Hemodialysis access failure: a call to action

Association of patient autonomy with increased transplantation and survival among new dialysis patients in the United States

BACKGROUND

It is unclear whether patients with chronic kidney disease who are more autonomous in medical decision making have better outcomes than those who are not. We examined the contribution of patient autonomy to treatment selection (peritoneal dialysis versus hemodialysis) and subsequent association with transplantation and survival.

METHODS

Data were obtained from the Dialysis Morbidity and Mortality Study Wave 2, a national random sample of 4,025 new dialysis patients enrolled during 1996 and 1997 and followed up until October 31, 2001. Responders were asked to quantify their contribution to treatment selection and were grouped based on perceived degree of participation as patient led, team led, or patient and team led. Groups were compared and subsequent outcomes were evaluated by using Cox regression.

RESULTS

Six hundred thirty-six patients (26.3%) reported a patient-led decision, 860 patients (35.6%) reported a team-led decision, and 922 patients (38.1%) reported a patient-and-team-led decision in treatment assignment. Unadjusted death rates were significantly lower (127 versus 159 versus 207 deaths/1,000 patient-years at risk; P < 0.0001), and transplantation rates were significantly higher (103 versus 88 versus 41 transplantations/1,000 patient-years at risk; P < 0.0001) for patients reporting the greatest contribution to modality selection. With adjustment for case mix, mortality risks were lowest (relative risk [RR], 0.84; 95% confidence interval [CI], 0.71 to 0.99) and transplantation rates were highest (RR, 1.44; 95% CI, 1.07 to 1.93) for the patient-led group.

CONCLUSION

Although the contribution of patient selection factors cannot be completely ignored, this analysis supports an association of patient autonomy with transplantation and survival. Greater efforts to empower patients with chronic kidney disease during the period before end-stage renal disease may improve clinical outcomes.

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.

A novel mouse model of autologous venous graft intimal hyperplasia

BACKGROUND

To investigate the molecular mechanism of autologous venous graft intimal hyperplasia, a mouse model is needed. Currently only vein to carotid artery mouse models are available and are hampered by a high thrombosis rate. We hypothesized that operating on the aorta would lead to intimal hyperplasia with decreased risk of thrombosis.

MATERIALS AND METHODS

In C57BL/6J mice, the left external jugular vein was grafted into the infrarenal abdominal aorta by end-to-end anastomosis with 11-0 Ethilon. Grafts harvested at 1, 2, 4, 8, and 16 weeks postoperatively were subjected to histological and immunohistochemical analysis.

RESULTS

Thirty-one of 35 mice survived; 2 mice were sacrificed secondary to thrombosis. The percentage lumen narrowing (+/-SE) was 7.8 +/- 0.3, 16.4 +/- 0.9, 19.2 +/- 0.9, 22.3 +/- 0.8, and 23.9 +/- 1.6% at 1, 2, 4, 8 and 16 weeks, respectively. Nuclear density decreased with each successive time point. The percentage of alpha-smooth-muscle actin-positive cells within the neointima peaked at 16 weeks (53%), and the percentage of cells positive for proliferating cell nuclear antigen peaked at 2 weeks (39%).

CONCLUSIONS

We thus report on a novel mouse model of intimal hyperplasia in autologous venous grafts with a low thrombosis rate. Further studies using this model, coupled with genetic and bone marrow transplantation mouse models, should lead to significant enhancement in understanding of the mechanism of intimal hyperplasia.

ASDIN Original Investigations: Salvage of a Severely Dysfunctional Arteriovenous Fistula with a Strictured and Occluded Outflow Tract

Arteriovenous fistulas (AVFs) created for the purpose of hemodialysis are frequently lost due to various vascular lesions. Endovascular therapies with percutaneous transluminal balloon angioplasty have become very valuable in treating AVF dysfunction due to vascular stenosis. Experience with these therapies is relatively limited. In this case report, we present a patient with a severely dysfunctional AVF. The vascular lesions affecting his AVF were numerous and severe. We show how the application of aggressive endovascular treatment succeeded in restoring use of his AVF. Throughout the discussion we share observations and personal experiences that may be useful for interventionalists and health care practitioners involved with the maintenance, use, and treatment of dialysis vascular accesses.

Remarks on Surgical Strategy in Creating Vascular Access for Hemodialysis: 18 Years of One Center's Experience

The aim of the study is to evaluate surgical methods for creating vascular access for hemodialysis (HD) in patients with chronic renal failure. Over the last 18 years, 1,827 surgical procedures were performed in 722 patients (399 men and 323 women, mean age 43.7 +/- 17 years) in order to provide and maintain permanent vascular access for HD. Among all the surgical procedures, 992 were based on the construction of arteriovenous fistulas (AVF) and 835 were undertaken as secondary reparative surgical procedures. A total of 992 vascular accesses have been performed, including 904 AVF on upper and 14 on lower extremities as well as insertion of 74 permanent catheters. Radiocephalic AVF (RCAVF) was the principal type of AVF (58.8%). While constructing secondary angio-access after using RCAVF on the other extremity, fistulas with usage of brachial vessels were preferred. A total of 228 AVF of this type were created, including 143 brachiocephalic (BCAVF) and 85 brachiobasilic (BBAVF) AVF. Lately, synthetic grafts (arteriovenous graft, AVG) have been used more frequently, in 90 AVF. A brachial straight graft was the main type procedure performed, with polytetrafluoroethylene (95.6%). The patency of the fistulas has been evaluated. Kaplan-Meier survival curves were calculated to determine primary, primary-assisted, and secondary patency. Log-rank analysis was used to determine differences between curves. Primary, primary-assisted, and secondary patency at 12 months and 24 months were calculated. Comparing AVF patency in two patients' age periods (18-65 years, >65 years), it may be concluded that in the elderly group AVG provides better treatment for AVF. Finally, we conclude that a multidisciplinary approach to vascular access strategy offers the best option to achieve good functional AVF. Autogenous arteriovenous access should be regarded as the most suitable type in creating VA. However, individual conditions should be taken into consideration.

Frequency of critical stenosis in primary arteriovenous fistulae before hemodialysis access: Should duplex ultrasound surveillance be the standard of care?

OBJECTIVE

Increasing use of primary arteriovenous fistulae (pAVFs) is a desired goal in hemodialysis patients (National Kidney Foundation /Dialysis Outcome Quality Initiative guidelines). However, in many instances, pAVFs fail to adequately mature due to ill-defined mechanisms. We therefore investigated pAVFs with color duplex ultrasound (CDU) surveillance 4 to 12 weeks postoperatively to identify hemodynamically significant abnormalities that may contribute to pAVF failure.

METHODS

From March 2001 to October 2003, 54 upper extremity pAVFs were subjected to CDU assessment before access. A peak systolic velocity ratio (SVR) of >/=2:1 was used to detect >/=50% stenosis involving arterial inflow and venous outflow, whereas an SVR of >/=3:1 was used to detect >/=50% anastomotic stenosis. CDU findings were compared with preoperative vein mapping and postoperative fistulography when available.

RESULTS

Of 54 pAVFs, there were 23 brachiocephalic, 14 radiocephalic, and 17 basilic vein transpositions. By CDU surveillance, 11 (20%) were occluded and 14 (26%) were negative. Twenty-nine (54%) pAVFs had 38 hemodynamically significant CDU abnormalities. These included 16 (42%) venous outflow, 13 (34%) anastomotic, and 2 (5%) inflow stenoses. In seven (18%), branch steal with reduced flow was found. In 35 of 54 (65%) pAVFs, preoperative vein mapping was available and demonstrated adequate vein size (>/=3 mm) and outflow in 86% of cases. Twenty-one fistulograms (38%) were available for verifying the CDU abnormalities. In each fistulogram, the arterial inflow, anastomosis, and venous outflow were compared with the CDU findings (63 segments). The sensitivity, specificity, and accuracy of CDU in detecting pAVF stenoses >/=50% were 93%, 94%, was 97%, respectively.

CONCLUSIONS

Before initiation of hemodialysis, an unexpectedly high prevalence of critical stenoses was found in patent pAVFs using CDU surveillance. These de novo stenoses appear to develop rapidly after arterialization of the upper extremity superficial veins and can be reliably detected by CDU surveillance. Turbulent flow conditions in pAVFs may play a role in inducing progressive vein wall and valve leaflet intimal thickening, although stenoses may be due to venous abnormalities that predate AVF placement. Routine CDU surveillance of pAVFs should be considered to identify and correct flow-limiting stenoses that may compromise pAVF long-term patency and use.

Surgical Salvage of Thrombosed Arteriovenous Fistulas and Grafts

Our clinical experience with surgical salvage of thrombosed arteriovenous (AV) fistula and grafts, performed by a skilled interventional nephrologist is presented. A total of 286 surgical interventions were performed in 246 chronic hemodialysis patients aged 12-87 years (55 +/- 16 years), 268/286 (93.7%) in AV fistulas, 18/286 (6.3%) in grafts, and analyzed retrospectively. A subgroup of 61 procedures was analyzed prospectively. The type of procedure, immediate success and patency after surgery were evaluated. Thrombectomy with reanastomosis was performed in 197/286 (68.9%) and simple thrombectomy in 89/286 (31.1%) of the procedures. The time from thrombosis to surgery was 1-60 days (3.7 +/- 1.8). Immediate success was achieved in 258/286 (90.2%) of surgical procedures, 95.5% (189/198) in thrombectomies with reanastomosis, and 77.5% (69/89) in simple thrombectomies. Primary and secondary patency rates for AV fistulas after surgical salvage at 3, 6, 9, and 12 months were 93.1, 84.0, 78.3, 75.0% and 96.6, 88.0, 78.3, 77.3%, respectively. In order to maintain secondary patency, 1.15 surgical procedures per AV fistula were needed. The time to thrombosis in grafts was on average 10.2 months, primary and secondary functioning time from thrombectomy (until the end of observation period) was from 1 to 19 months (average 6.9 +/- 6.3 months) and from 5.5 to 19 months (average 9.1 +/- 5.6 months), respectively. In 7/16 (43.8%) surgical procedures, transluminal angioplasty and in 3/16 endovascular stent was placed after angioplasty. To maintain secondary patency, 2.3 surgical procedures per graft were needed. The surgical salvage of thrombosed AV fistulas and grafts, performed by a skilled interventional nephrologist, is successful in the short and long-term.

Mathematical Model for Pressure Losses in the Hemodialysis Graft Vascular Circuit

Stenosis-induced thrombosis and abandonment of the hemodialysis synthetic graft is an important cause of morbidity and mortality. The graft vascular circuit is a unique low-resistance shunt that has not yet been systematically evaluated. In this study, we developed a mathematical model of this circuit. Pressure losses ΔPs were measured in an in vitro experimental apparatus and compared with losses predicted by equations from the engineering literature. We considered the inflow artery, arterial and venous anastomoses, graft, stenosis, and outflow vein. We found significant differences between equations and experimental results, and attributed these differences to the transitional nature of the flow. Adjustment of the equations led to good agreement with experimental data. The resulting mathematical model predicts relations between stenosis, blood flow, intragraft pressure, and important clinical variables such as mean arterial blood pressure and hematocrit. Application of the model should improve understanding of the hemodynamics of the stenotic graft vascular circuit.

Percutaneous balloon cryoplasty: A new therapy for rapidly recurrent anastomotic venous stenoses of hemodialysis grafts?

Vascular access dysfunction is a major source of morbidity for end-stage renal disease patients on hemodialysis. The arteriovenous graft is a common access type for many of these patients. Frequent stenosis formation and thrombosis complicate this form of access. Patients may have a rapidly forming and recurrent venous stenosis at the graft-vein anastomosis that has been seen in both animal models and end-stage renal disease patients to be the result of neointimal hyperplasia. This venous lesion is particularly resistant and sometimes intractable to conventional angioplasty. As a result, new therapies have been developed to reduce the formation and/or recurrence of neointimal hyperplasia. These include special cutting balloons, drug-eluting stents, and endovascular brachytherapy. The authors present the cases of 5 patients with rapidly recurrent venous lesions at the graft-vein anastomosis that derived benefit from angioplasty with the cryoballoon. The time to stenosis or thrombosis in the arteriovenous grafts was increased from a mean of 3 weeks to more than 16 weeks with this technology. Cryotherapy with the cryoballoon (cryoplasty) may represent a useful therapy for patients with intractable stenoses at or near the venous anastomosis of arteriovenous grafts.

The timely construction of arteriovenous fistulae: a key to reducing morbidity and mortality and to improving cost management

BACKGROUND

Some investigators have shown that the initial placement of a catheter or graft, instead of the timely construction of an arteriovenous fistula (AVF), late referral to nephrology services and unplanned dialysis increase morbidity and mortality in chronic haemodialysis (CHD) patients. Furthermore, a delay in providing an adequate AVF entails significant increases in treatment-related costs. This study was limited to the analysis of the effects of the lack of an adequate vascular access for CHD on morbidity and mortality.

METHODS

According to the vascular access they had in the first 3 months of CHD treatment 96 patients were divided into three groups (VA group): Group 1 (G1), having an adequate AVF in the first 3 months; Group 2 (G2), starting with a catheter but finishing with an AVF; and Group 3 (G3) starting and finishing with a catheter. Time-dependent Cox regression analysis was performed to identify variables associated with survival, and the standardized mortality index (SMI) was calculated. Finally, we studied cost-effectiveness.

RESULTS

Time-dependent Cox regression and logistic regression analyses showed the statistically significant variable to be the VA group. To ensure that mortality was comparable between VA groups, eliminating age bias, the findings were adjusted applying SMI. G1 patients appear to have a lesser risk of death (relative risk, 0.39) than G2 and G3 patients, as do G2 relative to G3 patients. Also, after adjustment with SMI, patients over 65 years, presumably at greater risk of death, have a lower mortality than the <or=65 age group. Patients with an adequate and functioning AVF lived longer than the others, and the cost of each 'death prevented' was lower (3318/patient).

CONCLUSIONS

The lack of an adequate AVF at the start of haemodialysis decreases survival significantly-even if patients are not diabetic, are referred to a nephrologist early and planned haemodialysis is initiated. It also increases the cost of each prevented death.

Monitoring and maintenance of arteriovenous fistulae and graft function in haemodialysis patients

PURPOSE OF REVIEW

Several options exist for detecting and preventing stenosis in polytetrafluoroethylene grafts and arteriovenous fistulae for haemodialysis. Although observational studies show a significant benefit of such strategies, data from randomized trials are limited. This review describes recently published information that has helped to advance this field during the past year.

RECENT FINDINGS

A new method for the measurement of access blood flow is discussed. This technique does not require special apparatus, which may facilitate its use in settings where resources are limited. The utility and potential shortcomings of access blood flow monitoring in grafts and fistulae are discussed, focusing on three key controlled studies published during the past year. Although much additional research is needed, regular access blood flow monitoring may improve outcomes in fistulae. Although there is less evidence that access blood flow monitoring is beneficial in grafts, regular dynamic venous pressure monitoring seems reasonable, because it can detect stenosis at a low capital cost. Neither radiotherapy nor combination therapy with aspirin and clopidogrel are useful for the prevention of stenosis in grafts.

SUMMARY

Large randomized trials of screening appear feasible for both types of permanent vascular access. Given the adverse patient outcomes associated with access failure, as well as the high costs attributable to the implementation of ineffective screening strategies, such trials should be a high priority for nephrology researchers.

Improvements in dialysis access survival with increasing use of arteriovenous fistulas in a Veterans Administration medical center

BACKGROUND

Native arteriovenous fistulas (AVFs) have been found to exhibit higher survival rates and lower complication rates than prosthetic grafts (AVGs).

METHODS

Between August 2001 and December 2003, 93 patients with end stage renal disease (ESRD) had primary dialysis access placed at a single Veterans Administration medical center. Of these 93 patients, 67 had AVFs created and 26 patients had AVGs implanted.

RESULTS

The percentage of patients who did not require additional intervention was 84% (56 of 67) for AVF and 78% (21 of 26) for AVG after 4 to 31 months of follow-up evaluation. In the AVF group, repeat interventions were as follows: collateral ligation (4), angioplasty owing to central stenosis (2), AVF ligation due to arterial steal phenomenon (1), and new AVF creation owing to clotting (1). Four AVFs were later converted to AVG. In the AVG group there were 4 venous anastomosis stenosis seen in 3 patients who required angioplasty. Two patients needed thrombectomy and revision, and 1 graft was removed because of infection. AVF prevalence in our dialysis patients was 63%, with 33% AVG and 4% temporary catheter.

CONCLUSIONS

The National Kidney Foundation-Dialysis Outcome Quality Initiative (NKF-DOQI) guidelines for dialysis access reawakened interest in maximizing the use of renal veins for AVF. AVFs created by using the patient's native vein provides the best vascular access for dialysis when compared with prosthetic grafts. AVF has better long-term patency with fewer complications.

Epidemiology of vascular access in the Australian hemodialysis population

BACKGROUND

A number of demographic and comorbid factors have been demonstrated to be associated with the placement of arteriovenous grafts (AVG) and central venous catheters (CVC) as opposed to native arteriovenous fistulas (AVF). However, no data are available regarding these factors in a hemodialysis population where AVF utilization is high.

METHODS

All adult patients on hemodialysis on September 30, 2001 in Australia were included in the study. Vascular access was recorded as AVF, AVG, or CVC. Patients were separated into incident (<150 days since first dialysis) and prevalent cohorts (> or =150 days). Multinomial logistic regression was used to assess factors associated with AVG and CVC use.

RESULTS

Of the 4968 patients who were studied, 877(17%) were classed as incident and the remainder prevalent. AVF were present in 61% versus 77%, AVG were present in 11% versus 19%, and CVC were present in 28% versus 4% in the incident and prevalent cohorts, respectively (all P < 0.001). After adjustment for confounding factors, age and female gender were associated with an increased frequency of AVG in both cohorts. In addition, type I diabetes mellitus was associated with increased frequency of AVG use in the incident cohort, whereas body mass index (BMI) > or =30 kg/m2 and peripheral vascular and cerebrovascular disease were significant in the prevalent group. For CVC, female gender, type I and II diabetes mellitus and late referral were associated with increased frequency in the incident cohort, while females, cigarette smoking, and peripheral vascular disease were predictive in the prevalent group. Significant variations in access type were also seen depending on geographic location.

CONCLUSION

Certain patient characteristics such as age and female gender, but not type II diabetes mellitus, remain significantly associated with AVG and catheter use despite the high prevalence of AVF use in Australia. However, the significant variation in risk by geographic location suggests more attention needs to be paid to physician practice patterns to increase AVF utilization rates.

Vascular access practice patterns in the New Zealand hemodialysis population

BACKGROUND

Native arteriovenous fistula (AVF) prevalence varies significantly among different populations and countries. Physician practice patterns may have a strong influence on access type. We assessed differences in vascular access practice patterns across all treating centers in New Zealand.

METHODS

Adult (age > or = 18 years) patients on hemodialysis therapy in the year ending September 30, 2001, were studied from the Australian and New Zealand Dialysis and Transplant Association Registry. Multinomial logistic regression was used to assess factors associated with arteriovenous graft (AVG) and catheter use.

RESULTS

Of 772 patients available for analysis, 461 patients (60%) underwent dialysis using an AVF; 122 patients (16%), an AVG; and 189 patients (24%), a catheter. On multivariable analysis, female sex (odds ratio, 5.92; P < 0.001), coronary artery disease (odds ratio, 1.89; P < 0.05), body mass index greater than 30 (odds ratio, 2.55; P < 0.05), and age (odds ratio, 1.03 per year increase; P < 0.001) were associated with an increased likelihood of AVG use. Maori and Pacific Island patients were less likely to use an AVG compared with Caucasians (odds ratio, 0.47; P < 0.05). Predictors of greater likelihood of catheter use were female sex (odds ratio, 3.9; P < 0.001), late referral (odds ratio, 1.60; P < 0.05), and age (odds ratio, 1.02 per year increase; P < 0.001). Proportions of access types varied significantly across the 7 treating centers (AVFs, 32% to 86%; AVGs, 2% to 32%; catheters, 9% to 33%; P < 0.001). After adjusting for confounding factors, significant differences persisted among access types in some centers and the national average.

CONCLUSION

Certain patient characteristics, such as age and female sex, are associated strongly with increased AVG and catheter use. However, the significant variation in risk across centers suggests more attention needs to be given to physician practice patterns to increase AVF use rates.

Long-term survival of arteriovenous fistulas in home hemodialysis patients

BACKGROUND

We report the outcome of arteriovenous (AV) fistulas created and managed by a multidisciplinary team in patients on hemodialysis (HD) over 20 years.

METHODS

We analyzed 432 AV fistulas in 301 home HD patients (12% diabetic; median age 47 years) followed for up to 161 months. Observed end points were spontaneous or surgical AV fistula closure, or construction of a new vascular anastomosis. Survival was analyzed for first and second AV fistulas and predictors of outcome for first AV fistulas.

RESULTS

One vascular surgeon constructed 58% of AV fistulas. Three hundred sixty-seven AV fistulas were in the forearm, 64 at or above the elbow, and 1 in the thigh. Four hundred fourteen AV fistulas used in situ vessels, and 18 were autografts. Two hundred thirty-one anastomoses were side-to-side. Only five grafts were placed during this time. There were 131 second and subsequent AV fistulas in 76 patients, 79 (60%) of which required primary construction, and 52 used arterialized vessels from a previous AV fistula. The median time from formation to use for first and second AV fistula, respectively, was 2.39 (SE 0.35) and 3.2 (SE 1.9) months. Assisted survival from first use for first AV fistula was 90% at 1 year, 66% at 5 years, 84% at 1 year, and 72% at 2 years for second AV fistula. AV fistula survival from creation was superior for side-to-side anastomoses (P < 0.0001) and in men (P= 0.05).

CONCLUSION

A multidisciplinary approach has been successful in providing durable AV fistulas for home HD for >95% of consecutive patients entering our program.

The natural history of autogenous radio-cephalic wrist arteriovenous fistulas of haemodialysis patients: a prospective observational study

BACKGROUND

Clinical practice guidelines have supported vascular access surveillance programmes on the premise that the natural history of the vascular access will be altered by radiological or surgical interventions after vascular access dysfunction is detected. The primary objective of this study was to assess the actual risk of thrombosis of autogenous radio-cephalic (RC) wrist arteriovenous fistulas (AVFs) without any pre-emptive interventions.

METHODS

We enrolled 52 randomly selected adult Caucasian prevalent haemodialysis (HD) patients, all with autogenous RC wrist AVFs, into this prospective, observational study aimed to follow the natural history of their AVFs for 4 years. The protocol prescribed avoiding any surgical or interventional radiological procedures until access failure (AVF thrombosis or a vascular access not assuring a single-pool Kt/V > or =1.2). The subjects underwent yearly assessments of vascular access blood flow rate by means of a saline ultrasound dilution method.

RESULTS

All failures of vascular access were due to AVF thrombosis; none were attributed to an inadequacy of the dialysis dose. AVF thrombosis occurred in nine cases; a rate of 0.043 AVF thrombosis per patient-year at risk. A receiver operating characteristic curve, evaluating the diagnostic accuracy of baseline vascular access blood flow rate values in predicting AVF failure, showed an under-the-curve area of 0.82+/-0.05 SD (P = 0.01). The value of vascular access blood flow rate, identified as a predictor of AVF failure, was <700 ml/min with an 88.9% sensitivity and 68.6% specificity. When subdividing the population of AVFs into two groups according to the baseline vascular access blood flow rates, two out of the nine thromboses occurred among the AVFs that had baseline blood flow rates >700 ml/min (n = 31), whereas seven occurred among the AVFs that had baseline blood flow rates <700 ml/min (n = 21). The 4 year cumulative actuarial survival was 74.36 and 20.80%, respectively (log-rank test, P = 0.04). The 24 AVFs that remained patent at the end of the 4 years maintained a median blood flow rate > or =900 ml/min at all time points studied. Worth noting is that, five of them (20.8%) remained patent throughout the study with a blood flow rate consistently < or =500 ml/min.

CONCLUSIONS

This study shows a very low rate of AVF thrombosis per patient-year at risk and a high actuarial survival of autogenous RC wrist AVFs, particularly of those having a blood flow rate >700 ml/min. Thus, a vascular access blood flow rate <700 ml/min appears to be a reliable cut-off point at which to start a closer monitoring of this parameter-which may lead to further investigations and possibly interventions relevant to the function of the AVFs.

Durability and cumulative functional patency of transposed and nontransposed arteriovenous fistulas

OBJECTIVES

Preoperative duplex scanning of arm and forearm veins has increased the creation of autogenous arteriovenous (AV) fistulas. However, the cumulative functional patency and durability of transposed AV fistulas (TAVF) compared with nontransposed AV fistulas (AVF) and prosthetic bridging grafts (AVG) remains ill-defined.

METHODS

From January 1998 to December 2002, 245 dialysis access procedures were performed at University Hospital and the Veteran Affairs Medical Center in New Jersey. Follow-up data were available for 125 procedures (TAVF, n = 42; AVF, n = 30; AVG, n = 53) performed in 97 patients. All access procedures were planned on the basis of preoperative duplex scans of arm and forearm veins. Functional patency was defined as ability to cannulate and hemodialyze patients successfully. Primary and secondary cumulative functional patency of TAVFs, AVFs, and AVGs was determined with life table analysis, and differences were analyzed with the log-rank test. Differences in revision rates, including thrombolysis, thrombectomies, and operative revisions, were determined with the Fisher exact t test.

RESULTS

Mean follow-up was 18 months (range, 4-24 months). For TAVFs, AVFs, and AVGs, primary functional patency rate at 1 year was 76.2%, 53.3%, and 47.2%, respectively, and at 2 years was 67.7%, 34.4%, and 25.5%, respectively. Similarly, secondary functional patency rate at 1 year was 83.2%, 66.7%, and 58.5%, respectively, and at 2 years was 74.6%, 56.2%, and 40.2%, respectively. Primary and secondary functional patency rates for TAVFs were superior to those for AVGs at 1 and 2 years (P <.001). AVFs had superior secondary functional patency rate at 2 years, compared with AVGs (P <.05), and TAVFs had superior primary and secondary patency rates at 2 years, compared with AVFs (P <.05). AVGs required significantly more revisions than did TAVFs (28.5% vs 54.7%; P <.001) or AVFs (36.7% vs 54.7%; P <.05).

CONCLUSIONS

Preoperative duplex scanning of upper arm and forearm veins facilitated successful creation of all types of autogenous fistulas at our institution. TAVF cumulative functional patency rates were superior compared with AVGs and AVFs. Furthermore, TAVFs and AVFs were more durable and required fewer revisions than did AVGs. When preoperative duplex criteria indicate that TAVFs can be performed, they should be the initial access of choice, because of their superior long-term patency and durability.

Local haemodynamics and shear stress in cuffed and straight PTFE-venous anastomoses: an in-vitro comparison using particle image velocimetry

OBJECTIVES

To use particle image velocimetry (PIV) to study the haemodynamics and shear stress associated with cuffed and straight PTFE-venous anastomoses.

METHODS

Silastic models of a straight and cuffed (Venaflo) PTFE-venous anastomoses were attached to a pulsatile flow 'Berlin Heart' circuit filled with glycerine/water and hollow glass tracer spheres. Instantaneous velocity fields were obtained PIV and shear rates and patterns calculated from frame-by-frame analysis.

RESULTS

A high velocity jet struck the anastomotic 'floor' and was deflected toward the venous outflow. Shear stresses near the floor were significantly higher, in the straight anastomosis. Sites of high shear stress correlated well with the known sites of intimal hyperplasia.

CONCLUSIONS

A cuffed anastomosis type may be favourable in terms of local haemodynamics so enhancing the long-term patency of PTFE-venous grafts.

Vascular access surveillance: evaluation of combining dynamic venous pressure and vascular access blood flow measurements

BACKGROUND/AIMS

Vascular access thrombosis is one of the most morbid problems encountered by hemodialysis patients. Surveillance protocols utilizing venous pressure (Vp) and vascular access blood flow (VABF) measurements have been employed to preserve vascular access. We undertook a study to evaluate combined dynamic Vp and VABF measurements in the identification of vascular access impairment. We also assessed the effect of preventive repair on thrombosis rates in impaired vascular accesses identified by surveillance.

METHODS

Eighty-six chronic hemodialysis patients with a functioning vascular access were enrolled into the surveillance protocol. All vascular accesses with greater than 50% of monthly Vp readings >120 mm Hg or VABF <500 ml/min in arteriovenous fistulas (AVFs) and VABF <650 ml/min in arteriovenous grafts (AVGs), or a decrease in VABF >25% compared to the highest previously measured value, were considered positive. Stenosis >50% on fistulography or a thrombotic event were defined as a 'vascular access impairment episode' while a stenosis <50% or the absence of a thrombotic event was defined as 'no vascular access impairment episode'. Thrombosis rates and intervention rates were calculated per access year at risk.

RESULTS

The sensitivity and specificity of the combined surveillance protocol for AVFs were 73.3 and 91%, respectively. In AVGs, they were 68.8 and 87.5%, respectively. The rate of thrombotic events was lower in patients who underwent early repair. The addition of dynamic Vp did not reduce the thrombosis rate any further than surveillance based on VABF alone.

CONCLUSION

Combined monitoring for surveillance of AVFs improved sensitivity but had little benefit in AVGs over VABF monitoring alone. Raising VABF cutoff levels might increase and improve identification of vascular access risk for thrombosis, but at the expense of lower specificity.

In vivo validation of glucose pump test for measurement of hemodialysis access flow

BACKGROUND

The glucose pump test (GPT) is a recently introduced method of measuring hemodialysis access blood flow (Qa). A validation of GPT during dialysis has not yet been done, and performance characteristics of the method have not yet been fully analyzed.

METHODS

The authors studied 33 patients (25 synthetic grafts, 8 autogenous arteriovenous fistulae). Qa measurements by ultrasound dilution (UD) and GPT were done in triplicate during dialysis. In GPT, a baseline blood sample (C(1)) was obtained, followed by infusion of a 10% glucose solution (C(i)) through the arterial needle into the access at 16 mL/min (Q(i)). After 11 seconds, a downstream blood sample (C(2)) was aspirated from the venous needle. C(1) and C(2) glucose were measured by glucometer. Qa was computed by the equation: Qa = Q(i)(C(i) - C(2))/(C(2) - C(1)). A model of the access vascular circuit was used to determine the influence of C(2) aspiration on the Qa measurement.

RESULTS

Mean Qa was 1413 mL/min by UD versus 1,496 mL/min by GPT (P = 0.11). There was a strong linear correlation between the 2 methods (r = 0.905; P <0.001). The pooled coefficient of variation was 6.4% for UD and 9.6% for GPT. The circuit model showed that aspiration of C(2) causes an increase in Qa (DeltaQa) that depends on the aspiration rate (Q(ASP)) and fraction of resistance in the circuit that is downstream to the venous needle: DeltaQa = Q(ASP)(Downstream resistance)/(Total resistance). The model predicts the overestimate is approximately 62 mL/min for grafts and 120 mL/min for fistulae but may vary depending on the balance of resistances upstream and downstream to the venous needle.

CONCLUSION

This study shows that GPT closely correlates with UD, and the method has adequate precision. GPT is an inexpensive method that may help make Qa measurements more widely available than previously possible.

Perioperative topical bovine thrombin exposure is not associated with hemodialysis graft thrombosis

Arteriovenous (AV) graft use as hemodialysis access remains highly prevalent, with a consequent high thrombosis rate. The magnitude of this problem requires that all potentially modifiable risk factors for graft thrombosis be thoroughly investigated. During graft surgery, topical bovine thrombin is often administered, which can lead to the development of antibovine thrombin antibodies and subsequent hemostatic changes. A recent study correlated the presence of plasma antibovine thrombin antibodies with graft thrombosis in hemodialysis patients. We therefore hypothesized that perioperative topical bovine thrombin exposure would lead to the development of antibovine thrombin antibodies and graft thrombosis. We screened 314 hemodialysis patients and identified 73 patients who had 74 grafts placed for whom complete data on perioperative topical bovine thrombin exposure and subsequent graft outcomes was available. Sixty-one of these patients were available for retrospective measurement of antibovine thrombin antibodies, antihuman thrombin antibodies, and the thrombin activation markers thrombin activatible fibrinolysis inhibitor (TAFI) and thrombin precursor protein (TpP). In these grafts, there was no significant association between topical bovine thrombin exposure and primary assisted patency (P = 0.37). The presence of antibovine thrombin antibodies (P = 0.13), antihuman thrombin antibodies (P = 0.10), and increased TAFI (P = 0.18) were associated with trends toward reduced primary assisted patency which did not reach significance. There was a correlation between antibovine thrombin antibodies and antihuman thrombin antibodies (r = 0.30, P < 0.0001) and between TAFI and TpP trade mark (r = 0.30, P < 0.0001), but no significant correlation between topical bovine thrombin exposure and elevated levels of antibovine thrombin antibodies, antihuman thrombin antibodies, TAFI or TpP trade mark. We conclude that perioperative topical bovine thrombin exposure is not associated with subsequent graft thrombosis.

A multicenter study of permanent hemodialysis access patency: beneficial effect of clipped vascular anastomotic technique

OBJECTIVE

There is an urgent and compelling need to reduce the morbidity and expense of maintaining hemodialysis vascular access patency. This large, long-term, retrospective, multicenter study, which compared access patency of autogenous arteriovenous fistulas (AVF) and synthetic bridge grafts (AVG) created with conventional sutures or nonpenetrating clips, was undertaken to resolve conflicting results from previous smaller studies.

DESIGN

Patency data for 1385 vascular access anastomoses (clipped or sutured) was obtained from 17 hospitals and dialysis centers (Appendix). Five hundred eighteen AVF (242 clip, 276 suture) and 827 AVG (440 clip, 384 suture) were analyzed. Statistical comparisons were made with Kaplan-Meier survival analysis, log-rank test, two-sample t test, and X(2) test. The Cox proportional hazards model was used to confirm Kaplan-Meier analysis.

RESULTS

Access patency (primary, secondary, overall, and intention to treat) was significantly improved in access anastomoses constructed with clips. In the intention-to-treat group, primary patency at 24 months was 0.54 for clipped AVF and 0.34 for sutured AVF, and was 0.36 for clipped AVG and 0.17 for sutured AVG. At 24 months, primary patency rate for AVF successfully used for dialysis was 0.67 for clips and 0.48 for sutures, and for AVG was 0.39 for clips and 0.19 for sutured constructs. Interventions necessary to maintain patency were significantly fewer in clipped anastomoses.

CONCLUSION

Replacing conventional suture with clips significantly reduces morbidity associated with maintaining permanent hemodialysis vascular access. This beneficial effect may be due to the biologic superiority of interrupted, nonpenetrating vascular anastomoses.

Nursing issues related to patient selection, vascular access, and education in quotidian hemodialysis

BACKGROUND

Increased interest in quotidian hemodialysis (HD) programs requires that nephrology nurses have a larger role in transitioning patients to more frequent HD. Nursing issues include the selection, training, and education of patients before they begin more frequent HD therapy.

METHODS

The London Daily/Nocturnal Hemodialysis Study directly compared data from patients undergoing either short daily HD (n = 11) or long nocturnal HD (n = 12) with those undergoing conventional thrice-weekly HD (n = 22). Patient training, education, safety, and vascular access data were collected.

RESULTS

The patient training period varied from 10 to 25 days, with an average length of 16.64 days. Patients used 1 of 3 types of vascular access: native arteriovenous (AV) fistulae, grafts, or central catheters. No statistically significant differences in access flow rates between the study and control groups were noted or when comparing different types of access. A significant decrease in catheter infection rate was seen when patients switched to daily HD therapy. Patient cannulation surveys showed that patients with AV fistulae or grafts showed improvements with ease and comfort as the study progressed, and patients widely preferred the buttonhole technique to the rotating-needle method for cannulation.

CONCLUSION

With growing interest in the development of quotidian HD programs, HD nursing personnel face the exciting challenge of improving on existing training programs and treatment modalities.

Proximal radial artery as inflow site for native arteriovenous fistula

BACKGROUND

Most vascular surgeons favor an initial radial-cephalic anastomosis at the wrist for dialysis access when possible. As populations age and more chronically ill patients are offered dialysis, this native arteriovenous fistula (NAVF) is less frequently available. A brachial-cephalic anastomosis is generally considered to be the second choice for NAVF site. We report our experience in a series of patients where the proximal radial artery (PRA) serves as the primary inflow vessel.

STUDY DESIGN

We reviewed 139 consecutive dialysis access operations performed by the senior author. One hundred fourteen had an NAVF constructed. Seventy-three of these procedures in 71 patients involved the PRA as arterial inflow and are the subject of this report.

RESULTS

Mean age was 57 years. Thirty-six of the 71 were men. Seventy-one percent of the patients were diabetic and more than half had previous access surgery. Twenty-nine patients underwent preoperative ultrasonographic evaluation for feasibility and planning of the NAVF fistula. The 1-month patency rate for patients undergoing PRA fistula was 98%. Cumulative patency was 80% during the followup period of up to 42 months. No infectious or ischemic complications were noted during the study period.

CONCLUSIONS

We find the anterior position and mobility of the PRA offers a simple and tension-free anastomosis to the median antebrachial vein or one of its tributaries. This anastomotic site frequently allows dialysis in both the forearm and upper arm. The PRA allows for adequate arterial inflow while avoiding the risk of steal syndrome found with brachial artery fistulas. More extensive procedures or use of prosthetic grafts can be avoided.

A randomized controlled trial of blood flow and stenosis surveillance of hemodialysis grafts

BACKGROUND

It is widely accepted that hemodialysis graft surveillance combined with correction of stenosis reduces thrombosis and prolongs graft survival. Nevertheless, few randomized controlled trials have evaluated this approach.

METHODS

In this randomized controlled trial, 101 patients were assigned to control, flow (Qa), or stenosis groups, and were followed for up to 28 months. All patients had monthly Qa measured by ultrasound dilution and quarterly percent stenosis measured by duplex ultrasound. Referral for angiography was based on the following criteria: (1) control group (N = 34), clinical criteria; (2) flow group (N = 32), Qa <600 mL/min or clinical criteria; and (3) stenosis group (N = 35), stenosis>50% or clinical criteria. Stenosis >or=50% during angiography was corrected by preemptive percutaneous transluminal angioplasty (PTA).

RESULTS

The preemptive PTA rate in the control group (0.22/patient year) was two thirds the rate in the flow group (0.34/patient year), and was highest in the stenosis group (0.65/patient year, P < 0.01). The percentage of grafts that thrombosed was similar in the control (47%) and flow groups (53%), but reduced in the stenosis group (29%, P = 0.10). Two-year graft survival was similar in the control (62%), flow (60%), and stenosis groups (64%) (P = 0.89).

CONCLUSION

Qa and stenosis surveillance were not associated with improved graft survival, although thrombosis was reduced in the stenosis group. The most important factors in this result may be that monthly Qa and quarterly stenosis measurements were not accurate or timely indicators of risk of thrombosis or progressive stenosis. This study does not support the concept that Qa or stenosis surveillance are superior to aggressive clinical monitoring.

Acesso vascular para hemodiálise: avaliação do tipo e local anatômico em 23 unidades de diálise distribuídas em sete estados brasileiros

OBJETIVO: Demonstrar os acessos vasculares para hemodiálise mais utilizados em 23 unidades de hemodiálise, distribuídas em sete estados brasileiros. MÉTODO: Entre outubro de 1999 a agosto de 2000, foram avaliados 2559 pacientes em 23 unidades de hemodiálise distribuídas em 23 estados brasileiros onde foi observado: A - A freqüência da utilização do acesso vascular, se externo através de cateteres ou se interno através de fístula arteriovenosa (FAV). B - Os tipos de cateteres, se de curta permanência ou de longa permanência, assim como os locais anatômicos utilizados para sua inserção. C - Os tipos de FAV, se direta ou com interposição de algum tipo de prótese e os locais anatômicos onde foram construídas, se distais ou proximais. D - O custo financeiro com os acessos vasculares. RESULTADOS: Constatou-se que 93,4% dos pacientes tinham um acesso vascular através de FAV e 6,6% através de cateter. As FAV diretas distais foram as mais utilizadas em 74,8% dos pacientes; as FAV diretas proximais foram construídas em 21,7% das vezes; as FAV com politetrafluoretileno expandido (PTFE) 3,2% da totalidade; a veia safena foi utilizada em 0,1% e as FAV consideradas como outras em 0,2%. Os cateteres de longa permanência foram utilizados em 8,7% da totalidade dos cateteres e os de curta permanência em 91,3%. Como via de acesso a veia jugular foi utilizada em 42,4%, a veia subclávia em 42,4% e a veia femoral em 6,5%. O custo financeiro com acesso para hemodiálise foi de 1% do custo total das unidades. CONCLUSÕES: O acesso vascular no Brasil tem características próprias. O acesso mais utilizado é a FAV distal e o uso do PTFE é baixo.

Increased venous proinflammatory gene expression and intimal hyperplasia in an aorto-caval fistula model in the rat

We hypothesized that the venous limb of an arteriovenous (AV) fistula would evince up-regulation of genes relevant to vascular remodeling along with neointimal hyperplasia and relevant histological changes. Using the aorto-caval model of an AV fistula model in the rat, we demonstrate marked up-regulation in such proinflammatory genes as monocyte chemoattractant protein-1, plasminogen activator inhibitor-1, and endothelin-1, 2 weeks after the creation of the fistula. Neointimal hyperplasia occurred in variable degrees by 5 weeks after establishing the fistula, and by 16 weeks, such neointimal hyperplasia was progressive and pronounced; at this time point, abundant extracellular matrix was also observed. Smooth muscle cells were present in the hyperplastic neointima as evidenced by staining for alpha-smooth muscle actin; ultrastructurally, smooth muscle cells with a synthetic as well as a contractile phenotype were readily observed. Accumulation of extracellular matrix in the model at 16 weeks was accompanied by increased expression of transforming growth factor-beta1 mRNA, the latter finding contrasting with the suppression of transforming growth factor-beta1 mRNA observed in this model at 2 weeks. In summary, we describe marked up-regulation in proinflammatory genes and progressive neointimal formation in the venous vasculature in an AV fistula model in the rat. We suggest that such alteration in gene expression and histological injury, in conjunction with the relative simplicity of this model, offer a new approach in the study of such timely biological and clinically relevant phenomena as differential gene expression in response to hemodynamic forces, processes involved in vascular remodeling, mechanisms of injury in venous bypass grafts, and mechanisms of dysfunction of AV fistulae used in hemodialysis.

Significance of platelet activation in vascular access survival of haemodialysis patients

BACKGROUND

Vascular access failure is the most common cause of morbidity and hospitalization in haemodialysis (HD) patients. Although there are reports that anti-platelet agents can prevent vascular access thrombosis, the relationship between platelet activation and vascular access failure is not clear. The aim of this study was to investigate the role of platelet activation in recurrent vascular access failure.

METHODS

The studied subjects were divided into three groups: group I included 23 HD patients with recurrent vascular access failure (native arteriovenous fistula <2 year survival or synthetic arteriovenous graft <1 year survival), group II included 15 HD patients with longer vascular access survival (>5 year survival) and group III included 10 healthy volunteers as controls. The expression of platelet activation markers (CD62P and fibrinogen receptor) and the numbers of platelet-derived microparticles were measured and compared between groups.

RESULTS

CD62P-positive platelets were significantly higher in group I than in both group II (7.3+/-3.7 vs 3.5+/-1.3%; P<0.0005) and group III (2.9+/-0.9%; P<0.00005). Fibrinogen receptor-positive (PAC-1-positive) platelets were also significantly higher in group I than in group II (2.2+/-2.1 vs 0.9+/-0.7%; P<0.01) and group III (0.8+/-0.6%; P<0.01).

CONCLUSIONS

A higher level of circulating activated platelets is associated with shorter survival of vascular access in HD patients. The higher level of circulating activated platelets may be a predictor of recurrent vascular access failure. The potential advantageous effects of anti-platelet therapy on this patient population warrant further investigation.

The role of interventional radiology in management of patients with end-stage renal disease

The aim of the paper is to review the role of interventional radiology in the management of hemodialysis vascular access and complications in renal transplantation. The evaluation of patients with hemodialysis vascular access is complex. It includes the radiology/ultrasound (US) evaluation of the peripheral veins of the upper extremities with venous mapping and the evaluation of the central vein prior to the access placement and radiological detection and treatment of the stenosis and thrombosis in misfunctional dialysis fistulas. Preoperative screening enables the identification of a suitable vessel to create a hemodynamically-sound dialysis fistula. Clinical and radiological detection of the hemodynamically significant stenosis or occlusion demands fistulography and endovascular treatment. Endovascular prophylactic dilatation of stenosis greater than 50% with associated clinical abnormalities such as flow-rate reduction is warranted to prolong access patency. The technical success rates are over 90% for dilatation. One-year primary patency rate in forearm fistula is 51%, versus graft 40%. Stents are placed only in selected cases; routinely in central vein after dilatation, in ruptured vein and elastic recoil. Thrombosed fistula and grafts can be declotted by purely mechanical methods or in combination with a lytic drug. The success rate of the technique is 89-90%. Primary patency rate is 8-26% per year and secondary 75% per year. The most frequently radiologically evaluated and treated complications in renal transplantation are perirenal and renal fluid collection and abnormalities of the vasculature and collecting system. US is often the method of choice for the diagnostic evaluation and management of the percutaneous therapeutic procedures in early and late transplantation complications. Computed tomography and magnetic resonance are valuable alternatives when US is inconclusive. Renal and perirenal fluid collection are usually treated successfully with percutaneous drainage. Doppler US, magnetic resonance angiography and digital subtraction angiography have a principle role in the evaluation of vascular complications of renal transplantation and management of the endovascular therapy. Stenosis, the most common vascular complication, occurs in 1-12% of transplanted renal arteries and represents a potentially curable cause of hypertension following transplantation and/or renal dysfunction. Treatment with percutaneous transluminal renal angioplasty (PTRA) or PTRA with stent has been technically successful in 82-92% of the cases, and graft salvage rate has ranged from 80 to 100%. Restenosis occurs in up to 20% of cases, but are usually amenable to repeated PTRA. Complications such as arterial and vein thrombosis are uncommon. Intrarenal A/V fistulas and pseudoaneurysms are occasionally seen after biopsy, the treatment requires superselective embolisation. Urologic complications are relatively uncommon, predominantly they consist of the urinary leaks and urethral obstruction. Interventional treatment consists of percutaneous nephrostomy, balloon dilation, insertion of the double J stents, metallic stent placement and external drainage of the extrarenal collections.

Slow-flow venous pressure for detection of arteriovenous graft malfunction

BACKGROUND

Early detection with elective intervention of malfunctioning arteriovenous (AV) grafts improves access viability. Herein, we evaluated outlet venous pressure (OP), normalized by mean arterial blood pressure (MABP), at varying blood flow (Qb) rates in the detection of venous outlet stenosis.

METHODS

This single-center, observational study included stable dialysis patients with polytetrafluoroethylene (PTFE) AV grafts. Phase I involved the determination of the optimal Qb (0, 50, 250, or 400 mL/min) and threshold OP/MABP. Sixty-one patients were followed up for 6 months. The primary end point was graft thrombosis. Phase II assessed serial slow-flow pressure (SFpr = OP/MABP at Qb of 50 mL/min) in a larger sample size (N = 152). The primary end point was graft thrombosis. Phase III implemented the use of SFpr monitoring in the detection and correction of outlet lesion(s).

RESULTS

In phase I, 21 patients developed graft thrombosis. The most significant difference in pressure between the functioning and thrombosed grafts was at Qb of 0 mL/min and SFpr. The threshold of OP/MABP at Qb 0 (>0.53) and SFpr (>0.6) were predictive of graft thrombosis. In phase II, 37 of 42 patients with graft thrombosis had SFpr>0.6 (sensitivity 88.1%; specificity 97.2%; positive and negative predictive values were 90.2% and 95.5%, respectively). In phase III, 13 patients with SFpr>0.6 had outlet lesions on angiography.

CONCLUSION

Serial SFpr used in conjunction with angiography and angioplasty provides a strategy for reducing the incidence of thrombosis. This technique has comparable sensitivity and specificity to other existing methods. This technique is both time-efficient and cost-effective.

Transrenal arteriovenous dialysis graft creation: survival and patency in a swine model

PURPOSE

To investigate transrenal arteriovenous graft creation in an animal model and to report survival and patency.

MATERIALS AND METHODS

Arteriovenous grafts were created from the renal artery to the renal vein in 10 swine. Renal access was accomplished with a combined percutaneous and transvascular approach. A reinforced 6-mm polytetrafluoroethylene conduit was tunneled between both flank access points, and stent-grafts were deployed from each of the renal origins into the conduit. Clopidogrel (10 mg per kilogram of body weight) was administered intravenously during the procedure, followed by a daily oral dose (75 mg) for up to 2 weeks. Animals were monitored with auscultation and angiography for up to 1 month; necropsy was performed in all animals.

RESULTS

Rapid arteriovenous flow at completion angiography was achieved in eight of 10 animals. Shunts were patent in five of six animals that were followed for 1 month. Diffuse pseudointimal hyperplasia was mild in three of six shunts and moderate in two (focal stenoses). Immediate thrombosis occurred in the first two animals when the clopidogrel bolus was administered after stent-graft deployment. These shunts were recanalized mechanically. Shunts were immediately patent in five of the six remaining shunts when the clopidogrel bolus was administered prior to stent-graft deployment. Complications occurred in four of 10 animals, three of which were euthanized within 1 week. The bowel was traversed in two animals, and renal vein laceration occurred during two procedures because of failure of the stent-graft delivery system.

CONCLUSION

Transrenal arteriovenous graft creation in swine is technically feasible, and long-term patency is possible with antiplatelet therapy.

Preventing vascular access dysfunction: which policy to follow

In the USA, three Clinical Performance Measures are currently in place: increasing the number of autologous arteriovenous fistulas (AVFs) among incident hemodialysis patients to 50% and to 40% in prevalent hemodialysis patients; to foster the surveillance of accesses with preemptive correction of problems before accesses thrombose or fail, and to reduce the use of catheters in prevalent patients to less than 10%. Reduction of catheters will automatically result from initiatives that increase the construction of AVFs and preemptive monitoring and surveillance of accesses for dysfunction. Therefore, policies that promote the latter two vascular access aspects are most important to develop and follow. Of these two, however, the most impact will be made by promoting a policy to increase AVF creation in the timeliest manner possible. Strategies and resources needed to achieve these policies are presented. The need for a team approach is emphasized.

Basic steps for increasing the rate of autogenic vascular accesses for hemodialysis

The number of patients on chronic hemodialysis (HD) is steadily increasing worldwide. The creation of a well-functioning vascular access represents a critical aspect in their management. Autogenous arteriovenous fistulas (AVF) are considered the first choice vascular access in terms of lower morbidity and costs, and higher survival rates when compared with grafts. However, creating AVF at high rates is a complex task that requires a multidisciplinary approach, which includes nephrologists, access surgeons, dialysis nurses and radiologists. In the present work we review concisely the basic steps, for preserving all potential autogenic sites at both upper extremities for future AVF creation and, for prolonging the length of AVF survival. We feel that a more proactive involvement of nephrologists in the basic steps for AVF creation would substantially contribute to increase AVF rates among HD patients.

Improving quality of vascular access care for hemodialysis patients

BACKGROUND

Because quality of care for patients with end-stage renal disease (ESRD) has improved, they require long-term vascular access for hemodialysis. Construction of a native vein arteriovenous fistula (AVF) on the arm is considered best practice; a prosthetic graft (PG) AVF on the arm is a good alternative, although insertion of a central venous catheter (CVC), the third choice, is sometimes necessary. A quality improvement project was initiated at the dialysis unit of Rijnland Hospital (The Netherlands) to improve quality of vascular access care.

METHODS

Seventy-four patients were treated from January 2001 through June 2002. The list of preferred access operations was adapted from evidence-based guidelines. The percentages of CVCs and PGs were chosen as quality indicators.

RESULTS

Twelve of 19 patients (34%) appeared to be using CVCs unnecessarily. Actions were taken, and the CVC indicator decreased by 11%. The PG indicator decreased gradually from 24% to 8%.

DISCUSSION

Reductions in the use of CVCs and PGs suggest that the vascular access improvement project resulted in improvement of long-term vascular access for hemodialysis patients. A considerable decrease in the use of PGs and CVCs was achieved in 2001. However, a decrease of CVCs to < 20% has still not been realized, perhaps because new hemodialysis patients referred to the dialysis unit have already had CVCs inserted.

SUMMARY AND CONCLUSION

Considerable improvement, as reflected in the number of hemodialysis patients with CVCs or PGs, can be achieved with a minimum of costs.

Isometric exercise increases the size of forearm veins in patients with chronic renal failure

OBJECTIVES

Delay in maturation or failure of maturation of Cimino-Brescia fistulae contributes to the significant vascular access-related morbidity of chronic hemodialysis patients. Increased size and capacitance of native veins before the formation of vascular access has been considered an important variable in the success rate of native fistulae. We evaluated whether a formal exercise program might alter the size of native veins.

METHODS

The effect of exercise on venous size was evaluated in 5 patients with severe chronic renal failure [glomerular filtration rate, 30.6 +/- 5.3 mL/min (mean +/- SD)]. Five male patients with a mean age of 57 +/- 9 years underwent a 6-week forearm exercise training program, involving nondominant arms, that included isometric hand-grip contractions to 25 to 35% of MVC lasting 40 to 120 seconds and repetitive squeezing of squash and racquet balls. Both the volume and intensity of exercise training was increased weekly based on strength measured by hand-grip dynamometer and on the patients' indicated level of comfort. Cephalic vessel size in both the nondominant (trained) and dominant (control) arms, with and without a tourniquet, were obtained using Doppler ultrasound before and after the 6-week exercise training program.

RESULTS

The size of the cephalic vein of the exercised arm increased significantly ( < 0.05) compared with the control arm when measured in both the absence (048 +/- 0.016 versus 0.024 +/- 0.023 cm ) and the presence of a tourniquet (0.056 +/- 0.022 versus 028 +/- 0.027 cm ).

CONCLUSIONS

These findings indicate that a simple, incremental resistance, exercise-training program can cause a significant increase in the size of the cephalic vein commonly used in the creation of an arteriovenous fistula. The increase in size and resultant probable increase in blood flow might accelerate the maturation of native arteriovenous fistulae, thereby lessening the morbidity associated with vascular access.

Primary Forearm Arteriovenous Fistula for Hemodialysis Access — An Integrated Approach to Improve Outcomes

Purpose

Maximizing the ratio of primary arteriovenous fistula (PAVF) over bridge graft fistula (BGF) for hemodialysis access is a primary recommendation of the National Kidney Foundation published as Dialysis Outcomes Quality Initiative (DOQI). Imaging, anesthetic and surgical techniques were taken into account to achieve this and other goals, including extensive use of forearm vessels to lower immediate and early failure rates and prolong the useful life of PAVFs.

Design

Prospective non-randomized study.

Methods

High-resolution duplex ultrasonography (DUS) was added to careful clinical assessment in planning and follow-up of the dialysis access. Brachial plexus block, which allowed the use of an arterial tourniquet and gave a postoperative sympathectomy type effect, was used for anesthesia, and together with meticulous surgical technique, prevented spasm. Access puncture, post-operative follow-up and surgical revisions were planned in close cooperation with the nephrology team.

Findings

Ninety (57.3%) of the 157 fistulas constructed for new hemodialysis access between August 1998 and March 2000 were PAVFs. Seventy-three (81.1%) of these were confined to the forearm and comprise the study population, with a mean follow-up of 8.4±4.4 months. There were no immediate failures in the study group. The early failure rate (1 month) was 6.8% and revisions based on DUS were easily accomplished in all cases. The one year assisted primary patency rate was 81.8% and the secondary patency rate at 18 months was 98.6%.

Conclusions

DUS for planning and follow-up of PAVF along with careful surgical technique under a brachial plexus blockade can achieve a PAVF/BGF ratio well above 50% with a low early failure rate and a high secondary patency rate. Algorithms are presented to achieve these goals.

Tumor necrosis factor-alpha -308 gene polymorphism is associated with synthetic hemodialysis graft failure

BACKGROUND

Progressive venous stenosis mediated, in part, by inflammatory cytokines is a major cause of synthetic hemodialysis graft failure. A tumor necrosis factor-alpha (TNF-alpha) gene polymorphism (G to A, position -308) has been shown to increase plasma cytokine levels and severity of diseases with an underlying inflammatory component.

METHODS

We genotyped 67 patients with synthetic polytetrafluoroethylene (PTFE) grafts and examined the association of the high-(AA or GA) and low- (GG) production TNF-alpha-08 genotypes with the rate of graft failures/thrombosis and graft survival.

RESULTS

Hemodialysis patients with the high-production TNF-alpha genotypes had a significantly increased rate of PTFE graft failure at 90 days (37.2% versus 14%) and 1 year (62.8% versus 34.4%) after graft placement compared with patients with the low-production genotype (respectively). Hemodialysis patients with the high-production TNF-alpha genotypes had significantly lower cumulative PTFE graft survival at 1 year (29.4% +/- 11.1% versus 71.2 +/- 6.8%) and 2 years (22.1% +/- 10.5% versus 48.2 +/- 8.1%) compared with patients with the low-production genotype (respectively). Patients with the A allele had approximately twice the mean thrombosis rate compared with those who had the low-production TNF-alpha genotype (3.3 +/- 0.8 versus 1.7 +/- 0.4 thromboses/patient/year, respectively; mean +/- SEM, p < .05).

CONCLUSIONS

These data suggest that the TNF-alpha -308 A allele is associated with increased PTFE graft thrombosis and failure in hemodialysis patients.

Association between vascular access failure and the use of specific drugs: the Dialysis Outcomes and Practice Patterns Study (DOPPS)

BACKGROUND

Several drugs have been proposed to improve vascular access patency based on favorable anticoagulant, antiplatelet, or vascular-remodeling properties. However, there is little evidence to guide drug strategies.

METHODS

The association between vascular access patency and the use of specific drugs was studied in a large sample of US hemodialysis patients enrolled in the Dialysis Outcomes and Practice Patterns Study, an international, prospective, observational study. In general, it was assumed that the drugs were prescribed for indications unrelated to vascular access preservation. Primary (unassisted survival) and secondary vascular access patency (assisted survival) were modeled using Cox regression (time to failure) adjusted for age, sex, race, body mass index, incidence to end-stage renal disease, diabetes mellitus, hypertension, valvular disease, chronic obstructive pulmonary disease, aortic aneurysm, deep-vein thrombosis, number of previous permanent accesses, and facility-clustering effects. Fistulae (n = 900) and grafts (n = 1,944) were evaluated separately. Technical failures within the first 30 days of surgical placement were excluded from the analysis.

RESULTS

Treatment with calcium channel blockers was associated with improved primary graft patency (relative risk [RR] for failure, 0.86; P = 0.034). Aspirin therapy was associated with better secondary graft patency (RR, 0.70; P < 0.001). Treatment with angiotensin-converting enzyme inhibitors was associated with significantly better secondary fistula patency (RR, 0.56; P = 0.010). Patients administered warfarin showed worse primary graft patency (RR, 1.33; P = 0.037).

CONCLUSION

These findings should help guide clinical trial priorities toward vascular access preservation using one or more of the agents that show significant risk reduction for access failure in this study.

The role of APD in the improvement of outcomes in an ESRD program

We review the role of automated peritoneal dialysis (APD) in improving outcomes of an end-stage renal disease (ESRD) program. As the "integrated care approach" becomes accepted as the preferred strategy for treatment of ESRD patients, we looked for the potential place of APD in such an approach. APD has probably the same advantages as CAPD as a first-line renal replacement modality in suitable patients willing to perform PD. There is currently no hard evidence that residual renal function (RRF) should decline more rapidly in APD than in CAPD, at least if a dry abdomen during the day is avoided. The detection of peritonitis is probably more delayed in APD, but the frequency of peritonitis is lower, and there is no hard evidence pointing to a poorer outcome of peritonitis in APD as compared to CAPD. Quality of life is at least as good in APD, which is mostly related to the increased possibilities for adapting the exchange pattern to employment-related time frames. APD also has the potential to prolong technique success in patients failing CAPD rather than transferring them to hemodialysis. Nevertheless, APD remains more expensive and technically complicated, thereby missing the beauty of CAPD's simplicity. Therefore we believe that APD has its role in an integrated approach and that all patients should be informed of its potential. It would, however, not be correct to present APD as the preferred PD method for all patients, as it also has some drawbacks that make it less suitable for some categories of patients. In all cases, patients should have a free and informed choice.

Increasing arteriovenous fistulas in hemodialysis patients: problems and solutions

National guidelines promote increasing the prevalence of fistula use among hemodialysis patients. The prevalence of fistulas among hemodialysis patients reflects both national, regional, and local practice differences as well as patient-specific demographic and clinical factors. Increasing fistula prevalence requires increasing fistula placement, improving maturation of new fistulas, and enhancing long-term patency of mature fistulas for dialysis. Whether a patient receives a fistula depends on several factors: timing of referral for dialysis and vascular access, type of fistula placed, patient demographics, preference of the nephrologist, surgeon, and dialysis nurses, and vascular anatomy of the patient. Whether the placed fistula is useable for dialysis depends on additional factors, including adequacy of vessels, surgeon's experience, patient demographics, nursing skills, minimal acceptable dialysis blood flow, and attempts to revise immature fistulas. Whether a mature fistula achieves long-term patency depends on the ability to prevent and correct thrombosis. An optimal outcome is likely when there is (1) a multidisciplinary team approach to vascular access; (2) consensus about the goals among all interested parties (nephrologists, surgeons, radiologists, dialysis nurses, and patients); (3) early referral for placement of vascular access; (4) restriction of vascular access procedures to surgeons with demonstrable interest and experience; (5) routine, preoperative mapping of the patient's arteries and veins; (6) close, ongoing communication among the involved parties; and (7) prospective tracking of outcomes with continuous quality assessment. Implementing these measures is likely to increase the prevalence of fistulas in any given dialysis unit. However, differences among dialysis units are likely to persist because of differences in gender, race, and co-morbidity mix of the patient population.

Association between blood pressure, ultrafiltration, and hemodialysis graft thrombosis: a multivariable logistic regression analysis

Although a low blood flow (Q(a)) is the most important cause of graft thrombosis, several studies have shown that Q(a) measurements do not accurately predict thrombosis. This suggests that additional variables may influence thrombosis. Identification of such variables may be essential to designing surveillance protocols that accurately predict thrombosis. In this nested case-control study, we prospectively followed 105 patients for up to 2.5 years in order to test the association of a number of variables with thrombosis. These included Q(a) (monthly by ultrasound dilution), percentage stenosis (quarterly by duplex ultrasound), mean arterial pressure (MAP), percentage ultrafiltration (%UF) during dialysis (%UF = 100[liters]/[kilogram of weight]), and other variables that defined patient and graft characteristics. Patients were divided into patent (n = 53) and thrombosed groups (n = 52), and MAP and %UF from seven consecutive dialysis sessions were analyzed. In the thrombosed group, the last session was the final session before thrombosis. A multivariable logistic regression model showed that Q(a), MAP (the predialysis average of seven sessions), and %UF (from the last session) were independently associated with thrombosis, whereas all other variables were not. The model yielded the following odds ratios for thrombosis: for a single Q(a) value (reduction of 1,000 mL/min), 12.0 (P < 0.01); for %UF (increase of 4%), 5.3 (P < 0.01); for MAP (reduction of 30 mm Hg), 4.1 (P = 0.02); and for percentage decrease in Q(a) (> or =20% versus <20%), 2.4 (P = 0.12). We conclude that in addition to Q(a), both %UF at the last session before thrombosis and average predialysis MAP from seven sessions are independently associated with thrombosis. These results help explain why Q(a) alone does not accurately predict thrombosis. A prospective study is needed to determine whether %UF at each session and a moving average MAP from seven sessions improve the prediction of thrombosis. However, it should be recognized that a large %UF is a preterminal event that likely provides too short a warning for intervention before thrombosis.

Vascular access: anatomy, examination, management

A systematic approach to managing vascular access problems is the key to reducing current high rates of access thrombosis and failure. This approach begins with a thorough knowledge of vascular access anatomy that, when combined with the physical examination, can help optimize access planning and maintenance. Because of the high complication rate of synthetic grafts, there has been increased emphasis on creating autogenous arteriovenous (AV) fistulae, which, once established, are more trouble-free. The benefit of increased fistula creation will not be realized, however, until the high rate of early fistula failure is reduced. It is widely recommended that graft surveillance programs be implemented and that stenosis be corrected when accompanied by graft dysfunction. Graft blood flow (Q(a)) is the preferred surveillance method, but has a poor accuracy in predicting thrombosis. Most studies that have evaluated the benefit of Q(a) surveillance have used historical control groups, or have been retrospective or nonrandomized. Consequently, we believe it is not currently possible to make definitive, evidence-based recommendations concerning Q(a) surveillance. The most important factor in access survival may be a team approach with an organized commitment to access planning followed by recognition and treatment of access problems.

A novel technique designed to minimize the morbidity of failure of arteriovenous access in hemodialysis patients

The failure of dialysis access grafts leads to significant morbidity rates in patients with end-stage renal disease. We describe a novel technique for the insertion of new polytetrafluoroethylene graft segments designed to reduce this morbidity rate. Patients found to have significant intragraft deterioration at thrombectomy undergo insertion of a new nonanastamosed graft parallel to the existing graft. At the next failure of the existing graft, the nonanastamosed segment is anastamosed and used immediately for dialysis, obviating the need for a temporary catheter. Thirty patients have undergone this technique, and 89% of those who returned to surgery have had successful anastamosis of their new segments. Two patients were found to have inadequate incorporation of their new segments into the subcutaneous tissue, and one became frankly infected.

Autogeneous elbow fistulas: the effect of diabetes mellitus on maturation, patency, and complication rates

OBJECTIVES

diabetes mellitus is an increasingly common cause of end stage renal failure (ESRF) and the establishment of adequate permanent vascular access for dialysis is a major cause of morbidity and mortality in these patients. The aim of this study was to compare the availability of suitable vein, maturation rates, patency and complication rates of autogeneous elbow fistulas in diabetics and non-diabetics at a single centre where an autogeneous vein only policy is employed.

DESIGN

retrospective series.

PATIENTS AND METHODS

two hundred and ninety-three elbow fistulas were attempted in 232 patients over a seven year period, [median age 60 years (range 14-94 years)], of which 210 were in non-diabetic and 83 were in diabetic patients. The diabetic group had a significantly higher proportion of male patients (p < 0.05), peripheral vascular disease and established ESRF.

RESULTS

there was a trend towards a higher technical success rate in the non-diabetic group (98% versus 93% p = 0.057). There was no significant difference between the primary failure rate, fistula maturation rate, revision rate or incidence of complications between the two groups. Diabetes had no effect on cumulative secondary fistula patency even when stratified for Type 1/Type 2 diabetes, female sex, old age or primary versus subsequent procedures.

CONCLUSION

diabetes mellitus has no significant detrimental effect on outcome following formation of autogeneous elbow fistulas for haemodialysis.

Hemodialysis vascular assessment by an ultrasound dilution method (transonic) in patients older than 65 years

Malfunction of vascular access is one of the most frequent causes of morbidity and mortality in hemodialysis patients (HD). Early diagnosis makes possible the most frequent vascular access (VA) used in HD patients. The arteriovenous fistula (AVF), both autologous or heterologous, is the appropriate correction by an interventional radiologist or by surgery, before thrombosis appears. For this purpose, a follow-up of VA is mandatory. New technologies offer non-invasive methods for this purpose. In HD sessions ultrasound 'on line' and ultrasound-dilution techniques permit us to monitor vascular access in HD patients. Also transonic technology has been validated for this purpose, although the limitations of its use among elderly patients is unknown. Using the Transonic HD01 monitor, we studied vascular access in 45 patients in HD older than 65 years, and compared them with 47 patients who were younger than 65 years. The parameters analyzed were: effective flow Qt, recirculation, venous pressure and access flow. We found no significant differences between these parameters but in both groups found that the effective flow measure by Transonic was lower than that measured by a blood pump. Both groups contained patients who had no recirculation but had an access flow that was lower than expected. To rule out stenosis of VA in those patients, we performed an Eco Doppler confirming that all patients had stenosis. With this method, one can determines the access flow and thus predicts the possibility of future thrombosis.

CONCLUSION

Our data confirm that one can evaluate VA in patients older than 65 years with Transonic HD01 monitor, and also in patients younger than 65 years. Due to the special characteristics of the vessels in elderly patients, Transonic HD01 monitor is a good method by which to monitor VA in them.