Does Short-Term Pre-Operative Aspirin in Coronary Bypass Patients Increase Post-Operative Bleeding?

A prospective physician blinded study was undertaken to evaluate post-oper ative bleeding in coronary artery bypass patients treated with aspirin pre-oper atively. Thirty patients were randomized: nine received no aspirin, eleven received 325 mg twelve hours pre-operatively, and ten received 650 mg aspirin every six hours beginning 48 hours pre-operatively and ending six hours prior to operation. There were no differences among the groups in patient age, grafts per patient, pre and post-operative hematocrit, platelet counts, aortic cross- clamp times, perfusion times, heparin dose, protamine dose, or units of blood transfused. Twenty-four hour chest tube drainage was 704 ± 235 cc in the un treated group (I), 874 ± 459 cc in the low dose aspirin group (II) and 1218 cc ± 892 cc in the high dose aspirin group (III). A t-test comparison of groups was conducted as follows: I vs. II (p = 0.7), II vs. III (p = .05), I vs. III (p = .001). Groups II and III required more units of platelets than Group I (4 units vs. 1 unit per patient) and more fresh frozen plasma (2 units vs. 0.2 units per pa tient). Low dose aspirin did not significantly increase bleedng above controls, but it was associated with an increased requirement for component therapy. High dose aspirin did significantly increase post-operative blood loss and also caused an increased requirement for platelets and fresh frozen plasma. The amount of post-operative bleeding appears to be dose related. Low dose pre- operative therapy may be used without excessive bleeding.