INTRAOPERATIVE HEPARINIZATION, BLOOD-LOSS AND MYOCARDIAL-INFARCTION DURING AORTIC-ANEURYSM SURGERY - A JOINT VASCULAR RESEARCH GROUP-STUDY

Objectives: The primary aim of this prospective multi-centre study inv olving patients undergoing elective abdominal aortic aneurysm (AAA) su rgery was to investigate the relationship between intraoperative intra venous heparinisation, blood loss during surgery and thrombotic compli cations. Methods: Two hundred and eighty-four patients were randomised to receive intravenous heparin (n = 145) or no heparin (n = 139). Gro ups were evenly matched for age, sex, weight, aneurysm size, haemoglob in concentration, platelet counts and distal occlusive disease measure d by ankle/brachial systolic pressure. Results: There were no statisti cally significant differences in blood loss (median 1400 ml vs. 1500 m l; z = 0.02, p = 0.98, 95% C.I. = -200 to 200), blood transfused (4.0 units vs. 4.0 units; z = 1.09, p = 0.28, 95% C.I. = -1 to 0) or distal thrombosis between the two groups. However, analysis of the clinical outcome revealed that 5.7% of the non-heparin group but only 1.4% of t he heparinised patients suffered a fatal perioperative myocardial infa rction (MI); p < 0.05. All MI, including non fatal events, affected 8. 5% and 2% respectively (p = 0.02). Conclusions: Heparin does not incre ase blood loss or the need for blood transfusion during surgery. Hepar in is not necessary to prevent distal thrombosis when the aorta is cro ss clamped. The results of the study are consistent with the known mec hanisms leading to intraoperative MI and strategies for its prevention . Intravenous heparin, given before aortic cross clamping, is an impor tant prophylaxic against perioperative MI in relation to AAA surgery.