Platelet function and coagulation parameters in sheep during experimental vascular surgery.

Various clotting parameters (prothrombin time, activated coagulation time, activated partial thromboplastin time, platelet counts, and platelet aggregation) were obtained from unanesthetized sheep and from sheep at various times during 5 hours of vascular surgery. The values obtained were not influenced by anesthesia and surgery and were consistent between sheep. Ovine platelets were less prone to aggregate in the presence of collagen, epinephrine, and ristocetin than those of man. Platelet aggregation induced by adenosine diphosphate was similar to that seen in man. Based on these parameters, the sheep would seem to be a reasonable model for experimental vascular surgery when results are to be applied to man.