Graft Evaluation

Question 1

Hemodialysis

Answer 1

Patients with end stage renal disease filter their blood through hemodialysis. Blood is cleansed by dialyzer.

Access to circulation is done via:
Avf
graft
Central venous dialysis catheter.

Question 2

Evaluating patient for hemodialysis

Answer 2

The non dominant forearm is assessed first.

Radial and ulnar artery evaluated and meas >2mm

Tourniquet is suggested to meas veins

Cephalic and basilic veins evaluated and measured.

Subclavian and Internal jugular evaluated for stenotic lesions.

Question 3

Native AVF

Answer 3

Own vessels are being used.
AVF surgically created
Direct anastomosis between artery and vein.

Want to see high volume of blood flow going through the fistula. Normal vel 100-140vm/s, 60-200cm/s in diastoli.

Place in forearm

Have to wait to mature before using.

Question 4

Evaluating AVF

Answer 4

PSV obtained 2cm cephalad to anastomosis in the feeding artery.

Types:

1. Radial-cephalic fistula at wrist.
2. Brachial-cephalic fistula at antecubital fossa
3. Brachial-basilic vein transposition.

Question 5

Graft

Answer 5

Used when AVF is not possible.
Graft is used to connect artery and vein. Can be a prosthetic material or a vein can be used.

Artificial grafts are seen in 2d as a parallel echogenic line.

Types: 
Forearm looped graft 
Upper arm straight graft 
Axillary loop graft 
Graft in groin.

Question 6

Duplex graft evaluation

Answer 6

Use hand to feel thrill or pulsatility of graft or fistula. Will feel like buzzing bees underneath fingertips.

Locate and record arterial and venous anastomosis.
Arterial and venous limb of graft.
And graft prox to distal

PSV 2cm prox to arterial anastomosis, prox anastomosis, mid graft, and distal anastomosis.

PSV ratio = PSV at stenosis / PSV outside stenosis

PSV ratio calculated. > or = 2.0 = 50% diameter stenosis.
PSV ratio > or = 3.0 = 75% diameter stenosis.

Evaluate flow direction to check for steal syndrome. Sometimes grafts can steal blood from hand. Must evaluate direction of blood flow in graft and vessels attached to it.

Question 7

Central venous dialysis catheter

Answer 7

Used when AVF or graft not an option or when needed immediately.

Flexible synthetic tube placed in large chest vein. Can be used while waiting for avf or graft.

Each cath has 2 openings called ports or limbs. One port takes blood from body to be cleaned. And the other returns the clean blood.

Cath can be used immediately once in vein. A fistula would have to wait to mature.

Downside: increase risk of infection and damage to the vein where inserted.

Question 8

Note any anomalies

Answer 8

Blood clots, stenosis, pseudoaneurysm, aneurysm, hematoma (can compress venous outflow)

Question 9

Bypass grafts

Answer 9

1. CABG coronary artery bypass graft
2. Femoropopliteal bypass graft
3. Femorotibial bypass graft
4. Femoral to femoral bypass graft aka fem to fem: bypass iliac disease.
5. Aorta-femoral bypass graft: used to bypass diseased aorta and or iliac arteries.
6. Axillary-femoral bypass graft: rare. Bypasses aorta.
7. Reversed vein graft (GSV)
8. In Situ vein graft (also GSV)

Question 10

GSV

Answer 10

MC mapped for bypass grafts
Great saphenous vein mapping

Other vessels may be evaluated: SSV, cephalic vein, basilic vein, radial artery.

Mapping- follow vessel from origin to termination and measure at specific spots around the way.

Some vein mapping require you to mark veins with a marker

Look for thrombus. Make note if GSV is a collateral pathway. AP 2-3mm.

Question 11

Radial artery harvest

Answer 11

Advantage. Size doesn’t vary as much. And size is good for bypass use.
Thicker walls with less hyperplasia
GSV May not be available to use due to a previous harvesting.

Palmar arch patency exam also performed.

Question 12

Radial artery harvesting contraindications

Answer 12

Ischemic digits
Raynauds 
Ipsilateral atherosclerosis of arm
Sclerotic, atretic or occluded radial a
Incomplete palmar arch in hand
Subclavian artery disease