Error in body weight estimation leads to inadequate parenteral anticoagulation

Published:April 05, 2010DOI:


      Parenteral anticoagulation is a cornerstone in the management of venous and arterial thrombosis. Unfractionated heparin has a wide dose/response relationship, requiring frequent and troublesome laboratorial follow-up. Because of all these factors, low–molecular-weight heparin use has been increasing. Inadequate dosage has been pointed out as a potential problem because the use of subjectively estimated weight instead of real measured weight is common practice in the emergency department (ED). To evaluate the impact of inadequate weight estimation on enoxaparin dosage, we investigated the adequacy of anticoagulation of patients in a tertiary ED where subjective weight estimation is common practice. We obtained the estimated, informed, and measured weight of 28 patients in need of parenteral anticoagulation. Basal and steady-state (after the second subcutaneous shot of enoxaparin) anti-Xa activity was obtained as a measure of adequate anticoagulation. The patients were divided into 2 groups according the anticoagulation adequacy. From the 28 patients enrolled, 75% (group 1, n = 21) received at least 0.9 mg/kg per dose BID and 25% (group 2, n = 7) received less than 0.9 mg/kg per dose BID of enoxaparin. Only 4 (14.3%) of all patients had anti-Xa activity less than the inferior limit of the therapeutic range (<0.5 UI/mL), all of them from group 2. In conclusion, when weight estimation was used to determine the enoxaparin dosage, 25% of the patients were inadequately anticoagulated (anti-Xa activity <0.5 UI/mL) during the initial crucial phase of treatment.
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        • Weitz J.I.
        • Crowther M.A.
        New anticoagulants: current status and future potential.
        Am J Cardiovasc Drugs. 2003; 3: 201-209
        • Gomez-Outes A.
        • Lecumberri R.
        • Pozo C.
        • Rocha E.
        New anticoagulants: focus on venous thromboembolism.
        Curr Vasc Pharmacol. 2009; 7: 309-329
        • Liu H.
        • Zhang Z.
        • Linhardt R.J.
        Lessons learned from the contamination of heparin.
        Nat Prod Rep. 2009; 26: 313-321
        • Montalescot G.
        • Collet J.P.
        • Tanguy M.L.
        • Ankri A.
        • Payot L.
        • Dumaine R.
        • et al.
        Anti-Xa activity relates to survival and efficacy in unselected acute coronary syndrome patients treated with enoxaparin.
        Circulation. 2004; 110: 392-398
        • Bloomfield R.
        • Steel E.
        • MacLennan G.
        • Noble D.W.
        Accuracy of weight and height estimation in an intensive care unit: implications for clinical practice and research.
        Crit Care Med. 2006; 34: 2153-2157
        • Machado J.V.E.A.
        • Auxiliadora-Martins M.
        • Campos Antonio D.
        • Basile Filho A.
        Análise comparativa entre os pesos corpóreos estimados e os medidos obtidos de pacientes em estado crítico.
        Rev Bras Ter Intensiva. 2005; 17: 237-244
        • Spinler S.A.
        • Inverso S.M.
        • Cohen M.
        • Goodman S.G.
        • Stringer K.A.
        • Antman E.M.
        • et al.
        Safety and efficacy of unfractionated heparin versus enoxaparin in patients who are obese and patients with severe renal impairment: analysis from the ESSENCE and TIMI 11B studies.
        Am Heart J. 2003; 146 (Ref Type: Journal (Full)): 33-41
      1. Stata statistical software. StataCorp, College Station (Tex)2005 ([computer program]. Version 9.2)
        • Kandrotas R.J.
        Heparin pharmacokinetics and pharmacodynamics.
        Clin Pharmacokinet. 1992; 22: 359-374
        • Frydman A.
        Low–molecular-weight heparins: an overview of their pharmacodynamics, pharmacokinetics and metabolism in humans.
        Haemostasis. 1996; 26: 24-38
        • Bates S.M.
        • Weitz J.I.
        Coagulation assays.
        Circulation. 2005; 112: e53-e60
        • Leary T.S.
        • Milner Q.J.
        • Niblett D.J.
        The accuracy of the estimation of body weight and height in the intensive care unit.
        Eur J Anaesthesiol. 2000; 17: 698-703
        • Coe T.R.
        • Halkes M.
        • Houghton K.
        • Jefferson D.
        The accuracy of visual estimation of weight and height in pre-operative supine patients.
        Anaesthesia. 1999; 54: 582-586
      2. Dose-ranging trial of enoxaparin for unstable angina: results of TIMI 11A. The Thrombolysis in Myocardial Infarction (TIMI) 11A Trial Investigators.
        J Am Coll Cardiol. 1997; 29: 1474-1482
        • Engstrom J.L.
        • Paterson S.A.
        • Doherty A.
        • Trabulsi M.
        • Speer K.L.
        Accuracy of self-reported height and weight in women: an integrative review of the literature.
        J Midwifery Womens Health. 2003; 48: 338-345