Acetylsalicylic acid alone or in combination with either enoxaparin or unfractionated heparin for postoperative thromboprophylaxis in coronary artery bypass surgery patients. A randomised clinical trial assessing surrogate outcomes.

Introduction: Coronary artery bypass graft surgery has considerable effects on patient haemostasis. Heparins as thromboprophylaxis may be beneficial but may also increase the risk of bleeding complications.

Objectives: To assess the effects of heparins on haemostasis in post-coronary artery bypass graft patients.

Methods: Across one year, we randomised 60 participants scheduled for an elective coronary artery bypass graft-procedure with or without aortic valve replacement. The trial was a prospective, open-label (though blinded for the laboratory), randomised, single-centre trial with three intervention groups (n = 20 in each): group 1 received acetylsalicylic acid, group 2 received subcutaneous low molecular weight heparin and acetylsalicylic acid, and group 3 received intravenous unfractionated heparin and acetylsalicylic acid. Primary outcomes were platelet activation (Multiplate® ASPI-test) and time to clot initiation (TEG® R-time). We secondly assessed several additional Multiplate® and TEG® parameters.

Results: Group 3 (intravenous unfractionated heparin) compared with group 1 (acetylsalicylic acid alone) showed evidence of 1) increased clot initiation time (R-time + 0.9 min; 95 % CI: +0.4 to +1.4 min; P = 0.009), and 2) decreased 30-min lysis (-1.3 %; 95 % CI: -2.1 to -0.5 %; P = 0.02). The remaining analyses of primary and secondary outcomes showed no evidence of a difference between the three groups.

Discussion: Intravenous unfractionated heparins may increase the clot initiation time post-operatively after coronary artery bypass graft surgery and reduce lysis. Otherwise, there seems to be no effect of low molecular weight or unfractionated heparin on haemostatic parameters after coronary artery bypass surgery patients.