ARTERIAL - HEMODIALYSIS ACCESS GRAFTS

hemodialysis av fistula/access graft

surgically created connection between an artery and vein for hemodialysis

hemodialysis use

removes creatinine, urea and water from the blood of patients w end-stage renal failure

in the pre op assessment for hemodialysis, vessels are measured

inner to inner

av fistula for dialysis

direct connection between artery and vein that is created to allow access point for dialysis port

av graft for dialysis

synthetic tube is connected to artery and vein to allow access point for dialysis port

vessel diameters needed for avf/av graft

• native vein >2.5 mm for avf

• native vein >4 mm for av graft

• native artery >2 mm

requirements for veins before avf/graft

straight course, located within 1 cm of skin surface, free of obstruction

before avf/graft, distal radial artery psv should be _____ cm/s

over 50

what can be performed to assess the feeding artery for appropriate increase in arterial diameter/vessel compliance for fistula placement

reactive hyperemia testing

reactive hyperemia testing for avf/graft

• clenching fist increases distal resistance and pulsatility in prox arteries

• clench held for 2 min

• release fist, resistance should drop distally, flow increases in hand

• resistive index is measured, anything over .7 indicates feeding artery will not work

avf/grafts are usually put in the patient’s _____ arm

nondominant

most common avf

brescia-cimino

brescia-cimino

radial artery to cephalic vein @wrist

snuffbox fistula

radial artery is connected to the cephalic vein at the distal wrist (snuffbox: triangular depression at the lateral aspect of dorsum of hand)

brachiocephalic avf

brachial artery and antecubital vein at elbow

brachiobasilic avf

brachial artery and basilic vein at elbow

radiobasilic avf

radial artery and basilic vein at forearm

when is a synthetic graft used

when native veins are inadequate or avf has failed

drawbacks of synthetic graft

shorter duration of use and lower patency rates than avf

most common type of synthetic graft

straight synthetic, looped synthetic

straight synthetic graft

brachial artery to basilic vein in upper arm

looped synthetic graft

brachial artery to antecubital or cephalic vein at elbow, loop extends distally to wrist

t/f: blood pressure can be taken on an arm with an avf or graft

false

#1 site of stenosis in av graft

venous anastomosis

how should the patient be positioned for evaluation of avf/graft

• patient seated or supine w arm extended and supported

• arm externally rotated and placed at a 45 degree angle to the body

venous outflow prox to an avf/graft becomes

pulsatile/turbulent due to inflow of arterial flow distally

arterial inflow prox to an avf/graft should be

low resistance w increased diastolic flow

normal psv within graft

100-400 cm/s

normal edv within graft

60-200 cm/s

velocity ratio of _____ at anastomosis is abnormal

over 3.0

if the flow velocity doubles between two points in a graft what is suspected

significant stenosis

what is suspected if the arterial inflow to a graft is triphasic

occlusion

if the venous outflow vein demonstrates a loss of spontaneous flow and phasicity what is suspected

stenosis/obstruction

how is volume flow measured in an avf/graft

1. obtained in a straight vein segment

2. measure diameter of vein in area of flow sampling

3. doppler measurement obtained by opening the sample volume size to include all flow from anterior to posterior wall, trace waveform

flow volume of _____ indicates stenosis

under 500 ml/min

flow volume of _____ indicates chf

over 1200 ml/min

in what kind of avf/graft does steal syndrome most commonly occur

radiocephalic fistula

what will flow look like in a radiocephalic fistula with steal syndrome

distal to the fistula, the ulnar artery will be antegrade and the radial artery will be retrograde (blood travels to hand via ulnar, moves through palmar arch to exit the hand in the radial artery)

what is steal syndrome in the avf/graft most commonly caused by

high volume flow but can sometimes be inflow stenosis