Preoperative use of enoxaparin increases the risk of postoperative bleeding and re-exploration in cardiac surgery patients.

Objective: The purpose of this study was to investigate if the preoperative use of new platelet inhibitors and low-molecular-weight heparins may contribute to bleeding after cardiac surgery.
Design: Retrospective data review.
Setting: University teaching hospital.
Participants: One hundred eleven patients divided in 5 groups.
Interventions: Patients were grouped according to preoperative antithrombotic regimen: group 1, control, no agents (n=55); group 2, clopidogrel (n=9); group 3, enoxaparin (n=17); group 4, any GP IIb/IIIa inhibitor (n=14); and group 5, any drug combination (n=15). Data included cumulative mediastinal chest tube drainage, allogeneic blood transfusions, total blood donor exposures, and re-exploration.
Measurements and Main Results: Use of any drug (groups 2-5) resulted in greater total blood transfusions and donor exposure (p=0.0003) than control, especially red cells (p=0.002) and platelets (p=0.006). A greater percentage of patients on enoxaparin required mediastinal re-exploration for nonsurgical bleeding versus control (3/17 v 0/55, p=0.001). The use of enoxaparin was associated with significantly higher chest tube output after the first 24 hours postoperatively (p=0.048).
Conclusion: Newer antithrombotic agents were associated with greater transfusion rates and total donor exposures. Enoxaparin use was associated with greater overall blood loss and with higher incidence of mediastinal re-exploration. The relative risk-benefit ratio of reduced periprocedure morbidity versus increased bleeding complications has yet to be determined.