Please select the eligibility criteria that correspond to the clinical trial below.
Title: Optimal Prophylactic Method of Venous Thromboembolism for Gastrectomy in Korean Patients
Brief Summary: This study is to define the optimal method of prophylaxis for patients with gastrectomy in Korea and the investigators hypothesized only mechanical method would be enough for preventing VTE on perioperative period.


Options:
A: 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.
B: Inclusion Criteria:

* Age ≥18 years
* Admitted to the intensive care unit
* Positive COVID-19 PCR
* Mechanical Ventilation for ≤ 48 hours
* PaO2/FiO2 ≤300

Exclusion Criteria:

* Heparin allergy
* Active bleeding
* Death or withdraw of care anticipated by intensivist within 24 hours
* Platelets\< 50,000 cells/µL
* Clinically significant coagulopathy, as decided by the intensivist
* O2 dependent at baseline
C: Inclusion Criteria:

1. Age ≥18 years (male or female)
2. Acute infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV2)
3. Currently admitted to an intensive care unit (ICU)

Key Exclusion Criteria:

1. Ongoing (\>48 hours) or planned full-dose (therapeutic) anticoagulation for any indication
2. Ongoing or planned treatment with dual antiplatelet therapy
3. Contraindication to antithrombotic therapy or high risk of bleeding due to conditions including, but not limited to, any of the following:

   1. History of intracranial hemorrhage, known central nervous system (CNS) tumor or CNS vascular abnormality
   2. Active or recent major bleeding within the past 30 days with untreated source
   3. Platelet count \<70,000 or known functional platelet disorder
   4. Fibrinogen \<200 mg/dL
   5. International normalized ratio (INR) \>1.9
4. History of heparin-induced thrombocytopenia
5. Ischemic stroke within the past 2 weeks

Patients who meet the following criterion are excluded from the second randomization (antiplatelet therapy vs. no antiplatelet therapy):

1. Ongoing or planned antiplatelet therapy, including aspirin monotherapy
D: Inclusion Criteria:

* Patients diagnosed as gastric cancer
* Elective and curative under general anesthesia
* ECOG score 0-2
* ASA score 3 or less than 3
* Informed consents

Exclusion Criteria:

* 2nd primary cancer
* VTE history within one year
* Anticoagulation history
* Allergic to heparin
* Pregnancy or expected pregnancy

Answer: D