Due to predictable pharmacokinetics and pharmacodynamics, patients receiving LMWH therapy do not require routine coagulation monitoring. Despite this, there is some concern that a fixed or weight-based dosing of LMWH may put certain patient populations at risk for suboptimal effectiveness and safety. Data are lacking regarding the clinical utility of anti-Xa-guided dosing in patients receiving LMWH for VTE prophylaxis. The goal of this study is to evaluate relevant thromboembolic or bleeding outcomes for patients within 30 days of initial treatment with LMWH.
This retrospective cohort study evaluated patients from the University of Utah health system receiving enoxaparin for VTE prophylaxis between September 1, 2018, and September 30, 2019. Patients were evaluated for the occurrence of bleeding or thromboembolic adverse events. The primary outcome for this study is the composite of any VTE, International Society of Thrombosis and Haemostasis major bleeding, and mortality in the 30 days following the initial enoxaparin dose in patients either receiving or not receiving anti-Xa monitoring. Secondary outcomes were the individual components of the composite outcome.
During the 13-month analysis period, a total of 6611 patients were analyzed for VTE or bleeding events. IPTW allowed matching of patients between those who received anti-Xa monitoring, and those that did not to control for confounding variables.
Patients receiving LMWH for VTE prophylaxis with anti-Xa monitoring were associated with higher odds of experiencing a composite outcome of VTE, bleeding or death from any cause. For individual components of the composite outcome, the odds of any adverse outcome did not increase in the unmonitored group. This evidence supports current evidence-based guidelines that recommend against routine anti-Xa monitoring