icu admission criteria. need for invasive or not invasive mechanical ventilation pregnancy. creatine clearance <30 ml / min (cockroft-gault). severe liver or pancreatic function disorder. acute bacterial endocarditis and slow endocarditis. patient previously anticoagulated (although it is allowed to have received heparin at a previous low dose without time limit). patient with high hemorrhagic risk due to previous medical-surgical history. severe thrombocytopenia (<80,000 platelets/ mm3) or known history of heparin-induced thrombocytopenia. active bleeding or increased risk of bleeding from haemostasis disorders or from organic lesions that are liable to bleed (eg, active peptic ulcer, hemorrhagic stroke, aneurysms, or brain malignancies). damage or surgical interventions in the central nervous system, eyes and ears that have taken place in the last 2 months. simultaneous participation in another clinical trial that could have a conflictive interaction with what it is intended to evaluate. any situation that in the opinion of the researcher could interfere with the treatment or with the evolution of the patient.

icu admission criteria. need for invasive or not invasive mechanical ventilation pregnancy. creatine clearance <30 ml / min (cockroft-gault). severe liver or pancreatic function disorder. acute bacterial endocarditis and slow endocarditis. patient previously anticoagulated (although it is allowed to have received heparin at a previous low dose without time limit). patient with high hemorrhagic risk due to previous medical-surgical history. severe thrombocytopenia (<80,000 platelets/ mm3) or known history of heparin-induced thrombocytopenia. active bleeding or increased risk of bleeding from haemostasis disorders or from organic lesions that are liable to bleed (eg, active peptic ulcer, hemorrhagic stroke, aneurysms, or brain malignancies). damage or surgical interventions in the central nervous system, eyes and ears that have taken place in the last 2 months. simultaneous participation in another clinical trial that could have a conflictive interaction with what it is intended to evaluate. any situation that in the opinion of the researcher could interfere with the treatment or with the evolution of the patient.

1. icu admission criteria. 2. need for invasive or not invasive mechanical ventilation 3. pregnancy. 4. creatine clearance <30 ml / min (cockroft-gault). 5. severe liver or pancreatic function disorder. 6. acute bacterial endocarditis and slow endocarditis. 7. patient previously anticoagulated (although it is allowed to have received heparin at a previous low dose without time limit). 8. patient with high hemorrhagic risk due to previous medical-surgical history. 9. severe thrombocytopenia (<80,000 platelets/ mm3) or known history of heparin-induced thrombocytopenia. 10. active bleeding or increased risk of bleeding from haemostasis disorders or from organic lesions that are liable to bleed (eg, active peptic ulcer, hemorrhagic stroke, aneurysms, or brain malignancies). 11. damage or surgical interventions in the central nervous system, eyes and ears that have taken place in the last 2 months. 12. simultaneous participation in another clinical trial that could have a conflictive interaction with what it is intended to evaluate. 13. any situation that in the opinion of the researcher could interfere with the treatment or with the evolution of the patient.

1. icu admission criteria. 2. need for invasive or not invasive mechanical ventilation 3. pregnancy. 4. creatine clearance <30 ml / min (cockroft-gault). 5. severe liver or pancreatic function disorder. 6. acute bacterial endocarditis and slow endocarditis. 7. patient previously anticoagulated (although it is allowed to have received heparin at a previous low dose without time limit). 8. patient with high hemorrhagic risk due to previous medical-surgical history. 9. severe thrombocytopenia (<80,000 platelets/ mm3) or known history of heparin-induced thrombocytopenia. 10. active bleeding or increased risk of bleeding from haemostasis disorders or from organic lesions that are liable to bleed (eg, active peptic ulcer, hemorrhagic stroke, aneurysms, or brain malignancies). 11. damage or surgical interventions in the central nervous system, eyes and ears that have taken place in the last 2 months. 12. simultaneous participation in another clinical trial that could have a conflictive interaction with what it is intended to evaluate. 13. any situation that in the opinion of the researcher could interfere with the treatment or with the evolution of the patient.