Hemostasis in COVID-19: an Adaptive Clinical Trial

Inclusion Criteria: * Adult ≥18 years of age at time of enrollment * Subjects with a positive COVID-19 diagnosis by RT-PCR or serologic testing * Subject (or legally authorized representative) must be willing, understanding and able to provide written informed consent. * Only at phase 2: * onset of symptoms must not exceed 4 weeks * ICU patients * PaO2 to FiO2 ratio \< 200 Exclusion Criteria: 1. General * Indications for therapeutic anticoagulation * History of chronic lung disease oxygen dependent * Pregnancy * Death considered imminent and inevitable within 24 hours * Patients under exclusive palliative care * Participation in another trial of investigational drug * Body weight \< 40 Kg * Total bilirubin \> 20 mg/dL * Severe active bleeding * Persistent GI bleeding * Known allergy to UFH or LMWH * History of heparin-induced thrombocytopenia (HIT) within the past 6 months 2. Exclusion criteria at phase 1 * Platelet count \< 25,000/mm3 * Bacterial endocarditis 3. Exclusion criteria at phase 2 * Platelet count \< 50,000/mm3 * History of surgery in the last 30 days * Intervention A: allergy to ASA and long-term use of antiplatelet drug * Intervention B: inhaled nitric oxide use