Week 4 Part 3 Flashcards
Who is hemodialysis for?
those with end stage renal disease
What does hemodialysis do?
removes waste products, creatinine, urea and excess water
What do sonographer’s look for post-operatively for hemodialysis?
assess fistulas and grafts for defects, stenosis or occlusion
evaluate access for aneurysms, PSA’s and perigraft abscess
What are some indications for the exam?
Pre-op distal limb ischemia abscence of palpable fistula "thrill" peri-graft fluids or mass poor dialysis elevated pressures during dialysis assess recirculation of 12% or greater unexplained urea reduction ratio <60% difficult cannulation or thrombus aspiration
What are the types of access? (3)
central venous catheter
synthetic AV bridge graft
primary AV fistula
What are other names for access? (2)
fistula
shunt
What’s used for the insertion point for a central venous catheter?
IJV or SCA
temporary
Where is a primary AV fistula done on the body?
lower arm or upper arm
Primary AV fistula:
surgical procedure that creates a direct connection b/w artery and vein preferred type "native" (racist) access fistula non dominant arm long term and low complication
What is another name for primary AV fistula?
Brescia-Cimino fistula
What are the common connections for AV fistula’s?
radial A to cephalic vein (most common)
brachial A to basilic vein
When the fistual is created and has matured, the __________ _________ _____ is used for dialysis puncture.
superficial efferent vein
becomes lumpy b/c of intraluminal pressure
Synthetic bridge graft:
surgical procedure where a flexible rubber tube is put in to create a path between an artery and v
graft sits under skin
may be straight or looped
Synthetic bridge grafts are used in the same way as a fistula except:
the needles used for the hemodialysis are placed into the graft material rather than patient’s own vein
When are synthetic access grafts used?
when veins are not accurate
fistulas have failed
50% of candidates are not eligible for AVF
Grafts have a shorter duration and lower patency rates than AVF. True or false
True
What are access sites for synthetic access grafts?
usually in forearm but if they fail then they move proximal
brachial A to basilic V
subclavian A to jugular V
femoral A to long saph V
What are some complications of grafts and fistulas
thrombus/occlusion
locations of stenosis: proximal and distal anastomosis, within graft, and in venous outflow tract due to hyperplasia or thrombus
What are some complications of grafts and fistulas con’t
arterial steal distal venous hypertension aneurysm and PSA (common) elevated right heart pressure due to excessive graft flow infection (mostly with synthetic grafts)
What are the flow findings for normal vessels involved in hemodialysis?
feeding a= monophasic w/ large diastolic component
anastomosis= perivascular tissue vibration; turbulent flow over long stretch
draining vein= pulsatile flow-arterialized
What’s the normal volume of flow?
> 500ml/min
What type of probe is used for evaluation of grafts?
> 9MHz
What do we evaluate once the graft is in?
artery feeding graft, anastomosis, graft body, venous anastomosis and draining vein
What are some abnormal Doppler results
venous anastomotic or draining vein stenosis with a PSV ratio of >2 is classified as >50% diameter reduction
stenosis with a PSV ratio >3 indicates a 75% stenosis
this would need to be confirmed with angiography
The IJV and SCV should be evaluated for respiratory phasicity and transmitted cardiac pulsations. True or false
True
It’s normal to see monophasic flow in the SCV with a stent. True or false
True– assuming no stenosis
Arterial steal:
occurs when the venous outflow from the graft exceeds the capacity of the inflow artery
causes graft to “steal” blood from more caudal portions of extremity
causes symptoms of arterial insuffiency
A complete steal is the direction of flow is reversed caudal to the graft. True or false.
True
Partial steals the spectral waveform is triphasic. True or false
False– biphasic
What corrects arterial steal?
graft litigation
