Improving longevity of prosthetic dialysis grafts in patients with disadvantaged venous outflow

A Comparative Study Regarding Deep and Superficial Veins for Venous Outflow in Forearm Loop Arteriovenous Grafts

BACKGROUND

The purpose of the study was to compare the access patency rates of forearm loop arteriovenous grafts (AVGs) using deep veins and superficial veins for venous outflow.

METHODS

The medical records of patients on dialysis were retrospectively reviewed to identify the individual risk factors and the outcomes of forearm loop AVGs according to their outflow types.

RESULTS

Overall, 170 cases were enrolled in this study. Of these, 103 cases (60.6%) used deep veins for outflow. Most patients using deep vein outflow had their venous anastomosis above the elbow (P = 0.000). Patients with venous anastomosis above the elbow were more likely to be female (P = 0.049) and have a lower albumin level (P = 0.025). The primary patency rates for superficial vein outflow and deep view outflow were 35.5% and 29.4% at 12 months and 18.9% and 4.9% at 24 months, respectively. There was a statistically significant difference between the two groups (P = 0.013). The assisted primary patency rates for superficial venous outflow and deep vein outflow were 85.5% and 79.5% at 12 months and 73.2% and 59.6% at 24 months, respectively (P = 0.139). Primary and assisted primary patency rates did not differ according to the crossing of the elbow.

CONCLUSIONS

The primary patency rate of AVGs using deep veins for outflow was inferior to AVGs using superficial veins. But the assisted primary patency rate showed no difference. The use of a deep vein for outflow in the forearm loop AVG is a safe strategy for patients with exhausted superficial veins.

Utility of Basilic Vein Transposition for Dialysis Access

Autologous arteriovenous access is the key to long-term success with hemodialysis and is strongly supported by the National Kidney Foundation's Dialysis Outcomes Quality Initiative guidelines. Basilic vein transposition (BVT) fulfills the need for a durable conduit with high patency and maturation rates. This retrospective review examines a single group's experience with this procedure.

All patients undergoing BVT for hemodialysis with available follow-up data were reviewed. Telephone interviews were used to supplement clinical data where needed. Functional assisted patency was used as the end point for this procedure, and if the access was never used for dialysis, then the patency was considered zero. Secondary interventions performed while the access remained patent and in use were not considered detrimental to the patency reported.

One hundred seventy BVTs in 162 patients were performed between November 1992 and October 2001. There were 87 women (53.7%) and 112 black patients (69.1%); hypertension was present in 138 patients (85.2%) and diabetes in 89 patients (54.9%). Each year, an increasing incidence of BVT was performed in our dialysis population. The BVT was performed as the first access in that extremity in 73 of the procedures (42.9%). Functional patency (primary assisted) was achieved in 40.0% at 2 years and 15.2% at 5 years. The mean assisted patency was 14.6 months. To maintain BVT patency, 40 percutaneous secondary interventions (69.0%) and 18 surgical revisions (31.0%) occurred in 32 patients (19.0%). Ligation for swelling was necessary in 4 patients (2.5%), and steal syndrome occurred in 3 patients (1.9%).

BVT is a useful autologous procedure for hemodialysis and the preferred access alternative in patients without an adequate cephalic vein. Although patencies remain poor relative to other conventional arterial vascular procedures, BVT is our most durable hemodialysis access procedure and is often the only available autologous conduit for hemodialysis.

Hemodynamics in a compliant hydraulic in vitro model of straight versus tapered PTFE arteriovenous graft

BACKGROUND

Hemodialysis patients require a vascular access to deliver sufficient blood flow to the artificial kidney. Of these vascular accesses, 30% are prosthetic (mainly polytetrafluorethylene [PTFE]) graft implants. These grafts are prone to the development of stenosis in the vein due to intimal hyperplasia, subsequently leading to thrombosis and graft failure.

AIM

We investigated the hemodynamics in a straight and a tapered PTFE-graft and compare the hydrodynamical behavior of both grafts.

MATERIALS AND METHODS

Two different vascular access geometry models were examined: a 6-mm diameter straight graft and a 4- to 7-mm tapered graft. The grafts were sutured to a compliant silicon model of an artery and vein in a loop configuration. Flow rate varied between 500 and 1500 mL/min. Two conditions were tested: 1). control: mean pressure is 100 mm Hg at the arterial inlet; and 2). low resistance condition: pressure is 20 mm Hg at the venous outlet. Pulse pressure is 60 mm Hg at the arterial inlet for both conditions. Pressure and flow velocity are measured continuously, while flow rate is measured volumetrically.

RESULTS

The pressure drop at the arterial anastomosis of the tapered graft is three times higher compared to the straight graft model. Intragraft pressure drops are similar in both graft types. Mean pressure and pulse pressure in the graft and vein are decreased in the low resistance condition. Also, the difference between maximum and minimum velocity is smaller in this.

CONCLUSIONS

No significant differences are noted between the graft geometries: pressure drop over the graft is almost equal. The major difference is the higher pressure drop at the arterial anastomosis of the tapered graft.