Early outpatient use of low-molecular-weight heparin benefits COVID-19 outcome in association with hospitalization -...

Covid-19 and venous thromboembolism (VTE) share risk factors and thrombo-inflammatory pathophysiology. In-hospital low-molecular-weight heparin (LMWH) use improved outcomes. Before vaccinations or available treatments, the Helsinki university hospital in Finland, initiated LMWH thromboprophylaxis to Covid-19 outpatients with progressing illness and high-risk of VTE (LMWH+ group), aligning with the existing in-hospital guidance for thromboprophylaxis.

We observationally studied whether pre-admission LMWH thromboprophylaxis impacted outcomes: hospital and ICU stay, and respiratory support after Covid-19 hospitalization. We compared control group (LMWH-) by propensity score-matching comorbidities, medications and Covid-19 severity and VTE risk with the LMWH+ group with 30-day follow-up.

Among 1189 hospitalized patients, 241 were stratified in the LMWH+ group and 482 were propensity-matched into the LMWH- group. The mean time (±SD) from Covid-19 diagnosis until outpatient thromboprophylaxis in the LMWH+ group was 1.9 (±3.0) days; ~80 % of patients received thromboprophylaxis ≤2 days after the diagnosis. Longer duration of pre-admission LMWH use was associated with shorter hospital stays and less days with respiratory support (p < 0.006-0.008). The incidences of bleeds and VTE (LMWH+ 4.6 %, LMWH- 5.4 %) were similar. Overall, 2.9-fold higher mortality (p = 0.014) occurred in the LMWH- (10.6 %) versus the LMWH+ group (3.7 %).

Outpatient LMWH given pre-admission for high-risk Covid-19 patients was associated with improved outcome following diagnosis: shorter respiratory support and hospital stay with reduced need for intensive care. Our findings support early initiation of LMWH in risk-stratified patients to manage thrombo-inflammation. While being Covid-19 aftermath, our study is relevant for any other severe viral outbursts associated with thrombogenicity.