Low-dose aspirin fails to inhibit increased platelet reactivity in patients with peripheral vascular disease

A study was performed to evaluate the effect of low‐dose aspirin (75 mg/day) on platelet reactivity in patients with peripheral vascular disease. Platelet function was measured in 31 patients with advanced peripheral vascular disease requiring surgery. Shear‐induced haemostasis and collagen‐induced thrombus formation were used as indicators of platelet reactivity. They were measured in non‐anticoagulated fresh whole blood samples ex vivo using a haemostatometer. Results were compared with those from 30 age‐ and sex‐matched controls. Shear‐induced haemostasis and collagen‐induced thrombus formation were also measured in 18 of the 31 patients before the start of aspirin administration (before operation) and I week after surgery. Patients with advanced peripheral vascular disease were found to have increased platelet reactivity with a mean(s.e.m.) shear‐induced haemostasis index of 1977(180) mmHgs compared with a control value of 3161(234) mmHg s (P < 0.001) and a mean(s.e.m.) collagen‐induced thrombus formation index of 3980(460) mmHg s compared with a control value of 5350(420) mmHg s (P = 0.02). Perioperative low‐dose aspirin failed to inhibit platelet function in patients with peripheral vascular disease.