(453) Bleeding and Thrombosis Outcomes Utilizing aPTT vs Anti-Xa Heparin Monitoring in Vascular Surgery

Introduction: Unfractionated heparin (UFH) is a widely used anticoagulant in the inpatient setting. Utilization of an UFH anti-Xa protocol vs an aPTT protocol may lead to different amounts of heparin administered which may increase bleeding risk in high-risk patients. The objectives of this study were to analyze the differences in bleeding and thrombosis outcomes, and continuous UFH performance characteristics when utilizing aPTT versus anti-factor Xa protocols in vascular surgery patients.

Methods: Vascular surgery patients who were administered UFH in the last 3 years were retrospectively reviewed. Patients were included if they were 18 years of age or older, received continuous UFH for 24 hours or more, and an aPTT or anti-Xa protocol was used. The primary endpoint was major or minor bleeding. Secondary outcomes were rates of thrombosis, as well as heparin protocol performance characteristics. Data collected included documented bleeding, thrombosis, time to therapeutic level, number of rate adjustments, and amount of heparin administered in units.

Results: A total of 85 patients were included, 47 (55.3%) in the aPTT group, 38 (44.7%) in the anti-Xa group. The median time of heparin infusion was 75 hours in the aPTT group, 94 hours in the anti-Xa group (p=0.605). The median time to therapeutic level was 1080 minutes in the aPTT group, 930 minutes in the anti-Xa group (p=0.807). The median number of rate changes per day was 0.79 in the aPTT group, 0.73 in the anti-Xa group (p=0.471). Levels were therapeutic 55.6% of the time in the aPTT group, 59.2% in the anti-Xa group (p=0.376). The median amount of heparin administered in units per hour was 1234.3 U/hr (standard-dose, aPTT), 1332 U/hr (standard-dose, anti-Xa) (p=0.725), and 982.4 U/hr (low-dose, aPTT), 767.7 (low-dose, anti-Xa) (p=0.637). Major bleeding events occurred in 14.9% of patients in the aPTT group, 21.1% of patients in the anti-Xa group (p=0.458). Minor bleeding events occurred in 8.5% of patients in the aPTT group, 15.8% of patients in the anti-Xa group (p=0.331). Two thrombotic events occurred in the study period, both occurring in patients in the anti-Xa group (p=0.197).

Conclusions: No difference in bleeding or thrombotic events, or heparin performance was observed when comparing aPTT and anti-Xa monitoring for unfractionated heparin.