A new study, led by University of Iowa researcher Brad Dixon, MD, shows for the first time that the anti-clotting drug dipyridamole combined with aspirin delays the initial failure of arteriovenous vascular access grafts used in hemodialysis for patients with end-stage kidney disease.
A functioning vascular access allows blood to be removed for cleansing. Grafts typically fail due to blood vessel narrowing at the graft site, which leads to clotting and blocks blood flow. A blocked graft cannot be used and is a major cause of worsening health for patients on dialysis.
"Access failure is the Achilles' heel of hemodialysis," said Dixon, the study's principal investigator and associate professor of internal medicine at the UI Roy J. and Lucille A. Carver College of Medicine. "Although the benefit was modest, the investigation is the first study to show that a drug can reduce narrowing within arteriovenous grafts. Depending on cost-analysis, it might be worthwhile to use this treatment approach preventively."
The study was part of the Dialysis Access Consortium and funded by the National Institute of Diabetes and Digestive and Kidney Diseases at the National Institutes of Health. The study found that drug therapy with extended-release dipyridamole plus aspirin was safe and decreased by 5 percent the rate of arteriovenous vascular access grafts that had a first failure within one year. The findings appeared in the May 21 issue of the New England Journal of Medicine.
More than 300,000 Americans with end-stage kidney disease receive hemodialysis several times a week. Each year, approximately one in three patients has a vascular access problem that requires hospitalization. Costs associated with vascular access maintenance are estimated to exceed $1 billion annually in the United States.
Preferred Method
The preferred access method is the fistula, which is a direct connection between artery and vein, because it has the fewest complications. The second preferred method is the arteriovenous graft, which is a surgically inserted piece of tubing connecting an artery and a vein. The least preferred type is the catheter.
"A fistula does not work for some patients. A graft is the next best option, but they frequently clot. We wanted to try to find a drug-based, rather than a procedure-based, approach to prevent that from occurring," said Dixon, who also is a staff physician and researcher with the Iowa City Veterans Affairs Medical Center.
Nearly half of the 649 participants received a capsule containing 200 milligrams of extended-release dipyridamole plus 25 milligrams of aspirin, and half received placebo twice a day for up to four-and-half years. After one year, 72 percent of the active treatment group and 77 percent of the placebo group had suffered at least one thrombosis or access intervention, and in contrast to earlier studies of anti-clotting drugs, no excess risk of bleeding was seen.
"The overall high rate of failure in both groups is daunting. Procedures needed to correct these graft failures contribute to the high costs of dialysis treatment for grafts," Dixon said. "This study represents an important step towards understanding and treating the problem. The next step is to examine new treatments and combination therapy for hemodialysis vascular stenosis." |
