Inclusion Criteria:  Age >18 years old positive reverse transcription-polymerase chain reaction (rRT-PCR) test for the qualitative detection of nucleic acid from SARS-CoV-2 in upper and lower respiratory specimens. Intensive care unit (ICU) patient or Step-down unit (SDU) patient on invasive mechanical ventilation, BiPAP, 100% non-rebreather mask, or high flow oxygen or supplemental oxygen of at least 4 liters per minute nasal cannula. peak d-dimer levels exceeding 1,000 mcg/mL at any time during admission.  Exclusion Criteria:  Hospital length of stay less than 5 days. Hemorrhage before ICU/SDU admission. Treatment with an anticoagulant other than low molecular weight heparin or unfractionated heparin. Constant treatment with the same dose of anticoagulant for less than 5 days.