(234) High- Versus Low-Range Anti-Xa Goals for IV Heparin in Patients With Mechanical Circulatory Support

Introduction: Mechanical circulatory support (MCS) devices are increasingly used in contemporary practice and are associated with high rates of bleeding and thrombosis. Intravenous (IV) unfractionated heparin was commonly used for anticoagulation, with anti-Xa monitoring therapeutic range being 0.3 to 0.7 units/mL. There is little data to help define the optimal therapeutic range in such patients. We aimed to evaluate if a low-range anti-Xa goal (0.2-0.5 units/mL) was associated with a decreased incidence of bleeding while maintaining adequate antithrombotic effect when compared to a higher anti-Xa goal (0.3-0.7 units/mL).

Methods: This was a single-center, retrospective study. Adult patients admitted to cardiovascular or cardiothoracic ICUs receiving IV UFH and an MCS device were included. The primary endpoint was the incidence of bleeding between groups, defined by Bleeding Academic Research Consortium criteria. Secondary endpoints included the incidence of thrombosis, independent confounding risk factors for increased bleeding risk, rate of mortality, and ICU length of stay.

Results: Of 304 patients included in present analysis, 152 patients in each cohort, patients in low-range anti-Xa group had numerically lower bleeding compared to those in high-range group (33 (21.7%) patients vs 47 (30.9%); p=0.068). Time to bleeding event was 41.4 (IQR 8.37-109.73) and 38 (IQR 8.84-104.79) hours after UFH infusion was initiated (p=0.969). Within 24 hours proceeding bleeding events, the highest UFH dose was 12.9 (IQR 11-16) and 12 (IQR 10-15.1) units/kg/hour (p=0.205). The anti-Xa was 0.32 (IQR 0.2-0.44) and 0.27 (IQR 0.18-0.37) units/mL (p=0.99), respectively. VA-ECMO was shown to be an independent predictor for bleeding (adjusted OR 1.91 7, CI 95%: 1.060-3.469, p< 0.001). Thrombotic events occurred in 7 patients (4.6%) and 4 patients (2.6%) in high-range vs low-range anti-Xa group (p=0.38). ICU length of stay was 12 (IQR 5.25-24.75) and 11 (IQR 4-25) days (p=0.56), and overall mortality rate was 31.3%.

Conclusions: There was a trend toward lower bleeding in patients who were managed with a low-range anti-Xa without increasing the thrombotic events, larger studies are needed to further test this hypothesis.