Intravascular ultrasonography is relatively new technique capable of detecting subtle vascular abnormalities. Intravascular ultrasonography can give a 3 dimensional, 360º visualization of the vessel and can detect more vascular abnormalities than can angiography.
Doppler techniques appear valuable in detecting stenosis in grafts. Percutaneous transluminal angioplasty performed under color Doppler ultrasonography guidance is useful in maintaining and improving graft patency. Percutaneous transluminal angioplasty with color Doppler ultrasonography guidance allows patients to avoid surgical intervention, hospitalization, and adverse reaction to contrast media and exposure to ionizing radiation, with reduced cost and with better graft survival.
CARE AFTER CRYOPRESERVED ALLOGRAFT PLACEMENT
Cannulation of cryopreserved allografts is possible 10-14 days after placement, and when swelling has subsided so that the course of the arteriovenous graft can be palpated. Aseptic technique during cannulation, including standard precautions for hand washing and glove changes, is recommended to minimize risk of access infection. Cannulation technique should be a hybrid of the techniques for expanded polytetra fluoroethylene arteriovenous graft regarding depth of the access and the texture of an autogenous vein. It is also necessary to rotate cannulation sites in order to avoid pseudoaneurysm formation. A retrospective study using constant cannulation (button hole technique) with cryopreserved femoral veins showed good outcomes related to patency and minimal infection risk.
A qualified individual should perform a physical examination to detect arteriovenous graft dysfunction at least monthly. The 3 preferred surveillance techniques for stenosis of arteriovenous graft are:
- intra access flow using sequential measurements with time analysis
- directly measured or derived static venous dialysis
- duplex ultrasound
Other acceptable techniques include physical findings of persistent swelling of the arm, presence of collateral veins, prolonged bleeding after needle withdrawal, or altered characteristics of pulse or thrill in the arteriovenous graft. Unstandarized dynamic venous pressures should not be used.
ALLOGRAFT METHOD VS GRAFT EXCISION METHOD
There are 2 methods for treating infected hemodialysis arteriovenus graft – the allograft method and the graft excision method. The graft excision method is generally used to manage a synthetic graft infection.
- The allograft method is a single procedure which involves removing the infected arteriovenous graft and implanting the cryopreserved allograft in the same infected site. Preserving the vascular access saves potential future arteriovenous access site. Access is possible 10-14 days after implantation.
- The graft excision method involves two separate procedures. First the infected arteriovenous graft is removed. After the infection has cleared, a new arteriovenous graft is placed in a different location, which diminishes potential sites for future access
A temporary central venous catheter and intravenous antibiotic therapy are needed for both methods. The duration of the central venous catheter is generally longer for the graft excision method because a central venous catheter is needed after the first and second procedures, until the new arteriovenous graft is ready for cannulation.
Cryopreserved allografts are cryogenically preserved cadaver vessels.
Cryopreserved allograft is an option for treating infected hemodialysis arteriovenous graft. Allografts have been implanted either adjacent to or directly into the infected fields using the same anastomotic regions, thus saving other sites for future access.
Total removal of infected arteriovenous graft and placement of a new access device at a remote site may be required. This involves placement of a temporary dialysis catheter until the infection is resolved and results in losing the original graft site. Because potential access sites are limited, partial graft excision to salvage a site is also an acceptable method for treating graft infection.
lastly, patient with forearm arteriovenous graft removed may have adequate upper arm veins for an arteriovenous fistula, or another expanded polytetrafluoroethylene graft may also be a consideration, since the time to cannulation can be as short as 24-hours post operatively.
Arteriovenous graft infection management is a balance between resolving the infection while preserving the vascular access as follows:
- Treat initially with broad-spectrum antibiotic therapy to cover both gram-negative and gram-positive microorganisms
- Base subsequent antibiotic therapy upon culture results
- Incision and drainage may be beneficial
- Treat with appropriate antibiotic therapy
- Resection of the infected graft material