Blood-Thinner No Help for Dialysis Treatment
TUESDAY May 13, 2008 -- A major trial has dashed the hope that the clot-preventing drug Plavix could help in the delicate balancing act needed to establish a blood vessel suitable for dialysis for kidney patients.
Giving Plavix (clopidogrel) did reduce the risk that a blood clot would block the vessel created by combining a vein and an artery, a standard procedure for kidney dialysis. But adding the clot-preventing drug did not increase the number of fistulas, as they are called, that could be used for artificial kidney treatment over the long run, the study authors reported.
The study was done because "early thrombosis [blood clotting] is one of the major causes of fistula failure," said Dr. Laura M. Dember, an associate professor of medicine at Boston University, and lead author of the report.
"What we found was that despite the reduction in thrombosis that was clear enough, there was an equal proportion of fistula failure," Dember said. "What is ultimately important is the usability of the fistula for dialysis."
The researchers published their findings in the May 14 issue of the Journal of the American Medical Association.
About 470,000 Americans have kidney failure and are kept alive by dialysis, in which their blood is run through a machine that filters out impurities. The preferred technique for linking to the artificial kidney is to create a fistula, which has lower rates of thrombosis -- blockage -- and infection than alternatives such as synthetic artery-vein grafts. But many fistulas never mature enough to allow dialysis.
The multi-center trial included 877 people with total or partial kidney failure who underwent surgery to create a fistula. Half were given Plavix for six weeks after the surgery, while the other half were not.
Plavix did reduce the risk of blockage by 37 percent over the six-week period. Among the 866 people who were tested, 12.2 percent of those given Plavix had a blockage, compared to 19.5 percent of those not given the anti-clotting drug.
But Plavix therapy did not reduce the incidence of cases in which the fistula could not be used for dialysis, which was 61.8 percent in those getting the drug and 59.5 percent in those getting a placebo.
The rate of fistula failure was about 50 percent higher than anticipated, Dember said, and that might have an effect on future practice.
"There has been an increased emphasis on trying to create fistulas in as many patients as possible," she said. "So, the criteria have changed. We need to develop better methods for selecting suitable candidates for fistula creation."
The trial also indicated the direction that that research should take, Dember said.
"Our future efforts should be directed at understanding the basic mechanisms of fistula maturation," she said. "If we better understand those mechanisms, we should be able to identify maturity-enhancing interventions."
The basics of kidney dialysis are explained by the U.S. National Library of Medicine.
Posted: May 2008