title: The incidence of symptomatic venous thromboembolism during and after prophylaxis with enoxaparin: a multi-institutional cohort study of patients who underwent hip or knee arthroplasty. Canadian Collaborative Group.
abstract: BACKGROUND
  Despite low molecular weight heparin prophylaxis, the incidence of venographically detected, residual deep vein thrombosis after hip and knee arthroplasty remains high, at approximately 15% and 30%, respectively. Most of these thrombi are asymptomatic and of unknown clinical significance. Nevertheless, because they have the potential to grow, limiting prophylaxis to the in-hospital period may provide inadequate protection.
  
  
  METHODS
  We studied a cohort of 1984 consecutive patients who had hip or knee arthroplasty at 1 of 28 participating hospitals. Patients received enoxaparin prophylaxis, 30 mg subcutaneously every 12 hours for up to 14 days, and underwent predischarge compression ultrasonography. Study end points were symptomatic deep vein thrombosis or pulmonary embolism during and after prophylaxis, asymptomatic venous thrombosis detected by predischarge compression ultrasonography, and major hemorrhage. The duration of follow-up was 84 days.
  
  
  RESULTS
  Enoxaparin treatment was started a mean (+/- SD) of 17.9 +/- 10.4 hours after the completion of surgery and was given for a mean of 18.0 +/- 6.9 doses. Eighty-two patients (4.1%; 95% confidence interval, 3.3%-5.0%) developed venous thromboembolism. The rates of thromboembolic events during and after prophylaxis were 2.1% and 2.0%, respectively. Only 3 patients (0.15%) had abnormal predischarge compression ultrasonography. Three patients (0.15%) died of pulmonary embolism. Major hemorrhage occurred in 58 patients (2.9%; 95% confidence interval, 2.2%-3.7%).
  
  
  CONCLUSIONS
  Postoperative prophylaxis with enoxaparin for a mean of 9 days is associated with a clinically acceptable rate of symptomatic venous thromboembolism and major hemorrhage. Predischarge compression ultrasonography cannot be justified.
authors.affiliation: The Montreal General Hospital, McGill University, Quebec. Leclerc_Jacques_R@Lilly.com
authors.forename: J R
authors.initials: JR
authors.lastname: Leclerc
authors.forename: M
authors.initials: M
authors.lastname: Gent
authors.forename: J
authors.initials: J
authors.lastname: Hirsh
authors.forename: W H
authors.initials: WH
authors.lastname: Geerts
authors.forename: J S
authors.initials: JS
authors.lastname: Ginsberg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects*; D002170:Canada; D015331:Cohort Studies; D004334:Drug Administration Schedule; D017984:Enoxaparin / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D011655:Pulmonary Embolism / Q000209:etiology / Q000401:mortality; D013923:Thromboembolism / Q000209:etiology* / Q000517:prevention & control*; D016896:Treatment Outcome
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin