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


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.


CONCLUSIONS
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.
Bauer
Seth R
SR
Department of Pharmacy/JJN1-02, Cleveland Clinic, Cleveland, OH 44195, USA. bauers@ccf.org
Ou
Narith N
NN
Dreesman
Benjamin J
BJ
Armon
Jeffrey J
JJ
Anderson
Jan A
JA
Cha
Stephen S
SS
Oyen
Lance J
LJ
D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects; D015992:Body Mass Index; D054796:Drug Dosage Calculations; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced / Q000517:prevention & control*; D006493:Heparin / Q000008:administration & dosage* / Q000009:adverse effects; D006801:Humans; D007262:Infusions, Intravenous; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D049451:Nomograms; D009765:Obesity; D010314:Partial Thromboplastin Time; D012189:Retrospective Studies
D000925:Anticoagulants; D006493:Heparin