Version May 2024
INTRODUCTION — Hemodialysis vascular access planning for every patient should begin with the development of an individualized end-stage kidney disease (ESKD) Life-Plan that is regularly reviewed, updated, and documented in the medical record [1]. This plan involves a patient-centered approach for vascular access that takes each individual patient's needs and preferences into consideration. This involves planning for, creating, and preserving the first access, but also being proactive in planning for the protection, creation, and preservation of the next vascular access prior to failure of the first access. Planning for subsequent access must take into consideration the individual patient's circumstances, needs, and preferences. The ESKD Life-Plan brings into focus and emphasizes the importance of the secondary arteriovenous (AV) fistula, which is defined as an AV fistula that is created following the failure of a previous AV access, generally in the lower arm, which can be either (AV fistula or AV graft). (See "Approach to the adult patient needing vascular access for chronic hemodialysis".)
The options, evaluation of the patient, and choice of secondary hemodialysis access are reviewed here. Primary hemodialysis AV access, including maturation and initial management of failed primary AV access, is discussed separately. (See "Early evaluation of the newly created hemodialysis arteriovenous fistula" and "Primary failure of the hemodialysis arteriovenous fistula".)
OVERVIEW — The concept of a secondary arteriovenous fistula (SAVF) is very important, given the known issues and complications associated with arteriovenous (AV) fistulas and, to an even greater extent, AV grafts. In the past, an SAVF was defined as an AV fistula constructed using the outflow vein of an AV graft. The definition has been expanded to include any AV fistula constructed following the failure of a prior AV access, regardless of whether the primary access was an AV fistula or AV graft. Two types of SAVF are defined. Although both are referred to as an SAVF, they differ conceptually. Each is described below.
Type I SAVF — A direct (type I) SAVF uses the outflow veins of a prior AV access. The creation of a type I SAVF is most often applicable to patients with forearm AV grafts. In patients with an established forearm AV graft, the veins of the upper arm undergo a process of maturation similar to that seen with AV fistula development and for similar reasons.
A large percentage of patients with dialysis access dysfunction are excellent candidates for a type I SAVF. In one study, for example, 100 consecutive patients with dysfunctional upper extremity prosthetic grafts referred for either an angioplasty or treatment of a thrombosed graft were evaluated using only the angiographic images that had been created during the procedure [2]. A total of 46 patients (74 percent) with a forearm loop graft had one or both of the upper arm veins that appeared as if they would be suitable for creation of an SAVF based upon size and absence of pathology.
Type II SAVF — A type II SAVF uses other autogenous access opportunities when existing AV access outflow will not permit a type I SAVF [2]. The creation of a type II SAVF is independent of the existing AV access. Every patient with a dysfunctional AV graft or a failing AV fistula should be considered a candidate and evaluated for the creation of a replacement AV fistula even if the outflow veins of the existing AV access are not optimal or evaluations performed in the past have failed to reveal suitable vessels. The type II SAVF concept emphasizes the need for a protocol to accomplish this in a timely manner rather than pursuing a problematic dialysis access with repetitive interventions that are unlikely to provide prolonged problem-free access use and are costly to the healthcare system.
The evaluation for and the creation of a type II SAVF follows the same principles as for primary AV access creation, the difference being that it is done in order to replace a failing access [3]. In cases where vascular mapping fails to identify a suitable outflow vein with imaging of the existing AV access, and thus there is no option for a type I SAVF, the patient should undergo detailed vascular mapping of the contralateral extremity. (See "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Types by anatomic location'.)
PLANNING — The patient's end-stage kidney disease (ESKD) Life Plan should include plans for a secondary arteriovenous fistula (SAVF) when a dysfunctional AV graft or a failing AV fistula occurs (algorithm 1). It is important to keep in mind that the mere presence of an AV graft should not be considered an indication for conversion to an SAVF [4]. Conversion of an AV graft should not be done unless it becomes significantly problematic and no longer provides adequate access without repeated interventions. Well-functioning AV grafts should never be converted to an SAVF.
Dialysis access dysfunction often occurs suddenly, and although treatment with angioplasty or surgical revision may extend function for short periods of time, such treatment, especially graft extension or stent placement, can jeopardize the opportunity for SAVF conversion. The goal of the nephrologist should clearly be to transition such patients to an AV fistula to the maximum degree possible and avoid the graft failure-catheter-new graft cycle.
A formalized protocol may serve to avoid this problem. Nephrologists caring for the dialysis patient should assume the responsibility for initiating such an SAVF protocol on each of their AV graft patients [5]. Although it should be individualized, the evaluation for an SAVF take place no later than the first sign of AV graft failure and that SAVF conversion take place no later than the second AV graft failure [1]. Although there may be exceptions based upon patient circumstances, these principles should be reflected in the SAVF protocol. (See 'Timing and creation of SAVF' below.)
Nephrologists should establish and follow a formalized protocol to evaluate patients for potential type I/type II SAVFs and the timing of conversion/creation. Patient and caregiver education should be an important aspect of the SAVF protocol. Issues such as risk of complications, longevity of use, and adequacy of dialysis should be discussed in detail. The importance of such an SAVF protocol was illustrated in a study that detailed the results of SAVFs in two groups, one following a protocol, and the other with no protocol [6]. The patients of the second group (n = 110) were referred for an SAVF later and had a higher number of prior procedures and accessories placed. The first group had a higher percentage of type I SAVFs created and a lower incidence of tunneled dialysis catheter use following access creation and for a much shorter period of time. The differences in primary and secondary patency (figure 1 and table 1) for the two groups were both excellent and not significantly different.
EVALUATION FOR SAVF — The evaluation for a secondary arteriovenous fistula (SAVF) falls into two categories: ongoing and episodic. The categories of SAVFs are described above. (See 'Type I SAVF' above and 'Type II SAVF' above.)
Dialysis facility staff and rounding nephrologists should examine the outflow vein of all arteriovenous (AV) graft patients ("sleeves up") during dialysis treatments at least once per month and, among those with problematic grafts, identify those who may be suitable for elective SAVF conversion.
Ongoing evaluation should be a continuous process directed toward identifying potential candidates for an SAVF. In doing so, suitable cases can be identified in advance to facilitate timing and to help avoid ill-advised procedures that might prevent the possibility of the SAVF conversion. There is value if the venous anatomy can be evaluated when the access in the lower arm is still functioning and the veins of the upper arm are under pressure [7]. A vein that might initially be discounted when a graft is thrombosed might actually offer an excellent opportunity for the creation of a type I SAVF if seen under optimal circumstances.
As with any type of AV dialysis access, vascular evaluation is important for the evaluation of a potential SAVF candidate [8]. However, this does not generally require a separate procedure. Most often, the vascular evaluation can be performed in conjunction with a procedure that is being performed to assess and/or treat dysfunction of the primary access using the images obtained in that procedure if the operator is alert to this issue. Whether identified through the ongoing or episodic evaluation, venous anatomy suitable for the creation of a type I SAVF should be recorded in the patient's individualized vascular access plan based upon the facility's SAVF protocol. (See "Hemodialysis arteriovenous graft dysfunction and failure".)
For patients in whom a type I SAVF is not possible, vascular mapping as a primary procedure is necessary to identify an appropriate artery and vein combination. This can be done either by ultrasound, angiography, or a combination of the two as with the creation of a primary AV fistula. (See "Patient evaluation prior to placement of hemodialysis arteriovenous access" and "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Physical evaluation'.)
TIMING AND CREATION OF SAVF — Arteriovenous (AV) access problems tend to be recurrent, and delays in the creation of a secondary arteriovenous fistula (SAVF) expose the patient to additional problems that could be avoided and increase the chances that an ill-advised endovascular or surgical procedure might be performed that could compromise the successful creation of an SAVF. Conversion should take place no later than the second AV graft failure, although there may be exceptions based upon individual patient circumstances. The same holds for the creation of a type II SAVF, which is the alternative for a patient whose current access does not have outflow veins suitable for the creation of a type I AV fistula. (See 'Planning' above and "Arteriovenous fistula creation for hemodialysis and its complications", section on 'Fistula creation'.)
The type I SAVF is analogous to a second stage of AV fistula creation. The first stage is represented by the existing AV access that has served the purpose of providing dialysis but also results in arterialization (maturation) of the outflow veins, making them better candidates for the second stage (ie, the SAVF), which uses these outflow veins for creation of an SAVF. The outflow vein options in the upper arm include the cephalic, basilic, and brachial veins. In most instances, type I SAVF creation will involve the creation of either a brachial-cephalic or a brachial-basilic AV fistula [9-12]. Even when one of these veins is not suitable, there may be an adequate vein (median antebrachial, for example) in the forearm that can be used as a bidirectional, middle-arm SAVF, after disrupting one or more valves [13].
●A brachial-cephalic AV fistula created in such circumstances can be safely used very early after creation, as soon as the operative trauma and swelling subside, if not immediately [5,6]. In many of these patients, cannulation of the outflow vein (cephalic vein) is possible prior to the creation of the SAVF. This has value in that it confirms that the prospective vein can be cannulated successfully. When the conversion occurs, it is just a matter of continuing what has already been initiated.
●A brachial-basilic (basilic vein transposition) AV fistula generally requires a period of at least one month after creation to allow for adequate healing of the tunnel before use.
For those without veins suitable for type I SAVF creation, type II SAVF construction should be undertaken as soon as feasible once other suitable vessels are identified. There is likely to be some delay as the total time for preoperative evaluation, surgery scheduling, and AV fistula maturation can be prolonged, generally requiring a temporary dialysis catheter for some period of time. If the failing access is still functional, construction of the new AV fistula should take place prior to abandonment of the current, minimizing the need for a temporary dialysis catheter.
Many patients with an SAVF will not require a temporary hemodialysis catheter. The need for a tunneled dialysis catheter following an SAVF conversion depends on several different variables, such as the timing of and the type of SAVF [4,6]. In the protocol study discussed above, the need for a temporary dialysis catheter was less in the patients with an established SAVF conversion plan [6]. With a type I SAVF, the use of catheter varies with the type of AV fistula that is created. In patients with a type II SAVF creation, an important factor determining the need for a temporary hemodialysis catheter was whether the patient was seen prior to the loss of the existing access. In these cases, a period of catheter dependency can generally be avoided. Otherwise, patients who are transitioned to a type II SAVF can be expected to be catheter dependent until the AV fistula matures adequately for use.
SAVF SERIES RESULTS — To understand the significance of survival data associated with secondary arteriovenous fistula (SAVF) creation, a point of reference is needed. The obvious one is primary arteriovenous (AV) fistula survival. However, it should be understood that the primary AV fistula and SAVF patient populations are not comparable. All patients with SAVFs will have had an episode of access failure, which in and of itself differentiates them from the population with a primary AV fistula. Furthermore, some may have had multiple access failures. Additionally, it should be noted that most reported AV fistula patency rates (figure 1 and table 1) are based upon the evaluation of only those AV fistulas that actually mature and are used clinically, not the total number that were created. When data based upon the total number of AV fistulas created are used, the picture is somewhat different, as was illustrated in a multicenter study [14]. In this study, patency data for 491 newly created AV fistulas in 395 patients were recorded. Group 1 included all AV fistulas that were created, and group 2 included only those that matured to the point of being clinically usable. Primary patency rates for group 1 versus group 2 at 3, 6, and 12 months were 71 versus 83 percent, 57 versus 70 percent, and 49 versus 61 percent, respectively. Secondary patency rates for group 1 versus group 2 at the same time intervals were 81 versus 96 percent, 75 versus 90 percent, and 70 versus 90 percent, respectively. The reduced patency rates for group 1 were due to the inclusion of primary failure (ie, failure to mature).
Only a few SAVF series have been reported upon from which one can draw conclusions concerning long-term results. Type I SAVFs and type II SAVFs are quite different and should be considered separately, though this has not always been the case. Patency rates for type I SAVFs should be expected to be good as these are created on a selective basis only in those with optimal veins. Lower patency rates might be expected for type II SAVFs.
In one study, 35 type I and 27 type II SAVFs were evaluated [15].
●Primary patency rates for type I SAVFs at 6 and 12 months were 87 and 14 percent, respectively.
●Primary patency rates for type II SAVFs at 6 and 12 months were 71 and 11 percent, respectively.
●Secondary patency rates for type I SAVFs at 12, 24, and 36 months were 100, 100, and 94 percent, respectively.
●Secondary patency rates for type II SAVFs at 12, 24, and 36 months were 96, 96, and 91 percent, respectively.
●Hemodialysis catheters were required in 21/35 of the patients with type I and in all 27 patients with type II SAVF.
In another study, 71 type II SAVFs were created over a 30 month period. These consisted of 40 brachial-cephalic and 22 brachial-basilic AV fistulas [16]. In this study, 29 of the brachial-cephalic AV fistulas and 16 of the brachial-basilic AV fistulas had previously undergone placement of an AV fistula while 20 of the brachial-cephalic AV fistulas and 6 of the brachial-basilic AV fistulas had prior placement of an AV graft. The one- and two-year primary patency rates for this group of type II SAVFs were 58 and 22 percent, respectively. For comparison, the one- and two-year primary patency rates for primary upper -rm AV fistulas in this program were 75 and 61 percent, respectively.
Finally, in the protocol study described above, the first group followed a protocol for SAVF creation, and the second group had no such protocol [6]. All individuals were able to have an SAVF created with no patient requiring a new AV graft. In this series of 141 cases, all patients with upper-arm AV grafts required type II SAVFs. The combined type I SAVF secondary patency for both groups was 97.4 percent at two years.
●In the first group, 40 consecutive patients transitioned from an AV graft to an SAVF; 26 had a forearm AV graft, and the remaining 14 had an upper-arm AV graft. The patients had 1 to 22 previous access operations (mean = 3). Of the 26 forearm AV grafts, 22 (85 percent) were converted to type I SAVFs, with the remaining 4 undergoing type II SAVF constructions because outflow veins were considered to be unsuitable for a type I SAVF. Of the 40 patients, 37 underwent SAVF surgery prior to abandonment of their AV graft. Only 22 patients required a catheter, and 17 of these were less than 10 days. The primary and secondary patency rates for these 40 SAVF operations (types I and II) were 82.5 and 92.5 percent at one year and 60.0 and 87.5 percent at two years. Secondary patency for type I SAVFs was 95.5 percent at two years.
●In the second group of this report, 102 consecutive patients were transitioned from an AV graft to an SAVF. Only 19.3 percent were referred for SAVF surgery prior to loss of the AV graft or outflow vein. These were the only patients in whom a type I SAVF was possible. The remaining patients required type II SAVF constructions. The primary and secondary patency rates for these 102 SAVF operations were 55.5 and 94.4 percent, respectively, at one year and 50.5 and 91.6 percent, respectively, at two years. Secondary patency for type I SAVFs was 100 percent at two years. Individual catheter time was not recorded for this group, but as 86 individuals (84.3 percent) had an SAVF created without a functioning AV graft for access, it is clear that prolonged catheter use was common.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Dialysis" and "Society guideline links: Hemodialysis vascular access".)
SUMMARY AND RECOMMENDATIONS
●Every patient presenting for dialysis should have an end-stage kidney disease (ESKD) Life-Plan not only for creating and preserving the first access, but which also includes proactive planning for the protection, creation, and preservation of the next vascular access before the current one fails. This plan also must take into consideration the individual patient's circumstances, needs, and preferences. (See 'Introduction' above.)
●A secondary arteriovenous fistula (SAVF) is defined as an arteriovenous (AV) fistula that is created following the failure of a previous AV graft or AV fistula. Two types of SAVF are described (type I: direct, utilizing previously arterialized outflow veins; type II: new AV fistula creation independent of prior outflow). (See 'Overview' above.)
●The AV fistula is most desirable among the options for chronic hemodialysis because it has the best long-term primary patency rate, requires the fewest interventions, and is associated with the lowest morbidity and mortality when compared with the alternatives (ie, AV graft, chronic indwelling central catheter). Thus, any patient with a failed or failing AV access should be considered a potential candidate for an SAVF, rather than continuing to perform interventions on the initial access that are unlikely to provide prolonged problem-free hemodialysis access. Treatment of AV access dysfunction by stent placement or surgical revision can jeopardize the opportunity for SAVF conversion. (See 'Planning' above.)
●Each dialysis facility should develop and adopt a formalized SAVF protocol containing specific criteria for the evaluation and timing of SAVF placement. Although these should be individualized, we agree with recommendations to evaluate the patient for an SAVF with the first sign of AV access dysfunction. Patient education should be an integral part of the SAVF protocol, stressing the advantages of the AV fistula. Conversion/creation to type I/type II SAVF should, in most patients, be attempted no later than the second AV access dysfunction. (See 'Timing and creation of SAVF' above.)
●When evaluating a patient with an AV graft as a potential candidate for a type I SAVF, we prefer to perform vascular mapping using angiography in conjunction with any salvage procedure at the time of the first access dysfunction. Evaluating the venous anatomy once the access is functioning again and the veins of the upper arm are under pressure may identify upper arm veins that would not be seen with a thrombosed access. For patients in whom a type I SAVF is not possible, vascular evaluation and mapping for type II SAVF is similar to primary AV fistula creation. Venous anatomy suitable for the creation of an SAVF (type I or type II) should be recorded in the patient's individualized vascular access plan. (See 'Evaluation for SAVF' above.)
●Most type I SAVFs will be a brachial-cephalic AV fistula or a brachial-basilic (basilic vein transposition) AV fistula. Because the outflow veins have already been arterialized, a brachial-cephalic fistula can often be safely used very early after creation, if not immediately. A basilic vein transposition AV fistula generally requires a period of at least one month after creation, and patients will require a temporary hemodialysis catheter. For type II SAVFs, the timing of access creation should take into account the time needed for the new AV fistula to mature. If the failing access is functional, construction of a type II SAVF should take place prior to abandonment of the current AV access to minimize the need for and duration of temporary hemodialysis catheter usage. (See 'Timing and creation of SAVF' above.)
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