Version May 2024
INTRODUCTION — Evaluation of the end-stage kidney disease (ESKD) patient in preparation for the placement of a hemodialysis access is extremely important. Proper patient selection enhances the opportunity to place the access most appropriate for the individual patient. This evaluation should be detailed and complete. (See "Patient evaluation prior to placement of hemodialysis arteriovenous access".)
Each predialysis and dialysis patient should have an individualized ESKD Life-Plan [1], which should start in the predialysis period if possible, with the goal of maximizing ESKD dialysis modality choices and utilization for a specific patient's foreseeable lifespan. In developing this plan, risk factors having a potential adverse effect on the success of the dialysis access must be taken into consideration.
Many patients have more than one risk factor because they have multiple comorbidities. The dialysis patient population is among the sickest with a symptom burden comparable to that of the cancer patient [2,3]. Older patients represent the most rapidly growing group of dialysis patients, and approximately one half of ESKD patients over 75 years of age have three or more comorbidities [4].
Definitions for the hemodialysis access time points used in this topic (eg, primary patency, assisted primary patency, postintervention patency) are provided in the figure (figure 1 and table 1).
Although this discussion is directed primarily toward factors that create a risk for failure of arteriovenous (AV) fistula development, it should be realized that some of these factors also represent a risk to the patient's well-being (life and limb).
The risk factors associated with failure of hemodialysis AV fistula maturation and failure of a mature AV fistula are reviewed here. The choice of hemodialysis AV access and placement and care of the AV fistula are reviewed separately. (See "Arteriovenous fistula creation for hemodialysis and its complications" and "Overview of hemodialysis arteriovenous fistula maintenance and thrombosis prevention" and "Approach to the adult patient needing vascular access for chronic hemodialysis".)
USE OF RISK FACTORS — Although risk factors are important, risk stratification schemes based on demographic and clinical parameters fail to accurately identify individuals in whom arteriovenous (AV) fistula placement is futile. The identification of a high-risk patient simply dictates the need for more intensive, individualized evaluation [5]. The most important determinant in the success of an AV fistula is the quality of the available vessels (ie, hemodynamic factors). Individualization based upon preprocedural vascular mapping is critical. No patient with end-stage kidney disease (ESKD) should be excluded from consideration for an AV fistula without vascular mapping and evaluation by an experienced hemodialysis access vascular surgeon. (See "Patient evaluation prior to placement of hemodialysis arteriovenous access".)
While the goal of patient evaluation prior to access placement is to facilitate the placement of an AV fistula, failure of AV fistula maturation remains a major problem with serious clinical consequences, not least of which is prolonging the period of catheter dependency. Thus, the patient with a low likelihood of AV fistula maturation based upon an individualized evaluation might be better served by placement of an AV graft. (See "Approach to the adult patient needing vascular access for chronic hemodialysis", section on 'Strategy for lifelong hemodialysis access'.)
RISK FACTORS — The risk of poor arteriovenous (AV) fistula maturation or subsequent AV fistula failure can be regarded as related to either hemodynamic factors, patient-related demographic or clinical factors, or other technical issues. Among these, hemodynamic factors are the most important. Demographic and clinical risk factors are generally realized only when they affect hemodynamics.
●Hemodynamic – Vein size, feeding artery size, blood flow
●Demographic – Patient age, sex, race/ethnicity
●Clinical – The presence of cardiac disease, peripheral arterial disease, pulmonary hypertension, diabetes mellitus, obesity
●Technical – Training and experience of surgeon, fistula creation, care and use of the AV fistula
Hemodynamic — The value of vascular mapping in assessing hemodynamic parameters has been well documented in the literature. (See "Patient evaluation prior to placement of hemodialysis arteriovenous access" and "Arteriovenous fistula creation for hemodialysis and its complications".)
Patients with inadequate size or quality of vessels may not be candidates for an AV fistula, at least initially. In these cases, the creation of an AV access in the forearm using graft material may be the best option. The purpose is twofold. The AV graft will provide a useable dialysis access, and the veins in the upper arm may develop over time such that a secondary AV fistula may be possible, if the AV graft becomes problematic [6]. (See "Hemodialysis access following a failed arteriovenous access".)
Demographic — Demographic factors include age, sex, and race/ethnicity. Demographic and clinical risks are generally realized only when they affect hemodynamics.
Age — Since the older patient represents the fastest growing group of end-stage kidney disease (ESKD) patients, age is an increasingly important factor to consider when planning hemodialysis vascular access. Renal failure behaves differently in older compared with younger adults [7]. Older patients lose renal function at a slower rate than is typical for younger patients, and fewer progress to ESKD requiring dialysis. However, older age is a risk factor for decreased life expectancy on dialysis [8]. However, it is the presence of comorbidities that appears to have a stronger effect on survival, rather than incremental age alone [9,10]. Rather than being a risk factor itself, advancing age largely acts as a surrogate for an increasing incidence of comorbidity that comes with age, particularly for diabetes and cardiovascular disease. Overall, age as an isolated variable should not greatly affect access decisions other than considerations related to the expected age-related longevity of the individual patient. As an example, there may be a concern that an older patient may die in the time interval between AV fistula creation and the initiation of dialysis [11,12].
A problem in analyzing published data related to age is the variability of the age groups being studied. In a meta-analysis involving 13 studies of dialysis access outcomes, the most commonly used age for the "older patient" category was >65 years [13]. However, age >75 years is associated with the highest incidence rate of ESKD (per million/year), with those 65 to 74 years having the second highest incidence [14]. Defining older age as a homogeneous group >65 years leads to skewed results.
The increased burden of comorbidity in the older patient may materially affect patient selection for AV fistula creation; however, once an AV fistula is established in these cases, patency appears to be comparable to that of younger age groups. This is illustrated by three points based upon 2016 United States Renal Data System (USRDS) data [14]:
●AV fistula time to maturation did not differ significantly between age groups. The average intervals of time from AV fistula placement to first use for age categories 22 to 44, 45 to 64, 65 to 74, and <75 years were 129, 132, 136, and 133 days, respectively.
●AV fistula use did not differ significantly between age groups. AV fistula use at 3 and 12 months by these age categories (22 to 44, 45 to 64, 65 to 74, and <75 years) was 22 and 63, 25 and 67, 27 and 65, and 24 and 60 percent, respectively.
●AV fistula primary failure rates differed only modestly between age groups. The AV fistula failure rates for age categories 22 to 44, 45 to 64, 65 to 74, and >75 years were 32, 34, 37, and 40 percent, respectively.
There is a general lack of concordance in the literature concerning the effect of age on AV fistula development and patency. There are studies showing that age has an overall negative effect [15], that primary patency is poorer but cumulative patency is equal [16], and that there is no age-related difference in AV fistula success [17]. The reasons for inconsistency are multiple. A major issue is that most studies have lumped all patients beyond a certain age into the same "older patient" category. In addition, all patients go through a selection process for the creation of an AV fistula, and due to the increasing comorbidity burden with age, the selection process is probably more rigorous for the older patient. There are also significant differences between individual surgeons and surgical programs that can make a difference [18]. Unfortunately, there are no randomized trials to provide a more definitive answer. However, the fact that there are studies showing that age is not a negative factor for AV fistula development indicates what can be accomplished with vascular mapping and individual patient evaluation of risk factors [19]. It should be noted that in some studies in which age over 65 was associated with increased risk of primary failure, preprocedure vascular mapping was not routinely performed [16].
In a study of 461 patients ranging in age from 65 to 94 (mean age 73 years) in whom vascular mapping was performed, primary, assisted primary, and cumulative patencies were 60, 94, and 97 percent at 12 months and 45, 90, and 95 percent at 24 months, respectively, with a mean follow-up of 17 months [17]. When the patients were stratified by age into 65 to 74, 75 to 84, and 85 to 94 year groups, there were no significant differences in AV fistula outcomes. In addition, a comparison of primary, assisted primary, and cumulative patency rates for all older (≥65 years) compared with all younger (<65 years) patients also showed no difference.
In another study of 525 patients who were followed for three years after AV fistula creation based upon vascular mapping, there were no significant differences for failure to mature or primary patency rates at one, two, and three years between groups stratified by age (<65, 65 to 75, and >75 years) [19]. However, age >75 years was associated with worse cumulative patency (hazard ratio [HR] 1.90, 95% CI 1.15-3.14).
An integral part of the patient's ESKD Life-Plan is the adoption of an anatomical progression in access planning that allows for maximum conservation of more proximal vessels. Classically, the order preference to accomplish this goal is to start distally with a radial-cephalic AV fistula, if possible. Studies that suggest that for the older patient this approach may not be appropriate [13,20]. As with AV fistulas in general, published studies using age as a factor in the analysis of access outcome and survival have yielded conflicting results and conclusions. However, studies using preprocedure vascular mapping and individualized patient selection have shown comparable results for radial-cephalic AV fistulas regardless of age.
In a review involving 361 patients with a radial-cephalic AV fistula and 297 with a brachial-cephalic AV fistula, primary and cumulative patencies were compared by age group: <65, 65 to 79, and >80 years of age [21]. The distribution of patients in these three groups was 43.8, 41.6, and 14.6 percent, respectively. Only 85.7 percent of patients progressed to hemodialysis. Primary patency for radial-cephalic AV fistulas at one and two years was 46.0 and 27.1 percent for the <65 year group, 47.0 and 36.0 percent for the 65 to 79 year group, and 45.7 and 38.1 percent for the >80 year group, respectively. Radial-cephalic AV fistula cumulative patency rates at one and two years were 46.1 and 27.8 percent for the <65 year group, 47.8 and 37.5 percent for 65 to 79 year group, and 47.8 and 39.9 percent for the >80 year group. These differences were not statistically significant.
Primary patency rates at one and two years for the brachial-cephalic AV fistula in this same study were 39.3 and 31.0 percent, 53.3 and 37.5 percent, and 46.3 and 42.6 percent for the same age groups and time intervals, respectively [21]. The brachial-cephalic AV fistula cumulative patency rates at one and two years were 41.0 and 33.6 percent for the <65 year group, 55.7 and 39.2 percent for the 65 to 79 year group, and 46.3 and 42.6 percent for the >80 year group (p = 0.25). In addition, there was no significant difference between age groups for the radial-cephalic versus the brachial-cephalic AV fistula for either primary or cumulative patency. The authors of this report emphasized that with proper patient selection, older patients of all age groups can be considered suitable for either a radial-cephalic AV fistula or a brachial-cephalic AV fistula.
Sex — As with older age, sex also presents several unique features related to dialysis and vascular access.
Males have a higher level of kidney function compared with females at the same level of serum creatinine as a result of greater muscle mass and creatinine generation. This is important to recognize because referrals for vascular access at a fixed level of serum creatinine would systematically refer women with more advanced disease [22]. However, although there are some conflicting data, several studies have shown that the rate of renal deterioration is slower in women compared with men, and women have improved renal survival and lower overall mortality compared with men (104 versus 123 per 1000 patient-years at risk) [14,22-27].
Although there are reports to the contrary [28,29], most investigations have found significant differences in outcomes of AV fistula creation when comparing males and females. In one study, females were at greater risk for failure of the AV fistula to mature compared with the males in spite of preoperative vascular mapping (hazard ratio 2.42, 95% CI 1.32-4.45) [30]. However, the 2016 USRDS data show a different picture [14]:
●Females had a higher overall rate of AV fistula maturation compared with in males (41.6 versus 31.5 percent).
●More males were using AV fistulas at the initiation of dialysis, 18.4 versus 14.8 percent in females.
●The duration of patency was shorter for females compared with in males, with AV fistula use at 3 and 12 months of 26.2 and 55.9 percent versus 27.9 and 70.6 percent, respectively.
The reasons for these differences are not clear. It has been suggested that females have smaller vessels [31]; however, comparative studies of preoperative vascular mapping have not supported this premise. In one study involving 106 females and 86 males, no significant difference in vein size was observed at any of 17 sites that were examined [32]. However, arterial size was significantly smaller in females at 3 of 12 different sites that were measured. These sites were all in the distal forearm. In another study involving 84 females and 105 males with preoperative vascular mapping, no differences in vein diameters were noted between the sexes [33]. However, arterial differences were also noted. Arteries used for AV fistula construction were smaller in females in both forearm and upper arm placements, but in a comparison between successful and unsuccessful AV fistulas, there were no differences in either arterial or venous diameters in either the forearm or upper arm.
Race/ethnicity — While some studies show racial/ethnic differences in AV fistula use and failure rates, the reasons for the difference are not totally clear. While a genetic difference between different racial/ethnic groups cannot be totally discarded, there are definite differences in comorbidities between the groups [14,34-37]. These factors have the potential to affect the development of ESKD and the creation of an AV fistula for dialysis.
There is a higher rate of both type 2 diabetes and hypertension in Black compared with White Americans, and the risk of type 2 diabetes in Native Americans and Hispanic Americans is even higher [38]. As an example, from USRDS data, the incidence of obesity is higher in Black hemodialysis patients compared with non-Hispanic White patients [39]. This can adversely affect AV fistula creation but had a positive effect on patient longevity due to the "obesity paradox" (see 'Obesity' below). In addition, disparities in health care delivery in the US, including the use of preventive services, are well documented [40].
Although not consistently reported, race has been listed as a risk factor for failure of AV fistula maturation in the United States and Canada [5,41-44], and racial/ethnic differences have been documented in AV fistula use in prevalent dialysis patients [45]. A US study was conducted using ESKD Medical Evidence Report data to determine the correlation between risk factors in AV fistula use in 195,756 adult patients initiating outpatient hemodialysis therapy who had six or more months of prior nephrology care [45]. The likelihood of Black American patients beginning outpatient hemodialysis therapy using an AV fistula was 60 percent lower compared with White Americans, and for Hispanic Americans, 10 percent lower compared with non-Hispanic Americans. Similarly, in a review of ESKD data for 2016, Black Americans were less likely to start dialysis using an AV fistula, using White Americans as the reference, as were Native Americans [14].
Racial and ethnic differences in AV fistula failure rates were also evident in the 2016 United States Renal Data System (USRDS) data [14]. By ethnicity, the highest AV fistula failure rate occurred in non-Hispanic Americans, with a rate of 36.2 compared with 29.2 percent in Hispanic Americans. Within the non-Hispanic population, the highest failure rate occurred in Black Americans (38.2 percent), followed by White Americans (35.7 percent). Although the case numbers were small, the remaining failure rates were given as 33.9 percent for Native Americans, 30.3 percent for Asian Americans, and 27.3 percent for other non-Hispanic Americans.
AV fistula use at 12 months was also lowest in Black Americans at 58.5 percent, compared with a high of 75 percent in the Native American group, 66.9 percent in the white group, and 69.7 percent in the Asian group. AV fistula use in the total group of prevalent patients, those on dialysis for >90 days, was lowest for the Black participants at 57.7 percent. The values for other groups were 68 percent for Hispanic Americans, 64.9 percent for White Americans, 75.1 percent for Native Americans, and 67.5 percent for Asian Americans.
Clinical comorbidities — Clinical risk factors for AV fistula failure include the presence of cardiac disease, pulmonary disease, peripheral arterial disease, diabetes, and obesity.
Cardiac disease — Cardiovascular disease (CVD) is an important comorbidity among patients with CKD. In 2016, 68.8 percent of patients >66 years of age with CKD had some form of CVD [14]. The prevalence of heart failure was 28.2 percent, and atrial fibrillation was present in 25.3 percent (nearly one half of patients with heart failure also had atrial fibrillation). In addition, CVD presents a mortality risk for the ESKD patient. Death from CVD is 10 to 20 times higher in these patients compared with in the general population [46].
The relationship between CVD and CKD is complex. The two share risk factors such as diabetes and hypertension. In addition, CKD is associated with changes that can increase the risk of developing CVD, such as abnormalities of mineral metabolism, anemia, volume overload, and CKD-associated vascular changes. CVD can also increase the risk of CKD [47]. In addition, all forms of CVD have an increased incidence in CKD patients. This close relationship should be given consideration in dialysis access planning. Classification during the predialysis period according to the severity of cardiac symptoms in one of four categories (New York Heart Association Functional class I to IV) can help guide the selection of the most appropriate hemodialysis access [48]. (See "Evaluation and management of heart failure caused by hemodialysis arteriovenous access".)
The heart is a critical part of the dialysis access circuit, providing the driving force for blood flow necessary to meet the demands of the dialysis access. The creation of an AV fistula produces a hyperdynamic state that increases cardiac workload (volume-loaded state) and exerts significant effects on cardiac systolic and diastolic performance. Many of the early cardiac changes are physiological and adaptive; however, there are those that are maladaptive and deleterious to cardiac function and can lead to increased cardiac strain and poor subendocardial perfusion [49].
For patients with relatively normal cardiac function, the creation of an AV fistula should not be expected to have adverse effects. Some reports have noted an improvement in cardiovascular function with the creation of an AV dialysis access [50]. However, poor cardiac function adversely affects blood flow to the developing AV fistula. In addition, by increasing demand for cardiac output, the AV fistula can adversely affect the heart.
ESKD patients with decreased cardiac reserve are at risk for developing heart failure after AV access construction while those with a history of heart failure are at risk for worsening their condition. The deleterious effect of an AV fistula on the heart is directly proportional to access blood flow [51]. Since flow rate is generally higher with a brachial artery-based AV fistula compared with a radial artery-based AV access, the increase in cardiac output will be proportionately more. In a prospective study involving 96 hemodialysis patients, 31 patients with an upper-arm AV fistula had a significantly higher mean flow rate, cardiac output, and flow rate to cardiac output ratio compared with 65 patients with a lower-arm AV fistula [52]. This difference was evident even in the early maturation period of AV fistula creation. In an observational study of 562 predialysis patients, the location of AV fistula was closely related to the incidence of heart failure (40 percent in brachial-cephalic versus 8 percent in radial-cephalic AV fistula) [49]. This suggests that in a patient with decreased cardiac function, if an AV fistula is created, a radial artery-based access with a lower flow rate would be desirable.
Peripheral arterial disease — To achieve a functional AV fistula, the feeding brachial artery must increase baseline blood flow 10- to 20-fold to deliver the required blood volume for the fistula, as well as to supply distal tissues [53]. To do this, the artery must increase diameter sufficiently by remodeling to accommodate the increased flow [54]. Peripheral arterial disease interferes with this process. In one study involving 784 incident hemodialysis patients, a history of peripheral artery disease was associated with a 24 percent higher risk of AV fistula failure [55].
Peripheral arterial disease changes in the vessel wall are characterized by intimal hyperplasia and calcification. At a histologic level, the presence of calcium deposits within the vessel wall of radial and brachial arteries in patients with CKD has been correlated with increased arterial stiffness and decreased elasticity [56].
In a study involving 59 patients in whom a radial-cephalic AV fistula was created, surgically obtained arterial specimens were examined for intimal hyperplasia, which was found in 45 cases [57]. Patients with intimal hyperplasia were older and had a higher incidence of diabetes. A strong correlation was seen between AV fistula failure and intimal hyperplasia. In another study involving 72 diabetic patients, macrocalcification (Mönckeberg type) in the vessel wall (determined radiologically) correlated with decreased long-term AV fistula patency [58]. It is of interest that in another publication, microcalcification (determined histologically) had no effect on AV fistula maturation [59].
Tests directed toward detection of feeding artery pathology have been advocated (eg, resistive index, assessment of arterial stiffness and elasticity, hyperemic response) [56]. A number of studies have reported a positive correlation between poor results in these tests and AV fistula failure [60-65]. As an example, in a small study of patients undergoing AV fistula placement, the average radial artery elasticity index (ie, less stiffness) was higher in the group that developed a mature AV fistula compared with the group in whom the AV fistula failed; however, the brachial artery elasticity index was not significantly different in the success and failure groups.
Pulmonary hypertension — Pulmonary hypertension is also an important comorbidity in those with CKD. Its presence can materially affect the life expectancy of the dialysis patient and influence dialysis access choices. (See "Pulmonary hypertension in patients with end-stage kidney disease".)
A high incidence of pulmonary hypertension (PH) occurs in patients with CKD, where it is associated with an increased risk of cardiovascular events and overall mortality [66-68]. Although the highest level occurs in the dialysis patient, an increased incidence has been reported prior to the initiation of dialysis. In one study of 211 patients, an incidence of 21.6, 24.1, and 31.7 percent was reported in nondialysis patients with CKD stages 3, 4, and 5, respectively [69].
Although not directly related to renal disease, chronic obstructive pulmonary disease (COPD) is a significant cause of mortality in the population at large; this is no less so for the patient with ESKD. In 2013, the overall incidence in the United States was 6.4 percent [70]. In the years 2000 to 2010, the prevalence of COPD in the patient age group 60 to 79 years (the fastest-growing ESKD age group) was 13.5 percent [71,72].
Diabetes mellitus — Although diabetes mellitus is generally listed as a risk factor for AV fistula failure, the diabetic state does not exert a direct adverse effect on the success of the access; however, the comorbidities associated with diabetes do have definite effect. As was the case with advanced age, diabetes serves as a surrogate for other comorbidities. Individuals with diabetes have a high risk for developing cardiovascular disease, including peripheral arterial disease [73]. The relationship is even greater in patients with CKD [14]. There is also an interplay between other clinical and demographic risk factors. (See 'Race/ethnicity' above.)
Since it is not diabetes as such but the associated burden of comorbidities that exerts the effect, pre-access clinical and hemodynamic evaluation can make a marked difference in achieving success with AV fistula creation. While some reports indicate a negative effect of diabetes on AV fistula success [74-76], most investigators have reported that diabetes is not significantly associated with primary AV fistula failure and that the success rate of a forearm AV fistula is comparable in patients with and without diabetes [59,77-80].
Obesity — Two issues are of importance when considering the creation of an AV fistula in the obese patient. First, obesity is a major risk factor for the development of type 2 diabetes. Therefore, these patients frequently present with the same issues as discussed for the patient with diabetes (see 'Diabetes mellitus' above). The second is the technical issue related to the depth of the vessels used to create the fistula. An added consideration is the obesity paradox (ie, higher body mass index [BMI] is paradoxically associated with better survival among renal failure patients) [81-83]. This, in addition to the fact that patients with severe obesity may be excluded from transplant consideration, means that their accesses must last longer than those of other patients.
When presented with a patient with obesity, there is no reason to avoid the creation of an AV fistula, but evaluation of hemodynamic factors by vascular mapping becomes particularly important. A retrospective cohort analysis was performed using the USRDS Dialysis Morbidity and Mortality Wave II data set to evaluate the relationships between obesity and vascular access outcomes [84]. Obesity was associated only with poorer AV fistula maturity at the highest BMI quartile (≥35 kg/m2) and not with increased AV fistula revision rates or failure. However, although the likelihood of fistula placement and primary patency rates were similar across groups, secondary patency was significantly lower in patients with obesity [85]. It has been suggested that the decreased secondary patency in these patients could be due to soft tissue compression of the venous outflow of the upper extremity in the adducted position [86].
In addition, a technical problem can occur in patients with obesity related to the depth of the veins, which tend to be deep due to the adiposity of the extremity, particularly in the upper arm. If the AV fistula is located too deeply from the skin surface, a procedure can be performed to elevate the fistula, which has been reported to be very successful [87]. Alternatively, lipectomy or liposuction has also been proposed as a means to minimize the depth of AV fistulas in obese arms [88-91].
Technical
Surgical training and experience — The training and experience of the surgeon available to create AV access varies and can affect the success of AV fistula creation [18,92-97].
In a study designed to investigate whether intensity of surgical training influenced the type of vascular access placed and AV fistula survival, prospective data from 12 countries in the Dialysis Outcomes and Practice Patterns Study (DOPPS) were analyzed [95]. Significant predictors of AV fistula versus AV graft placement included number of AV fistulas placed and degree of emphasis on vascular access creation during training. In the United States, surgeons in training created fewer AV fistulas compared with those in other countries (mean 16 versus 39 [from 426 in other countries]) and noted less emphasis on vascular access placement compared with surgeons elsewhere. The risk of primary AV fistula failure was 34 percent lower when placed by surgeons who created >25 (compared with <25) AV fistulas during training. However, no difference was noted between categories of 25 to 75 or >75 AV fistulas created during training.
Once out of training, surgeons' experience continues to vary in the number of AV fistulas they place, which in turn can impact the outcome of the procedure. As an example, in a United States study, the number of AV fistula or grafts placed by nearly 5000 surgeons ranged from 10 to 681 over a two-year period [97]. A successful outcome (ie, mature fistula) was more likely at six months follow-up for surgeons who performed >85 AV fistula placements compared with those who performed fewer than 13 (odds ratio 1.5, 95% CI 1.4-1.6).
Creating the AV fistula — Related to training and experience is the appropriate choice of vessel and conduct of the procedure used to create the hemodialysis AV fistula. Perioperative factors that may lead to immediate issues following AV fistula creation are reviewed separately. (See "Arteriovenous fistula creation for hemodialysis and its complications" and "Primary failure of the hemodialysis arteriovenous fistula".)
Care and maintenance of the AV fistula — Factors associated with the use, care, and maintenance of the AV fistula may contribute to AV fistula failure. These are reviewed separately. (See "Overview of hemodialysis arteriovenous fistula maintenance and thrombosis prevention" and "Failure of the mature hemodialysis arteriovenous fistula".)
MULTIPLE RISK FACTORS — As can be seen, there are a variety of risk factors that affect the success of an arteriovenous (AV) fistula. Most patients have more than one risk factor, and the burden increases with age. It is difficult for the clinician to determine the relative importance of these potential risk factors and to assess the effect of combinations when assessing the likelihood of achieving a functional AV fistula in the individual patient. While evaluating risk factors is important, risk stratification schemes have failed to accurately identify individuals in whom AV fistula placement is futile. While comorbid conditions affecting vascular access success become increasingly more common with age, they are not necessarily present [98]. Further, although potential demographic and clinical factors may be relevant, the most important determinant is the quality of the available vessels. Thus, no patient with end-stage kidney disease should be excluded from consideration for an AV fistula without vascular mapping and evaluation by an experienced hemodialysis vascular access surgeon. Decisions should be based on the individual patient status as determined by the clinical comorbidities that are present.
A study was conducted toward the development of an algorithm to be used in assessing individual patients having a combination of risk factors [5]. The goals of the study were to identify clinical characteristics that predicted failure of AV fistula maturation and to develop and validate a risk equation using these characteristics to stratify patients according to their risk. A clinical prediction rule was used to assign a prediction score ranging from 0 to 10.5. These scores were then used to define four risk categories: low risk (score <2), moderate risk (score 2 to 3), high risk (score 3 to 7), and very high risk (score >7). The algorithm was externally validated using 445 patients receiving a new AV fistula derived from five large dialysis centers. The four defined categories predicted the risk of failure to mature as 24, 34, 50, and 69 percent, respectively. The authors suggested that this scoring system could be used to guide the aggressiveness with which the individual patient is evaluated prior to dialysis access placement and postoperatively to detect failure maturation. As an example, in the low-risk patient, vascular mapping by physical examination only may be possible with routine postoperative monitoring, while the patient in the high-risk category might require angiographic evaluation (both vein and artery) and very close postoperative monitoring, anticipating the need for aggressive intervention to facilitate maturation.
In a later study, 195,756 incident adult dialysis patients with an AV fistula who had been followed for at least six months by nephrologists prior to initiation of dialysis were examined based upon the presence of risk factors for AV fistula failure of maturation [45]. The risk factors for AV fistula failure, determined by logistic regression, were substantially different from those predicted by the clinical prediction algorithm above. Based upon a comparison with the low-risk group, the likelihood of AV fistula use was 0.90 (95% CI 0.88-0.93) for the moderate-risk group, 0.80 (95% CI 0.78-0.83) for the high-risk group, and 0.68 (95% CI 0.63-0.73) for the very-high-risk group.
In assessing the importance of risk factors, it is important to realize that these two studies are based upon different patient populations [5,45]. The first proposed a scoring system to predict problems with AV fistula maturation and emphasizes the importance of using this data in presurgical selection and postsurgical management of individual patients [5]. The second study demonstrates actual prevalence of AV fistula utilization, the results, presumably, a reflection of presurgical selection and postsurgical management [45].
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
●Recognition of risk factors, especially the presence of multiple risk factors, is important in planning arteriovenous (AV) access creation for hemodialysis. However, no patient with end-stage kidney disease should be excluded from consideration for an AV fistula without vascular mapping and evaluation by a dialysis-access-experienced surgeon. Individualization is critically important. (See 'Use of risk factors' above and 'Multiple risk factors' above.)
●Adverse hemodynamic characteristics (poor-quality vessels) are the most important factors contributing to failure of AV fistula maturation and subsequent failure of a mature AV fistula. Demographic and clinical factors increase the risk of AV fistula failure primarily only when they affect hemodynamics. Although patients with poor-quality vessels are not ideal candidates for an AV fistula initially, a secondary fistula may be possible after a period of AV graft use, if the AV graft becomes problematic. (See 'Hemodynamic' above.)
●Older age is a risk factor for decreased life expectancy on dialysis, but age is largely a surrogate for an increasing burden of comorbid conditions (particularly diabetes and cardiovascular disease). The presence of comorbidities more strongly influences survival compared with age alone. (See 'Age' above and 'Clinical comorbidities' above.)
●Female sex is a risk factor for failure of AV fistula maturation and subsequent failure of the mature AV fistula. The reasons for sex-related differences are not clear. While it has been suggested that females have smaller vessels, diameter differences have not been consistently related to unsuccessful AV fistulas. (See 'Sex' above.)
●Race and ethnicity have been identified as significant risk factors for failure of AV fistula maturation. The reasons for the difference are not totally clear but may be related to differences in comorbidities between the groups. (See 'Race/ethnicity' above.)
●Clinical comorbidities (cardiac disease, peripheral arterial disease, pulmonary disease, diabetes mellitus, obesity) adversely affect the placement and clinical success of AV fistulas. These generally exert their effect by adversely affecting hemodynamics. (See 'Clinical comorbidities' above.)
●Other factors that may affect the outcomes of AV fistula creation include the experience of the surgeon and other technical issues in creating, using, and caring for the fistula. (See 'Technical' above.)
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