Does heparin pretreatment affect the haemostatic system during and after cardiopulmonary bypass?

In this clinical pilot study, the influence of heparin pretreatment on the haemostatic system during and after cardiopulmonary bypass (CPB) was invest igated. Thirteen patients scheduled for elective coronary artery bypass gra fting (CABG) were divided into two groups: heparin pretreated (HP, n = 6) a nd non-heparin pretreated (NHP, n= 7). Blood samples were taken for measure ments of plasma antithrombin-III (AT-III) activity, plasma heparin levels, activated clotting time with (HACT) and without (ACT) heparinase, whole blo od platelet function, platelet count, thrombin-antithrombin-III complexes a nd D-dimer levels. Also, the mediastinal blood loss within the initial 20 h after surgery, and the blood transfusion requirements were monitored. The mean duration of the heparin pretreatment was 55 h (range 24-161 h). There was no significant difference in plasma AT-III activity and platelet count between the groups. Before and after CPB, the platelet responsiveness was b etter in the NHP group (p< 0.05). The HACT was prolonged in the NHP group d uring and after CPB compared to baseline values (p < 0.05), whereas, in the HP group, no significant changes were found. Plasma heparin levels and ACT values suggested adequate anticoagulation during CPB. However, the extent of thrombin inhibition and fibrinolysis increased with time on CPB, but did not differ between the two groups. Twenty hours after surgery, the thrombi n inhibition showed to be significantly higher in the NHP group. Furthermor e, mediastinal blood loss showed a tendency to be lower in the HP group (p = 0.08). However, there was no difference in blood transfusion requirements between the groups. These data suggest that short-term heparin pretreatmen t affects the perioperative platelet responsiveness and attenuates the cons umption of coagulation factors.