Thrombin generation during collection and storage of blood

Thrombin generation, as evidenced by radioimmunologic fibrinopeptide A (FPA) determination, was studied upon drawing and storage of blood. Blood from 5 healthy subjects was drawn into Fenwal bags (PL 146, 16-gauge needle, 92-cm collecting tube), and blood samples for FPA analysis were taken from the proximal and distal part of the collecting tubes. The FPA concentrations were considerably higher in the distal part of the tubes both at zero time and after 5 and 10 min, implying substantial thrombin generation to have occurred upon blood passing through the tubes. In 20 healthy blood donors (age 19-52 years) subjected to a standard collection procedure (Fenwal bags PL 146, CPDA formula-1 anticoagulant solution, 450 ml blood), higher FPA values were observed in the bags immediately upon collection, as compared to control venipuncture values (p less than 0.02). Furthermore, in 6 women using oral contraceptives, even larger increases were observed, indicating thrombin generation to be more pronounced in such donors (p less than 0.01). No statistically significant increase in FPA concentrations was found upon storage of CPDA-blood at 4 degrees C for 24 h. There was no correlation between FPA and beta-thromboglobulin (BTG) concentrations after blood collection, indicating alpha-granule release from platelets to be non-thrombin-mediated.