Please select the eligibility criteria that correspond to the clinical trial below.
Title: Laparoscopic Bariatric Surgery: Two Regimens of Venous Thromboprophylaxis: Prospective Randomized Study
Brief Summary: Obese patients undergoing bariatric surgery warrant VTE prophylaxis because they are at high risk for developing a fatal pulmonary embolism or postthrombotic syndrome. However, a consensus does not exist on the most effective prophylactic approach.


Options:
A: Inclusion Criteria (all required):

* Positive SARS-CoV-2 diagnostic (on pharyngeal swab of deep airways material)
* Severe pneumonia defined by the presence of at least one of the following criteria:

  1. Respiratory Rate ≥25 breaths /min
  2. Arterial oxygen saturation≤93% at rest on ambient air
  3. PaO2/FiO2 ≤300 mmHg
* Coagulopathy, defined by the presence of at least one of the following criteria:

  1. D-dimer \>4 times the upper level of normal reference range
  2. Sepsis-Induced Coagulopathy (SIC) score \>4
* No need for invasive mechanical ventilation

Exclusion Criteria:

* Invasive mechanical ventilation
* Thrombocytopenia (platelet count \< 80.000 mm3)
* Coagulopathy: INR \>1.5, aPTT ratio \> 1.4
* Impaired renal function (eGFR calculated by CKD-EPI Creatinine equation \< 30 ml/min)
* Known hypersensitivity to enoxaparin
* History of heparin induced thrombocytopenia
* Presence of an active bleeding or a pathology susceptible of bleeding in presence of anticoagulation (e.g. recent haemorrhagic stroke, peptic ulcer, malignant cancer at high risk of haemorrhage, recent neurosurgery or ophthalmic surgery, vascular aneurysms, arteriovenous malformations)
* Concomitant anticoagulant treatment for other indications (e.g. atrial fibrillation, venous thromboembolism, prosthetic heart valves).
* Concomitant double antiplatelet therapy
* Administration of therapeutic doses of LMWH, fondaparinux, or unfractionated heparin (UFH) for more than 72 hours before randomization; prophylactic doses are allowed
* Pregnancy or breastfeeding or positive pregnancy test
* Presence of other severe diseases impairing life expectancy (e.g. patients are not expected to survive 28 days given their pre-existing medical condition)
* Lack or withdrawal of informed consent
B: Inclusion Criteria:

* BMI \>40 OR \>35 with comorbidities

Exclusion Criteria:

* No
C: Inclusion Criteria:

* Patients with confirmed diagnosis of COVID-19 admitted to hospital;
* Duration of symptoms related to hospitalization ≤ 14 days;
* Patients ≥ 18 year old;
* D-dimer above the upper limit of normal (collected until 72 hours before the randomization);
* Agreement to participate by providing the informed consent form (ICF).

Exclusion Criteria:

* Patients with indication for full anticoagulation during inclusion (for example, diagnosis of venous thromboembolism, atrial fibrillation, mechanical valve prosthesis);
* Platelets \< 50,000 /mm3
* Need for ASA therapy \> 100 mg;
* Need for P2Y12 inhibitor therapy (clopidogrel, ticagrelor or prasugrel);
* Chronic use of non-hormonal anti-inflammatory drugs;
* Sustained uncontrolled systolic blood pressure (BP) of ≥180 mmHg or diastolic BP of ≥100 mmHg;
* INR \> 1,5;
* Patients contraindicated to full anticoagulation (active bleeding, liver failure, blood dyscrasia or prohibitive hemorrhage risk as evaluated by the investigator);
* Criteria for disseminated intravascular coagulation (DIC);
* A history of hemorrhagic stroke or any intracranial bleeding at any time in the past or current intracranial neoplasm (benign or malignant), cerebral metastases, arteriovenous (AV) malformation, or aneurysm;
* Active cancer (excluding non-melanoma skin cancer) defined as cancer not in remission or requiring active chemotherapy or adjunctive therapies such as immunotherapy or radiotherapy;
* Hypersensitivity to rivaroxaban;
* Use of strong inhibitors of cytochrome P450 (CYP) 3A4 and/or P-glycoprotein (P-gp) (e.g. protease inhibitors, ketoconazole, Itraconazole) and/or use of P-gp and strong CYP3A4 inducers (such as but not limited to rifampin/rifampicin, rifabutin, rifapentine, phenytoin, phenobarbital, carbamazepine, or St. John's Wort);
* Known HIV infection;
* Creatinine clearance \< 30 ml/min according to the Cockcroft-Gault Formula;
* Pregnancy or breastfeeding.
D: Inclusion Criteria:

* Coronavirus Disease 2019 (COVID-19) positive diagnosis by locally obtained viral diagnostic test (example, polymerase chain reaction \[PCR\]). This may be nasal swab or saliva test or other available technology to demonstrate current infection
* Confirm that participant is known to health system, with at least 1 contact in electronic medical records (EMR) prior to screening
* Symptoms attributable to COVID-19 (example, fever, cough, loss of taste or smell, muscle aches, shortness of breath, fatigue)
* Initial treatment plan does not include hospitalization
* Presence of at least 1 additional risk factor: a) age more than or equal to (\>=) 60 years; b) prior history of VTE; c) history of thrombophilia; d) history of coronary artery disease (CAD); e) history of peripheral artery disease (PAD); f) history of cerebrovascular disease or ischemic stroke; g) history of cancer (other than basal cell carcinoma) h) history of diabetes requiring medication; i) history of heart failure; j) body mass index (BMI) greater than or equal to (\>=) 35 kilogram per meter square (kg/m\^2); k) D-dimer greater than (\>) upper limit of normal for local laboratory (within 2 weeks of the date of the COVID-19 test and prior to randomization)

Exclusion Criteria:

* Increased risk of bleeding such as a) significant bleeding in the last 3 months; b) active gastroduodenal ulcer in the last 3 months; c) history of bronchiectasis or pulmonary cavitation; d) need for dual antiplatelet therapy or anticoagulation; e) prior intracranial hemorrhage, f) known severe thrombocytopenia g) active cancer and undergoing treatment
* Any illness or condition that in the opinion of the investigator would significantly increase the risk of bleeding (example recent trauma, recent surgery, severe uncontrolled hypertension, gastrointestinal cancer, renal failure requiring dialysis, severe liver disease, known bleeding diathesis)
* Known allergies, hypersensitivity, or intolerance to rivaroxaban or its excipients
* Positive COVID-19 antibody or serology test after 2-week period of acute, symptomatic COVID-19 infection
* Known diagnosis of triple positive (positive for lupus anticoagulant, anticardiolipin, and anti-beta 2-glycoprotein I antibodies) antiphospholipid syndrome

Answer: B