Endothelial nitric oxide synthase gene intron 4 (VNTR) polymorphism and vascular access graft thrombosis.

Vascular access thrombosis is a leading cause of vascular access failure in hemodialysis patients. Thrombosis is a multifactorial condition and genetic makeup can affect thrombosis risk. We conducted a study to investigate for possible associations between ecNOS gene intron 4 variable-number tandem repeat (VNTR) polymorphism and thrombosis of polytetrafluoroethylene hemodialysis arteriovenous access grafts (AVG) in Turkish patients. Fifty-five patients with end-stage renal disease who had AVGs implanted between 2000 and 2002 and 167 healthy individuals representing our healthy population were enrolled in this prospective study. Each subject provided a venous blood sample from which DNA was isolated, and polymerase chain reaction analysis was done to identify genotypes (aa, bb, ab) for ecNOS gene intron 4 VNTR polymorphism. All grafts were placed in brachioaxillary position. The subjects were divided into two groups based on duration of graft patency. The thrombosis group (Group I) comprised 26 patients who developed AVG thrombosis in the first 12 months after placement. The no-thrombosis group (Group II) comprised 29 patients whose grafts remained patient for at least 12 months. The frequency of the aa genotype in Group I was significantly higher than that in Group II (p = .005). At 6, 12, and 24 months, the primary patency rates for the AVGs in patients with the aa genotype were significantly lower than the corresponding rates for the bb and ab genotype groupings (p = .01, p = .01 and p = .04 for the three respective time points; Kaplan-Meier). ecNOS gene intron 4 VNTR polymorphism is linked with the pathogenesis of vascular access thrombosis in Turkish patients undergoing hemodialysis.     

Permanent vascular access survival in children on long-term chronic hemodialysis

The aim of this study is to report a single-center experience regarding the management and outcome of permanent vascular accesses (VA) in children on chronic hemodialysis (HD). We analyzed the survival of permanent VA in 79 pediatric patients with end-stage renal disease patients on chronic HD between January 2000 and December 2008. One hundred and thirty-seven VA [89 native fistulas (AVFs) and 48 grafts (AVGs)] were created in 79 children. The creation of AVFs was significantly more frequent in children weighing >25 kg and AVGs in children weighing <25 kg (p = 0.003). The 1-year primary patency rate was 50% for AVF and 30% for AVG. The secondary patency rates at 1, 2, and 3 years for AVFs were 73, 50, and 20% and for AVGs were 64, 36, and 20%, respectively. The total number of surgical and endovascular interventions was significantly higher in AVGs (p ≤0.05). Access stenosis, thrombosis and infection episodes occurred more frequently in AVG (p = 0.02). VAs had a high rate of interventions. Our study demonstrated better results of AVFs formation over AVGs, for long-term HD access in pediatrics. Surveillance and radiologic procedures are necessary for early detection and treatment of access complications in order to extend access survival.     

Secondary arteriovenous fistulas: converting prosthetic AV grafts to autogenous dialysis access

As existing arteriovenous grafts (AVGs) fail, the National Kidney Foundation KDOQI Guidelines and the AV Fistula First Breakthrough Initiative ("Fistula First") project recommend that each patient be re-evaluated for conversion to an arteriovenous fistula (AVF). AVFs created following failure of an AVG have been termed secondary fistulas (SAVF). We review our experience and outcomes converting AVGs to SAVFs, utilizing the mature outflow vein of the AVG when possible, otherwise creating a new AVF at a remote site. We reviewed two groups of consecutive patients undergoing operations for vascular access at different centers. Group 1 had a SAVF protocol in place during the study period with specific criteria for timing SAVF construction. Patients from group 2 were referred for evaluation by nephrologists or dialysis nurses as access problems were recognized, without a formal protocol in place. All patients had preoperative ultrasound or contrast imaging in addition to physical examination. Indications for creating a SAVF were AVG thrombosis, dysfunction, erosion, bleeding, or steal syndrome involving the existing AVG. The simple presence of a functional AVG without evidence of dysfunction was not an indication for conversion to a SAVF. SAVFs were classified according to location and the potential for utilizing the existing mature AVG outflow vein. Group 1: 40 consecutive patients, age 26-78 (mean = 62), 42% were female; 55% were diabetic. These patients had 1-22 previous access operations (mean = 3). 92.5% underwent SAVF surgery prior to loss of the AVG, minimizing catheter use. Cumulative patency was 92.5% at 1 year and 87.5% at 2 years. Group 2: 102 consecutive patients, age 24-87 (mean = 55), 52% were female; 50% were diabetic. These patients had 1-50 previous access operations (mean = 3). Only 19.3% were referred for SAVF surgery prior to loss of the AVG or outflow vein. Cumulative patency was 94.4% at 1 year and 91.6% at 2 years. Failure, dysfunction, or complications of AVGs may be resolved by conversion to a SAVF. Further, the limited lifespan of AVGs and the superiority of AVFs dictates that a plan be in place to transition the AVG patient to an AVF. Most, if not all, hemodialysis patients whose access is an AVG will have one or more anatomic sites and vessels suitable for an autogenous SAVF. Vessel mapping is critical in the evaluation of failing AVGs and in preparation for a SAVF. Cumulative patency rates exceeded 90% at 12 months for SAVFs in both patient groups in this report. The need for catheters was dramatically less in the patient group with an established SAVF conversion plan.     

Vascular access complications in long-term pediatric hemodialysis patients

Current data demonstrate pediatric patients who remain on hemodialysis (HD) therapy are more likely to be dialyzed via central venous catheters (CVCs) than arteriovenous grafts (AVGs) and fistulae (AVFs). We retrospectively compared complications and health-related quality of life (HRQOL) associated with different vascular access types at two large centers over a 1-year period. Patients included in the study were younger than 25 years of age, weighed >20 kg, and had received HD for at least 3 months. Thirty CVC patients and 21 AVG/AVF patients received a total of 2,393 and 3,506 HD treatments, respectively. The infectious complication rate was higher for CVC patients, who were hospitalized 3.7 days for each 100 HD treatments versus 0.2 days for AVG/AVF patients (p < 0.01). CVC patients also had a much higher rate of access revision, needing 2.7 hospital days every 100 HD treatments compared with 0.2 days for AVG/AVF patients (p < 0.01). HRQOL scores did not differ between groups. Thus, despite similar HRQOL, CVCs were associated with more complications and greater morbidity when compared with AVG/AVFs. These findings further emphasize the need to use AVG/AVFs as primary HD access for pediatric patients expected to receive a long course of maintenance HD.     

Permanent hemodialysis vascular access survival in children and adolescents with end-stage renal disease

BACKGROUND: Transplantation is the optimal therapy for pediatric end-stage renal disease (ESRD) patients, but in a subset of patients with peritoneal membrane failure, failed transplants or poor social situations, chronic hemodialysis (HD) remains the only option. Long-term survival of arteriovenous fistulas (AVFs) and arteriovenous grafts (AVGs) in pediatric patients has not been well described. METHODS: We studied the survival of permanent vascular access in 34 pediatric ESRD patients treated with chronic HD at our institution between 1/1/89 and 12/1/95 and followed to 12/31/2000. RESULTS: Twenty-four AVFs and 28 AVGs were created in 19 and 23 patients, respectively. Mean age and weight at insertion were 15.1 years (range 7.1 to 20.9) and 46 kg (18 to 81) for AVFs and 13.3 years (3.8 to 21.1) and 41.5 kg (10.5 to 145) for AVGs. Fifteen patients weighed <35 kg at the time of access creation (7 AVFs in 5 patients, 14 AVGs in 13 patients). Excluding primary failures, one-year, three-year and five-year patency rates for AVFs (74%, 59%, 59%) and AVGs (96%, 69%, 40%) were not significantly different. Patency did not correlate with patient weight or age at access creation. Primary access failure occurred more often (P < 0.01) in AVFs (8/24) compared to AVGs (1/28). Access thrombosis, stenosis and infection occurred more frequently in AVG (P = 0.02). CONCLUSIONS: Both AVF and AVG function well even in small pediatric patients and have survival rates equivalent to adult series and longer than cuffed venous catheters in pediatric patients. Both AVFs and AVGs are preferable for long-term HD access in pediatrics.     

Difficult vascular access in patients with end-stage renal failure

BACKGROUND/AIM: End-stage renal failure patients requiring long-term hemodialysis need a durable vascular access. The arteriovenous fistula (AVF) with its long patency rate and low complication profile is usually the first choice for vascular access creation. However, when superficial veins are not suitable for AVF creation or all have been exhausted as a result of repeated AVF procedures, arteriovenous grafts (AVGs) using expanded polytetraflouroethylene (ePTFE) is an alternative. This study reviewed our experience in using PTFE AVGs for vascular access in patients requiring chronic hemodialysis. MATERIALS AND METHODS: In a prospective study, from September 2002 to October 2004, 21 PTFE AVGs were placed in 21 patients. We evaluated the complications and patency. RESULTS: There were 12 female and nine male patients of mean age 58+/-8.7 years (range=45 to 76 years). Nine patients (43%) had hypertensive nephrosclerosis, 6 (29%) diabetic, 2 (10%) glomerulonephritis, 3 (14%) systemic lupus erythematosis requiring long-term steroids, and 1 (4.7%) unknown cause. The patency rate at 24 months was 85.7%. Complications included graft thrombosis (three; 14.3%), wound infection (three; 14.3%) and graft infection (one; 4.8%). CONCLUSION: ePTFE AVGs offer reasonable patency and serviceability rates as a vascular access modality, but in view of their complication profile, the native vein arteriovenous fistula should continue to be the first choice for vascular access for patients requiring chronic hemodialysis.     

A prospective randomized study of bovine carotid artery biologic graft and expanded polytetrafluoroethylene for permanent hemodialysis access

Objective

Arteriovenous grafts (AVGs) remain reliable substitutes for permanent hemodialysis access in scenarios that preclude the placement of native arteriovenous fistulas (AVFs). The majority of AVGs are constructed of expanded polytetrafluoroethylene (ePTFE), which is relatively inexpensive and readily available, but synthetic AVGs have poor patency rates. On the other hand, biologic grafts confer an advantage by virtue of their inherent similarity to the native human vasculature. However, evidence to support the current preference of synthetic conduits over biologic grafts in clinical practice is scarce. The aim of this protocol is to propose a contemporary re-evaluation and comparison between ePTFE and bovine carotid artery (BCA) grafts.

Outcomes of endovascular salvage of clotted arteriovenous access and predictors of patency after thrombectomy

ObjectiveThis study aimed to report the outcomes of endovascular salvage of clotted arteriovenous (AV) accesses and to determine potential predictors of poor patency rates after thrombectomy.MethodsRecords of hemodialysis patients who underwent endovascular salvage of clotted AV access were reviewed retrospectively. Technical and clinical success rates, complication rates, and 3- and 6-month patency rates were determined. Multivariate analysis was performed to determine the predictors of patency after thrombectomy.ResultsA total of 294 patients underwent endovascular salvage of clotted AV access during the study period; 156 patients had arteriovenous fistula, whereas the remaining 138 were arteriovenous grafts (AVGs). The technical and clinical success rates were 96.3% and 93.2%; the major and minor complication rates were 0.7% and 9.9%. Post-thrombectomy primary, assisted primary, and secondary patency rates were 62.9%, 76.2%, and 77.6% at 3 months and 43.9%, 59.5%, and 61.6% at 6 months. The patency rates were significantly better for arteriovenous fistula than for AVG except for 6-month assisted primary and secondary patency. Multivariate Cox regression analysis showed that prior thrombosis within 90 days was significantly associated with loss of primary patency (hazard ratio [HR], 1.90; 95% confidence interval [CI], 1.21-2.98; P < .01), assisted primary patency (HR, 2.42; 95% CI, 1.42-4.13; P < .01), and secondary patency (HR, 2.52; 95% CI, 1.40-4.53; P < .01). Having an AVG was also negatively associated with primary patency.ConclusionsMost clotted AV accesses can be salvaged by endovascular technique. Recurrent thrombosis within 90 days is associated with poor short- and long-term patency even after successful endovascular reinterventions.     

Successful treatment of the chronically thrombosed dialysis access graft: resuscitation of dead grafts

The most common contributing cause of thrombosis of an arteriovenous graft (AVG) in the hemodialysis patient is the presence of venous stenosis. In the face of a recovery of renal function either spontaneously or as a result of renal transplantation, an AVG commonly thromboses. In cases in which the AVG was recently placed, it is unlikely to have had a significant anatomic lesion at the time function was lost. Even though the access that has been left untreated has become a "dead" AVG, it offers an opportunity for "resuscitation." Thirteen cases that met the specific criteria of being placed only a short period of time prior to thrombosis (3 weeks to 6 months), thrombosing after a return of renal function and having been left untreated (3 months to 8 years) were attempted over a 12 year period. The technique applied was modified from the one routinely used based on the presumption that very little or no thrombus was present. The effort was met with success in 8 of the 13 patients. After being opened, the AVG appeared to follow the same patency pattern as other AVGs. It appears that attempting restoration of function of an AVG meeting these criteria may be indicated. Limited experience using this approach in AVGs that do not meet these specific criteria has uniformly met with failure.     

Effect of Secondary Interventions on Patency of Vascular Access Sites for Hemodialysis

PURPOSE: To determine the impact of secondary procedures performed to maintain arteriovenous fistula (AVF) and arteriovenous graft (AVG) patency. METHODS: There hundred and eighty six vascular access procedures were retrospectively evaluated. 156 (40.4%) patients required radiological interventions to treat acute thrombosis, swelling of the extremity with the access site, insufficient hemodialysis, or stenosis at an anastomotic site. RESULTS: The 386 cases comprised 106 AVGs and 280 AVFs. In 138 of the 156 cases, which required a radiological intervention, the treatment was successful and saved the vascular access site. The unassisted post-intervention patency time for these 138 successful cases was 13.1 +/- 12 months (range, 1-65 months). Twenty-nine (63%) of the 46 access sites treated with surgical thrombectomy were saved. CONCLUSIONS: Frequent, regular follow-up of hemodialysis patients with vascular access sites is the best way to diagnose problems early and allow the best chance of long-term function.     

Automated Intravascular Access Pressure Surveillance Reduces Thrombosis Rates

Although monitoring of vascular accesses by physical examination is nearly as sensitive as surveillance measurements by vascular access pressure when performed by examiners, the frequency of examinations is limited by time. We developed intravascular access pressure surveillance as a surrogate to physical examination. Using real‐time data from hemodialysis machines, we derived intravascular access pressure ratios for each dialytic procedure. An automated, noninvasive surveillance algorithm that generated a “warning” list of patients at risk for thrombosis was formulated. We hypothesized that this algorithm would reduce access thrombosis frequency. We designed a study comparing thrombosis rates during a baseline 6‐month interval to three subsequent 6‐month periods of active surveillance. Referrals for interventions during this 18‐month period were based on persistently abnormal elevated vascular access pressure ratio tests (VAPRT) >0.55. Thrombosis rates declined progressively for arteriovenous grafts (AVG) during the intervention period compared with the baseline period. Arteriovenous fistula (AVF) thrombosis rates decreased during postintervention months 13–18 during employment of the VAPRT. We conclude that use of VAPRT can reduce thrombosis rates in vascular accesses, and the magnitude of the effect is larger and more consistent in arteriovenous grafts (AVGs) than autologous AVFs.     

Analysis of nonpenetrating clips versus sutures for arterial venous graft anastomosis

The use of nonpenetrating clips (NPC) for vascular anastomosis is quickly becoming accepted. Studies attest to decreased anastomotic time, comparable patency rates, and decreased blood loss. Few human studies on the use of NPC have been done to date. The purpose of this study was to evaluate primary patency rates, operative time, and complications associated with NPC compared to those with standard sutures for arterial venous graft (AVG). We retrospectively reviewed the clinical course of 82 patients with a mean age of 45 years (range, 22 to 87) from February 1996 to July 1999. All patients underwent upper extremity AVG construction. The procedures were performed at a single institution, by a single, well-experienced surgeon who has extensive experience with NPC. Primary patency rates, operative time, and complications were analyzed. Overall thrombotic incidence of AVG when NPC were used (27/48, 56%) was similar to that of sutures (17/34, 50%). Thrombotic incidence within the first year was similar as well (23/48, 48% and 13/34, 38%). The mean time to primary thrombosis was similar in both groups (6.9 and 6.8 months). The operative time required to construct an AVG with NPC (83 min) was significantly less than that with sutures (96 min) (p = 0.015). There was no significant difference in incidence of graft infection or pseudoaneurysm formation. NPC for AVG reduced operative time and resulted in primary patency and complication rates similar to those associated with use of sutures. The mean time to primary thrombosis was similar for both groups. Our findings suggest an intimai hyperplastic response of a similar nature resulting in thrombosis of both NPC and sutured AVGs. Presented at the Twenty-fifth Annual Meeting of the Peripheral Vascular Surgery Society, Toronto, Ontario, Canada, June 10, 2000.     

An intron 4 gene polymorphism in endothelial cell nitric oxide synthase might modulate lipid metabolism in nondiabetic patients on hemodialysis

We investigated the relationship between endothelial constitutive nitric oxide synthase (ecNOS) gene polymorphism and lipid metabolism in patients with nondiabetic chronic renal failure on hemodialysis. Serum from 181 nondiabetic patients on hemodialysis were examined. A genomic DNA fragment was amplified by polymerase chain reaction (PCR) for determining the ecNOS genotype. The PCR products were designated as a and b alleles by electrophoresis. In hemodialysis patients, the frequency of the ecNOS4 for b/b, b/a and a/a genotype was 76.6, 22.8 and 0.6%, respectively. There was not significant difference in the levels of total cholesterol (TC), triglyceride (TG) and calculated low-density lipoprotein cholesterol (LDL-c) in sera between patients (aa and ba) with the a allele and patients (bb) without the a allele. On the other hand, the levels of serum high-density lipoprotein cholesterol (HDL-c) in patients with the a allele (51.9 +/- 3.33 mg/dl) were significantly higher than those in patients without the a allele (43.05 +/- 1.40 mg/dl) (p = 0.005). The frequency of patients with the a allele and low levels of serum HDL-c among patients with a long duration of dialysis (> or =10 years) was significantly lower than that in patients with short duration of dialysis (<10 years) (p = 0.05). It appears that an intron 4 gene polymorphism in ecNOS may modulate lipid metabolism in nondiabetic patients on hemodialysis and the a allele of ecNOS gene polymorphism may affect the prognosis of hemodialysis patients with low levels of serum HDL-c.     

Timing of the first cannulation and survival of arteriovenous grafts in hemodialysis patients: a multicenter retrospective cohort study

Arteriovenous graft (AVG) is an important vascular access route in hemodialysis patients. The optimal waiting time between AVG creation and the first cannulation is still undetermined, therefore the current study investigated the association between ideal timing for cannulation and AVG survival. This retrospective cohort study used data from the Taiwan National Health Insurance Database, which included 6,493 hemodialysis patients with AVGs between July 1^st 2008 and June 30^th 2012. The waiting cannulation time was defined as the time from the date of shunt creation to the first successful cannulation. Patients were categorized according to the waiting cannulation time of their AVGs as follows: ≤30 days, between 31 and 90 days, between 91 and 180 days, and >180 days. The primary outcome was functional cumulative survival, measured as the time from the first cannulation to shunt abandonment. The AVGs which were cannulated between 31 and 90 days (reference group) after construction had significantly superior functional cumulative survival compared with those cannulated ≤30 days (adjusted HR = 1.651 with 95% CI 1.482–1.839; p < 0.0001) and >180 days (adjusted HR = 1.197 with 95% CI 1.012–1.417; p = 0.0363) after construction. An analysis of the hazard ratios in patients with different demographic characteristics, revealed that the functional cumulative survival of AVGs in most groups was better when they received cannulation >30 days after construction. Consequently, in order to achieve the best long-term survival, AVGs should be cannulated at least 1 month after construction, but you should avoid waiting for >3 months.     

Der arteriovenöse Zugang mit biologischem Material

Aims and methods

In order to decrease arteriovenous graft (AVG) failure and improve long-term patency, Omniflow II was used to perform AVG for hemodialysis access in 38 patients with very compromised vessels who were not suitable for other forms of AVG.

Results

At a median follow-up of 38 (range 6–55) months, 31 out of 38 (81%) patients were still alive. At 6, 12, 18 and 24 months, primary patency was 83, 80, 68 and 60% whereas secondary patency was 92, 83, 78 and 75% respectively. The cumulative 38-month prosthetic AVG patency was 70%. No infective event related to the vascular prosthesis occurred. Neither AVG thrombosis nor modifications in thrombophilic patterns were observed. These findings confirm the high hemocompatibility of this prosthetic vascular device.

Conclusion

Our experience is extremely encouraging for the use of new biosynthetic devices such as Omniflow II.     

Hemodialysis graft infections treated with cryopreserved femoral vein

Introduction. Treatment of infected hemodialysis grafts is associated with prolonged hospitalization and wound care. The use of cryopreserved femoral vein (CFV) for angioaccess in infected hemodialysis grafts was prospectively evaluated.Methods. Forty-three CFV arteriovenous grafts (AVGs) were placed in 43 patients with prosthetic AVG infections. Thirty-two of the CFV AVGs were constructed adjacent to the infected AVG using a parallel tunnel tract, while 11 were placed into the infected field. All patients were prospectively followed at three-month intervals for graft complications and recurrent infections.Results. With a mean follow-up of 418 days, there was one recurrent infection (2.3%). The one-year primary and secondary graft patency rates were 42% and 68%, respectively. The two-year primary and secondary patency rates were 31% and 63%, respectively.Conclusions. Cryopreserved femoral vein proved useful in the treatment of infected hemodialysis grafts. The absence of infection after implantation around an infected area shows promise for salvaging an angioaccess site that would otherwise have been abandoned.     

Occult infection of old nonfunctioning arteriovenous grafts: a novel cause of erythropoietin resistance and chronic inflammation in hemodialysis patients

BACKGROUND: Occult infection of old nonfunctioning arteriovenous grafts (AVGs) is frequent among hemodialysis patients. It is a recognized cause of bacteremia and other infectious complications. Additionally, old nonfunctioning AVGs may be harbingers of other noninfectious complications. The aim of this study was to investigate whether occult infection of old nonfunctioning AVGs is a cause of a chronic inflammatory state in hemodialysis patients. METHODS: This study was performed in two phases: In the first phase (study 1), 22 patients with clinically proven occult infection of old nonfunctioning AVG were identified, and data on hemoglobin, weekly erythropoietin dose, and albumin levels were collected retrospectively. Comparisons were made between values obtained pre- and post-AVG resection. In the second phase (study 2), we examined whether the presence of a chronic inflammatory state is associated with occult AVG infection in old nonfunctioning AVGs. Twenty hemodialysis patients were identified with chronic inflammatory state based on erythropoietin dose (units/wk)/hematocrit ratio>470, serum albumin <3.3 g/dL, and CRP>25 mg/L. Among these patients, we found eight with old nonfunctioning AVGs. We then performed indium-labeled white blood cell (WBC) scans on the eight patients to screen for occult infection of old nonfunctioning AVGs. The AVGs with positive indium scan were resected and cultured. Data on hematocrit, erythropoietin dosing, serum albumin, ferritin, and CRP were obtained at 2 months following AVG resection and compared to pre-resection values. RESULTS: In study 1, the 22 patients with occult infection of old nonfunctioning AVG exhibited profound anemia and hypoalbuminemia. Their mean hemoglobin was 9.2 +/- 1.2 g/dL which improved to 11.6 +/- 0.8 g/dL (P < 0.05) 3 months after AVG resection. Their mean serum albumin was 3.3 +/- 0.5 g/dL which improved to 3.8 +/- 0.2 g/dL (P < 0.05) 3 months after AVG resection. Their mean erythropoietin dosages (units/patient/wk) fell from 14,240 +/- 350 to 6,675 +/- 455 (P < 0.05). In study 2, among the 8 patients with chronic inflammatory state and old nonfunctioning AVG, 6 (75%) had positive indium scans and underwent surgical resection that proved bacterial infection. Upon follow-up, the 2-month data showed a remarkable improvement in the following parameters: weekly erythropoietin dose/hematocrit ratio from 622 +/- 137 to 254 +/- 28 (P < 0.05), plasma ferritin values from 690 +/- 126 ng/mL to 247 +/- 42 ng/mL (P < 0.01), and plasma CRP from 56.7 +/- 9.0 to 14.5 +/- 3.8 mg/L (P < 0.01). Serum albumin values also improved from 3.07 +/- 0.08 g/dL to 3.34 +/- 0.14 g/dL (P = 0.13). Percent plasma iron saturation did not appreciably differ from baseline (20.5% +/- 4.4% to 19.8 +/- 1.9%, P = 0.89). CONCLUSIONS: Occult infection of old nonfunctioning AVG is a common cause of erythropoietin resistance and chronic inflammatory state among hemodialysis patients. Resection of old nonfunctioning AVGs with occult infection is associated with resolution of markers of chronic inflammatory state.     

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.     

Brachial-basilic autogenous access

The emphasis on autogenous arteriovenous hemodialysis access has increased the focus on the brachial-basilic autogenous configuration currently recommended by the national guidelines when the cephalic vein is not suitable. The brachial-basilic autogenous access has been extensively studied and compared with both prosthetic (arteriovenous graft [AVG]) and other autogenous accesses. The literature suggests that the brachial-basilic autogenous access is superior to AVGs in terms of patency, reintervention rates, and infectious complications. However, controversy still remains with respect to its role in the treatment algorithm and the technical conduct of the operation. This review will address the ongoing issues and controversies surrounding the brachial-basilic autogenous access and define its role for the hemodialysis access surgeon.