Background: The risk of thrombosis and bleeding in hospitalized patients with Coronavirus disease 2019 (COVID-19) is uncertain. Early studies suggested patients with COVID-19 may develop a unique coagulopathy marked by elevated thrombotic risk which has led some institutions to recommend stronger thromboprophylaxis in these patients. Our goal was to quantify the incidence of thrombosis and bleeding in COVID-19 inpatients in a non-surge setting in which patients were managed according to standard inpatient thromboprophylaxis protocols.
Methods: We performed a retrospective chart review study of patients hospitalized with COVID-19 at two academic hospitals between March 2 and July 11, 2020. We determined the incidence of in-hospital venous and arterial thrombosis as well as bleeding events. For each demographic and clinical characteristic, we calculated the standardized mean difference (SMD) between the patients with and without thrombosis. The higher the SMD, the greater the difference between the two groups with the following recommended interpretation of magnitude: small SMD = 0.2; medium SMD = 0.5; and large SMD = 0.8.
Results: Out of 207 patients hospitalized with COVID-19, 11 patients (5.3% [95% CI, 2.7 to 9.3%]) experienced thrombotic events (Table 1). These included 6 patients with venous thromboembolism (VTE) alone, 2 with arterial thrombosis alone, and 3 with both arterial thrombosis and VTE (Table 2). Of the 19 patients who were ever on mechanical ventilation, 5 (26%) experienced a thrombotic event. One patient (0.5% [95% CI, 0.01 to 2.7%]) had major bleeding. The thrombosis event rate in our study was 0.7 per 100 patient-days and the major bleeding event rate was 0.06 bleeding events per 100 patient-days.
Conclusions: The incidence of thrombosis in patients with COVID-19 has varied across published retrospective cohort studies. Our data are consistent with prior studies that have shown a higher incidence of thrombosis in critically-ill compared to non-critically-ill patients, and a higher incidence of thrombosis compared with bleeding. Further investigation is needed to determine the optimal anticoagulation strategy for COVID-19 inpatients, including several ongoing randomized clinical trials.
