Low Molecular Weight Heparin in Adults Inpatient COVID-19

Background: The intensity of thromboprophylaxis as potential factor related to in-patient mortality associated to COVID-19 remains unclear.   Methods: This is a retrospective study to evaluate the effect of anticoagulation intensity in the in-patient mortality of unselected adults COVID-19. Patients were stratified according to the low molecular weight heparin (LMWH) regimen received: non-heparin, low-dose heparin (standard dose of prophylaxis) or high-dose heparin (dose higher than standard prophylaxis).  Findings: 690 patients were included and the median age was 72 years. Heparin was administered to 611 patients from hospital admission (88·6%). 422 patients (61·2%) were in the low-dose group and 189 patients (27·4%) in the high-dose group. The overall inpatient mortality rate was 28·7%. The adjusted risk for in-patient mortality in the non-heparin group was 6·2‐fold higher (OR 6·2, 95% CI: 2·6–14.6) compared with the high-heparin group and receiving low-dose heparin increased the risk for in-patient mortality 2·0-fold (OR 2·0, 95% CI: 1·1–3.6) compared with the high-dose group. The age, underlying disease, LDH levels and the - disseminated intravascular coagulation of International Society of Thrombosis and Hemostasis (DIC-ISTH) score on admission were also independently associated with inpatient mortality rate. Concerning safety, 24 patients (3·4%) experienced major hemorrhage (fatal in 1) and 14 of them were receiving high-dose heparin. By contrast, 18 patients (2·6%) developed an episode of thromboembolism (fatal in 3).  Interpretation: LMWH at the time of admission significantly reduced the mortality in unselected adults inpatient COVID-19 and the magnitude of the benefit was greater for the high-dose heparin subgroup. As the major bleeding rate was also higher in this group, the risk/benefit should be individualized.  Funding Statement:  None Declaration of Interests: The authors declare no competing interests. Ethics Approval Statement: This study was conducted according to the Declaration of Helsinki and approved by the Ethics Committee of University Hospital of Salamanca (Code: CEIm PI2020-04-472).