Is Anti-Factor Xa Associated With Outcome in Patients With Critical COVID-19 on Low-Molecular-Weight Heparin?

Patients with critical COVID-19 are hyper-coagulable and optimal thromboprophylaxis treatment differs with stage and severity. The most commonly used drug for thromboprophylaxis in the intensive care unit (ICU) is low-molecular-weight heparin (LMWH). In contrast to unfractionated heparins, the effects of LMWH usually do not require monitoring. Exceptions from this are when elimination of LMWH is impaired, extremes in age and weight, to identify deviations from predicted pharmacokinetics, and if there is an unexpected clinical response. The unexpected high incidence of thromboembolic complications among patients with critical COVID-19 compared to critically ill non-COVID-19 patients could motivate monitoring. The activity of LMWH is monitored by quantifying the presence of anti-Factor Xa (aFXa). The aim of this study is to investigate if the level and the monitoring frequency of aFXa is associated to mortality, thrombosis and bleeding in patients with critical COVID-19 treated with LMWH and therefore could be used as a potential tool to guide LMWH-treatment.