Effect of aspirin on collateral blood flow after experimental thrombosis of the feline aorta

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Abstract
SUMMARY: In 11 cats, the caudal aorta was occluded with a thrombus to inhibit opening of collateral vessels to the hindlimbs. Five cats were not treated, and 6 cats were given aspirin (650 mg, orally) 1 hour before aortic occlusion. Before the aortas were occluded, platelet counts were measured in the 11 cats, and platelet aggregation by adenosine diphosphate was assessed in 4 cats scheduled for aspirin treatment. Cats were maintained for 3 hours after surgery, and the tests were repeated. In addition, serum salicylate concentrations were determined for all aspirin-treated cats. Collateral circulation was assessed as the time necessary for contrast media to appear in the iliac arteries caudal to the thrombus during aortography. Platelet counts were significantly (P ≤ 0.05) reduced in nontreated cats, but not in the aspirin-treated cats. Serum salicylate concentrations indicated that aspirin had reached therapeutic blood concentrations. Inhibition of adenosine diphosphate-induced platelet aggregation was observed in all postthrombosis aspirin-treated cats. Contrast media did not appear in the iliac arteries of nontreated cats until 7.5 ± 0.5 s after injection. In all aspirin-treated cats, contrast media appeared in the iliac arteries within 2.3 ± 0.3 s after injection. Platelet thromboxane A2 may be the factor promoting collateral inhibition after aortic thrombosis in cats.