Inclusion Criteria:

1. Patients over 18 years who have given their informed consent to participate in the study.
2. Patients receiving oral anticogulants during at least 3 months and who require outpatient surgery, laparoscopy surgery or invasive procedures
3. Procedures must be performed from 8 am to 15 pm.

Exclusion Criteria:

1. Patients with severe renal failure (creatinine clearance <30 ml/min) or hepatic insufficiency (AST and/or ALT>5 times the normal value established by the reference range of the local hospital laboratory).
2. Patients who have shown thromboembolic events with an appropriate INR.
3. Known hypersensitivity to LMWH, heparin or substances of porcine origin.
4. Patients with organic lesions susceptible to bleeding (e.g. active peptic ulcer, stroke, aneurysms).
5. Patients with a history of heparin-induced thrombocytopenia.
6. Patients with suspected inability/or inability to comply with treatment and/or complete the study.
7. Patients who are participating in another clinical trial or have been participated in the past 30 days.
8. Patients with antithrombin deficit and C and S protein deficit
9. Women who are pregnant or breast-feeding, or with the possibility of becoming pregnant during the study.
10. Acute bacterial endocarditis or slow endocarditis.
11. Severe arterial hypertension (systolic blood pressure over 200 mmHg and/or diastolic blood pressure over 120 mmHg).
12. Patients with antiplatelet therapy
13. Patients with mechanical cardiac valves in mitral position and body weight  90 Kg with/or bone mass index (BMI) > 30 or  50 kg
14. Patients with Starr-Edwards valves.