Previous failures of anticoagulants in critical illness notwithstanding, compelling observations of coagulopathy and high rates of VTE in COVID-19 raise the possibility that heparin may benefit patient outcomes. The utility of heparin as an anticoagulant in COVID-19 was first posited by a retrospective report of 449 patients with COVID-19 from Wuhan, China, where prophylaxis in medical patients is relatively uncommon due to a low incidence of VTE (48). In this cohort, 350 patients received no heparin therapy (neither low-dose prophylactic nor high-dose therapeutic), whereas 99 had received low-dose prophylactic doses of heparin. Patients with an elevated D-dimer (>6-fold higher than the upper limit of normal) or elevated sepsis-induced coagulopathy scores that received prophylactic heparin had ~20% lower mortality than patients who had not (38). It has also been reported that intravenous tissue plasminogen activator, a potent thrombolytic, can transiently improve oxygenation in COVID-19-related acute respiratory distress syndrome, supporting clinical relevance of thrombosis in severe disease (41).