Dialysis therapies: a National Dialogue.

The National Institute of Diabetes, Digestive, and Kidney Diseases-supported Kidney Research National Dialogue asked the scientific community to formulate and prioritize research objectives that would improve our understanding of kidney function and disease. Kidney Research National Dialogue participants identified the need to improve outcomes in ESRD by decreasing mortality and morbidity and enhancing quality of life as high priority areas in kidney research. To reach these goals, we must identify retained toxins in kidney disease, accelerate technologic advances in dialysate composition and devices to remove these toxins, advance vascular access, and identify measures that decrease the burden of disease in maintenance dialysis patients. Together, these research objectives provide a path forward for improving patient-centered outcomes in ESRD.

Academic interventional nephrology: a model for training, research, and patient care.

Dialysis vascular access dysfunction is currently a huge clinical problem. We believe that comprehensive academic-based dialysis vascular access programs that go all the way from basic and translational science investigation to clinical research to a dedicated curriculum and opportunities in vascular access for nephrologists in training are essential for improving dialysis vascular access care. This paper reviews the fundamental concepts and requirements for us to move toward this vision.

Dialysis vascular access management by interventional nephrology programs at University Medical Centers in the United States.

The development of interventional nephrology has undoubtedly led to an improvement in patient care at many facilities across the United States. However, these services have traditionally been offered by interventional nephrologists in the private practice arena. While interventional nephrology was born in the private practice setting, several academic medical centers across the United States have now developed interventional nephrology programs. University Medical Centers (UMCs) that offer interventional nephrology face challenges, such as smaller dialysis populations, limited financial resources, and real or perceived political "turf" issues." Despite these hurdles, several UMCs have successfully established interventional nephrology as an intricate part of a larger nephrology program. This has largely been accomplished by consolidating available resources and collaborating with other specialties irrespective of the size of the dialysis population. The collaboration with other specialties also offers an opportunity to perform advanced procedures, such as application of excimer laser and endovascular ultrasound. As more UMCs establish interventional nephrology programs, opportunities for developing standardized training centers will improve, resulting in better quality and availability of nephrology-related procedures, and providing an impetus for research activities.

Role of access surveillance and preemptive intervention.

Vascular access dysfunction continues to be a major cause of morbidity and mortality in the end-stage renal patient. Thrombosis is the primary cause of prosthetic arteriovenous access (ie, graft) failure caused by the progressive development of neointimal hyperplasia, which eventually leads to a stenosis, usually at the venous anastomosis. More than 20 years ago, observational studies using a variety of surveillance techniques, coupled with preemptive angioplasty, convincingly demonstrated the ability to detect venous stenosis, and elective treatment of stenoses significantly decreased both thrombosis and access loss. Although multiple observational studies have shown a benefit from surveillance, these studies generally had no control population, used historical controls, or used incorrect statistical analysis. However, five randomized controlled trials that evaluated the effect of graft surveillance coupled with preemptive angioplasty have failed to demonstrate a benefit on graft outcomes, including prolongation of graft survival. This review will examine the role of access surveillance and preemptive angioplasty in achieving the goal of reducing vascular access thrombosis and prolonging access survival.

Avoiding a cutdown--use of the transcatheter extractor in removal of tunneled dialysis catheters.

The purpose of our study was to evaluate the use of a transcatheter extractor (TCE) device in removing cuffed tunneled dialysis catheters without a surgical cutdown. We report eight cases where a TCE was used to successfully remove cuffed tunneled dialysis catheters through the exit site that would have otherwise required a second incision. The cuff was above the clavicle in all cases and varied 3-5 cm from the exit site. The method included inserting the device over the catheter through the exit site and engaging it over the cuff. A to-and-fro motion was then used in the same plane as the catheter to dissect the cuff from the surrounding tissue. Once the cuff was freed, the catheter was removed easily without resistance. The fibrous cuff was removed intact in all cases. We conclude that the use of this device may help avoid a cutdown and minimize trauma to the patient. It is an effective technique to remove tunneled dialysis catheters and is particularly useful in catheters with ingrown cuffs further from the exit site.

Successful models of interventional nephrology at academic medical centers.

The foundation of endovascular procedures by nephrologists was laid in the private practice arena. Because of political issues such as training, credentialing, space and equipment expenses, and co-management concerns surrounding the performance of dialysis-access procedures, the majority of these programs provided care in an outpatient vascular access center. On the basis of the improvement of patient care demonstrated by these centers, several nephrology programs at academic medical centers have also embraced this approach. In addition to providing interventional care on an outpatient basis, academic medical centers have taken a step further to expand collaboration with other specialties with similar expertise (such as with interventional radiologists and cardiologists) to enhance patient care and research. The enthusiastic initiative, cooperative, and mutually collaborative efforts used by academic medical centers have resulted in the successful establishment of interventional nephrology programs. This article describes various models of interventional nephrology programs at academic medical centers across the United States.

Controversial vascular access surveillance mandate.

The Centers for Medicare and Medicaid Services (CMS) recently revised the requirements that end-stage renal disease (ESRD) dialysis facilities must meet to be certified under Medicare. The CMS ESRD Interpretive Guidance Update states that the dialysis facility must now have an ongoing program of hemodialysis vascular access surveillance. Surveillance usually refers to monthly access blood flow or static dialysis venous pressure measurements combined with preemptive correction of stenosis. However, surveillance as currently practiced does not accurately predict synthetic graft thrombosis or prolong graft life. There is limited evidence that monthly surveillance may reduce native arteriovenous fistula thrombosis without prolonging fistula life, but the effect on thrombosis awaits further confirmation. Thus, the CMS surveillance requirement is not evidence based. We recommend the following changes to the ESRD Interpretive Guidance Update: only monitoring (e.g., physical examination) is required, whereas the proper role of surveillance awaits the results of further research. Such changes would allow nephrologists to apply the clinical judgment and individualized care that is most beneficial to their patients.

Risk of hemodialysis graft thrombosis: analysis of monthly flow surveillance.

BACKGROUND: During clinical application of flow surveillance of hemodialysis grafts, the risk of thrombosis is assessed month after month, rather than after one or several measurements, as has been done in published studies. Adequate assessment of risk should consider the many measurements obtained over time. STUDY DESIGN: Prospective cohort diagnostic test study. SETTING & PARTICIPANTS: 176 patients with hemodialysis grafts from 2 university-affiliated dialysis units during a 6-year period. INDEX TESTS: Monthly measurement of graft blood flow or change in flow. OUTCOME: Graft thrombosis. RESULTS: We used logistic regression analysis to compute the risk of thrombosis and used receiver operating characteristic (ROC) curves to assess the accuracy in predicting thrombosis within 1 month. Newer grafts were most likely to thrombose, whereas older grafts were unlikely to thrombose even at low flows or large decreases in flow. Areas under the ROC curves were 0.698 for flow and 0.713 for change in flow measured over 2 months. Flow predicted thrombosis with a sensitivity of 53% at a specificity of 79%, and change in flow had a sensitivity of 58% at a specificity of 75%. More than half the thromboses lacked a change in flow measurement, usually because thrombosis occurred before a change could be measured. Thus, the effective predictive accuracy of change in flow was much less than the ROC curves indicated because the curves do not consider missing measurements. LIMITATIONS: Performance characteristics of index tests may vary across patient populations. CONCLUSION: Flow and change in flow are inaccurate predictors of thrombosis. Many thromboses are not predicted, and intervention based on surveillance likely yields many unnecessary procedures. Thus, this study does not support routine application of surveillance to prevent thrombosis.

Inflow stenosis obscures recognition of outflow stenosis by dialysis venous pressure: analysis by a mathematical model.

BACKGROUND: Recent studies have shown that inflow stenosis of haemodialysis grafts is more common than previously realized. The influence of inflow stenosis on graft haemodynamics and venous pressure (VP) surveillance has not been previously systematically studied. METHODS: We used a well-established mathematical model to determine the relation between inflow stenosis and static VP (adjusted for mean arterial pressure, VP/MAP), outflow stenosis and artery and vein luminal diameters. We applied low, median and high ratios of artery/vein diameters from 94 patients with grafts. The median ratio was 0.77, indicating that the artery was generally narrower than the vein. RESULTS: The model shows that inflow stenosis reduces VP/MAP. More importantly, however, as outflow stenosis progresses, fixed inflow stenosis causes a delayed increase in VP/MAP followed by a rapid increase at critical outflow stenosis. When both stenoses progress together, their relative rates determine whether and how rapidly VP/MAP increases. The increase in VP/MAP is remarkably abrupt when the rate of inflow stenosis approaches that of outflow stenosis. No increase occurs when inflow stenosis progresses as fast or faster than outflow stenosis. CONCLUSION: Inflow stenosis exerts its most important haemodynamic effect through its interaction with outflow stenosis. As outflow stenosis progresses, inflow stenosis causes a delayed and then rapid increase in VP/MAP at critical outflow stenosis. This increase may not be detected before thrombosis unless measurements are very frequent. Inflow stenosis has an important impact on graft haemodynamics and surveillance because of its location in the relatively narrow inflow tract.

Frequency of swing-segment stenosis in referred dialysis patients with angiographically documented lesions.

BACKGROUND: The segment of the vein mobilized for arterial anastomosis in the creation of an arteriovenous fistula (AVF) is the swing segment. This segment may experience turbulent flow and altered shear mechanical stress that result in stenosis. We sought to determine the frequency of stenotic lesions in the swing segment. STUDY DESIGN: Case series. SETTINGS & PARTICIPANTS: From January 31, 2003, to June 30, 2005, records of all patients referred to an outpatient hemodialysis vascular access center for AVF dysfunction were reviewed (n = 484). Of these, 278 patients had angiographically documented stenosis (any degree of luminal narrowing) on their first visit. OUTCOMES & MEASUREMENTS: Distribution of stenoses in different segments of the AVF. Swing-segment stenoses were classified as proximal (outflow into axillary vein system), distal or juxta-anastomotic (adjacent to the anastomosis), and the cephalic arch. RESULTS: Overall prevalence of angiographically documented swing segment stenosis (proximal, distal or juxta-anastomotic, and cephalic arch) was 45.7% (127 of 278 patients), whereas the remaining stenoses (151 of 278 patients) were distributed among the puncture zone, arterial, arterial anastomosis, and central veins. The most frequent location of the swing-segment stenosis was juxta-anatomosis (63%; 80 of 127 patients), followed by cephalic arch (19%; 24 of 127 patients) and proximal swing segment (18%; 23 of 127 patients). The distribution of swing-segment stenosis (n = 127) was equivalent among the various fistulas (brachial-cephalic, 35.4%; radial-cephalic, 33.9%; and brachial-basilic, 30.7%). Eighty-three percent of swing-segment stenoses were significant (>50% luminal narrowing) and underwent percutaneous transluminal angioplasty, with a 93% success rate. LIMITATIONS: Retrospective nature of the study and potential selection bias. CONCLUSION: In our population, swing-segment stenosis is the most common lesion in dysfunctional AVFs; juxta-anastomotic stenosis is the predominant lesion independent of fistula type. Whether the occurrence of swing-segment stenosis is caused by mobilization of the vein during surgery is not clear.

Efficacy and safety results with the LifeSite hemodialysis access system versus the Tesio-Cath hemodialysis catheter at 12 months.

PURPOSE: To compare the performance and safety of a fully subcutaneous vascular access device, the LifeSite hemodialysis access system, versus a tunneled hemodialysis catheter, the Tesio-Cath, at 1 year after implantation. MATERIALS AND METHODS: Sixty-eight patients who required hemodialysis received implantation of the LifeSite device or a Tesio-Cath device as a part of this multicenter study. Thirty-four patients were treated in each group. The endpoints observed included blood flow rates and associated venous pressures, overall and device-related adverse events, the need for thrombolytic infusions, device-related infections (DRIs) and associated hospitalizations, and technical device survival. RESULTS: During the 12-month observation period, significantly higher venous pressures were required in patients with the Tesio-Cath to achieve blood flow rates comparable with those achieved with the LifeSite device. Patients in the LifeSite group experienced a significantly lower rate of non-device-related adverse events (P < .001), device-related adverse events (P < .016), need for thrombolytic infusions (P < .002), and DRIs (P < .013) compared with patients in the Tesio-Cath group. There was a trend toward a lower number of hospital days per month for DRIs in the LifeSite group, with the rate for the Tesio-Cath group being twice that in the LifeSite group. The use of the LifeSite device was also associated with a significantly higher probability of device survival for 12 months after censoring for planned removals (P < .031). CONCLUSIONS: The results of the present study demonstrate superior device performance and technical device survival, reduced complications, and the need for fewer interventions with the LifeSite hemodialysis access system compared with a standard hemodialysis catheter during a 1-year time period after implantation.

Fluoroscopy-assisted placement of peritoneal dialysis catheters by nephrologists.

In the early 1950s and 1960s, peritoneal dialysis (PD) was used primarily to treat patients with acute renal failure. Continuous ambulatory peritoneal dialysis (CAPD) was introduced in 1976 and continues to gain popularity as an effective method of renal replacement therapy for patients with end-stage renal disease (ESRD). The PD catheter is inserted into the abdominal cavity either by a surgeon, interventional radiologist, or nephrologist. We have adopted a percutaneous approach with fluoroscopic guidance for PD catheter insertion that is easy, safe, and provides good patency and infection rate results. In this article we describe the technique and our results. From August 2000 to May 2003, 34 PD catheters out of 36 were successfully inserted using the percutaneous fluoroscopic technique in selected patients referred from the nephrology clinic. All the PD catheters were placed in our Interventional Nephrology Vascular Suite by nephrologists.

Stenosis surveillance of hemodialysis grafts by duplex ultrasound reduces hospitalizations and cost of care.

Most recent randomized controlled trials (RCTs) have found that hemodialysis graft surveillance combined with preemptive correction of stenosis does not prolong graft survival. Nevertheless, such programs may be justified if they reduce other adverse outcomes or decrease the cost of care. This study tested this hypothesis by applying a secondary analysis to our original RCT. This study of 101 patients evaluated correction of stenosis based upon blood flow (Q) and stenosis surveillance. Patients were randomly assigned to control, flow, or stenosis groups, and were followed for up to 28 months. Q was measured monthly by ultrasound dilution; stenosis was measured quarterly by duplex ultrasound. Stenosis of 50% was corrected by percutaneous transluminal angioplasty (PTA) after referral for angiography. Referral criteria were: control group, clinical criteria; flow group, Q < 600 ml/min or clinical criteria; stenosis group, stenosis > 50% or clinical criteria. We compared access-related hospitalizations and cost of care, and use of central venous dialysis catheters (CVCs), among the three groups. Hospitalization rates were higher in the control and flow groups than in the stenosis group (0.50, 0.57, 0.18/patient-year, respectively [p < 0.01]), and hospitalization costs were lowest in the stenosis group (p = 0.026). The stenosis group had a trend toward lowest CVC rates (0.44, 0.32, 0.20/patient-year, respectively [p = 0.20]). The costs of care were higher in the control and flow groups than in the stenosis group (dollar 3727, dollar 4839, dollar 3306/patient-year, respectively [p = 0.015]). The costs of stenosis (dollar 142/patient-year) and Q (dollar 279/patient-year) measurements were minimal compared to the total cost of access-related care. In conclusion, stenosis surveillance by duplex ultrasound combined with preemptive correction yielded reduced hospitalization rates and costs, reduced total cost of access-related care, and a trend of reduced CVC rates. In contrast, flow surveillance did not yield a significant benefit. Stenosis surveillance provides important benefits that may justify application of such programs.

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.