Hospital General Universitario Vall d'Hebron, Servicio de Nefrologia, Barcelona, Spain
Correspondence and offprint requests to: J. A. Rodriguez, Hospital General de la Vall d'Hebron, Servicio de Nefrologia, Psg. Vall d'Hebron 119129, E-08035 Barcelona, Spain.
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Abstract |
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Methods. In a retrospective analysis we analysed the types, duration and primary rate of patency of 1033 permanent vascular accesses in 544 consecutive patients established during a 13-year period in a tertiary care hospital. Patient characteristics, incidence, and risk factors related to VA failure were registered. In addition, VA outcomes in patients who started haemodialysis with a catheter and in whom initial VA failure occurred were analysed separately.
Results. Forty-five per cent of patients required a central catheter at the start of HD, but 92% of them were being dialysed with an a-v fistula at the last observation. The total number of complications was 0.24 episodes per patient per year at risk and the rate of thrombosis 0.1. A total of 52% of patients were dialysed throughout the observation period with their initial a-v fistula; 9.3% had more than three episodes of VA failure. The radiocephalic a-v fistula was the VA with the best median duration, exceeding 7 years, but also the type that had the highest initial failure rate, i.e. 25% of patients and 13% of the events. The brachiocephalic a-v fistula was the second most frequent type of VA, with a median duration of function of 3.6 years, in contrast to the humerobasilic a-v fistula, which exceeded 5 years. Average patency of the different types of grafts did not exceed 1 year, with the exception of the autologous saphenous graft with a median duration of function of 1.4 years. Patients with glomerulonephritis had the best function rates for their VA, the median exceeding the duration of the study, whereas in half of the diabetic patients it was less than 1 year. The duration of patency of the VA was twice in patients below age 65 years and in elderly males compared to elderly females. Patients who started HD with a catheter, as well as those with initial VA failure, had a higher rate of VA failure in the subsequent course on RRT.
Conclusion. The radiocephalic and the humerobasilic a-v fistulae are the two types of VA with the longest duration of function, although a high rate of initial failure is seen with the radiocephalic a-v fistula. Age, female gender, presence of diabetic nephropathy, start of dialysis with a catheter, and failure to wait for initial maturation of the VA are risk factors, and account for the majority of VA failures during RRT.
Keywords: end-stage renal disease; haemodialysis; renal replacement therapy; vascular access
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Introduction |
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This rapid progress of innovations in vascular access (VA) has not continued at the same rate as in the first decade of haemodialysis. Contributions in recent years were not paralleled by improvements in results and in quality of life. Currently, complications of vascular access, i.e. dysfunction, thrombosis, or infection are a major cause of hospital admission. They affect the quality of life. For this there are objective reasons (they make it difficult to administer sufficient dose of dialysis) and subjective ones (anxiety because of uncertainty about correct functioning). Furthermore they give rise to frustration in health care personnel [68]. Recently, repeated VA failure has been identified as a risk factor for mortality [9]. Finally, VA failure causes high economical costs, accounting for up to one-third of ESRD expenditure [10].
The radiocephalic a-v fistula is the preferred VA, because of its low complication rates, its long survival, and its ease of puncture once it has matured [1113]. Nevertheless, its establishment on the wrist or in the tabaquière anatomique (anatomical snuffbox) of the non-dominant arm is potentially inconvenient for two reasons (i) 48 weeks are necessary until the venous wall has arterialized, and (ii) a high rate, 830%, of initial failure or insufficient development is observed, necessitating the use of other modalities of VA [14]. Recently, a-v fistulae higher up in the forearm and on the upper arm have been put forward as acceptable alternatives. Some studies have documented primary patency rates, >80%, in the first 2 years of observation [15], but there is no information on the long-term outcome for this type of a-v fistula.
The second mode of permanent VA are grafts, the use of which has increased in recent years, and in numerous centres it is today the most frequently used type of VA [16]. This tendency has been related to recent demographic changes in the HD population, the scarcity of transplants with the consecutive increased time on HD treatment, and increased comorbidity of patients beginning RRT. In fact the median age of incident patients is actually around 60 years, more than half of the patients have at least two comorbid conditions, and 2040% are diabeticall factors that could affect the success of the VA [10,17]. On top of this, patients are not infrequently referred to the nephrologists in the terminal stages of renal failure or during an episode of acute deterioration of pre-existing renal failure. In these circumstance it is frequently impossible to create a VA in time [18].
It is of obvious interest to the nephrologists to identify the different problems related to the VA and to improve results by consensus. With this in mind, we performed the present retrospective study with the following aims: (i) to assess the relative proportions of the different modalities of VA and the respective duration of their function, (ii) to analyse the clinical and demographic factors associated with VA failure, and (iii) to verify whether absence of a functioning VA at the time when HD is started and/or initial failure of the VA affects the results of long-term VA.
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Subjects and methods |
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Primary renal disease was categorized as glomerular, interstitial (mostly ascending infection), vascular (nephroangiosclerosic or ischaemic), cystic (ADPKD), or diabetic nephropathy. The designation `others' includes different systemic diseases, particularly SLE and vasculitis.
We analysed clinical and demographic characteristics of patients who started HD treatment using a catheter and compared them with patients who at that moment had a mature VA. We also studied whether there were differences in the total number of VA in the two populations in the course of HD treatment. Similarly, we compared the patients with an initial failure of the primary VA or failure of adequate development of the VA with those patients in whom the VA matured normally.
Every patient who needs a VA is examined in our hospital by a vascular surgeon who assesses, as the first option, the possibility of creating a radiocephalic a-v fistula in the upper extremity of the non-dominant arm. If this VA fails, we tend to place a similar VA on the opposite arm. In cases of failure we systematically try to place new a-v fistulae in the upper forearm or the upper arm in the following order: brachiocephalic (BC) and humerobasilic (HB) with subsequent transposition. Generally, implantation of grafts is not considered unless all possibilities of a-v fistulae in both extremities have been exhausted.
Statistical analysis
Using descriptive statistics, we analysed all patients and separately analysed all accesses. The 2 test was used to assess associations between qualitative variables. Student's t-test was used for group comparisons. To assess the association between the number of VA in a given patient and the type of initial vascular access (catheter or a-v fistula) the
2 test for trend was used. To assess time to access failure, the KaplanMeier-method was used. To study the association between this time interval and potential risk factors, the log-rank-test was used. To estimate reasons for the incidence of VA failures, proportional hazards regression models were used. To evaluate the association between failure of the initial a-v fistula and potential risk factors, odds ratios were tested using the
2 test. To identify independent predictors of initial VA failure, the multiple regression technique was used with a model that included variables consecutively into the model if their log-likelihood ratios were significant by
2 test. To evaluate the association between numbers of VA in a given patient and initial VA failure the chi-square test for linear trends was used. Calculations were carried out using SPSS for Windows, Release 6.0, (SPSS Inc., Chicago, IL, 1993).
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Results |
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During the study period, 456 patients (84%) used only native a-v fistulae as permanent VA; in 75 (14%) was it necessary to resort to alternative a-v fistulae or grafts, whilst only 13 patients were dialysed with grafts exclusively. In three patients, complete obliteration of accessible vessels necessitated treatment with a central catheter (two cases) or PD (one patient).
Number of required accesses per patient
Out of the total number of patients in this study, 286 (52.5%) required creation of only a single VA, and no complication whatsoever of the VA was present during the time of treatment. Of the remaining cases, 141 patients required two VAs, 66 patients three VAs, and 51 patients, i.e. 9.3%, four VAs or more. The mean age of the latter group (27 males) was 57.2 years compared to 55.8 years in the other patients (NS). In the patients with higher numbers of VA failures, no significant relation to the type of primary renal disease was noted.
Complications
Table 3 lists the complications encountered. On 546 occasions, the VA was complication-free until the end of the study, whereas on 489 occasions some type of intervention was required. The rate of complications was 0.24 per patient and year at risk. Most interventions were associated with fistula dysfunction (51%), most frequently insufficient development of the VA, i.e. in one-quarter of the cases. The other interventions concerned repair for episodes of VA thrombosis, i.e. 0.1 episodes per patient and year at risk. The mechanism causing thrombosis could not be determined in the majority of patients; technical complications were involved only in 8%.
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The survival rates of grafts is comparable with that of a-v fistulae during the first 6 months, with the exception of PTFE forearm grafts, for which the survival rate at that point in time is lower by 50%. After the first 6 months, the function rate of grafts diminishes progressively and at a faster rate with PTFE grafts and with saphenous grafts. Of the latter, more than 40% function at the end of the second year compared to 20% of the PTFE grafts in a similar location.
Table 4 gives median duration of a-v survival as a function of different variables.
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Age.
In patients aged above 65 years, median survival of the VA is somewhat higher (P<0.03) than in younger individuals.
Gender.
The median duration of VA in males, i.e. 7 years, is three times higher than in females (RR 1.35, 95% confidence interval 1.131.61, P<0.012).
Primary renal disease.
In patients with primary glomerular disease, longer duration of VA was noted and more than half of them had a duration exceeding 13 years. ADPKD came second with a median duration of 7 years (RR 1.15, confidence interval 0.81.7). Patients with interstitial nephropathy or vascular nephropathy had intermediate durations, whilst in patients with diabetic nephropathy the average duration of function of VA did not exceed 1 year (RR 2.4, confidence interval 1.83.2, P<0.001).
Patients with a central catheter as first vascular access
Somewhat less than half of the patients (45%) had to start dialysis using a central catheter because a well-developed a-v fistula was not available (Table 5). When this cohort was compared to patients who initially had a functioning a-v fistula it became obvious that patients who required a catheter were significantly older (58.9 vs 55.4, odds ratio 1.7, 95% confidence interval 1.22.5, P<0.04). Notable differences were also found according to the type of primary renal disease. Absence of a mature a-v fistula was most frequently seen in patients with vascular or diabetic disease, compared to patients with ADPKD or interstitial disease (P=0.006).
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Patients with initial vascular access failure
Of the 531 patients who received a-v fistulae, the VA did not achieve definite function in 135 cases (121 radiocephalic and 14 humerocephalic a-v fistulae, see Table 6). Causes were immediate thrombosis for technical reasons (40 cases, 7.5%) and insufficient maturation to permit puncture (95 patients, 18%). When patients with normal VA development are compared to patients with initial VA failure, one finds a predominance of females amongst the latter (OR 1.67, 95% CI, 1.122.49, P<0.01). Half of the patients with diabetic nephropathy had initial failure, whilst approximately 20% of patients with other primary renal diseases had this complication, with no significant differences between the disease categories. Multivariate analysis showed that female gender and diabetic nephropathy are independent predictors of initial VA failure (see Table 7
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Discussion |
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The factors that determine the patency of the VA depend mainly on patient characteristics, surgical skill, and care of staff. It is therefore scarcely surprising that published results differ. Some non-randomized studies report that the duration of function of fistulae and grafts is similar [20], but the majority of reports finds the opposite [6,8,19]. In our study, the patency rate of a-v fistulae is markedly superior to grafts, although detailed statistical analysis is not possible, because creation of an a-v fistula had priority over a graft.
The radiocephalic a-v fistula was tried first, as generally accepted, in view of its technical advantages for implantation and high function rate [13,19]. In this study, the rates of patency of this type of VA are similar to reports in literature, i.e. 90 and 80% in the first and second year respectively. Long-term observations show that more than half of our patients have a patent fistula at more than 7 years post-operatively and 36% more than 12 years post-operatively. Undoubtedly, the radiocephalic approach has the inconvenience that there is a high initial failure rate. Studies published since the late 60s report a primary failure rate between 9 and 30%; in our study it was 25%, a figure which undoubtedly could be improved with new non-invasive techniques that allow the estimation of calibre and flow of vessels before creation of a fistula and to predict the potential of adequate vessel maturation [21].
The brachiocephalic a-v fistula is the preferred type of VA, if the radiocephalic approach fails. It should be created as the primary fistula if adequate vessels are not available, which is frequently the case in diabetic patients. Four-year permeability rates of 80% have been reported [15]. In our study, survival of the brachiocephalic a-v fistula was lower than that of the radiocephalic: slightly more than one-half of patients have patent fistulae after 4 years and one-third after more than 8 years.
If the cephalic vein cannot be used, one has the alternatives of implantation of a forearm graft and creation of a humerobasilic a-v fistula. Selection of this type of VA has certain technical disadvantages, i.e. the basilic vein must be superficialized to make it easily accessible for puncture. The technique can also cause steal phenomenon and local oedema. On the other hand it has certain advantages. Since the basilic vein is not visible, it has usually not been damaged by cannulations prior to end-stage renal disease. Published information on patency rates gives values of 75% at 8 years [22]. In our study, the patency rate of humerobasilical a-v fistulae resembles that of the radiocephalic (excluding early failure) and is superior to the brachiocephalic a-v fistula.
As in other studies, age, female gender, and diabetes are the principal factors that determine the long-term function of VA [23,24]. More than 50% of patients keep their initial VA over 13 years of follow-up. We believe that such remarkable function rates in patients with glomerular disease are due to several facts: (i) patients with this disease are referred to the nephrologist early; (ii) the disease course is progressive but predictable; and (iii) the disease affects relatively young individuals: all these are points that contribute to adequate timing and early creation of a VA. ADPKD also has a long disease course, but the results of VA are not so good as in glomerular disease, presumably because of the higher age of the patients. The short duration of functional VA in patients with interstitial nephropathy could be explained by the preponderance of the female sex, which is an independent risk factor for VA failure.
Recently, Woods and Port emphasized the importance to define the factors which are involved in the failure of the first VA, since such predisposing factors could predict future failures and poor overall results as well [22,25]. Our study is in line with this recommendation and shows that more than two-thirds of patients in whom the first VA developed successfully did not have any subsequent VA failure, whereas initial failure increased the risk of subsequent failure by a factor of 28. Again, female gender and presence of diabetes were risk factors related to VA failure (Table 7); in female diabetic patients, the risk was elevated by a factor of 6. Another factor predisposing to multiple episodes of VA failure is absence of a mature VA at the start of haemodialysis [26]. In almost half of the patients of our study, treatment had to be started with a central catheter. In this subgroup, the risk of future VA failure was double that of patients starting dialysis with a mature VA.
An ideal VA must provide sufficient flow for HD and cause minimal complications. This ideal type of VA is not available, but autologous a-v fistulae come closest to satisfying this requirement. In order to minimize morbidity and cost, a multidisciplinary effort should be directed at the goal that all patients starting HD treatment have a VA ready to be punctured.
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Acknowledgments |
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References |
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