|Generic regular strength enteric coated 325mg aspirin tablets, distributed by Target Corporation. The orange tablets are imprinted in black with "L429". (Photo credit: Wikipedia)|
Low dose aspirin is a well established means of prevention of a second heart attack or stroke also known as secondary prevention. The evidence is less compelling for patients who have never had a heart attack or stroke, with the preventative benefit competing with a steadily increasing risk of bleeding from the intestines over time. Under the latter circumstances in some studies aspirin will come out ahead and in others slightly behind.
Patients on hemodialysis are at increased risk of bleeding, yet one of the main reasons for the discontinuation of dialysis remains access complications related to thrombosis (clotting). The question of whether the survival of dialysis access can be prolonged by the prescription of agents to prevent clotting has been asked before. At that time low dose coumadin therapy was associated with an unacceptably high rate of bleeding complications.
Several small studies have shown that aspirin and clopidogrel (the two main antiplatelet drugs tested) increased the risk of bleeding in patients on hemodialysis.
An article published in the clinical journal of the american society of nephrology collected data from multiple studies by a technique known as metanalysis. By combining data from multiple smaller studies the investigators hoped to gain the kind of quality statistical information required to answer the question.
The current study analysed results for 40,676 patients and concluded that the use of a single drug such as clopidogrel does not increase the risk of bleeding in patients on dialysis, the use of aspirin by itself was associated with mixed results however. In fact in patients who used grafts as a form of dialysis access aspirin increased the risk of graft thrombosis. No agent was successful at increasing primary patency of AV fistula in patients at risk of thrombosis. While using two or more antiplatelet agents increased the risk of bleeding significantly.
The current study failed to show any benefit in terms of patency rates for vascular access and overall discourages the use of antiplatelet agents in general for any form of primary prevention in dialysis patients. The role of aspirin in terms of secondary prevention of cardiovascular disease in dialysis patients is yet to be resolved.