Guidelines of the European Society for Vascular Surgery1 give an overview of the current best evidence for vascular access for dialysis. Although these guidelines are largely similar to their predecessors, Nicholas Inston argues they may not always lead to best practice or outcomes. In this article, Inston looks at the current state of dialysis access, providing insight into the challenges and opportunities the field is facing.
Despite major advances in surgical technologies the autologous radiocephalic arteriovenous (AV) fistula first described by nephrologists over 50 years ago2 is still considered the gold standard form of vascular access for haemodialysis, and the role of the surgeon in dialysis care remains as critical as ever.
The alternatives for vascular access—the arteriovenous graft (AVG) and the central venous catheter (CVC)—are both associated with increased rates of complications and lower patient survival.
It is on this basis that guidelines have been directed towards AV fistulae as the recommended option, and this “one size fits all” approach has subsequently been adopted as policy in many healthcare systems and directed quality improvement initiatives.
Unfortunately, these policies have had the opposite effect. In the UK, the proportion of patients starting dialysis on a fistula or graft in 2011 was 41.4%. Following the introduction of best-practice tariff, it had dropped to 38.6% in 2015. More concerning definitive access in the prevalent dialysis population incrementally dropped from 79% in 2012 to 68.6% in 2015,3 with similar trends seen in the USA following the introduction of the Fistula First initiative.4
A possible explanation for this is a phenomenon known as “surgical fatigue”, wherein increased efforts to create AV fistulae in patients with a higher risk of failure results in patient disillusionment and disengagement.5
The use of guidelines to drive policy has inherent flaws. Firstly, the evidence base for most aspects of vascular access is poor. The very basic concept that survival is better in patients with an AV fistula is questionable. The statement may be correct, but underlying concepts such as of lead time effect and comorbidity must also be considered. Renal failure is a chronic disease; few patients have only one form vascular access, and many will have a lifespan of a combination of catheters, fistulae and grafts, peritoneal dialysis and/or kidney transplant(s).
The implication that catheters are inherently more dangerous than fistulae is simplistic. When patients in each group are analysed, the cause of death is not related to the device but to the comorbidity of patients.6,7 Whilst it cannot be denied that death from line sepsis is an issue, it is much less frequent than death from cardiovascular causes which accounts for around 30% of all dialysis deaths. Indeed, mortality from infection is proportionally higher for transplant patients than dialysis patients.3
Withdrawal from treatment is also a considerable cause of death in dialysis patients at around 20%, yet healthcare policy rarely includes patient choice. Patient preferences have also been shown to be disparate to clinicians’ views.8
It is well documented that patients who start dialysis on a catheter are more likely to continue dialysis on a catheter, and an important area that avoids this is early referral to a surgeon. However, judging the time to create a fistula is difficult.
AV fistulae have a significant early failure rate and there is little that has been shown to improve this. The basic science of this problem is still poorly understood, and we have no pharmacological way of manipulating it. Failure to mature (FTM) is furthermore likely to be underreported, as definitions of maturation are multiple and many do not involve use for dialysis. Even functional maturation does not have a clear and universal definition.
Many patients will have a series of failed fistula attempts, as FTM is unpredictable. Earlier fistula creation attempts to avoid starting patients on a catheter dialysis. Renal function (glomerular filtration rate; GMR) has traditionally been used and once it has declined below a trigger value, a fistula is created. However, as decline is unpredictable, patients may not reach end stage and have an unnecessary operation, complications may occur, or the AV fistula may fail. More sophisticated approaches to the timing of access creation are therefore required, and kidney failure risk equations (KFRE), whilst not yet validated, may enhance this effort.9
Once a patient has an AV fistula, maintenance of it requires a multidisciplinary team of trained and enthusiastic specialists, as the combined roles of nephrologist, surgeon and radiologist are required to maintain good outcomes.
Surveillance is another ill-defined area, and studies have shown conflicting outcomes. Dialysis patients are intensively followed up, with data recorded three times per week and examined at the same time. The role of the dialysis nurse in monitoring, surveillance and diagnostics should not be underestimated, as physical examination can be as accurate as imaging. Focused and structured education for these team members is therefore essential and should be a key area to target for quality improvement.
Education of trainees is another area which should not be forgotten. The exposure to VA in training programmes is lacking. For many surgeons and radiologists, their knowledge of dialysis is limited and experience is from the clinic, theatre or interventional radiology suite rather than beside a dialysis machine.10
Progress and breakthroughs
We have recently seen some notable advances in devices for treating VA complications. However, most of the development has been rapid and lacked evidence. One such example is the management of central venous stenosis and thoracic central vein occlusion. Treatment choices and modalities are often based on availability, experience or improvisation. The recent classification of thoracic central vein obstruction11 is welcomed and will assist in the description and study of these lesions, allowing more stringent comparisons of outcomes. It is also encouraging that a number of trials of drug-coated balloons in vascular access are currently underway.
Important advances in grafts technology have also occurred. PTFE as a material was not designed to be repeatedly cannulated, but in the last few years grafts designed specifically for dialysis and early cannulation have become available. The test bed for a novel bioengineered human artificial vessel (Humacyte graft) was in dialysis patients and the results of a large global trial are eagerly awaited. This may guide applications in other areas of vascular practice.
Another major and novel advance is in AV fistula creation, using a non-surgical approach. The endovascular AV fistula (endoAVF) is the first major innovation in fistula creation since the surgical fistula, with two platforms for endoAVF creation emerging simultaneously. Studies are promising, with improved functional outcomes and decreased complications.
Looking to the future
Vascular access in 2018 continues to develop rapidly, and options available to the surgeon, radiologist or interventional nephrologist are ever-increasing. Consequently, it is imperative that those involved in performing vascular access are up to date with all the available options.
Dialysis care has also improved, and patients are now living longer. It is important that along this journey they have all the opportunities for a lifetime journey of renal replacement. Guidelines can assist in decision making, but ultimately the quality approach should be the right access, for the right patient, at the right time.
Nicholas Inston is the chairman of the Vascular Access Masterclass at the annual Charing Cross Symposium (CX) in London, UK, and a consultant renal transplant and vascular access surgeon at the University Hospitals Birmingham in Birmingham, UK.
References
- Schmidli J, Widmer MK, Basile C, et al. Editor’s Choice – Vascular Access: 2018 Clinical Practice Guidelines of the European Society for Vascular Surgery (ESVS). Eur J Vasc Endovasc Surg. 2018 Jun;55(6):757–818. doi: 10.1016/j.ejvs.2018.02.001.
- Brescia MJ, Cimino JE, Appel K, Hurwich BJ. Chronic hemodialysis using venipuncture and a surgically created arteriovenous fistula. N Engl J Med 275:1089–1092, 1966.
- https://www.renalreg.org/reports/2016-nineteenth-annual-report/
- Lok CE. Fistula first initiative: advantages and pitfalls. Clin J Am Soc Nephrol. 2007 Sep;2(5):1043–53.
- Yuan J, Dheeraj R, Bhola C, et al. Reasons for Hemodialysis Catheter Use and Its Complications: Patient and Vascular Access Coordinator Perspectives. Presented at the spring meeting of the National Kidney Foundation; 10–14 April 2007, Orlando, USA.
- Lee T, Allon M. Reassessing Recommendations for Choice of Vascular Access. Clin J Am Soc Nephrol. 2017 Jun 7;12(6):865-867.
- van der Veer SN, Haller MC, Pittens CA, et al. Setting Priorities for Optimizing Vascular Access Decision Making–An International Survey of Patients and Clinicians. PLoS One. 2015 Jul 7;10(7):e0128228.
- Ravani P, Palmer SC, Oliver MJ, et al. Associations between hemodialysis access type and clinical outcomes: a systematic review. J Am Soc Nephrol. 2013 Feb;24(3):465-73.
- Inston N, Lok CE. Improving precision in prediction: Using kidney failure risk equations as a potential adjunct to vascular access planning. J Vasc Access. 2018 Jul 1:1129729818786630.
- Inston N, Singh TM. Training vascular access surgeons: technicians or specialists? J Vasc Access. 2018 Mar;19(2):117-118.
- Dolmatch BL, Gurley JC, Baskin KM, et al. Central Vein Work Group and the Technology Assessment Committee. Society of Interventional Radiology Reporting Standards for Thoracic Central Vein Obstruction: Endorsed by the American Society of Diagnostic and Interventional Nephrology (ASDIN), British Society of Interventional Radiology (BSIR), Canadian Interventional Radiology Association (CIRA), Heart Rhythm Society (HRS), Indian Society of Vascular and Interventional Radiology (ISVIR), Vascular Access Society of the Americas (VASA), and Vascular Access Society of Britain and Ireland (VASBI). J Vasc Access. 2018 Aug 13:1129729818791409
