Dialysis access preservation

Mark B. Saker, MD; Howard B. Chrisman, MD; Alan H. Matsumoto, MD

Dr. Saker and Dr. Chrisman are with the Division of Vascular and Interventional Radiology at Northwestern University Medical School in Chicago, IL. Dr. Matsumoto is Director of the Division of Angiography and Interventional Radiology at University of Virginia Health Systems in Charlottesville, VA. He is also a member of the editorial advisory board of this journal.

Partly in response to the skyrocketing healthcare costs for dialysis patients (estimated to be more than $1 billion for 1996), ¹ the National Kidney Foundation proposed the Dialysis Outcomes Quality Initiative (DOQI) in 1997. The purpose of this initiative was to review the published literature and make recommendations for establishing clinical practice guidelines for managing patients with end-stage renal disease, with a goal of improving patient outcomes and survival.

Practice guidelines addressed hemodialysis adequacy, peritoneal dialysis adequacy, vascular access, and anemia. Specifically, the guidelines for vascular access were established by a multidisciplinary group that included five nephrologists, two surgeons, two nurses, and one interventional radiologist. Of a total of 114 clinical practice guidelines developed, 38 were created to address the area of vascular access. ² A brief summary of those vascular access guidelines pertinent to interventional radiologists will be reviewed.

Guidelines regarding patient evaluation prior to access placement

Guideline 1: Patient history and physical examination prior to permanent access selection -Pertinent aspects of the history and physical examination that will help to dictate the type and location of the vascular access are emphasized. A detailed evaluation of the venous, arterial, and cardiopulmonary systems is mandatory. Some of the most relevant issues include previous central venous catheter and cardiac pacemaker placement, and history of prior angio access for hemodialysis. These have been associated with central venous stenosis. Patients with conditions such as diabetes mellitus, malignancy, and prior surgery or trauma to the chest area are at higher risk for developing abnormalities in their venous system. On physical examination, the presence of upper extremity edema or collateral veins suggests a central venous stenosis.

Guideline 2: Diagnostic evaluation prior to permanent access selection -Preoperative venography is recommended if there is 1) edema or size discrepancy in the target limb; 2) presence of collateral veins; 3) a current or prior history of subclavian vein catheterization; 4) a current or prior history of transvenous pacemaker placement; 5) a previous history of surgery or trauma to the chest, arm, or neck; or 6) prior access in the same limb. Ultrasound and MRI evaluation can be used when venography is contraindicated. Arteriography is also indicated if there are diminished pulses in the target limb (figure 1).

FIGURE 1. A left upper extremity venogram was performed in this patient with a history of multiple central catheter placements for hemodialysis. The presence of collaterals and significant narrowing preclude the creation of a native fistula or implantation of a graft.

Guideline 3: Selection of a permanent vascular access and order of preference for placement of arteriovenous (AV) fistulae -The use of tunneled catheters for permanent access is discouraged; the use of AV fistulae, preferably the radial-cephalic fistula, is recommended. If the AV fistulae fail, an AV graft or transposed brachial-basilic fistula should then be considered.

Guideline 4: Type and location of dialysis AV graft placement -If a native fistula can not be created, the use of a synthetic AV graft with polytetra-fluoroethylene (PTFE) is recommended. Graft placement can be varied in configuration, and the type and location can be determined by the patient's anatomy and access history.

Guideline 5: Type and location of tunneled cuffed catheter placement -Tunneled cuffed venous catheters are to be used when vascular access is needed for more than 3 weeks or when all other options are no longer available. These catheters can allow for the maturation of native AV fistulae. Insertion via the right internal jugular vein is preferred. Catheterization of the subclavian vein should be avoided due to a 40 to 50% incidence of subclavian vein stenosis following its use. ³ Additionally, fluoroscopic guidance is mandatory for line placement, and ultrasound guidance for venous puncture is desirable. There is no data to support the use of one catheter type over another (figure 2).

FIGURE 2. Subclavian artery perforation is found during an attempt to place a catheter without sonographic or fluoroscopic guidance.

Guideline 6: Acute hemodialysis vascular access: non-cuffed catheters -Vascular access for less than 3 weeks can be provided with cuffed and non-cuffed venous catheters. Non-cuffed catheters can be inserted at the bedside, and positioning should be confirmed with an x-ray. Femoral vein catheters should be at least 19 cm in length and should not be left in place for more than 5 days.

Guideline 7: Preservation of veins for AV access -All upper extremity veins should be preserved in any patient with a condition likely to lead to dialysis. Therefore, in patients such as those with end-stage renal disease (creatinine > 3.0 md/dl) and diabetes mellitus, vein puncture should be limted to the dorsum of the hand and should be on a rotational basis. Subclavian vein puncture should not be performed.

Guideline 8: Timing of access placement -Patients should be referred for vascular access when creatinine clearance is less than 25 ml/min, when serum creatinine is greater than 4 mg/dl, or within one year of anticipated dialysis. AV fistulae should be allowed to mature for at least one month and preferably for 3 to 4 months. AV grafts should be placed 3 to 6 weeks prior to the anticipated need for dialysis. Central venous catheters for dialysis should be avoided until they are absolutely necessary.

Guideline 9: Access maturation &madsh;AV fistulae maturation may be improved by selective obliteration/embolization of venous side branches. When a new fistula is infiltrated (hematoma), it should be rested until the swelling has resolved. Persistent arm swelling following the creation of an AV fistula or graft should be evaluated with venography.

Guideline 10: Monitoring dialysis AV grafts for stenosis -Monitoring AV grafts for the development of a hemodynamically significant stenosis is recommended. It has been shown that with surveillance and preemptive intervention, graft thrombosis rates can be reduced from 0.58-1.0 episodes per year to 0.19-0.28 episodes per year. ⁵ In addition, 6-month primary patency rates after graft declotting range from 18 to 43%, as compared with 38 to 64% after percutaneous angioplasty (PTA), without the need for declotting. ⁴ Therefore, AV grafts should be monitored on a weekly basis with physical examination and an organized screening program that includes one or more of the following: 1) dynamic venous pressure measurements during dialysis, 2) static pressure measurements, and 3) intra-access flow using transonic methods.

A baseline dynamic pressure reading should be acquired when the vascular access is first used, followed by repeat measurements at least once a month. Three successive elevated pressure measurements suggest an underlying problem with the AV graft and warrants further evaluation with fistulography. Additional information can be obtained with urea and non-urea recirculation methods, decreased hemodialysis delivery (Kt/V), and elevated negative pre-pump pressures.

Duplex and color ultrasound also can be used for graft surveillance but may not be cost-effective as a screening tool. ⁶ Criteria described as normal on ultrasound studies include peak systolic velocities of 100 to 400 cm/sec and end-diastolic velocities of 60 to 200 cm/sec. Stenoses of greater than 50% are indicated by peak systolic velocity ratios of greater than 3.5. ⁷ The reported sensitivity of color Doppler is 84%, and it has a 60% specificity. ⁸ However, most patients with greater than 50% stenosis detected by ultrasound surveillance are asymptomatic, and only 13 to 22% are found to have increased venous pressures or urea recirculation (figures 3A, 3B). ^8,9

FIGURE 3. (A) A diagnostic fistulogram in a patient with elevated venous pressures shows a high grade lesion at the venous anastomosis. (B) This postangioplasty angiogram shows resolution of the lesion with no retrograde venous flow.

Guideline 11: Monitoring primary AV fistulae for stenosis -Flow rates during dialysis are the most accurate indicator of dysfunction of a native AV fistula. Failing fistulae may manifest by high in-flow pressures during dialysis, the inability to achieve desired flow rates, elevated out flow pressures, or upper extremity edema. If aspiration pressures during dialysis exceed 200 mm Hg, an inflow lesion should be suspected. When out-flow pressures are greater than 200 mm Hg, an outflow lesion usually is present. When upper extremity edema develops, a stenosis or occlusion of an essential central vein should be excluded.

Guideline 12: Recirculation methodology, limits, evaluation, and follow-up -The determination of urea circula tion is highly variable and depends upon multiple factors (e.g., needle position, graft size, dialysis pump speed, and central venous pressures). Generally, it is considered to be abnormal when it is greater than 10%. However, an elevated urea recirculation is an insensitive parameter, as many fistulae fail despite the presence of "normal urea recirculation". ⁶

Guidelines addressing prevention of complications

Guidelines 13, 14, and 15 -These guidelines address how to prevent access infection, adequately handle needle cannulation of grafts and fistulae, and care for venous catheters. The patient and staff should be educated in how to prevent graft or catheter infection. Infection rates should be monitored, and cannulation of vascular access should comply with OSHA regulations. Simple maneuvers such as the application of a dry gauze dressing with povidone iodine can reduce infection rates.

Guidelines on management of complications and when to intervene

Guideline 16: Managing potential ischemia in a limb bearing an AV access -Diabetic patients and those with poor in-flow to the angio-access site or poor run-off distal to the angio-access site are at greater risk for developing limb ischemia. The symptoms can be seen acutely or chronically. Treatment usually requires surgical intervention, although endovascular therapy can be helpful.

Guideline 17: When to intervene on dialysis AV grafts for venous stenosis, infection, graft degeneration, or pseudoaneurysm formation -A stenosis greater than 50% accompanied by a clinical indicator of access failure should undergo prophylactic intervention with either PTA or surgery. Surgical intervention will be necessary for the management of infection, degeneration, and pseudoaneurysm formation (figure 4).

FIGURE 4. Multiple pseudoaneurysm formation here requires surgical repair.

Guideline 18: When to intervene on primary AV fistulae -An intervention on primary AV fistulae is recommended when there is inadequate flow to achieve the prescribed dialysis, a hemodynamically significant stenosis is detected, or when a clinically significant aneurysm is present.

Guidelines for optimizing treatment of failing dialysis access

Guideline 19: Treatment of stenosis without thrombosis in dialysis AV grafts and AV fistulae -The expected outcome for the treatment of a stenosis without thrombosis in an AV graft or primary AV fistulae are as follows: primary patency at 6 months for PTA should be 50%, and the primary patency of surgery at 12 months should be 50%. Surgery is held to a higher standard due to its invasiveness and the loss of a usable vein with each surgery. If PTA fails twice within 3 months, surgical revision should be done, if possible. The use of stents is reserved for PTA failures in non-surgical situations. However, stents used for the treatment of peripheral venous stenoses in association with ipsilateral dialysis fistulae have primary patency rates reported to be as low as 33% at 12 months. ¹⁰

Guideline 20: Treatment of central vein stenoses -Central vein stenoses should be treated with PTA. Stents should be reserved for use when there is a recurrent stenosis within 3 months of a PTA, or if there is immediate elastic recoil during the PTA procedure. Stents in this setting are associated with 1-year primary patency rates of 25 to 40% (figures 5, 6). ^11,12

FIGURE 5. A previous central venous stent placed for failed angioplasty is seen. Patency maintenance was achieved with repeated angioplasty.

FIGURE 6. Brachiocephalic vein reconstruction with the use of stents is seen here, following failed angioplasty.

Guideline 21: Treatment of thrombosis and associated stenoses in dialysis AV grafts -The treatment of thrombosed AV grafts should be initiated expeditiously, with no more than one femoral catheterization performed for the purpose of temporary dialysis. Declotting is performed with pharmacomechanical techniques, the use of thrombectomy devices, or with surgery, and a post-procedure fistulogram should always be done for evaluation. If an underlying stenosis is detected, it can be corrected with either PTA or surgery. Declotting of a graft should be done on an out-patient basis, using local anesthesia. Clinical screening parameters should return to normal following the procedure. There should be an immediate technical success rate of 85% for all techniques. Surgical intervention is associated with a 50% primary patency at four months and 40% at 1 year. Percutaneous interventions are associated with a 40% primary patency at 3 months.

Guideline 22: Treatment of primary AV fistulae thrombosis -Primary AV fistulae thromboses are difficult to treat. Selection of procedure should be on an individual basis, according to local expertise. Practitioners may consider surgery and mechanical and pharmaco-mechanical thrombolysis.

Guideline 23: Treatment of poorly functioning tunneled catheters -Dysfunction of a dialysis catheter is defined as a failure to give flow rates of at least 300 ml/min. The use of low-dose urokinase (Opencath, Abbott Laboratories) is recommended for inital management. If this fails, any of the following methods to reestablish catheter function can be undertaken, depending upon the expertise of those at your institution: fibrin sheath stripping, urokinase infusion (i.e., 40,000 units/hour for 6 to 12 hours), catheter exchange, or repositioning of a malpositioned catheter.

Guidelines 24 and 25: Treatment of infection of dialysis AV grafts and primary AV fistulae -Endovascular intervention in this clinical setting should be avoided, due to the risk of bacteremia and sepsis.

Guideline 26: Treatment of infected tunneled catheters -Tunneled catheters with exit site or tunnel infections should be managed with antibiotics. The catheter should be removed only if antibiotic therapy is unsuccessful in managing the infection. In the presence of bacteremia in an unstable patient or in a patient with symptoms which last for more than 36 hours, the tunneled catheter should be removed. If the patient is stable, the catheter can be exchanged over a guidewire, but antibiotics should be administered for at least 3 weeks. A new permanent tunneled catheter should not be placed unless there have been negative blood cultures for 48 hours.

Guidelines 27 and 28: Surgical management of AV graft pseudoaneurysms and AV fistulae aneurysms -During a fistulogram, direct puncture of these aneurysms and pseudoaneurysms should be avoided.

Guidelines addressing quality of care standards

Guideline 29: Goals of access placement: maximizing primary AV fistulae -At least 50% of new patients electing hemodialysis should have construction of an AV fistula. Approximately 15% of these patients in the United States currently have native fistulae, though the goal is to have at least 40% of the hemodialysis patients in the United States with native AV fistulae. Each center should maintain a database to track access types and complication rates.

Guideline 30: Goals of access placement: use of catheters for chronic dialysis -This guideline states that less than 10% of patients on chronic hemodialysis should have chronic catheters (defined as those placed for more than 3 months in the absence of a maturing access).

Guideline 31: Center-specific thrombosis rates -AV dialysis graft thrombosis rates should not exceed 0.5 episodes per patient year, though currently about 1.2 episodes of thrombosis occur per patient year in the United States. Thrombosis rates for an AV fistula, after adjusting for initial failures, should be less than 0.25 episodes per patient year. Each institution should have an ongoing quality assurance program to evaluate thrombosis rates and their causes. Again, creating a screening program is the key to achieving these goals.

Guideline 32: Infection rates -Infection rates should not exceed 1% in native fistulae and 10% in AV grafts, as calculated over the usable life of the access. Tunneled catheters should have less than a 10% systemic infection rate at three months, and less than 50% at one year.

Guideline 33: Primary access failure rates: AV grafts -The 30-day primary AV graft failure rates should not exceed 15% for a straight forearm graft, 10% for a forearm loop graft, and 5% for an upper arm graft. Again, each institution should create monitoring programs to identify failures and problems with access creation and use.

Guideline 34: Primary access failure rate: tunneled catheters -More than 90% of tunneled catheters should be able to exceed flow rates of 300 ml/min during the initial dialysis session. Significant complication rates (pneumothorax requiring a chest tube, symptomatic air embolism, hemothorax, hemomediastinum, or hematoma requiring evacuation) related to tunneled catheter insertion should not exceed 2%.

Guideline 35: Primary access failure rate: AV fistulae -No recommendations were made for primary native AV fistula failure.

Guideline 36: Cumulative patency rates of dialysis AV grafts -The cumulative patency rates of newly created AV grafts should be at least 70% at 1 year, 60% at 2 years, and 50% at 3 years.

Guideline 37: Cumulative patency rates of tunneled catheters -The chronic use of tunneled catheters is discouraged.

Guideline 38: Cumulative patency rates of native AV fistulae -No recommendations were made.     AR

FIGURE 7. Successful mechanical thrombolysis is achieved with the use of the Castaneda-Cragg brush.