title: Comparison of heparin dosing based on actual body weight in non-obese, obese and morbidly obese critically ill patients.
abstract: BACKGROUND
  Obesity is endemic in the United States and obese patients are at increased risk of thromboembolism but little data are available for dosing unfractionated heparin (UFH). We evaluated the relationship between obesity and UFH efficacy during critical illness by examining UFH infusions in non-obese, obese, and morbidly obese critically ill patients.
  
  
  METHODS
  Retrospective review of UFH infusions in non-obese, obese, and morbidly obese critically ill patients. Heparin was initiated without a bolus at 16 units/kg/h or 12 units/kg/h in obese and morbidly obese patients. Demographics, UFH dosage/therapy duration, laboratory values, and bleeding events were reviewed for patients receiving UFH for >24 h. Steady state (SS) was defined as the dosage that resulted in three consecutive activated partial thromboplastin times (aPTT) within target range.
  
  
  RESULTS
  Sixty-two patients were analyzed including 21 non-obese (mean body mass index (BMI) 24.2 ± 2.3); 21 obese (BMI 34.1 ± 3.1); and 20 morbidly obese (mean BMI 55.3 ± 13.7). Patients had otherwise similar demographics. Although 92% had at least one therapeutic aPTT, only 55% of patients reached SS. Six patients developed minor bleeding, but no major hemorrhagic complications. The dosing of heparin based on actual body weight (units/kg/h) and time to first therapeutic aPTT was similar between groups, but dose was statistically higher at steady state in the non-obese (16.3 ± 5.3 non-obese, 11.6 ± 5.5 obese and 11.1 ± 1.2 obese, P = 0.01) with similar times to steady state.
  
  
  CONCLUSIONS
  Dosing of UFH in morbidly obese and obese critically ill patients based on actual body weight and a reduced initial dose was associated with similar time to first therapeutic aPTT and steady state.
authors.affiliation: Department of Pharmacy, Wexner Medical Center at the Ohio State University, USA.
authors.forename: Anthony T
authors.initials: AT
authors.lastname: Gerlach
authors.affiliation: Department of Pharmacy, Wexner Medical Center at the Ohio State University, USA.
authors.forename: Jerilynn
authors.initials: J
authors.lastname: Folino
authors.affiliation: Department of Anesthesiology, Wake Forrest University, USA.
authors.forename: Benjamin N
authors.initials: BN
authors.lastname: Morris
authors.affiliation: Department of Pharmacy, Wexner Medical Center at the Ohio State University, USA.
authors.forename: Claire V
authors.initials: CV
authors.lastname: Murphy
authors.affiliation: Department of Surgery, Wexner Medical Center at the Ohio State University, USA.
authors.forename: Stansilaw P
authors.initials: SP
authors.lastname: Stawicki
authors.affiliation: Department of Surgery, Wexner Medical Center at the Ohio State University, USA.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Cook
keywords: Critically ill; heparin; obesity