Routine use of arteriovenous fistula construction to dilate the venous outflow prior to insertion of an expanded polytetrafluoroethylene (PTFE) loop graft for dialysis

For long-term haemodialysis to be successful an adequate lengthof vessel with correspondingly high flow is necessary, and theuse of a peripheral arteriovenous fistula (AVF) between brachialartery and median cephalic vein is well described for long-termvascular access. However, the length of vessel available isoften insufficient for dialysis and the time-lag between formationand availability for use may be prolonged. Primary insertionof a PTFE interposition graft is an alternative but may be technicallydifficult due to the small diameter of vein available for run-off,resulting in a significant rate of thrombosis. We advocate earlyAVF formation in most patients, even where the fistula is unlikelyto prove usable for dialysis, with the express purpose of dilatingthe veins prior to PTFE graft insertion. The time-lag betweenAVF formation and PTFE graft insertion may be as short as 1week. Although conversion of a functioning AVF to PTFE interpositiongraft has been described by others, we believe the routine useof AVF formation prior to PTFE insertion has not been previouslyadvocated and gives a considerable advantage in patients withdifficult dialysis access.     

Midgraft curettage as a routine adjunct to salvage operations for thrombosed polytetrafluoroethylene hemodialysis access grafts

We believe that midgraft stenosis due to intimal hyperplasia of the needle puncture zone is a clinically important cause of polytetrafluoroethylene (PTFE) dialysis graft thrombosis. Our simple dialysis graft salvage technique employs conventional exploration through a venous end graftotomy, thrombectomy with a Fogarty catheter, and venous end revision as needed. Midgraft curettage is routinely performed with a Kevorkian-Younge endometrial biopsy curette. This instrument is readily available and has a box-shaped back-cutting tip ideal for thorough, safe curettage of the PTFE graft lumen. This technique results in both direct assessment and simultaneous treatment of the entire thrombosed dialysis graft. The patency rates of first salvage procedures of thrombosed PTFE dialysis grafts with and without adjunctive curettage were retrospectively compared. Patency of the curettage group was superior at 1 month (97 percent versus 71 percent) and 6 months (65 percent versus 36 percent), with ultimate crossing of the plotted curves at 10 months (p = 0.053 by Wilcoxon test). It is our strong clinical impression that premature rethrombosis of PTFE dialysis grafts after salvage procedures has been greatly reduced by midgraft curettage.     

Haemodialysis dose is independent of type of surgically-created vascular access

Background: In the United States, the use of polytetraflourotheylene (PTFE) graft compared with native arteriovenous fistula (AVF) for haemodialysis vascular access has been increasing despite a greater than two-fold higher incidence of thrombosis and infection associated with PTFE grafts. Methods: We studied 214 haemodialysis patients with not more than two revisions of their vascular access, to determine whether any relationship exists between the type of haemodialysis vascular access and dialysis dose assessed primarily by urea reduction ratio (per cent reduction in blood urea nitrogen concentration after a dialysis session). Serum albumin concentration was used as a secondary outcome measure of dialysis adequacy. Urea reduction ratio and predialysis serum albumin concentration were measured at onset of study and at 4-week intervals and mean values were calculated for each subject. Results: The 214 patients (118 males, 96 females) included 173 Blacks (81%), 26 Whites (15%), and 15 Hispanics (7%), of mean (±SD) age 55.6±15.5 years. Of these 214 subjects, 111 (52%) had a native AVF, while 103 (48%) had a PTFE graft. Both mean urea reduction ratio (native AVF=69±6.7% vs PTFE graft=70±7.3%; P=0.31), and mean serum albumin concentration (native AVF=4.02±0.39 g/dl vs PTFE graft=4±0.33 g/dl; P=0.59) were equivalent in both groups. Separate multiple logistic regression analyses with type of vascular access as one of the independent variables, found no significant relationship between type of vascular access and either a urea reduction ratio >65% (P=0.67), or a serum albumin concentration >4 g/dl (P=0.89), after adjustment for age of vascular access, access revision, location of access, dialyser urea clearance, length of dialysis treatment, body weight, and age. Conclusion: We conclude that PTFE grafts do not permit delivery of better dialysis than native AVF. The increasing use of PTFE grafts in the United States does not have any clinical justification.     

Aggressive venous neointimal hyperplasia in a pig model of arteriovenous graft stenosis

BACKGROUND: Vascular access dysfunction is the most important cause of morbidity and hospitalization in the hemodialysis population in the United States at a cost of well over one billion dollars per annum. Venous neointimal hyperplasia characterized by stenosis and subsequent thrombosis, is the major cause of polytetrafluoroethylene (PTFE) dialysis graft failure. Despite the magnitude of the problem, there are currently no effective therapies for the prevention or treatment of venous neointimal hyperplasia in PTFE dialysis grafts. We believe that this is partly due to the lack of a validated large animal model of arteriovenous stenosis that could be used to test out novel interventions. METHODS: Seven-centimeter PTFE loop grafts were placed between the femoral artery and vein of domestic pigs. The grafts were removed at 2, 4, 7, 14 and 28 days after surgery and subjected to a detailed histological and immunohistochemical examination. RESULTS: Significant neointimal hyperplasia and venous stenosis developed by 28 days at the graft-vein anastomosis. There was minimal neointimal hyperplasia at the graft-artery anastomosis. Venous neointimal hyperplasia (VNH) was characterized by (a) the presence of smooth muscle cells/myofibroblasts; (b) angiogenesis within both the neointima and adventitia; and (c) the presence of an active macrophage cell layer lining the PTFE graft material. These results are very similar to the human lesion previously described by us in dialysis patients. CONCLUSIONS: We have developed and validated a pig model of venous neointimal hyperplasia that is very similar to the human lesion. We believe that this is an ideal model in which to test out novel interventions for the prevention and treatment of clinical hemodialysis vascular access dysfunction.     

Management of tunnel infections of dialysis polytetrafluoroethylene grafts

Extensive tunnel infections of polytetrafluoroethylene (PTFE) dialysis grafts have traditionally been managed by total excision, including venous and arterial anastomoses. This article describes an alternative vascular approach to excision of infected dialysis PTFE grafts; success occurred in 14 of 15 excised grafts in 12 patients. The surgical procedure consisted of a 2 to 3 mm oversewn cuff of PTFE left at the arterial anastomosis, with excision of the remaining graft including the venous anastomosis. The entire tunnel tract was opened, debrided, and irrigated extensively with cefazolin solution. Wounds were closed over drains. Fourteen PTFE graft excisions healed without sequelae. This small but successful series of excised, infected PTFE dialysis grafts supports the procedure to leave a small cuff of oversewn PTFE on the artery and to close the wounds primarily over drains.     

The straight radial-antecubital PTFE angio-access graft in an era of high-flux dialysis

Straight radial-antecubital polytetrafluoroethylene (PTFE) grafts were placed in 10 older (greater than 55 years) male patients with significant intercurrent diseases who were considered candidates for high-flux dialysis. Graft patency was 90% at 6 months, and suitable flow for high-flux dialysis (greater than 400 mL/minute) could be achieved with all grafts. Shorter dialysis times with no major cardiovascular, hemodynamic, or extremity complications were achieved with this mode of therapy. The principles and practicalities of high-flux dialysis are reviewed. This small series of patients demonstrates that the relatively low resting flow of the straight radial-antecubital PTFE graft should not be a major consideration in the choice of this vascular access procedure in patients being considered for high-flux dialysis. Straight radial-antecubital PTFE grafts preserved both the ulnar collateral to the hand and the brachial artery for later access, yet provided adequate flow in all patients in whom they remained patent.     

Haemodialysis access: a single centre UK Experience

Background: The aim of this study was to determine whether the US National Kidney Foundation Disease Outcome Quality Initiative (K/DOQI) guidelines on haemodialysis access could be achieved and to examine its relevance to patients on dialysis in the UK. Method: A cross sectional study of chronic haemodialysis patients at our institution which involved case note review and measurements of biochemical parameters and dynamic venous pressure (dVP) was performed. Patients with polytetrafluoroethylene (PTFE) grafts were followed prospectively for 18 months. Results: 262 patients were studied - 12%, 43%, 30% and 15% underwent dialysis through dialysis catheters, radial-cephalic fistulae (rAVF), brachial-cephalic fistulae (bAVF) and PTFE grafts respectively. RAVFs, bAVFs and PTFE grafts were the primary access (i.e. the first access created for the patient) in 58%, 35% and 7% respectively. Compared with patients of Caucasian origin, patients of Afro-Caribbean race were 3.80 times (95% confidence limit: 1.51 - 9.53) more likely to have a PTFE graft. Patients with higher 'dry weights' were more likely to have PTFE grafts (p<0.005 by ANOVA). Dialysis adequacy was similar irrespective of type and site of access. We found that 64% of PTFE grafts, 46% of bAVFs and 13% of rAVF had dVPs greater than 150 mmHg, (p<0.0001 by c2). This threshold recommended by DOQI predicted 12 of 13 dysfunctional grafts, but had a positive predictive value of only 50%. Conclusion: We have demonstrated that the K/DOQI guidelines are not only achievable, but that they can be exceeded by a considerable margin. Our data also suggest that the demographic details of patients within a unit will influence the achievable proportion of AVF: PTFE grafts (the proportion of PTFE grafts in Afro-Caribbeans being 3 times higher than in whites). Although a dVP >150 mmHg proved sensitive in predicting future graft dysfunction, it had low specificity.     

Clinical trials of a new polytetrafluoroethylene-silicone graft

A self-sealing polytetrafluoroethelene (PTFE)-silicone graft designed to be used early after implantation was placed in 30 end-stage renal disease patients. Thirty-five conventional PTFE grafts were used in the control group. All patients were followed for 1 year. In the PTFE-silicone graft group, median time for first use was 1 day after implantation. Conventional PTFE grafts were first used 2 to 4 weeks after implantation. Early punctures of the PTFE-silicone grafts (first 10 sessions), although more difficult to perform than late punctures, were not more difficult than punctures of conventional PTFE grafts. Late punctures in PTFE-silicone grafts were easier than conventional PTFE graft punctures. Bleeding after needle removal was significantly decreased after early and late punctures of PTFE-silicone grafts compared with conventional PTFE grafts (p less than 0.001). The PTFE-silicone graft can be used immediately after implantation, sparing patients additional access procedures for short-term dialysis. This results in less morbidity, decreased bleeding complications, shorter hospital stay, and a significant reduction in expenses.     

Bovine carotid artery and expanded polytetrafluroethylene grafts for hemodialysis vascular access

Seventy-six bovine carotid artery heterografts (BCAH) and 100 expanded polytetrafluroethylene (PTFE) grafts were inserted as chronic hemodialysis arteriovenous fistulas. Cumulative patency at 1 year was 70% for the BCAH group and 87% for the PTFE group and at 2 years was 45 and 73%, respectively. Infection accounted for 38% of BCAH failures and none of the PTFE failures. BCAH required twice as many revisions per dialysis month to maintain patency as did the PTFE grafts (0.036 vs 0.019, respectively). Graft configuration and location did not affect patency rates. At present the PTFE grafts appear superior to the BCAH for construction of arteriovenous dialysis fistulas.     

Increased risk of infection associated with polyurethane dialysis grafts

Conventional polytetrafluoroethylene (PTFE) dialysis grafts cannot be cannulated for 2-3 weeks following their creation. Polyurethane grafts, made of a self-sealing material, can be cannulated within 24 hours of implantation, representing a potential advantage in patients with limited catheter options. However, early cannulation may increase the risk of graft infection. We retrospectively queried a prospective, computerized access database to identify 31 patients receiving a polyurethane graft, and 56 date-matched controls with a PTFE graft. Survival techniques were used to plot graft survival. Thrombosis-free graft survival (from creation to first thrombosis or failure) was similar for polyurethane and PTFE grafts (1-year survival, 28%, vs. 32%, p = 0.98). Cumulative graft survival (from creation to permanent failure) was also similar (1-year survival 42% vs. 52%, p = 0.40). Finally, the cumulative risk of graft infection was 37.5% for polyurethane thigh grafts, 23% for polyurethane upper extremity grafts, 21% for PTFE thigh grafts, and 5% for PTFE upper extremity grafts (p = 0.06 for polyurethane vs. PTFE grafts). The likelihood of thrombosis and failure is similar for polyurethane and PTFE grafts. However, polyurethane grafts may have a higher risk of infection, particularly when they are placed in the thigh. In patients with an access emergency, implantation of a polyurethane graft incurs a tradeoff between earlier cannulation and a higher risk of infection.     

Radiation therapy for dialysis access stenosis: unfulfilled promise or false expectations

Hemodialysis vascular access dysfunction is a major cause of morbidity and hospitalization in the hemodialysis population at a cost of well over $1 billion per annum. Venous stenosis (due to venous neointimal hyperplasia [VNH]) is the most common cause of polytetrafluroethylene PTFE) dialysis access graft and arteriovenous fistula (AVF) failure. Despite the magnitude of the clinical problem, however, there are currently no effective therapies for this condition. We and others have previously demonstrated that VNH in PTFE dialysis grafts and AVF is composed of smooth muscle cells/myofibroblasts, endothelial cells within neointimal microvessels, and peri-graft macrophages. Radiation therapy blocks the proliferation and activation of all these cell types. The current review will dissect out the available in vitro, experimental, and clinical data on the use of radiation therapy for vascular stenosis in general, and for dialysis access dysfunction in particular. It is important to try and identify whether there is still a role for radiation therapy in this specific clinical setting. We believe that this is a critically important question to answer in view of the huge unmet clinical need that is currently associated with hemodialysis vascular access dysfunction.     

Transluminal angioplasty of venous stenoses in polytetrafluoroethylene vascular access grafts

Since 1984, percutaneous transluminal angioplasty (PTA) utilizing high pressure balloon catheters has been used as an initial approach to restore patency of PTFE (polytetrafluoroethylene, GORE-TEX) hemodialysis vascular access grafts. Seventeen stenotic lesions detected by fistulogram underwent elective PTA. Twelve of these lesions were detected after thrombectomy and five were detected because of increased venous pressures during dialysis. Fourteen attempts at PTA were completely successful in restoring functional patency to the vascular graft. Three attempts were unsuccessful; two of these three grafts were subsequently repaired surgically. Venous stenoses that extended far greater than 6 cm were not considered for PTA. We conclude that PTA is a technique of promise in the non-surgical salvage of failing PTFE grafts. PTA can prolong the useful life of PTFE vascular access grafts and can be performed on an outpatient basis, eliminating the hospitalization that is usually required for surgical revision.     

Back to the Future: How Biology and Technology Could Change the Role of PTFE Grafts in Vascular Access Management

Although the arteriovenous fistula (AVF) is the preferred mode of dialysis vascular access, AVF maturation failure remains a huge clinical problem, often resulting in a prolonged duration of use of tunneled dialysis catheters. In contrast, polytetrafluoroethylene (PTFE) grafts do not suffer from early failure, but have significant problems with later stenosis and thrombosis. This review will initially summarize the pathology and pathogenesis of PTFE graft dysfunction and will then use this as a basis for describing some novel therapies, which may have the potential to reduce PTFE graft dysfunction. Finally, we will emphasize that the introduction of such therapies could be an important first step toward individualizing overall vascular access care.     

Vascular Access in Hemodialysis Patients with Central Venous Obstruction or Stenosis: One Center’s Experience

The purpose of this study was to evaluate the value of complex hemodialysis access procedures among patients with central venous obstruction who were running out of access sites. Between September 2002 and December 2003 we performed a total of 640 new hemodialysis access procedures in 3 renal units. Ten of these patients presented central vein stenosis or obstruction and were not suitable for peritoneal dialysis. Each of the 10 patients had 3 or 4 previous failed access procedures and numerous infected central lines and their dialysis catheters were not functioning adequately. Nine patients presented with a severely stenosed or occluded superior vena cava and 1 had both subclavian veins occluded. Three patients were diabetics, 2 were obese and 6 had hypertension. We performed 12 procedures on these 10 patients. Saphenous veins were used 6 times, twice as a loop to the femoral artery and 4 times as a transposition to the popliteal artery above the knee. Femoral vein transposition to the popliteal artery was carried out in 2 cases. We performed 3 axillary artery to popliteal vein polytetrafluoroethylene (PTFE) bypasses, 1 on an obese woman who had no saphenous vein and was not suitable for a femoral vein transposition, 1 on a diabetic woman whose saphenous vein loop clotted after 5 months and 1 on a female patient with severe peripheral vascular disease. The patient with bilateral subclavian vein occlusion had a brachial artery to internal jugular vein PTFE graft. The PTFE graft to the jugular vein has been patent and regularly needled with a follow-up of 4 months. Four saphenous vein fistulae were regularly used for dialysis; 2 were never used. Five saphenous fistulae clotted after an average life span of 4 months (range 3 weeks-9 months) and 1 is still patent and in use (5 months). Both femoral vein transpositions have been patent and have been needled 3 times a week with a follow-up of 10 and 4 months; one had to be revised surgically after 9 months. Of the 3 axillary artery to popliteal vein grafts, 1 had to be tied off after a week because of severe steal syndrome and 2 have been patent (20 months follow-up) and have been needled regularly ever since. Seventy percent of these patients have been dialyzed line-free through their fistula despite severe central vein stenosis or obstruction for periods of 9-18 months when this review was undertaken. Although the follow-up needs to be longer, we discuss the surgical, radiologic, and dialysis features of these patients and propose a management pathway for central vein stenosis or occlusion.     

Regular ultrasonographic screening significantly prolongs patency of PTFE grafts

BACKGROUND: Polytetrafluoroethylene (PTFE) dialysis grafts have considerably shorter patency than native arteriovenous fistulas, despite the use of a complex of screening monitoring methods (venous pressure, access flow). PTFE grafts are used often in subjects with depleted subcutaneous veins after previous abandoned accesses, so keeping the access patent is crucial. We hypothesized that regular duplex Doppler ultrasound screening for access stenoses, together with their sooner treatment, would prolong PTFE graft patency. METHODS: We performed a randomized, prospective study of PTFE grafts' cumulative patency in 192 subjects. In group 1, regular ultrasound examinations performed every 3 months was added to traditional screening (i.e., regular access examination at hemodialysis unit, monitoring of venous pressure and access flow). Group 2 was screened only traditionally (without ultrasound). Interventions of suspected stenoses were indicated by nephrologists, vascular surgeon, and, in group 1, also by ultrasonography. Classic ultrasound criteria for significant stenosis were used, even if the access flow had not been decreased. The mean follow-up lasted 392 +/- 430 days. RESULTS: Groups were similar with respect to age, gender, diabetes status, and number of previous abandoned accesses. Group 1 had significantly longer access patency (P < 0.001). Number of interventions per graft was 2.1 +/- 1.8 and 1.3 +/- 1.0 in group 1 and group 2. CONCLUSIONS: Regular screening duplex Doppler ultrasonography results in significantly longer PTFE graft patency due to early detection of access stenosis and, thus, more frequent elective interventions of access stenoses.     

Expanded polytetrafluoroethylene graft fistula for chronic hemodialysis.

In a retrospective study of 66 PTFE arteriovenous fistulae and 71 BCH arteriovenous fistulae for dialysis access, PTFE had a higher patency rate than BCH at 12 months (62.4 versus 32.5%). PTFE was easier to work with and easier to handle in the face of infection. The lateral upper arm approach to placement of the PTFE graft is desirable in patients who have had multiple previous access procedures because this area is usually free from scarring, is distant from neurovascular structures, and provides a greater length of graft for needle punctures.     

Vascular access for hemodialysis in patients with central vein stenosis or obstruction

The aim of our study was to report our experience with complex haemodialysis access procedures for patients presenting central vein stenosis or obstruction. Between September 2002 and December 2003 we performed 12 procedures on 10 patients presenting central vein stenosis or obstruction; all of them presented contraindications to peritoneal dialysis. Saphenous veins were used 6 times, twice as loops to the femoral artery and 4 times as transpositions to the popliteal artery above the knee; 3 axillary artery to popliteal vein PTFE bypasses; and 1 brachial artery to internal jugular vein PTFE graft. The PTFE graft to the jugular vein has been patent and regularly needled with a follow-up of 4 months. Four saphenous vein fistulae were regularly used for dialysis; 2 were never needled. Five saphenous fistulae clotted after an average life span of 4 months (range: 3 weeks-9 months) and one is still patent and in use (5 months). Both femoral vein transpositions have been patent and have been needled 3 times a week with a follow-up of 10 and 4 months; one had to be revised surgically after 9 months. Of the 3 axillary artery to popliteal vein grafts, one had to be closed after a week because of severe steal syndrome and 2 have been patent (1 year and 8 month follow-up) and have been needled regularly ever since. Seventy percent of these patients has been dialysed line free through their fistula despite severe central vein stenosis or obstruction. Although the follow-up needs to be longer we discuss the surgical, radiological and dialysis features of these patients and propose management guidelines for cases of central vein stenosis or occlusion.     

Complications of renal dialysis access procedures

The complications of 2,179 dialysis access procedures of various types have been reviewed in an effort to determine their possible prevention and management. Scribner arteriovenous shunts or central venous catheters were preferred for temporary dialysis. Infection was a common complication of central venous catheters, but responded well to removal of the catheter. Brescia-Cimino fistulae were preferred for long-term dialysis, but were often not possible because of inadequate veins or the need for relatively urgent hemodialysis. The most useful secondary shunt was the straight forearm synthetic polytetrafluoroethylene (PTFE) graft whose most common complication was thrombosis due to intimal hyperplasia at the venous anastomosis. In most cases, this complication could be corrected by patch grafting or by extension bypass. Infection was infrequent with PTFE shunts and, when localized, was sometimes successfully treated by drainage, antibiotic therapy, and topical povidone-iodine. The principal complications of long-term peritoneal dialysis were peritonitis and tunnel infection that responded to antibiotic therapy and/or removal of the catheter. Compulsive care in access insertion and meticulous management during dialysis has permitted very satisfactory long-term hemodialysis and peritoneal dialysis.     

Patency Rates and Complications of Exxcel Yarn-Wrapped Polytetrafluoroethylene Grafts Versus Gore-Tex Stretch Polytetrafluoroethylene Grafts: A Prospective Study

Purpose. Polytetrafluoroethylene (PTFE) has long been used for hemodialysis access when there is no suitable superficial vein. We conducted a prospective randomized study to compare two PTFE grafts; the stretch Gore-tex graft and the Exxcel graft.Methods. Between May 2000 and February 2001, PTFE grafts were implanted for hemodialysis access in the upper extremities of 94 consecutive patients with end-stage renal disease. Graft selection was randomized, with patients receiving either a Gore-tex or an Exxcel graft. All grafts were monitored for signs of thrombosis or other complications. Graft survival was analyzed using a life-table analysis and the log-rank test was applied to compare graft patency.Results. The primary patency rates 1 and 2 years after implantation were 51% and 36% for the Exxcel grafts, and 71% and 45% for the Gore-tex grafts, respectively. The difference between the two groups was not significant at any time. The incidence of complications needing further surgical management was 8.2% in the Exxcel group and 6.7% in the Gore-tex group, without a significant difference.Conclusion. Exxcel grafts or Gore-tex stretch grafts can be used for dialysis access with similar expected outcomes for up to 2 years, despite the differences in their outer surface design. The yarn-wrapped design does not appear to enhance the graft patency and we found no remarkable difference.     

External beam radiation therapy for PTFE dialysis grafts: a pilot study

Purpose: The aim of this study was to identify the effects of external beam radiation on PTFE dialysis graft dysfunction. Methods: Seven patients who underwent PTFE dialysis graft angioplasty were randomized to receive either two 8 Gy doses of external beam radiation or no radiation. The primary endpoint was time to graft thrombosis with a secondary endpoint of time to first intervention. Results: There was no statistically significant difference between the two groups in either of the endpoints, although grafts in the radiation group had a shorter time to thrombosis or intervention. Conclusions: Our results demonstrate technical feasibility for use of external beam radiation in the setting of dialysis vascular access graft dysfunction. Larger randomized studies are required to identify whether there is a clinical benefit from this intervention.