Hemodialysis sccess grafts and fistulas Flashcards
Why was hemodialysis created?
to sustain patients with end stage renal disease
hemodialysis removes? (4)
- waste products
- creatinine
- urea
- excess water
Role of sono pre-operative?
Assess arterial inflow and to determine the suitability of efferent(outflow) veins for hemodialysis access creation
role of solo post-operatively?
- Assess fistulas and grafts for defects, stenosis or occlusion
- Evaluate the access for aneurysms,pseudoaneurysms and perigraft abscess
Indications for the exam?
Pre-op assessment Distal limb ischemia Absence of palpable fistula “thrill” Peri-graft fluids or mass Poor dialysis Elevated pressures during dialysis Access recirculation of 12% or greater Unexplained urea reduction ratio <60% Difficult cannulation or thrombus aspiration
Types of access-3 major types?
1-Central venous catheter
2-synthetic AV bridge graft
3-primary AV fistula
- An access creates a way for blood to be removed from the body, circulate through the dialysis machine, and then return to the body at a rate that is higher than can be achieved through a normal vein.
- Other names for access include a fistula or shunt
Central venous catheter?
- IJV or subclavian vein are used as the insertion point
- Temporary-short term solution
- Sometimes tunneled under the skin to be less obtrusive and for easier access
What is a Primary A-V fistula?
- a surgical procedure that creates a direct connection between an artery and a vein
- This is often done in the lower arm, but can be done in the upper arm as well
- Preferred type of vascular access
- Sometimes called-”native” access fistula
How is primary A-V fistula created?
- Usually created in the non-dominant arm
- Called Brescia-Cimino fistula
- Radial artery to Cephalic vein fistula is most common
- Brachial artery to Basilic vein is also common
- AVF are autogenous and known for long term patency and low complication rate
- AVF must be allowed to mature prior to use otherwise adequate flow volume may not occur
Brescia-cimino fistula?
Side to side anastomosis
What occurs when the A-V fistula has matured?
- superficial efferent vein is used for dialysis puntcture
- vein becomes lumpy due to increased intraluminal pressure
Why are flow volumes difficult to obtain in the efferent vein?
due to inconsistent vein diameter
Synthetic bridge graft?
- used when patients veins are not suitable for a fistula
- surgeon used a flexible rubber tube to create a path between an artery and vein
- needles used for hemodialysis are placed into the graft material rather than the patient’s own vein
Synthetic access graft?
- placed?
- used for?
- used when?
- helpful when?
The synthetic tube graft is placed between an artery and a vein
It is used for dialysis puncture
Used when veins are not adequate
Useful when fistulas have failed
How many patients are not candidates for AVF?
50%
What are synthetic access grafts made of?
Teflon (gore-tex0
Locations used for grafts and fistulas?
- usually in the forearm
but when this fails other locations used are:
- Brachial A to Basilica V
- Subclavian A to Jugular v
- Femoral A to Long saphenous V
Complications of grafts?
thrombus within the graft
Graft and fistula complications- stenosis locations?
- proximal and distal anastomosis
- within the graft
- in venous outflow tract due to intimal hyperplasia or thrombus
Graft and fistula complications? (5)
- thrombosis/occlusion
- arterial steal
- aneurysms and pseudoanurysms
- Elevated right heart pressure
- infection (mostly with synthetic grafts)
Hemodialysis feeding artery waveform?
monophasic with large diastolic component
Hemodyalysis anastomosis waveform?
perivascular tissue vibration; turbulent flow over a long stretch
hemodyalysis draining vein waveform?
pulsatile flow- arterialized
hemodyalysis volume of flow?
> 500 mL/min
Hemodialysis- sono evaluation?
- probe
- what to evaluate (5)
- probe: A high resolution linear probe with > 9MHz
Evaluate:
- The arterial anastomosis
- The graft body
- The venous anastomosis
- The draining vein
Doppler graft protocol ( 5)?
- 2 cm cranial to the arterial anastomosis within the feeding artery
- 2 cm caudal to the venous anastomosis within the graft
- At the arterial and venous anastomoses
- Mid graft
- A PSV ratio is calculated at the anastomosis and at any visible stenosis
Abnormal doppler results?
- A venous anastomotic or draining vein stenosis with a PSV ratio >2 is classified as > to 50% diameter reduction
- A stenosis with a PSV ratio > 3 indicates a 75% stenosis
Arterial steal?
- An arterial steal distal to the arterial anastomosis occurs when the venous outflow from the graft exceeds the capacity of the inflow artery
- This causes the graft to “steal” blood from more caudal portions of the extremity
- This can cause symptoms of arterial insufficiency,particularly during dialysis
How to assess for arterial steal?
- Doppler spectral waveform is obtained from the radial artery caudal to the graft insertion-usually at the wrist
