The findings of a new study call into question the longstanding belief that the higher risk of premature death seen in hemodialysis patients who are treated with catheters is due to an elevated risk of complications. The result, which appear in an upcoming issue of the Journal of the American Society of Nephrology (JASN), point to the need for additional studies on the safety of methods used to access dialysis patients' blood.
Most patients with kidney failure are treated with hemodialysis, which requires access to the bloodstream so that blood can be removed, passed through a filter, and returned to the patient's body after it has been rid of toxins. Arteriovenous fistulas (a connection between an artery and vein in the arm) and catheters (a large tube, like an intravenous inserted in the neck) are 2 common types of vascular access. Fistulas are preferred because it's believed that catheters have a higher risk of complications, and Canadian, American, and European guidelines recommend that all suitable candidates undergo an attempt at creating fistulas prior to starting hemodialysis.
When researchers led by Rob Quinn, MD, PhD, FRCPC and Pietro Ravani, MD, MSc, PhD (University of Calgary, in Canada) examined information on adults who initiated hemodialysis between 2004 and 2012 at 5 Canadian dialysis programs, they found that death rates in patients who had a fistula created prior to starting dialysis were lower than rates in patients who started dialysis using a catheter for vascular access. The team also found that use of a fistula was associated with a lower risk of death in patients <65 years old, but not in patients aged ≥65 years. Importantly, only 2.3% of deaths were related to complications of vascular access, suggesting that a fistula attempt could be a surrogate marker for a healthy patient who has had good care prior to starting dialysis while catheters were used preferentially in patients with acute kidney injury, short life expectancy, and in those with poor blood vessels.
"Our findings suggest that prior comparisons of patients treated with catheters compared with fistulas may be confounded by underlying differences in the health of patients who receive different access types," said Dr. Quinn. "In other words, sicker patients who are more likely to die from other causes are preferentially treated with catheters, while the healthiest patients are referred for fistula attempts." The only way to reliably address this issue when designing a study is to randomize patients to their vascular access type and follow them for outcomes in a randomized trial. "To date, this has never been done and we feel this is a necessary next step," said Dr. Quinn.
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