title: Fixed-dose enoxaparin after bariatric surgery: the influence of body weight on peak anti-Xa levels.
abstract: BACKGROUND
  There is lack of data on the pharmacodynamics of low-molecular-weight heparins in obese patients.
  
  
  BACKGROUND
  The aims of this study are to investigate the correlation between anti-factor Xa (anti-Xa) levels and body weight with fixed-dose enoxaparin after bariatric surgery and to investigate the percentage of patients that reach the desired prophylactic range for anti-Xa levels.
  
  
  METHODS
  Blood for anti-Xa peak levels measurement was drawn 3-5 h after administration of enoxaparin at the planned visit 8-16 days after surgery. Patients were included in three categories: <110 kg (group 1), 110-150 kg (group 2), and >150 kg (group 3).
  
  
  RESULTS
  Fifty-one patients were included (43.9 ± 9.9 years, 75% women). Mean anti-Xa level was 0.37 ± 0.14 IU/ml. This level was the highest in group 1 (0.47 ± 0.13 IU/ml) and lowest in group 3 (0.23 ± 0.07). No subprophylactic (<0.2 IU/ml) anti-Xa levels were detected in group 1, whereas this was observed in 38% in patients in group 3. Supraprophylactic levels (>0.5 IU/ml) were most often present in group 1 (36%). With multivariable regression analysis, body weight (β -0.720 (95 % confidence interval -.717; -.993), p < 0.001) was an independent predictor of anti-Xa levels, whereas lean body was not independently associated. This was confirmed in a non-linear mixed effects analysis of the data.
  
  
  CONCLUSIONS
  Patients with excessive body weight may not be adequately treated with fixed-dose enoxaparin thromboprophylaxis while patients with lower body weight may have an increased bleeding risk. Body weight is a better predictor of anti-Xa levels compared to lean body weight.
authors.affiliation: Department of Internal Medicine, 9B, Slotervaart Hospital, Louwesweg 6, 1066 EC, Amsterdam, The Netherlands, fundacelik170@hotmail.com.
authors.forename: Funda
authors.initials: F
authors.lastname: Celik
authors.forename: Alwin D R
authors.initials: AD
authors.lastname: Huitema
authors.forename: Jan H
authors.initials: JH
authors.lastname: Hooijberg
authors.forename: Arnold W J M
authors.initials: AW
authors.lastname: van de Laar
authors.forename: Dees P M
authors.initials: DP
authors.lastname: Brandjes
authors.forename: Victor E A
authors.initials: VE
authors.lastname: Gerdes
mesh_terms: D000328:Adult; D000925:Anticoagulants / Q000008:administration & dosage*; D050110:Bariatric Surgery / Q000009:adverse effects; D001835:Body Weight / Q000502:physiology*; D004305:Dose-Response Relationship, Drug; D017984:Enoxaparin / Q000008:administration & dosage*; D065427:Factor Xa Inhibitors / Q000097:blood*; D005260:Female; D006495:Heparin, Low-Molecular-Weight / Q000627:therapeutic use; D006801:Humans; D007279:Injections, Subcutaneous; D008297:Male; D008875:Middle Aged; D009767:Obesity, Morbid / Q000097:blood / Q000601:surgery*; D011183:Postoperative Complications / Q000097:blood / Q000517:prevention & control; D054556:Venous Thromboembolism / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D065427:Factor Xa Inhibitors; D006495:Heparin, Low-Molecular-Weight