URR Hemodialysis Access Graft

Question 1

what is a hemodialysis AV fistula/graft

Answer 1

surgically created connection between A and V for hemodialysis
-AV fistula is direct connection between A and V that is created to allow access point for dialysis port
-AV graft uses synthetic tube to connect and A to vein to allow access point for dialysis port

Question 2

what is hemodialysis?

Answer 2

removes creatinine, urea H2O from blood of patients in end stage renal failure

Question 3

the closer the fistula to the heart, the greater teh risk of developing what?

Answer 3

heart failure
-this is why they are placed at the antecubital fossa and not the shoulder
-the vessels at the antecubital fossa offer the minimum sizes needed for the native vessels, while increasing the distance from the heart

Question 4

what is included for pre op assessment?

Answer 4

-eval native vessels for selecting graft
-obtain brachial pressures
-brachial and radial eval for stenosis
-vessel diameters measured from inner wall to inner wall
-veins should be evaled to determine if they are straight and located 1 cm of skin surface
-requires allen test prior to graft harvesting and insertion
-distal radial A should demonstrate >50 cm/s
-reactive hyperemia can be performed to assess the feeding A for appropriate increase in arterial diameter and vessel compliance for fistula placement and maturation

Question 5

what is reactive hyperemia?

Answer 5

-clenching the ipsilateral fist during an upper extrem doppler eval should increase distal resistance and pulsatility in the prox As (high resistance, triphasic flow)
-clenching should be held for 2 mins
-upon release of the clenched fist, distal resistance drops significantly and flow increased to the hand (low resistance, monophasic flow)
-RI is measured and a valve over .7 indicates the feeding A will not work for a successful AVF creation

Question 6

vessel diameters measured from inner wall to inner wall for pre op assessment?

Answer 6

-requires native vein >2.5 mm for AVF
-native vein > 4 mm synthetic graft
-native artery >2 mm
-tourniquet can be placed on the upper arm to dilate the veins to assess max diameter

Question 7

indications for post op AVF/AVG eval

Answer 7

-dialysis equipment provides info regarding the functionality of the graft
-palp mass
-significant hand pain
-venous HTN
-water hammer pulse
-decreased or absent thrill; patent graft will produce a thrill - not an indication of normal or abnorm, just patency

Question 8

what is the water hammer pulse

Answer 8

thumping pulse palpated w/ an acute occlusion of a graft; an occluded graft must be replaced, CANNOT be recanalized

Question 9

what is the brescia-cimino AVF/AVG?

Answer 9

-most common type
-radial artery to the cephalic vein at wrist

Question 10

what is the suffbox fistula

Answer 10

-anatomical suffbox is also called the radial fossa
-triangular depression on the lateral aspect of the dorsum of the hand
-radial A, a branch of the radial nerve, and cephalic vein are found in the snuffbox
-radial A is connected to the cephalic V at distal wrist
-because the artery courses directly over the vein in this location, little vessel movement is required during surgery

Question 11

what is the brachiocephalic AVF/AVG?

Answer 11

brachial A and antecubital V at elbow

Question 12

what is brachiobasilic AVF/AVG?

Answer 12

brachial A and basilica V at elbow

Question 13

radiobasilic AVF/AVG?

Answer 13

radial A and basilic V in the forearm

Question 14

what is a synthetic graft?

Answer 14

-used when native veins are inadequate or an AVF has failed
-PTFE gore-tex made of synthetic polyester
-shorter duration of use and lower patency rates than AVF

Question 15

straight synthetic graft?

Answer 15

most common; brachial A to basilic V in upper arm

Question 16

looped synthetic graft?

Answer 16

most common; brachial A to antecubital or cephalic V at elbow; loop extends distally to wrist

Question 17

what should not be taken on an arm with a dialysis graft/fistula present?

Answer 17

blood pressure

Question 18

protocol for AVF/AVG

Answer 18

-patient seated with arm extended and supported
-arm externally rotated and placed at a 45 degree angle to the body
-manually palpate the graft for the expected “thrill”
-AVF has single anastamosis site; eval inflow A prox and dist to the fistula, fistula, outflow vein prox and distal to the fistula

Question 19

1 site of stenosis in AVF/AVG

Answer 19

venous anastamosis
(more common in graft than AVF)
-outflow vein

Question 20

how does flow look in AVF/AVG?

Answer 20

-venous flow prox to an AVF or AVG becomes pulsatile and turbulent due to the inflow of arterial flow distally
-A flow prox to AVF should be low resistance w/ increased diastolic flow
-norm flow PSV within the graft should be 100-400cm/s
-EDV should be 60-200 cm/s

Question 21

abnorm findings on AVF/AVG

Answer 21

-graft stenosis suspected w/ velocities greater than 400 cm/s
-velocity ratio= PSV at stenosis / PSV prox to stenosis
-ratio at a stenosis > 2.0 is abnorm
-ratio at the anastomosis > 3.0 abnorm
-if flow velocity doubles between two points in the graft, significant stenosis is suspected
-increase in flow velocity between two segments of 100% or more is abnormal
-if inflow A demonstrates a triphasic waveform, graft occlusion is suspected
-if venous outflow demonstrates loss of spontaneous flow and respiratory phasicity, stenosis or obstruction of the vein is suspected

Question 22

how to do volume flow

Answer 22

-obtained in straight vein segment, midgraft/fistula is preferred
-measure the diameter of the vein in the area of flow sampling
-measurement obtained by opening sample volume size to include all flow from anterior wall to posterior wall
-abnorm flow volume <500 ml/min indicates stenosis
->1200 ml/min indicates CHF

Question 23

due to arterial flow hitting venous wall, causes damage to the lining resulting in what?

Answer 23

hyperplasia

Question 24

complications?

Answer 24

-#1 cause of hemodialysis graft failure is thrombosis of the graft
-stenosis/occlusion
-aneurysm of the graft
-pseudoaneurysm caused by needle puncture for dialysis
-can cause CHF due to increased flow in venous return to heart
-portion of extrem distal to graft may suffer from ischemic symptoms due to steal syndrome
-infection

Question 25

what is steal syndrome

Answer 25

-most commonly occurs in a radiocephalic fistula
-ulnar A will be antegrade and radial A will be retrograde
-blood travels from the ulnar A into the hand and moves through the palmar arch to exit the hand in the radial A
-caused by high volume flow in most cases, but can also occur w/ inflow stenosis
-both cause flow to be “sucked up into” the radial A and into the outflow vein
-PVR or PPG assessment of the affected digits should be compared to the unaffected digits of the opposite hand
-diminished radial pulse on palpation
-symptoms include pain, polar sensation, paresthesia, finger/brachial index <.8, cyanotic finger tips
-symptoms increase w/ use of the arm
-must be treated by clearing the inflow stenosis or removing the high volume fistula completely in order to prevent permanent damage to the hand/fingers

Question 26

what does steal syndrome flow look like?

Answer 26

-inflow A w/in the 2 cm prox to the fistula anastamosis site
-inflow A w/in the first 2 cm distal to the fistula anastamosis site
-this waveform is used to diagnose steal syndrome, if flow is retrograde in the distal radial (inflow) A, then flow is moving from the ulnar A through the palmar arch and cephalad toward the radial A/Fistula
-fistula at the confluence of the artery and vein
-outflow vein at multiple locations along the arm, above and below the fistula