Renal vascular access – who's problem is it?

Created - 15.07.2014

The incidence of renal replacement therapy (RRT) for established renal failure (ERF) in many developed countries has shown signs of stabilising over recent years. This relative stability disguises the fact that the demographic of the ERF population is changing.

In the modern era approximately 50% of patients on RRT will be expected to have developed ERF from diabetes or another multisystem disease. Furthermore, nearly 50% of patients on RRT are now over the age of 65 years, with nearly two-thirds of these patients expressing at least one other significant co morbidity. 

Despite this increasingly elderly and co morbid population, the prevalent number of people on RRT has continued to rise year on year. This suggests that the survival of patients on RRT is improving. Patients are living longer with their renal disease and its associated co morbidity. 

Whilst this relative improvement in patient survival is encouraging, the absolute life-expectancy of patients on RRT remains poor when compared with the general population. The life-expectancy of RRT patients can vary considerably between different age groups and primary renal diagnoses, but when looking at all-comers onto RRT the median survival of incident RRT patients in poor. 

Cardiovascular disease accounts for the highest proportion of primary causes of death in RRT patients. Infection runs a close second and in the UK accounts for 17% of deaths within the dialysis population and is frequently implicated in many deaths primarily attributed to cardiovascular disease.

When examining the causes of infection, up to 90% of blood culture positive events in dialysis patients are known to be caused by staphylococcal sub-species. This strongly implicates haemodialysis vascular access as a key determinant in the transmission of infection and subsequent outcome. Detailed scrutiny of prevailing staphylococcal bacteraemia rates across the different haemodialysis vascular access methods has demonstrated a clear hierarchy of risk association. Patients using arteriovenous fistulae (AVF) or grafts (AVG) for haemodialysis access have notably lower rates of infection and mortality than those patients who use central venous catheters (CVC). 

The successful creation of a functioning AVF or AVG, however, is challenging. It depends on target vessels of suitable calibre, unblemished structural integrity and with reasonable blood flows, a patient who is fit and amenable to undergoing a surgical procedure under anaesthesia, and inherently incurs a significant lead time between access creation and first access usage. It is no surprise therefore that patients who are elderly, co morbid, have concurrent vascular disease or diabetes, significant cardiac failure or have presented late in the course of their renal disease may not successfully attain a functioning AVF or AVG when required. These patients may therefore rely on CVC placement for short, medium and long-term dialysis access.

Several specialties must coordinate effectively to deliver the optimal haemodialysis access for a patient in a timely fashion. Nephrologists generally are involved in supporting patients in their choice of RRT modality, assessing their suitability for procedures and entering them into an appropriate vascular access pathway. Many centres routinely seek imaging studies for vein mapping prior to the creation of arteriovenous access or alternatively for the assessment of established arteriovenous access that has failed to mature or has developed an associated complication. Interventional radiology has become a fundamental component in delivering haemodialysis access services by extending the capacity to assess the vasculature before and after access creation with the added capability of being able to place central venous catheters, perform angioplasty and place intravascular stents. Surgical specialties are ultimately required in the creation of de-novo access and maintenance of access that has been subject to structural complications.

When considering the growth in the numbers of prevalent haemodialysis patients in recent years, the co morbidities these patients express, the high likelihood of concurrent vascular disease and the greater accumulated time on RRT, the demand on haemodialysis access provision has increased considerably. When also considering that many renal units within the UK now deliver haemodialysis on more than one site, often over quite a wide geographic area, the logistical challenges in delivering such a multidisciplinary service are enormous. There is wide heterogeneity in how health care providers structure their haemodialysis access services, however in many units where there are large numbers of haemodialysis patients and/or several haemodialysis centres over a wide geographic area, the role of a specialist vascular access coordinator has evolved in an effort to provide a consistent level of stewardship in running access services.

So who is responsible? In the modern era, it is becoming increasingly difficult to defend the position that one specific clinician is responsible for all elements of haemodialysis access provision. Each of the specialties outlined above have a key role in delivering their specific component of the service. Sometimes those roles overlap, especially when considering the options for patients with complicated access. In such instances the vascular access multidisciplinary team (MDT) meeting may be a useful vehicle in exploring these areas of overlap, gain a wider picture of the range of options open to the patient, and allow the generation of a collective position on the best way forward. Our own experience of vascular access MDT meetings has seen nephrologists raise the possibility of exploring alternative RRT modalities such as peritoneal dialysis or transplantation, interventional radiologists and vascular surgeons explore combined declotting procedures and weigh-up the relative risks/benefits of exploring lower extremity central venous catheter insertion versus arteriovenous graft placement – all of these in the same patient with a complex access history and challenging further native access options. The collective value of such a collaborative approach can thus be seen to be potentially quite considerable and can only serve to enhance the possibility of more safe, effective and person-centred care.

The other value in a collective approach to running haemodialysis access services lies in the appraisal of current systems performance, identifying and highlighting 'sticking points' in the system, considering where practice development is required and contemplating research opportunities. Traditionally the definition of a quality haemodialysis access service has focussed on incident and prevalent arteriovenous access rates, and limiting dialysis access associated bloodstream infections. Taking a wider view of what a quality access service may be should take into account the number and complexity of planned procedures, expected and unexpected hospitalisation and patency rates/chances of successful access establishment. A collaborative approach to defining quality, choosing relevant auditing targets within the system and fostering quality improvement initiatives is likely to have a greater 'yield' than viewing the service through the prism of a single specialism.

The provision of haemodialysis vascular access remains a considerable problem. Looking forward, it is likely that the prevalent numbers of patients requiring access work is likely to grow, as is the relative hostility of patients' vascular anatomy, cardiovascular function, level of co morbidity and cumulative exposure to vascular access procedures. No longer can it be regarded as the domain of a single specialism and the contemporary view is that a multidisciplinary collaborative 'whole' will be greater than the sum of the individual parts.

Peter C. Thomson & David B. Kingsmore