Act Guided Heparin Administration in Elective Open Abdominal Aortic Aneurysm Repair: Results of A Pilot Study

Abstract

Introduction: Almost all vascular surgeons use a bolus of 5 000 IU of unfractionated heparin (UFH). However, its dose-response and elimination curves are non-linear, and display a high inter-patient variability. The activated clotting time (ACT) is an established method to measure the level of anticoagulation. The purpose of this study was to evaluate the rate of arterial thrombo-embolic complications (ATEC) and bleeding complications in patients undergoing elective open abdominal aortic aneurysm repair (AAA), in which a bolus of 5 000 IU of UFH was compared to an ACT guided additional UFH dose protocol. Methods: All consecutive patients that underwent primary elective open AAA repair were included from a multicentre (1 academic and 2 peripheral hospitals) prospective study on ACT guided heparinization (MANCO: Measuring the ACT during non-cardiac arterial procedures, Clin. Trials.gov NCT 03426293). ACT measurements were performed as a bedside point-of-care test. During the first part of the study patients received a bolus of 5 000 IU. During the second part of the study patients received an initial bolus of 5 000 IU or 100 IU/kg and additional UFH dosages were administered, with a target ACT of 200 - 250 sec. The primary study endpoints were ATEC (graft thrombosis, embolism, myocardial infarction, transient ischemic attack, minor and major stroke, pulmonary embolism, bowel ischemia) detected during the procedure or during 30 day follow-up or during the same admission of the primary procedure, bleeding complications and mortality during 30 day follow-up. The secondary study endpoints were all other complications, the level of periprocedural anticoagulation as measured by the ACT and the additional and total UFH dosages administered. Results: 46 primary elective open AAA procedures were included, 18 patients in the standard dose group and 28 patients in the additional dose group. In the standard dose group 28% of patients reached an ACT of 200 sec. compared to 100% in the additional dose group. In the additional dose group the mean total periprocedural UFH dose administered was 9874 ± 2909 IU. ATEC occurred in 27.8% of patients in the standard dose group versus 14.3% in the additional dose group (P= 0.26). Bleeding complications did not increase in the additional dose group (38.9 versus 35.7%, P= 0.83). In both groups no patient died during 30 day follow-up. Conclusion: A standard dose of 5000 IU UFH leads to inadequate levels of heparinisation. Higher dosing of UFH aimed at an ACT of 200 sec. is safe, does not lead to increased bleeding, and potentially leads to a reduction in ATEC. A randomized controlled trial is needed to provide evidence on potential reduction in thrombo-embolic complications. Disclosure: Grant of Medtronic to perform the ACT measurements.