arterio venous fistulae using grafts

ARTERIO-VENOUS

FISTULAE USING GRAFTS

BY

DR. MUHAMMAD SAIFULLAHPOST-GRADUATE RESIDENTDEPARTMENT OF UROLOGY AND RENAL TRANSPLANTATIONPMC/ALLIED HOSPITAL, FAISALABAD.

INTRODUCTION» Establishing and maintaining

hemodialysis access is a cornerstone of long term renal replacement therapy.

» Vascular access is an

ACCESS TO LIFE….

» 1944…… WJ Kolff designed the first practical dialysis machine but was only used for Acute Renal Failure because of

repeated cutdowns.

» 1960…… Scribner, Dillard, and Quinton introduced the Teflon-Silastic arteriovenous (AV) shunt.

» 1966…… Subcutaneous AV fistula by Brescia, Cimino, Appel and Hurwich.

» 1969 …… Autogenous Saphenous Vein Loop was introduced by May, Tiller, Johnston, Stuart & Sheilds.

» 1976…… Introduction of polytetrafluoroethylene (PTFE) for bridge fistulae.

ARTERIO-VENOUS GRAFT» An AVG is created by joining a vein

to the artery using an biological (e.g. Long Saphenous Vein, Bovine vein) material or synthetic (e.g. PTFE).

» Also known as “BRIDGE FISTULA”

IDEAL AV Graft» Easy to handle.» Non-thrombogenic.» Immunologically inert.» Resistant to infection and puncture

trauma.» Able to retain tensile strength. » Manufactured at a reasonable cost.

Patency AVF vs AVG

AV Graft Formation Vs AVF

Why grafts are required?» Repeated thrombosis after insertion of

shunts.» Poor flow in AV Fistulae.» Rejection of initially successful renal

transplant with thrombosis of fistula.

AV Grafts

Biological Grafts

Human

Long Saphenous Vein Autografts

Denatured homologous vein allograft.

Cryopreserved saphenous vein

Human umbilical vein

Bovine Heterograft

s

Bovine Carotid Artery

Bovine ureter vascular graft

Bovine mesenteric vein

Sheep Collagen Grafts

Biohybrid and bioresorbable prostheses

Synthetic Grafts

AV Grafts

Biological Grafts

Synthetic Grafts

Dacron Graft

PTFE Graft

Standard

Stretch Expanded (ePTFE)

Polyurethane

Polyether-urethaneurea (Vectra graft)

Biological grafts (Human)1. Autogenous great saphenous vein graft

» Taken between groin and knee» disappointing results with patency rates of 20%

at 2 years.» Other sites include long saphenous V. from

ankle to knee, Cephalic vein from wrist to elbow, Cephalic vein from Elbow to shoulder or external jugular veins.

2. Denatured homologous vein allograft.3. Cryopreserved Saphenous vein.

Biological grafts (Human)4. Umblical Vein Graft.

» Successful dialysis for a period of 2 years» Also prone to infection.» Difficult to use and handle.

» Bovine carotid artery (removed from calf and treated with FICIN to remove elastic and muscular material….. A tube of collagen is left which is used for graft.

» Bovine ureter vascular graft (for patients with a history of multiple failed synthetic grafts).

» Bovine mesenteric vein 1. Obtained by a patented process of gluteraldehyde

cross linking and gamma radiation)2. Physiological properties similar to those of the

human saphenous vein due to its high elastin to collagen ratio.

Biological grafts (Bovine)

» Sheep collagen grafts –Formed from gluteraldehyde-tanned bovine collagen grown around a polyester mesh.

» Biohybrid and bioresorbable prosthesis, Graft pretreatment with endothelial cell culture, methods of affixing antibiotics, anticoagulants and growth factor to graft surfaces.

Biological grafts (Bovine)

» DACRON: The commonly used synthetic grafts include

Dacron. The fibrillar structure of Dacron was expected to encourage tissue ingrowth and provide greater durability for recurrent cannulation. Not used on a wide scale.

Synthetic grafts

Synthetic graftsPTFE» Fluorocarbon polymer» Prosthetic graft of choice» Stretch expanded PTFE

(ePTFE) is preferable to standard PTFE.

» Lower risk of disintegration with infection

» Low thrombogenicity» Low tissue reactivity» Prolonged patency» Improved surgical handling

Synthetic grafts» POLYURETHANE

SITES FOR AV GRAFT

TECHNIQUEShould be used to connect the brachial artery to a distal vein in the forearm….. Ideally

Or Connect radial or ulnar artery to a proximally located vein…... Alternatively

LOOP CONFIGURATION1. Oblique Incision in

Anticubital fossa2. Identify Brachial Artery & a

Suitable vein3. Mobilze upto 5 cm

distance4. Opening the vein and

passage of Fogarty catheter to confirm patency.

5. Lay the graft over the forearm and make the incision over the base of the course.

6. Make subcutaneous tunnels

7. Pull the vein through the tunnel so that proximal end is near the vein and distal end near the artery.

8. 5000 IU heparin & clamping the artery.

9. Longitudenal arteriotomy is made

10.Vessel is anastomosed in end to side fashion using prolene 6/0.

11.Release the arterial clamp and check for patency.

12.Anastomose the vessel with the vein in the same fashion.

13.Skin stitching.

Straight or J-Shaped Configuration

1. Better arrangement than loop.

2. Mobilize Brachial Artery3. Mobilize suitable distal

vein.4. Make a tunnel between

the two.5. Anastomose the artery

first and then vein.6. J-Shaped is best

hemodynamically.7. Make the brachial artery

anastomosis below the elbow crease.

Retrograde ArterializationGraft is taken from the Ulnar Artery to a suitable vein in the anticubital fossa or Cephalic vein in the Delto-pectoral groove.

THIGH GRAFTS

Loop configuration is done by mobilizing the Long Saphenous Vein upto the knee and left attached to the femoral vein and distal end is tunneled subcutaneously for attachment with the femoral artery.

THIGH GRAFTS

If used as a straight graft, it has to be completely removed, reversed and sutured to the femoral vein above and the popliteal artery below.

POST-OPERATIVE CARE» Patient is heparinized for 24 hours.» Check the graft regularly for patency

and bleeding.» Keep arm elevated to reduce edema.» Encourage hand and finger movement.» Cephalosporins or Ampicillin with

cloxacillin should be given to cover operation and continued thereafter 2-3 days.

COMPLICATIONS OF LONG TERM ACCESS

1. Central vein stenosis/arm swelling

2. Thrombosis

3. Infection

4. Hematoma/bleeding

5. Aneursymal degeneration.

6. Pseudoaneursym of AV graft

7. Steal syndrome

CENTRAL VEIN STENOSIS / ARM SWELLING

• Patients with extremity edema that persists beyond 2 weeks after graft

• Evaluate patency of the central veins

• Preferred treatment for central vein stenosis is PTA.

• Stent placement (Recur inside 3 weeks, >50 % elastic recoil of vein)

THROMBOSIS» Can occur early or after months of use.» If occurs early, re-explore and correct

the problem.» If occurs late, thrombectomy is done

using Fogarty catheter # 2.» Late thrombosis can be due to distal

stenosis. Commonly seen in PTFE graft because of intimal proliferation at venous anastomosis site.

INFECTION Commonly occurs with artificial grafts like

bovine, PTFE and umblical vein. Four times more common than infection

occurance in AV Fistula. Once graft is infected, no choice but to remove

it.

HEMATOMA / BLEEDING

ANEURYSMAL DEGENERATIONOccurs if vein is varicose or used too early.Can be repaired or excised following the replacement of the graft material.

HIGH VENOUS BACK PRESSURE Outflow obstruction Due to stenosis in the

draining vein Can be overcome by

passing fogarty catheter per-operatively to check for venous obstruction.

Suspected when high venous pressure is noted during dialysis.

Go for bypass graft to bypass the stenotic segment.

VASCULAR STEAL SYNDROME» 1.6% to 8% of all individuals with a functioning

shunt.» Risk factors include female sex, age > 60 years,

diabetes, arteriosclerosis, multiple operations on the same limb, the construction of an autogenous fistula, and most commonly the use of the brachial artery as the donor vessel.

» Symptoms associated with the ischemic steal syndrome range from vague neurosensory deficits to ischaemic rest pain or tissue loss.

VASCULAR STEAL SYNDROME» Classification:Stage I, Pale/blue and/or cold hand

without pain.Stage II, Pain during exercise.Stage III, Pain at rest.Stage IV, Ulcers/necrosis/gangrene.

VASCULAR STEAL SYNDROME

PSEUDO-ANEURYSMS