New approach needed to evaluate vascular access options
When it comes to selecting a vascular access type for a patient with late-stage CKD or ESKD, the arteriovenous fistula, once labelled the ‘gold standard’ for creating permanent access, may not always be the ideal one, according to a viewpoint published in the Clinical Journal of the American Society of Nephrology.
Michael Allon, MD, nephrologist at University of Alabama at Birmingham (UAB), wrote that “key assumptions and recommendations in the 2006 Kidney Disease Outcomes Quality Initiative vascular access guidelines ... are not relevant to the contemporary United States hemodialysis population.” As a member of the division of nephrology at UAB, Allon helped guide recent updates to the KDOQI vascular access guidelines, which will be presented at the National Kidney Foundation’s Spring Clinical Meetings in Boston next month.
Challenging the AVF
The accepted view in the kidney community – and verified in the 2006 guidelines – has been that the natural, arteriovenous fistula (AVF) is superior to the synthetic arteriovenous graft (AVG) based on better secondary survival and lower frequency of interventions and infections. “However, intent-to-treat analyses that incorporate the higher primary failure of AVFs demonstrate equivalent secondary survival of both access types,” Allon wrote. “Moreover, the lower rate of AVF versus AVG infections is counter balanced by the higher rate of catheter-related blood stream infections before AVF maturation,” he said, referring to the use of temporary central venous catheters (CVCs) to initiate dialysis while the fistula matures.
“In addition, AVFs with assisted maturation (interventions before successful AVF use), which account for about 50% of new AVFs, are associated with inferior secondary patency compared with AVGs without intervention before successful use.”
CVCs for compromised patients
A lack of AVF maturation means a higher rate of CVC dependence, Allon reported. Previous reports that provided research for the original KDOQI guidelines observed AVF nonmaturation in only 10% of patients.
“More recent publications, reflecting widespread AVF creation in the great majority of patients on dialysis, have reported substantially higher (30%–60%) AVF nonmaturation rates,” Allon wrote.
CVC use is believed to result in excess mortality in patients on hemodialysis, “however, recent data suggest that CVC use is simply a surrogate marker of sicker patients who are more likely to die, rather than being a mediator of mortality,” Allon wrote. “The challenge in comparing patient survival between patients who do or do not undergo AVF creation, is that there are important differences not easily captured in administrative databases. If a patient with advanced CKD is perceived by the nephrologist or surgeon to have a reasonable life span, it is likely that an AVF will be placed promptly.
“In contrast,” Allon said, “if the patient has a poor functional status or limited life expectancy, the physician is more likely to postpone AVF creation until after the patient starts hemodialysis ... (T)he association between starting hemodialysis with a CVC and dying is confounded by their age. Similarly, a high comorbidity or poor functional status confound the association between CVC use and patient mortality.”
Ultimately, Allon said, data released since the 2006 KDOQI vascular access guidelines were released “should be incorporated to re-inform current decision making about vascular access.”
Disclosure: Allon is supported by grant 1R21DK104248-01A1 from the National Institute of Diabetes, Digestive and Kidney Diseases, and reports personal fees from CorMedix.