Low anti-Factor Xa level predicts 90-day Symptomatic Venous Thromboembolism in Surgical Patients Receiving Enoxaparin Prophylaxis: A Pooled Analysis of Eight Clinical Trials. Annals of surgery Pannucci, C. J., Fleming, K. I., Varghese, T. K., Stringham, J., Huang, L. C., Pickron, T. B., Prazak, A. M., Bertolaccini, C., Momeni, A. 2020


OBJECTIVE: To examine the relationship between enoxaparin dose adequacy, quantified with anti-Factor Xa (aFXa) levels, and 90-day symptomatic venous thromboembolism (VTE) and post-operative bleeding.SUMMARY BACKGROUND DATA: Surgical patients often develop "breakthrough" VTE events-those which occur despite receiving chemical anticoagulation. We hypothesize that surgical patients with low aFXa levels will be more likely to develop 90-day VTE, and those with high aFXa will be more likely to bleed.METHODS: Pooled analysis of eight clinical trials (N = 985) from a single institution over a four year period. Patients had peak steady state aFXa levels in response to a known initial enoxaparin dose, and were followed for 90 days. Survival analysis log-rank test examined associations between aFXa level category and 90-day symptomatic VTE & bleeding.RESULTS: Among 985 patients, 2.3% (n = 23) had symptomatic 90-day VTE, 4.2% (n = 41) had 90-day clinically relevant bleeding, and 2.1% (n = 21) had major bleeding. Patients with initial low aFXa were significantly more likely to have 90-day VTE than patients with adequate or high aFXa (4.2% vs. 1.3%, p = 0.007). In a stratified analysis, this relationship was significant for patients who received twice daily (6.2% vs. 1.5%, p = 0.003), but not once daily (3.0% vs. 0.7%, p = 0.10) enoxaparin. No association was seen between high aFXa and 90-day clinically relevant bleeding (4.8% vs. 2.9%, p = 0.34) or major bleeding (3.6% vs. 1.6%, p = 0.18).CONCLUSIONS: This manuscript establishes inadequate enoxaparin dosing as a plausible mechanism for breakthrough VTE in surgical patients, and identifies anticoagulant dose adequacy as a novel target for process improvement measures.

View details for DOI 10.1097/SLA.0000000000004589

View details for PubMedID 33086312