title: The EFFORT trial: Preoperative enoxaparin versus postoperative fondaparinux for thromboprophylaxis in bariatric surgical patients: a randomized double-blind pilot trial.
abstract: BACKGROUND
  Prophylaxis for venous thromboembolism is routinely performed for all patients undergoing bariatric surgery. However, there is disagreement regarding the optimal dosing and duration of anticoagulant therapy. Furthermore, there is little data regarding the incidence of asymptomatic deep venous thrombosis (DVT) in this population. Our objective was to conduct a pilot randomized double blind study to evaluate the pharmacodynamic parameters of 2 different anticoagulation medications (enoxaparin and fondaparinux) administered to patients undergoing bariatric surgery.
  
  
  METHODS
  From July 2010 to August 2013, 198 consecutive bariatric surgery patients from an academic institution were randomized in a double blinded manner to receive either 40 mg enoxaparin twice daily or 5mg fondaparinux sodium once daily. Antifactor Xa activity was measured on all patients in both study arms, 3 hours after the first dose (on the day of the operation), immediately before the second dose (postoperative day one), and 3 hours after the second dose. At the routine 2 week postoperative visit, patients underwent magnetic resonance venography (MRV) to detect DVT. The primary outcome was attainment of therapeutic antifactor Xa levels. The secondary outcome was DVT, as detected by MRV. Safety outcomes were perioperative bleeding, perioperative complications, and death.
  
  
  RESULTS
  Of 198 patients randomized, 177 underwent MRV and 137 had interpretable antifactor Xa levels. Nearly half of the patients (47.4%) did not attain target prophylactic antifactor Xa levels. Adequate antifactor Xa levels were more common with fondaparinux (74.2%) than with enoxaparin (32.4%). Antifactor Xa levels were also associated with preoperative D-dimer level. 4 of the 175 patients who underwent MRV developed DVT, 2 in each arm of the study. No major adverse events occurred in either arm.
  
  
  CONCLUSIONS
  Fondaparinux was much more likely to produce target prophylactic antifactor Xa levels than enoxaparin. Both regimens appear to be equally effective at reducing the risk of DVT. Further prospective studies are needed to determine the optimal DVT prophylaxis regimen in the bariatric surgical population.
authors.affiliation: Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland. Electronic address: ksteele3@jhmi.edu.
authors.forename: Kimberley E
authors.initials: KE
authors.lastname: Steele
authors.affiliation: Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Joseph
authors.initials: J
authors.lastname: Canner
authors.affiliation: Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Gregory
authors.initials: G
authors.lastname: Prokopowicz
authors.affiliation: Department of Radiology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Franco
authors.initials: F
authors.lastname: Verde
authors.affiliation: Research Pharmacy, The Johns Hopkins Bayview Medical Center, Baltimore, Maryland.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Beselman
authors.affiliation: Department of International Health, The Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland.
authors.forename: Ransom
authors.initials: R
authors.lastname: Wyse
authors.affiliation: Department of Pathology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Junnan
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Hematology, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Michael
authors.initials: M
authors.lastname: Streiff
authors.affiliation: Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Magnuson
authors.affiliation: Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Anne
authors.initials: A
authors.lastname: Lidor
authors.affiliation: Department of Surgery, The Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Michael
authors.initials: M
authors.lastname: Schweitzer
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage; D050110:Bariatric Surgery / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D017984:Enoxaparin / Q000008:administration & dosage*; D005260:Female; D005500:Follow-Up Studies; D000077425:Fondaparinux; D006801:Humans; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000601:surgery*; D010865:Pilot Projects; D011134:Polysaccharides / Q000008:administration & dosage*; D011182:Postoperative Care / Q000379:methods*; D011183:Postoperative Complications; D011300:Preoperative Care / Q000379:methods*; D011446:Prospective Studies; D016896:Treatment Outcome; D054556:Venous Thromboembolism / Q000209:etiology / Q000517:prevention & control*; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D011134:Polysaccharides; D000077425:Fondaparinux
keywords: Anticoagulation; Bariatric surgery; Clinical trial; Prophylaxis; Venous thromboembolism