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Critical Care

Open Access

Relationship between peak anti-Xa levels and calculated creatinine clearance in ICU patients receiving low molecular weight heparin

  • E McDonald1, 2,
  • F Landry1, 2,
  • C Rabbat1, 2,
  • C Boudreau1, 2,
  • M Crowther1, 2,
  • M Meade1, 2,
  • W Geerts1, 2 and
  • D Cook1, 2
Critical Care20037(Suppl 2):P112

Published: 3 March 2003


Molecular WeightCreatinineRenal FunctionHeparinEmergency Medicine


To evaluate serial anti-Xa 'peak' levels drawn 2 or 4 hours post LMWH prophylaxis in 13 consecutive ICU patients with a range of renal function.


Multidisciplinary, closed, university-affiliated 15-bed medical–surgical ICU.


We measured anti-Xa blood levels either 2 or 4 hours post dalteparin administration each day until death or discharge. We calculated creatinine clearance daily using the Cockroft-Gault formula. We graphed these peak anti-Xa levels against calculated creatinine clearance values, and examined their relation to bleeding events.


We performed 287 anti-Xa levels on these ICU patients, and found that peak anti-Xa levels were consistently less than 0.5 U/ml. We did not demonstrate a relationship between the timing of the peak anti-Xa levels, and a) the value of the peak anti-Xa levels, b) the patients' calculated creatinine clearance, or c) bleeding events.


Anti-Xa levels drawn 2 or 4 hours post subcutaneous injection of 5000 U dalteparin in this sample of patients were consistently less than 0.5 U/ml, but did not vary significantly with renal function.

Authors’ Affiliations

McMaster University, Hamilton, Canada
University of Toronto, Toronto, Canada


© BioMed Central Ltd 2003