Intraoperative heparinisation, 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 involving patients undergoing elective abdominal aortic aneurysm (AAA) surgery was to investigate the relationship between intraoperative intravenous heparinisation, blood loss during surgery and thrombotic complications.Methods:Two hundred and eighty-four patients were randomised to receive intravenous heparin (n = 145) or no heparin (n = 139). Groups were evenly matched for age, sex, weight, aneurysm size, haemoglobin concentration, platelet counts and distal occlusive disease measured by ankle/brachial systolic pressure.Results:There were no statistically significant differences in blood loss (median 1400 ml vs. 1500 ml; 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 the heparinised patients suffered a fatal perioperative myocardial infarction (MI); p < 0.05. All MI, including non fatal events, affected 8.5% and 2% respectively (p = 0.02).Conclusions:Heparin does not increase blood loss or the need for blood transfusion during surgery. Heparin is not necessary to prevent distal thrombosis when the aorta is cross clamped. The results of the study are consistent with the known mechanisms leading to intraoperative MI and strategies for its prevention. Intravenous heparin, given before aortic cross clamping, is an important prophylaxic against perioperative MI in relation to AAA surgery