1. expected survival for less than 48 hours after randomization 2. child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis 3. stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis 4. requirement for extra-corporeal membrane oxygenation (ecmo) 5. acute myocardial infarction (ami) 6. active bleeding requiring transfusion 7. concurrent participation in another clinical trial of experimental treatment for sarscov-2 8. female patients who are pregnant or breastfeeding 9. requirement for concurrent treatment with nitrates

1. expected survival for less than 48 hours after randomization 2. child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis 3. stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis 4. requirement for extra-corporeal membrane oxygenation (ecmo) 5. acute myocardial infarction (ami) 6. active bleeding requiring transfusion 7. concurrent participation in another clinical trial of experimental treatment for sarscov-2 8. female patients who are pregnant or breastfeeding 9. requirement for concurrent treatment with nitrates

expected survival for less than 48 hours after randomization child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis requirement for extra-corporeal membrane oxygenation (ecmo) acute myocardial infarction (ami) active bleeding requiring transfusion concurrent participation in another clinical trial of experimental treatment for sarscov-2 female patients who are pregnant or breastfeeding requirement for concurrent treatment with nitrates

expected survival for less than 48 hours after randomization child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis requirement for extra-corporeal membrane oxygenation (ecmo) acute myocardial infarction (ami) active bleeding requiring transfusion concurrent participation in another clinical trial of experimental treatment for sarscov-2 female patients who are pregnant or breastfeeding requirement for concurrent treatment with nitrates

1. expected survival for less than 48 hours after randomization 2. child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis 3. stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis 4. requirement for extra-corporeal membrane oxygenation (ecmo) 5. acute myocardial infarction (ami) 6. active bleeding requiring transfusion 7. concurrent participation in another clinical trial of experimental treatment for sarscov-2 8. female patients who are pregnant or breastfeeding 9. requirement for concurrent treatment with nitrates

1. expected survival for less than 48 hours after randomization 2. child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis 3. stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis 4. requirement for extra-corporeal membrane oxygenation (ecmo) 5. acute myocardial infarction (ami) 6. active bleeding requiring transfusion 7. concurrent participation in another clinical trial of experimental treatment for sarscov-2 8. female patients who are pregnant or breastfeeding 9. requirement for concurrent treatment with nitrates

expected survival for less than 48 hours after randomization child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis requirement for extra-corporeal membrane oxygenation (ecmo) acute myocardial infarction (ami) active bleeding requiring transfusion concurrent participation in another clinical trial of experimental treatment for sarscov-2 female patients who are pregnant or breastfeeding requirement for concurrent treatment with nitrates

expected survival for less than 48 hours after randomization child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis requirement for extra-corporeal membrane oxygenation (ecmo) acute myocardial infarction (ami) active bleeding requiring transfusion concurrent participation in another clinical trial of experimental treatment for sarscov-2 female patients who are pregnant or breastfeeding requirement for concurrent treatment with nitrates

1. expected survival for less than 48 hours after randomization 2. child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis 3. stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis 4. requirement for extra-corporeal membrane oxygenation (ecmo) 5. acute myocardial infarction (ami) 6. active bleeding requiring transfusion 7. concurrent participation in another clinical trial of experimental treatment for sarscov-2 8. female patients who are pregnant or breastfeeding 9. requirement for concurrent treatment with nitrates

1. expected survival for less than 48 hours after randomization 2. child-pugh stage c hepatic impairment and/or portal hypertension secondary to cirrhosis 3. stage iv chronic kidney disease or end-stage kidney disease on maintenance hemodialysis 4. requirement for extra-corporeal membrane oxygenation (ecmo) 5. acute myocardial infarction (ami) 6. active bleeding requiring transfusion 7. concurrent participation in another clinical trial of experimental treatment for sarscov-2 8. female patients who are pregnant or breastfeeding 9. requirement for concurrent treatment with nitrates