Worldwide, more than 2 million people with chronic kidney failure receive treatment via hemodialysis therapy. Reliable access to the bloodstream is achieved using an arteriovenous fistula, an arteriovenous graft, or a central venous catheter. The most common forms of access in Canada are fistulas and catheters; grafts are used in <5% of patients. Relative to use of a graft or catheter, fistulas are associated with lower mortality and infection rates; catheter use is associated with a higher risk for adverse events. Initiatives have been implemented in Canada to increase fistula use, and worldwide guidelines have adopted a fistula-first/catheter-last paradigm.
The risk for primary fistula failure due to early clotting following surgical creation or failure of the fistula to mature are barriers to increasing fistula use. Primary failure occurs in approximately one in four created fistulas, and, despite interventions to restore patency, one in five fistulas is nonfunctional at 1 year.
Results of previous studies have not provided clear evidence-based criteria to identify people who, based on clinical characteristics, would most benefit from fistula creation. In those studies, definitions of fistula maturation were based on achieved hemodialysis blood flow rates on fistula cannulation. According to Fareed Kamar, MD, and colleagues, “These definitions do not discern whether a fistula has become sufficiently reliable to allow catheter avoidance or removal, the main goal of creating a fistula. The proportion of time spent catheter free following fistula creation would be a better measure of success.”
There are few data available on the proportion of catheter-free time following one or two fistula creations and the relationship between the outcome of an initial fistula and the outcome of a second fistula. Dr. Kamar et al. conducted a cohort study to examine catheter-free use of the first fistula versus second fistulas, and to determine whether use of the first fistula predicts successful use of the second fistula in patients who received two fistulas. Results of the study were reported in the American Journal of Kidney Diseases [2019;73(1):62-71].
The researchers utilized data from five Canadian Programs using the Dialysis Measurement Analysis and Reporting system on individuals who initiated hemodialysis and underwent at least one attempt of fistula creation. Outcomes of interest were catheter-free fistula use during 1 year following start of hemodialysis therapy or, following fistula creation if created after hemodialysis initiation; the proportion of time with catheter-free use; time to catheter-free use; and time of functional patency.
At the five participating programs, a total of 3145 people initiated dialysis therapy between 2004 and 2012; of those, 1091 met inclusion criteria. Mean age was 64 years, 63% were men, and 59% had diabetes. Mean patient follow-up was 28 months. At time of study end, 660 participants (60.5%) were still receiving hemodialysis therapy. Of the remaining participants, 25.2% (n=275) died, and 14.3% (n=156) were censored because they were transferred to another center (n=71), recovered sufficient kidney function to stop dialysis therapy (n=11), or started peritoneal dialysis (n=22).
Baseline characteristics were generally similar between the group of those who received one fistula (n=901) and those who received two fistulas (n=190), with the exceptions of location of the first fistula (more likely to be in the upper arm in those who underwent only one attempt) and duration of total follow-up (shorter in those who underwent only one attempt). When the two groups were stratified based on access type at study end date (more likely a catheter in those who received two fistulas), results were similar.
One year following creation, second fistulas were significantly less likely to be used catheter free compared with first fistulas (adjusted subhazard ratio [aSHR], 0.56; 95% confidence interval [CI], 0.44-0.72); although they displayed similar 1-year functional patency when catheter-free use was achieved. Those who had two fistulas were significantly less likely to achieve catheter-free use at 1 year from creation (aSHR, 0.44; 95% CI, 0.36-0.54) and more likely to lose functional patency at 1 year from first use (aSHR, 2.36; 95% CI, 1.61-3.46). Outcomes of the second fistula were superior to those of the first fistula in the group that received two fistulas.
Following exclusion of fistulas with follow-up shorter than 1 year (295 first fistulas and 49 second fistulas), catheter-free use for any duration within 1 year of initiation of hemodialysis therapy (or fistula creation if created after hemodialysis therapy initiation) was achieved in 46% of first fistulas and 38% of second fistulas. The average percentages of time that second and initial fistulas were used catheter free were 34% and 42%, respectively (odds ratio, 0.72; 95% CI, 0.54-0.94).
In the group that received two fistulas, the second fistula was used catheter free at least once in 39% of those who used the first fistula successfully and in 38% of those who did not. Results were similar in adjusted analysis of catheter-free use for any duration. The proportion of time that the second fistula was used catheter free was 11% higher with each 10% greater proportion of time that the first fistula was used catheter free (95% CI, 1%-22%).
Study limitations cited by the researchers included the lack of data for fistula cannulation dates, access flow, and dialysis adequacy; unknown criteria for patient selection of one or two fistulas; and unknown reasons for prolonged catheter use.
In conclusion, the researchers said, “Further research is needed to better clarify the mechanisms resulting in fistula success or failure and potential strategies to improve fistula outcomes. Clinical research is also needed to better understand patients’ views and perspectives of the vascular access for hemodialysis, care providers’ perceptions of these views and perspectives, which vascular access end points are meaningful to patients, and how available outcome data can be best discussed in vascular access counseling.”
- Results of a cohort study to examine catheter-free use of first versus second fistulas and whether use of the first fistula predicts successful use of the second fistula in patients who received two fistulas were reported.
- The cohort included 1091 participants: 901 received one fistula and 190 received two fistulas.
- Thirty-eight percent of second fistulas were used catheter free at least once, versus 46% of first fistulas.