened walls
reduced flow lumen
disturbed color-flow patterns
elevated velocities in region of stenosis
occluded AVF characteristics
intraluminal echogenicity
loss of flow lumen
no flow
absent Doppler signal
The National Kidney Foundation Kidney Dialysis Outcomes Quality initiative recommends ____% of future hemodialysis access be constructuted with autogenous AV access
50
Goal of AVF or AV graft creation
provide repeared hemodialysis access while maintaining a low frequency of reinterventions and complication rates
An autogenous fistula should be created as _____ as possble in ______ arm.
distal
nondominant
Why is autogenous AVF creation the preferred finrst line therapy?
superior patency rates
lower rate of complication
surgically created anastamosis between any artery and vein
native AVF
Thr room should be kept comfortably warm to prevent _____
vasospasms
Acceptable diameter of an artery for fistula
> 25 mm
Why are arteries interrogated before AV procedure?
calcifications
intimal thickness
stenosis
compliance
The quality of the arterial wall determines the ____ of the artery to dilate and accomodate increased flow
capacity
Where is atherosclerosis most often observed in the upper extremities?
subclavian artery
In the diabetic patient where can you find atherosclerosis?
radial and ulnar arteries
Focal narrowing of vein at any level may prevent ______
fistula maturation
The basicilic vein needs to be greater than ___ cm in legtnth with adequate diameters for transposition
10
central venous occlusion doppler characteristics
loss of phasic flow, presence of a continuous wavefore
Routine unilateral upper extremity mapping should take __-__ minutes
30
40
Contraindications to upper extremity mapping
local infections
obtrustive dressing
open wounds
restricting patient positioning
The radial, ulnar, and brachial arteries need to have an arterial diameter greater than ___ mm.
20
bright white echoes along or within vessel walls
calcifications
Normal arterial Doppler spectral waveform
high resistive with a rapid upstroke, sharp peak, and low diastolic flow
Favorable diameter for AV creation
2.5 cm
Venous Doppler criteria from central veins
respiratory phasicity
cardiac pulsatility
augmentation
The goal of hemodialysis access evaluation
provide a durable means for vessul cannulation that is located distally in the limb; allows the option for creating of a more proximal access should distal AVF fail
frequently performed fistula; involves mobilizing distal cephalic vein at wrist and anastamosing it to distal radial artery in an end-to-side configuration
Brescia-Cimino fistula
connecting posterior branch of radial artert to cephalic vein
snuffbox fistula
requires vein to be transposed and juxtaposed to a distal artery (radial or ulnar) in order to creat AVF
medial location of forearm basilic vein
Most common upper arm access
brachial artery to cephalic vein fistula; created at or just distal to the antecubital fossa
Possible sites for arterial infolow of basilic transposition
brachial, radial, ulnar
Lower extremeity hemodialysis access sites
common femoral artery
superficial femoral artery
transposed great saphenous of femoral veinFi
Fistula maturation takes place __-__ weeks after creation of fistula
10-12
defined by a dilated cein, ,palpable thrill, audible bruit
Matured fistula
Flow rates are greater than ___ mL/min for fistulas that failed to mature
500
You should change system presets to ____ flow setting for hemodialysis access examination
high flow
Inflow artery supplying dialysis access waveform
low-resistance waveform with constant antegrade flow throughout cardiac cycle
volumetric flow calculation
time average velocity x area x 60
Hemodilaysis access examiantion takes about __-__ minutes
30
45
hypoechoic to anechoic depending on age
thrombosisb
bright white relfectirs within vessel walls
calcifications
valve protruding into vessel lumen; potentially a site for initmal hyperplasia formation
incompetent valve
Well function fulsta demonstrate PSV between ____-___ cm/s
150
300
EWll functioning fistulas demonstrate an EDV of ____-____ cm/s
60
200
Stenosis may be present if PSV is less than ___ cm/s
50
inflow artery blood flow characteristics
low resistance flow
increased PSC (30-100 mL/min)
pulsatile flow in outflorw vein
Expected flow through fistula
marked spectral broadening, continuous forward diastolic flow; high velocity
Account for ___% access-related complications
anastomotic and vein or graft stenosis
echogenic intraluminal lesions; luminal flow reduction on B-mode
outflow vein stenosis
high resistance signal, absent flow lumen, intraluminal echogenic thrombus
fistula or graft occlusion
Normal flow volume in a fistula
greater than 800 mL/min
mild-to-moderate stenosis in fistula
500-800 mL/min
severe stenosis in fistula
less than 500 mL/min
retrograde flow in artery distal to fistula or graft anastamosis
steal phenomenon
Occurs in 75-90% of patients after access creation
steal phenomenon
based on fluid dynamics, low resistance outflow vein draws antegrade flow from inflow artery and in addition “steals” retrograde flow from distal artery
steal phenomenon
symptoms of steal phenomenon
pain during hemodialysis
rest pain
weakness
paresthesias
tissue loss if advanced
cause of steal phenomenon
problem with high flow through fistula, insufficient distal collateral circulation, inflow arterial occlusive disease
Significant steal syndrome if digital pressure is less than ___ mm Hg
40
Significant steal syndrome if digital brachial pressure index is less than ___
0.6
novel minimally invasive percuteaneous AVF creation devices
EndoAVF
use magnetic catheters and radiofrequency energy to create in vivo anastomosis
EndoAVF
For an endoAVF an adequate perforating vein is needed at the ______
antecubital fossa
The WavelinQ EndoAVF system requires two access sites, the _______ and the ______ in the distal forearm
brachial artery
radial or ulnar vein
The Ellipsys Vascular Access System requires one single point of access, through a perforating vein into the ______
radial artery
The goal of the Kidney Dialysis Outcomes Quality Initiative was to increase and expand the creation of which of the following?
a. prosthetic hemodialysis access grafts
b. autogenous hemodialysis access fistulae
c. lower extremity hemodialysis access
d. central venous port access
b
What is the most common cause of maturation failure of dialysis access fistulae?
small or suboptimal veins
Which of the following should be included during the physical examination for preoperative artery mapping for dialysis fistula creation?
a. bilateral arm blood pressure measurements
b. pulse examination of brachial, radial, and ulnar arteries
c. Allen’s test for palmar arch assessment
d. all of the above
d
Which of the following is NOT a finding suggestive of a central venous stenosis or occlusion?
a. are edema
b. prominent chest wall veins
c. painful, cool, pale hand
d. presence of arm collaterals
c
Which of the following describes the proper patient positioning for upper extremity venous evaluation before fistula creation?
a. supine with arm elevated
b. supine or sitting with arm dependent
c. standing with weight held in arm to be examined
d. Trendelenburg with feet elevated
b
With what does standard protocol for evaluation of the upper extremity arteries and veins for fistula creation begin?
arteries of nondominant arm
All Doppler studies should be performed at an angle of ____ or less, even if actual velocities are not recorded to achieve adequate Doppler signals.
60 degrees
What is the acceptable minimum vein diameter for favorable fistula creation?
2.5 mm
Which of the following should venous Doppler signals from central veins NOT display?
a. respiratory phasicity
b. cardiac pulsatility
c. augmentation
d. continuous flow
d
The most common upper arm access is made between the cephalic vein and which artery?
brachial artery
What is a type of fistula created by connecting the posterior branch of the radial artery to the cephalic vein?
snuffbox fistula
Approximately how long should it take an autogenous fistula to mature?
8-12 weeks
During evaluation of the upper extremity either before or after fistula creation, the examination room should be kept warm to avoid what?
vasospasm
Which of the following is NOT included in a physical examination of a patient with a current AV fistula?
a. assessment of thrill
b. assessment for edema or redness
c. bilateral radial blood pressures
d. visual inspection for focal dilations and collateral veins
c
During duplex assessment of the hemodialysis fistula, what should Doppler settings be adjusted to detect?
high flow
Which of the following describes how volumetric flow is calculated?
a. time average velocity/PSV
b. time average velocity x area x 60
c. time average velocity x vessel diameter
d. PSV-EDV/PSV
b
What can remaining valve leaflets that project into the lumen of a fistula become a source for?
pseudoaneurysm development
A patient presents to the vascular lab for follow up evaluation of a dialysis fistula. Velocities within the fistula are 40 cm/s. What are these findings consistent with?
inflow artery stenosis
What should be the approximate normal volume flow in a fistula?
800 mL/min
The goal of arteriovenous access is to provide long-term hemodialysis access with a ____ frequency of reintervention and a low _____ rate.
low
complication
______ access has been the preferred first-line therapy because is has superior patency rates and lower complication rates compared to ________
autogenous AVF
prosthetic grafts and tunneled catheters
AV fistulas have higher long-term patency rates; however, they suffer from lower _______ rates and higher early _____ rates.
maturation
AVF thrombosis
Placement of central venous catheters, pacemakers, defibrillators, or prior mastectomy with lymph node dissection may _____ the creation of an arteriovenous hemodialysis fistula.
preclude
AV fistula creation is usually first attempted in the ______ upper extremity as far _____ as possible
non-dominant
distal
Atherosclerosis is uncommon in the upper extremities, but when it occurs, it most commonly affects the _____ artery.
subclavian
To maximally dilate the veins, a(n) ______ may be used either just below the antecubital fossa for forearm veins or at the axillary level for upper arm veins
tourniquet
Patency of veins should be confirmed both with transducer _____ and spectral Doppler waveforms.
pressure
A dilated, easily palpable, usable fistula with a flow rate of greater than 350 cc/min defines a fistula that has _____
matured
A partially or noncompressible vein suggests the presence of an occluding ______ within the vein lumen, making it ______ as an autogenous conduit.
thrombus
unusable
A Brescia-Cimino fistula is the most frequently created fistula and involves the ______ vein and the _____ artery at the wrist.
cephalic
radial
Because of its deep location, the ______ vein requires that is be transposed and juxtaposed to a distal artery to create an AV fistula.
basilic
While performing duplex assessment either preoperatively or after hemodialysis fistula placement, the examination room should be kept warm to avoid ______
vasospasm
To assess for edema, redness, presence of collateral veins, rotation of access sites, and focal dilations, the arm should be _______ by the technologist before duplex assessment.
physically inspected
Presence of perigraft masses, pseudoaneurysms, stenotic valves, and intimal flaps should be assessed during _____ imaging evaluation of a dialysis fistula.
B-mode
When stenosis is found, spectral Doppler velocities should be measured ____, _____, and _____ the area of interest.
proximal
distal
within
When measuring volume flow rates of a hemodialysis fistula, the ______ is used and is best measured over ____ cardiac cycles to obtain an accurate calculation.
time average velocity
3-4
As fistulas mature, they typically become tortuous and can become aneurysmal, thus requiring larger amounts of ___ to maintain proper skin contact over these surface irregularities
gel
If a hemodialysis fistula has a volume flow measurement less than 500 mL/min, this would indicate ____ in the fistula.
stenosis
When performing preoperative duplex evaluation for endovascular AVF creation, closer attention is paid to the ______ between the superficial and deep venous systems
tributaries
