THE ROLE OF PROTEIN-C AS AN INHIBITOR OF BLOOD-CLOTTING DURING EXTRACORPOREAL-CIRCULATION

The plasma levels of protein C, AT III, the perioperative administration of fresh frozen plasma (FFP) and AT III concentrate were compared under the use of various drugs in a randomized, prospective double-blind study in 40 patients in whom an aortocoronary bypass operation was carried out. We formed four groups of ten patients: group A served as a control group, group B received a prostacyclin (PGI2) infusion of 10 or 20 ng/kg/min, group C high-dose aprotinin substitution, and group D was treated with a combination of prostacyclin and aprotinin. After an initial short-term rise in the inhibitors protein C and AT III, there was a fall in all groups in the further course of extracorporeal circulation. The initial preoperative values were reached again on the morning of the first postoperative day. This indicates a raised turnover and in association with this a raised rate of elimination of these factors caused by an increased thrombin activation during the extracorporeal circulation which cannot be prevented by the usual heparinization. Whereas prostacyclin had no effect on our results mediated by thrombocytic mechanisms, use of aprotinin led to a significant saving in the requirement for perioperative fresh frozen plasma and AT III substitution therapy. A clinical advantage of prostacyclin and aprotinin combination was not observed. In view of our results (individual analyses were mainly in the normal range), we consider that AT III and fresh frozen plasma should not be substituted routinely during or after extracorporeal circulation.