Volume 48, Issue 5, Supplement , Pages S31-S33, November 2008
Timing of referral for vascular access placement: A systematic review
Article Outline
Objective
This review was conducted to determine the optimal timing for referring patients with end-stage renal disease to vascular surgery for access placement.
Methods
A systematic review of the electronic databases (MEDLINE, EMBASE, Current Contents, Cochrane CENTRAL and Web of Science) was conducted through March 2007. Randomized and observational studies were eligible if they compared an early referral cohort with a late referral cohort in terms of patient-important outcomes such as death, access-related sepsis, and hospitalization related to access complications.
Results
We found no studies that fulfilled eligibility criteria.
Conclusion
At the present time, the optimal timing for referral to vascular surgery for vascular access placement is based on expert opinion and choices made by patients and physicians.
A consensus statement by the vascular access group of the National Kidney Foundation Kidney Disease Outcomes Quality Initiative (NKF KDOQI) recommended that patients with chronic kidney disease should be referred for surgery to attempt the construction of a primary arteriovenous (AV) autogenous access when their creatinine clearance is <25 mL/min, their serum creatinine level is >4 mg/dL, or ≤1 year of an anticipated need for dialysis.1 However, guideline authors acknowledged at the time that this recommendation was only based on experts' opinions.
The Society for Vascular Surgery has formed a multispecialty committee to develop guidelines for the management of vascular access for hemodialysis. To assist in this process, this task force required the conduct of a systematic review of the best available research evidence on this topic. Because the availability of a functional arteriovenous access when the patient is ready for dialysis is very important to avoid placement of temporary dialysis catheters, known for a high rate of complications, the Society specifically requested a study on the issue of the timing of referral of patients to access surgeons and its effect on the type of access placed.
Methods
Eligibility criteria
We searched for randomized controlled trials (RCTs), cohort studies, and studies with nested case-control designs that compared patients who were referred to vascular surgery for access placement at different time intervals before the start of hemodialysis. Studies were eligible regardless of their publication status, language, size, duration of patient follow-up, or their primary objectives. The outcomes of interest were death, access-related sepsis, and hospitalization related to access complications.
Study identification
An expert reference librarian designed and conducted the electronic search strategy with input from study investigators with expertise in conducting systematic reviews. To identify eligible studies, we searched electronic databases (MEDLINE, EMBASE, Current Contents, Cochrane CENTRAL and Web of Science) through March 2007. Subject headings and keywords were selected to describe hemodialysis, including the MeSH terms exp renal dialysis, renal replacement therapy, or exp renal insufficiency, chronic. Then, we used subject headings and keywords to describe the intervention, including arteriovenous fistula, arteriovenous shunt, surgical, vascular access, and vascular grafts. The results were limited using the Haynes filter for clinical trials. The concept of timing was described by using the keywords timing, before, early, or late. These strategies were adapted with some modifications in EMBASE, CENTRAL, and Current Contents/Web of Science. We also sought references from experts.
References were uploaded in a Web-based software package developed for systematic review data management (SRS, TrialStat Corp, Ottawa, Ontario, Canada). Paired reviewers working independently screened all abstracts and titles for eligibility. References that were deemed potentially relevant were retrieved in full text and uploaded for a full-text evaluation against eligibility criteria. The chance-adjusted inter-reviewer agreement (κ statistic) was 0.85. Disagreements were resolved by consensus (the two reviewers discussed the study and reached a consensus) and by arbitration (a third reviewer adjudicated the study) when disagreement continued.
Results
We reviewed 468 potentially relevant articles identified by search and selected 107 articles for full text retrieval. We found no studies that fulfilled the eligibility criteria. The study selection process is described in the Fig.
Fig.
Flow chart shows study selection process.
We found two studies that did not fulfill the eligibility criteria of this review but provided indirect evidence that early referral to vascular surgery may improve patient outcomes. Besarab et al2 studied 1411 patients who started chronic hemodialysis in the Renal Network of the Upper Midwest. They reported that <5% of patients who were seen by a vascular surgeon more than 1 month before hemodialysis used a catheter as their first access. Considering catheter use as a potential surrogate for increased incidence of sepsis and death, this study indirectly supports early referral to a vascular surgeon.2
The second study, by Oliver et al,3 used Canadian administrative and billing databases to determine whether the timing of access placement was associated with increased risk of hospitalization for sepsis or death. We considered this study to indirectly answer the question of this review because they evaluated the timing of actual access placement and not the timing of referral. Access placement is influenced by factors other than referral, for example, patient's acceptance of the procedure and insurance decisions, among others. Furthermore, the outcome of sepsis was based on hospitalization for any bacteremia or sepsis and not necessarily for access-related infections. They identified 5924 incident hemodialysis patients and monitored them for 1 year from the start of hemodialysis. Compared with late access construction (≤1 month of hemodialysis), early access construction (≤4 months before hemodialysis) was associated with lower risk of death and sepsis, with relative risks of 0.76 (95% confidence interval [CI], 0.58-1.00) and 0.57 (95% CI, 0.41-0.79) respectively. Introducing catheter use and sepsis into the mortality model made the association nonsignificant.3
Discussion
Although ample evidence demonstrates that patients who are referred early to a nephrologist have better survival,4, 5 the decision about when to refer patients to a surgeon for AV access placement seems to be based on experts' inferences drawn from unsystematic clinical observations and indirect evidence, systemic constraints (eg, reimbursement policies, access to vascular surgery services), and physician and patient preferences.
Evidence-based guidelines can offer recommendations in the setting of very low-quality evidence, such as from unsystematic clinical observations and potentially biased and confounded observational studies, as long as the evidence brought to bear is explicitly and clearly described. Often, these recommendations are weak (ie, suggestions), implying that they should not be used as quality parameters and clinicians should not be held accountable when departing from the suggested path. Furthermore, acting on suggestions requires careful attention to systemic constraints (ie, cost and access to surgery services proficient in the placement of AV access) and patient values and preferences.
One very important drawback of early placement of an access is when autogenous venous tissue is not available and a prosthetic AV access is placed long before dialysis is initiated. A prosthetic access has a limited life span unrelated to whether the access is being used for dialysis, and the failure of such access is mostly due to the development of outflow intimal hyperplasia at the venous anastomosis. Therefore, the early placement of prosthetic access will lead to its premature failure, sometimes even before dialysis is initiated. Unfortunately, this extensive review of the evidence failed to provide information on this issue due to paucity of published data. Clinical practice recommendations associated with the findings of this systematic review are published separately.
Conclusion
Future research is needed to determine the optimal time for referring patients with chronic kidney disease to vascular surgery for access placement.
Author contributions
References
- NKF-KDOQI Clinical Practice Guidelines and clinical practice recommendations for Vascular Access, update 2006. Am J Kidney Dis. 2006;48(suppl 1):S177–S247
- Unraveling the realities of vascular access: the Network 11 experience. Adv Ren Replace Ther. 2000;7(suppl 4):S65–S70
- . Late creation of vascular access for hemodialysis and increased risk of sepsis. J Am Soc Nephrol. 2004;15:1936–1942
- Effect of early nephrology referral on the initiation of hemodialysis and survival in patients with chronic kidney disease and cardiovascular diseases. Circ J. 2007;71:511–516
- . Decline in kidney function before and after nephrology referral and the effect on survival in moderate to advanced chronic kidney disease. Nephrol Dial Transplant. 2006;21:2133–2143
This review was funded by a contract from the Society for Vascular Surgery.
STATEMENT OF CONFLICT OF INTEREST: These authors report that they have no conflicts of interest with the sponsor of this supplement article or products discussed in this article.
PII: S0741-5214(08)01397-9
doi:10.1016/j.jvs.2008.08.046
© 2008 The Society for Vascular Surgery. Published by Elsevier Inc. All rights reserved.
Volume 48, Issue 5, Supplement , Pages S31-S33, November 2008
