Effect of body mass index on bleeding frequency and activated partial thromboplastin time in weight-based dosing of unfractionated heparin: a retrospective cohort study

Mayo Clin Proc. 2009 Dec;84(12):1073-8. doi: 10.4065/mcp.2009.0220.


Objective: To assess bleeding and activated partial thromboplastin time (APTT) in relation to body mass index (BMI) in patients prescribed weight-based dosing of intravenous unfractionated heparin (UFH) for cardiac indications without a maximum (dose-capped) initial bolus or capped initial infusion rate.

Patients and methods: Consecutive patients admitted to an academic medical center from February 1, 2002, through November 31, 2003, who were treated with a UFH nomogram consisting of a 60-U/kg intravenous bolus plus an initial continuous intravenous infusion of 12 U/kg hourly and titrated to a goal APTT range corresponding to thromboplastin-adjusted target heparin levels of 0.3 to 0.7 U/mL by anti-Xa assay were evaluated for this retrospective cohort study. Patients were excluded if they concomitantly received a fibrinolytic, glycoprotein IIb/IIIa inhibitor, or any other antithrombotic agent (except warfarin). Study patients were divided into quartiles by BMI.

Results: Of the 1054 patients included in the study, 807 (76.6%) had an initial bolus dose higher than 4000 U, and 477 (45.3%) had an initial infusion rate higher than 1000 U/h. Despite a significant difference among BMI quartiles in proportion of supratherapeutic first APTT values (P<.001), no statistically significant difference was found in bleeding frequency (P=.26) or frequency of first APTT within the goal range (P=.27). Logistic regression analyses revealed that BMI was not a significant predictor of bleeding or first APTT within the goal range.

Conclusion: We did not find any difference in the proportion of first APTT values in the goal range or an increased risk of bleeding in obese patients treated with UFH without a capped initial dose. Our data demonstrate the safe use of weight-based UFH without a capped initial bolus dose or capped initial infusion rate in patients with medical cardiac conditions.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Aged
  • Anticoagulants / administration & dosage*
  • Anticoagulants / adverse effects
  • Body Mass Index
  • Drug Dosage Calculations*
  • Female
  • Hemorrhage / chemically induced
  • Hemorrhage / prevention & control*
  • Heparin / administration & dosage*
  • Heparin / adverse effects
  • Humans
  • Infusions, Intravenous
  • Logistic Models
  • Male
  • Middle Aged
  • Multivariate Analysis
  • Nomograms
  • Obesity*
  • Partial Thromboplastin Time
  • Retrospective Studies


  • Anticoagulants
  • Heparin