Background: Enoxaparin has become an attractive therapy for use during acute coronary syndrome (ACS) because of its potential superior efficacy over unfractionated heparin (UFH), its longer activity, and its subcutaneous route of administration. However, because a significant number of patients presenting with ACS may be sent directly to open heart surgery while still on anticoagulation, it is important to understand any potential bleeding risks that may be associated with the use of enoxaparin under these circumstances.
Methods: From 1998 to 2001, 1159 consecutive patients presenting with an acute coronary syndrome who received either UFH (n=1008) or enoxaparin (n=151) before proceeding to open heart surgery for urgent therapy during the same hospitalization were included in this study. Incidence of perioperative bleeding as evidenced by the units of blood products (packed red blood cells or platelets) transfused or the need for surgical re-exploration for postoperative bleeding was recorded.
Results: Average age was 65+/-11 and 67+/-11 years for patients receiving UFH and enoxaparin, respectively (P=0.005). Seventy-five percent of those receiving UFH and 64% of those receiving enoxaparin (P<0.005) were males. After discharge, the incidence of rehospitalization for hemorrhage requiring return to surgery for re-exploration was 7.9% in the enoxaparin group and 3.7% in the UFH group (adjusted hazard ratio=2.6, P=0.03). The use of blood products did not differ between groups (UFH=2.7+/-6.5 U and enoxaparin=2.3+/-4.5 U; P=NS).
Conclusion: The preoperative use of enoxaparin compared with UFH in patients presenting with an ACS who undergo open-heart surgery during the same hospitalization is associated with a significantly increased incidence of re-exploration for postoperative bleeding. Further study is needed to understand the mechanism of this phenomenon and to develop appropriate guidelines to address this potentially important issue.