Changes in antiplasmin and plasmin activities during extreme hemodilution and open heart surgery in dogs

The effects of extreme hemodilution and open heart surgery on antiplasmin and plasmin activities were investigated in dogs. Assays for plasmin and antiplasmin activities were performed with a chromogenic peptide substrate for plasmin. After hemodilution and during cardiopulmonary bypass (CPB), plasmin activity on the substrate was observed and levels of both "fast-reacting" and "total" antiplasmins fell. The plasmin activity was shown to be due to the formation of alpha2-macroglobulin-plasmin complex which exhibited amidolytic activity on the chromogenic substrate. The falls in antiplasmin activity together with the appearance of the alpha2-macroglobulin-plasmin complex revealed that activation of the fibrinolytic system had occurred. After the operation and following reinfusion of autologous blood, decreased plasmin and increased antiplasmin activities were observed. On the first and sixth days following the operation plasmin activities were still slightly higher than pre-operation values, whilst antiplasmin activities were normal.