For patients receiving maintenance hemodialysis, vascular access provides a critical conduit for the delivery of blood to the extracorporeal circuit. More than 80% of patients initiating hemodialysis in the United States do so with a central venous catheter (CVC); most then undergo placement of a permanent vascular access, either an arteriovenous fistula (AVF) or graft (AVG). Until the AVF or AVG can be successfully used for dialysis, patients remain catheter dependent; there is an association between longer duration of dependence on a CVC and increased risk for catheter-related bacteremia and mortality.
Recommendations from the Fistula First Initiative, launched by the Centers for Medicare & Medicaid Services in 2002, call for providers to maximize AVF use in preference to an AVG, because AVFs have long-term survival compared with that of AVGs and fewer interventions are required to maintain such patency.
Timmy Lee, MD, MSPH, and colleagues previously compared outcomes (mortality and hospitalizations) in a national cohort of elderly patients who initiated dialysis therapy with a CVC and then had an AVF or AVG placed. That study found an association between the placement of an AVF and greater patient survival despite longer dependence on a CVC. The researchers recently conducted a retrospective cohort study designed to compare several clinically relevant outcomes related to vascular access type in the same cohort and to better understand the tradeoffs between AVF and AVG selection in that patient population. Results were reported in the American Journal of Kidney Diseases [2018;72(4):509-518].
The outcomes of interest were successful use of vascular access, interventions to make vascular access functional, duration of catheter dependency prior to successful vascular access use, frequency of interventions, and abandonment after successful use of vascular access. Comparison of the need for intervention prior to successful use of AVFs and AVGs was determined using multivariable logistic regression analysis; the frequency of intervention after successful use of vascular access was calculated using bionomial regression. The researchers also calculated the adjusted odds ratios (ORs) or relative risks (RRs) of those outcomes for patients receiving an AVF versus an AVG.
The original cohort included 46,634 patients ≥67 years of age who initiated hemodialysis therapy from July 1, 2010, to June 30, 2011. Of those patients, 29,178 initiated hemodialysis with a CVC only, without an AVF or AVG placed in the pre-ESRD period, awaiting successful use. Application of other exclusion criteria (no pre-ESRD Medicare claims; with pre-ESRD AVF/AVG surgeries; no AVF/AVG within 6 months of initiation of dialysis therapy; and/or received a kidney transplant or switched to peritoneal dialysis), resulted in a final cohort for the current study of 9458 elderly patients who received an AVF (n=7433) or AVG (n=2025) in the 6 months following initiation of hemodialysis therapy.
Compared with the patients receiving an AVG, those in the group with an AVF creation were younger, had a greater proportion of men and whites, had a lower Liu comorbidity index score, and was less likely to have a history of stroke, peripheral vascular disease, and chronic obstructive pulmonary disease. Patients in the AVF group also had fewer hospital days in the 6 months prior to hemodialysis therapy initiation. Both groups had similar duration of catheter dependence from the time of dialysis initiation to vascular access placement (~10 weeks).
In the 6 months following placement, a higher proportion of AVFs than AVGs failed to be used successfully for dialysis (51% vs 45%; adjusted hazard ratio [HR], 1.86; 95% confidence interval [CI], 1.73-1.99). A substantial proportion of vascular accesses required an intervention to make the vascular access functional. A higher proportion of patients in the AVF group required an intervention to make their access functional, compared with patients in the AVG group (42% vs 23%; OR, 2.66; 95% CI, 2.26-3.12).
In the group requiring interventions to make AVFs functional, the median duration of catheter dependence following vascular access creation and prior to first use was greater than in those who did not require interventions (4 vs 3 months; P<.001). It was also greater in patients with AVGs who required interventions for successful access use compared with no interventions required (2 vs 1 months; P<.001). Among patients with interventions required for successful access use, catheter dependence was greater in those with an AVF compared with those with an AVG (4 vs 2 months; P<.001). Likewise, among patients who did not require interventions, catheter dependence was greater in those undergoing AVF than in those undergoing AVG placement (3 vs 1 months; P<.001).
Patients receiving an AVF or an AVG were equally as likely to lose primary access patency (i.e., require at least one intervention) in the 1-year period after successful use of the vascular access (HR, 0.95; 95% CI, 0.88-1.03). One-year access abandonment was lower in patients receiving an AVF versus an AVG (HR, 0.71; 95% CI, 0.62-0.83). The overall frequency of vascular access interventions in the year following successful vascular access use was also lower among AVF versus AVG patients (2.35 vs 3.12; adjusted RR, 0.75; 95% CI, 0.69-0.81).
Limitations to the study cited by the authors included limiting the study population to elderly patients ≥67 years of age, potentially limiting the generalizability to younger dialysis patients; the analysis including only 1-year of follow-up after successful use of vascular access; and the observational design of the study, creating the possibility of confounding due to patient characteristics or local practice patterns.
The researchers said, “In summary, our study demonstrates clear tradeoffs among elderly patients who initiate hemodialysis therapy with a catheter and have a subsequent permanent vascular access placed. Compared with AVGs, AVFs are less likely to have successful use after creation, more likely to require interventions to make them functional, and associated with longer catheter dependence. In contrast, AVFs require fewer interventions to maintain patency after successful use and experience fewer abandonments in the first year after successful use. Ultimately, when considering selection and placement of the best vascular access in elderly patients initiating hemodialysis therapy with a catheter, the clinician must balance the importance of removing the catheter and minimizing the need for interventions to make the vascular access functional (favoring AVG placement) versus a longer lasting vascular access with fewer maintenance interventions (favoring AVF placement).”
- Researchers conducted a retrospective cohort study using national data to examine clinically relevant vascular access outcomes in elderly patients receiving an arteriovenous fistula (AVF) or graft (AVG).
- The analysis revealed tradeoffs in that patient population regarding the two types of vascular access: AVG placement favored shorter duration of catheter use and minimized the need for interventions to make the vascular access functional.
- In contrast, AVF placement favored a longer lasting vascular access with fewer maintenance interventions.