Medical factors affecting patency of arteriovenous access

Arteriovenous access failure is multifactorial in nature with contributions from both medical and surgical etiologies. Medical causes of arteriovenous access failure are rare, and therefore infrequently identified as a major contributing source of malfunction. Although they account for only 10-15% of all cases of access failure, their importance should not be underestimated, especially in cases where a surgical source cannot be identified. Most medical causes are derived from Virchow's triad of endothelial cell injury, stasis, and hypercoaguability. Endothelial cell injury occurs through oxidative stress, activated platelets, increased levels of circulating tumor necrosis factor-alpha, and preexisting intimal hyperplasia. Stasis can occur through prolonged access compression, hypotension, or hypoalbuminemia. Finally, patients with renal failure requiring hemodialysis are frequently at increased risk for hypercoaguable states, except for situations of platelet dysfunction, and therefore access failure. Potential treatments include identifying and removing the offending source, as well as innovative, new medications to prevent their reoccurrence. Treatment is aimed at improving quality of life, as well as decreasing morbidity and hospital admissions in this difficult patient population.     

Experience with dacron graft arteriovenous fistulas for dialysis access.

The technique, hemodynamics, and results of a new, more successful Filamentous Velour Dacron graft dialysis fistula between brachial artery and axillary vein are described. Hemodialysis has been successfully instituted in 15/16 patients. One graft was removed for infection and one for overlying skin erosion. There have been five episodes of thrombosis, all with successful restoration to function. After a median nine-month follow-up, nine of 16 grafts have been complication-free and 13 of 16 remain functional or functioned until the time of death. Hemodynamic studies revealed that with high flows (even 1900 cc/min), there was no evidence of cardiac failure or peripheral "steal". One patient with low flow (less than 300 cc/min) had transient distal ischemic symptoms and another with similar flow later developed arterial occlusion distal to the fistula after suffering a myocardial infarction. With increased attention to technical details observed in this early experience, it appears that greater than 80% of these grafts should provide long-term dialysis access for this difficult patient population.     

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.     

Maturation and failure rates in a large series of arteriovenous dialysis access fistulas

The objective of this study was to document maturation and failure rates in a large homogeneous series of arteriovenous fistulas (AVFs). Between January 1, 1996, and December 31, 2001 (60 months), a single surgeon (AFS) in 1 academic medical center, constructed 374 AVFs. In this series, all AVFs were developed in vessels that had not undergone previous vascular access surgery. Recently, a retrospective review of these records revealed that 291 subjects had had complete follow-up for at least 3 months, and they constitute the material for this study. AVFs were considered a failure if an early occlusion/thrombosis occurred, if in 3 months the AVF had not matured on clinical examination, or if cannulation in the dialysis center was not feasible. A total of 91 AVFs did not mature, for an overall failure rate of 31%. An evaluation of failure rates indicated rates in females were higher than in males (41% versus 27%). Other risk factors, including HIV+ status, hypertension, and diabetes, demonstrated minimal failure differences (33%, 31%, and 36%, respectively).     

Strategies of arteriovenous dialysis access

Surgical management of the patient who requires hemodialysis access, while continuing to demand more attention from the vascular surgeon, suffers from discrepancies of approach and strategy. With the increase in incidence of dialysis dependent renal failure among our population, many have attempted to present a uniform, logical strategy with which the vascular surgeon can most effectively treat the hemodialysis patient in the long term. Most notably, the multidisciplinary Dialysis Outcomes Quality Initiative (DOQI) guidelines present the surgeon with a rough outline of hemodialysis access insertion strategy, and it has become nationally recognized as an acceptable summary of treatment strategy and goals. The decision as to the most appropriate surgical access to offer a patient depends on immediate need for hemodialysis, history and physical examination findings, and suitability of available veins in the extremity. While percutaneous, catheter based access affords the luxury of immediate access, these devices suffer from several complicating factors, such as infection, and damage to large, proximal veins. For long-term access, the autogenous access, while perhaps less successful in the immediate short term, is always the preferred access type given its favorable longevity. The surgeons should focus on sites distally on the extremity, reserving proximal sites for potential future access insertions should the primary access fail. In the absence of suitable vein, prosthetic access may be considered. When both the upper and lower aspects of both upper extremities have been exhausted, the surgeon should consider access insertion elsewhere, such as the lower extremity.     

Timely thrombectomy can improve patency of hemodialysis arteriovenous fistulas

Objective

The urgency with which salvage of thrombosed vascular accesses for dialysis should be attempted remains unknown. We examined the effect of a timely thrombectomy approach on vascular access outcomes for dialysis.

Long and short term patency of radiocephalic arteriovenous fistulas

Eighty-three radiocephalic fistulas in 71 uremic patients were retrospectively investigated. The fistulas were grouped according to construction, viz. side of radial artery to side of cephalic vein and end of cephalic vein to side of radial artery. The aim was to find and evaluate factors influencing fistula patency rate, with special emphasis on type of anastomosis. The early failure rate was significantly higher in the end-to-side group. The late failure rate was not influenced by mode of fistula construction. The fistula failure rate showed no correlation to patient age. Diabetes did not influence failure rate, but significantly shortened the mean patency time.     

Preserving function and long-term patency of dialysis access

Of the 283, 932 patients with end stage renal disease (ESRD) receiving replacement therapy in the US in 1996, 62% were being treated with haemodialysis. Improved survival of haemodialysis patients coupled with the inability to provide enough renal transplants for the growing ESRD population has resulted in an increase in the average length of time patients spend on dialysis. Vascular accesses are, therefore, required to function for longer periods of time. Maintenance of a reliable access to the circulation has been described as the Achilles' heel of modern haemodialysis. Preserving access function and long-term patency are essential for efficient dialysis delivery.     

Outcomes of upper arm arteriovenous fistulas for maintenance hemodialysis access

HYPOTHESIS: Radiocephalic fistulas for maintenance hemodialysis access are not feasible in all patients with end-stage renal disease. Our aim was to review our experience with 3 types of upper arm arteriovenous fistula (AVF) to ascertain whether they are reasonable alternatives to radiocephalic fistulas and which, if any, have superior performance. PATIENTS AND METHODS: Patient medical records were retrospectively reviewed. The main outcomes were maturation rate, time to maturation, assisted maturation rate, complication rates, reintervention rates, primary and assisted primary patency rates, and effects of comorbidities. RESULTS: Eighty-six patients with end-stage renal disease underwent creation of a brachiocephalic, brachiobasilic, or brachial artery-to-median antecubital vein AVF. Overall, 80% matured, with 23% requiring an intervention to achieve maturity. The mean time to maturation was 3.8 months; 47% had a complication (inability to access, thrombosis, and so on), and 43% required additional interventions. The overall primary patency and assisted primary patency rates at 12 months were 50% and 74%, respectively. Brachiobasilic AVFs not superficialized immediately often needed a second operation. There were no significant differences in patency rates among the 3 AVF types. The AVFs in patients with diabetes took 2 months longer to mature than did those in patients without diabetes. CONCLUSIONS: An upper arm AVF is a reasonable alternative for maintenance hemodialysis access when a radiocephalic AVF is not possible. There are 3 valid options from which to choose to best accommodate each patient's antecubital anatomy. Diabetes may adversely affect outcomes. Our data suggest that brachiobasilic AVFs should be superficialized at the initial procedure, if feasible.     

Salvage of hemodialysis access in infected arteriovenous fistulas

Infection combined with additional complications of arteriovenous fistulas is a serious threat to access in patients with upper-extremity polytef (polytetrafluoroethylene) grafts. We present three cases of infected access grafts that were treated with systemic antibiotics, excision of the grafts, and primary anastomosis of the arterialized vein to artery for access salvage. The new arteriovenous fistulas were used immediately, preventing interruptions in hemodialysis regimens. This technique of immediate reconstruction allows the surgeon to utilize the arterialized outflow vein and save other sites of access for future use.     

Factors affecting the patency of infrainguinal bypass

Two hundred forty-nine well-characterized difficult distal bypasses, entered into a multicenter dextran 40 trial, were reevaluated after 3 years. Seventy in situ (IS) vein grafts, 49 reversed saphenous (RS) vein grafts, 60 polytetrafluoroethylene (PTFE) grafts, and 70 umbilical vein (UV) grafts were used. Primary and secondary patency rates at 3 years were, respectively, 84% and 90% for IS, 66% and 73% for RS, 35% and 48% for PTFE, and 24% and 32% for UV. Subgroup analysis according to the site of distal anastomosis showed no significant differences in primary patency among these grafts at the above-knee level but significant differences between both vein grafts (IS and RV) and the others (PTFE and UV) below the knee (78% vs 31%, respectively). This difference increased at the tibial level (78% vs 10%) but there was also a significant difference between IS grafts (88%) and RS grafts (63%) at this level. Hazard functional analysis showed all grafts except IS grafts begin to fail at an increasing rate again by 24 months. Although overall results appeared to favor PTFE over UV, 62% of PTFE vs 16% of UV terminated at the above-knee level and the patency results of these two grafts were not significantly different at any level. The only other factor than graft type and distal anastomotic site that consistently correlated with late patency was tobacco use. Diabetic patients actually fared significantly better than nondiabetic patients, presumably because of the higher use of IS grafts and lower use of tobacco. The choice of graft overshadows all other factors affecting patency and its influence is magnified with more distal terminal anastomosis.     

前臂远端贵要静脉转位建立自体血管内瘘手术

目的 探讨前臂远端贵要静脉转位建立自体血管内瘘的方法.方法 自2007年12月至2009年12月我们对26例维持性血液透析患者进行前臂远端贵要静脉转位建立自体血管内瘘手术治疗.26例中有17例为原桡动脉-头静脉内瘘因并发症失去功能,9例初次行血管内瘘手术.手术方式采用贵要静脉转位与肱动脉端侧吻合;贵要静脉转位与桡-动脉端端吻合;贵要动脉与尺动脉端侧或端端吻合,吻合口直径为5.0～8.0 mm.结果 26例患者中有1例因术后血肿压迫闭塞,2例因术后内瘘成熟不良,其余手术患者一次取得成功,术后血流量达200～350 ml/min.对患者的心功能未造成不良影响,也未出现严重并发症.结论 只要适应证选择合适,前臂远端贵要静脉转位建立自体血管内瘘手术,是尽量利用自身血管条件,建立内瘘的一种行之有效的方法.     

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.     

Arteriovenous fistulas for dialysis: Blood flow,viscosity, and long-term patency

A prospective study of the influence of blood flow at the time of operation on subsequent performance of dialysis fistulas is reported. Flow was measured in 33 consecutive arteriovenous fistulas using an electromagnetic flowmeter. During the mean follow-up time of 7 months (range, 2–12 months), 19 fistulas were used for dialysis, 9 have not yet been used, 4 were never used because of thrombosis or failure to develop adequately, and 1 patient died before using the fistula for hemodialysis. There were 9 complications (thrombosis, stenosis, and failure to develop). Operative blood flow for these 9 fistulas averaged 221 ml/min as compared to 214 ml/min for the group with no subsequent problems. No critical flow rate below which the fistula would not develop could be defined. An analysis of influences on flow rate at the time of operation showed that there was a significant correlation between flow and blood pressure, vessel dimensions, and whole blood viscosity, but it was not possible to predict fistula failure from these data.     

Vascular access for haemodialysis with autogenous vein graft arteriovenous fistulas.

Nine autogenous vein grafts (AVG) have been used in nine patients to create arteriovenous fistulae for haemodialysis. All the patients lacked vessels for construction of a regular arteriovenous fistula. Three of the AVG failed during dialysis treatment 3, 10 and 14 months respectively following construction. Another AVG thrombosed but function was restored by thromboectomy. The same graft was later complicated by a false aneurysm and rupture but was then reconstructed with a vein patch. One AVG with a false aneurysm in the proximal anastomosis was repaired within six weeks.