MODERATE DOSES OF ASPIRIN AND RISK OF BLEEDING IN RENAL FAILURE

Uraemic patients have a bleeding tendency thought to be due to platelet functional abnormalities, but haemodialysis paradoxically exposes patients to the thrombotic complications of arteriovenous shunts. Possible treatments of the latter have been debated. The effect of 100 mg/m2 aspirin on haemostatic function was studied in 29 uraemic patients on chronic haemodialysis who had normal or only slightly prolonged bleeding times. Aspirin did not significantly affect bleeding time in healthy controls but prolonged it in uraemic patients. In 12 of the 29 uraemic patients, the bleeding time after aspirin was longer than 15 min. Aspirin completely abolished thromboxane A2 generation by both control and uraemic platelets, indicating that its effect in uraemic patients is not due to differential inhibition of platelet cyclo-oxygenase. Products of lipoxygenase enzyme and factor VIII von Willebrand factor did not seem to have a role. A careful risk-benefit evaluation is necessary before giving aspirin to uraemic patients on haemodialysis to prevent thrombosis of the arteriovenous shunt.