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Enoxaparin, effective dosage for intensive care patients: double-blinded, randomised clinical trial

Sian Robinson1*, Aleksander Zincuk1, Thomas Strøm1, Torben B Larsen2, Bjarne Rasmussen2 and Palle Toft1

Author Affiliations

1 Department of Anaesthesia and Intensive Care, Odense University Hospital (OUH), Sdr. Boulevard 29. Odense C, DK 5000, Denmark

2 Department of Biochemistry, Pharmacology & Genetics and Centre for Thrombosis and Haemostasis, OUH, Sdr. Boulevard 29. Odense C, DK 5000, Denmark

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Critical Care 2010, 14:R41 doi:10.1186/cc8924

Published: 18 March 2010

Abstract

Introduction

Intensive care unit (ICU) patients are predisposed to thromboembolism. Routine prophylactic anticoagulation is widely recommended. Low-molecular-weight heparins, such as enoxaparin, are increasingly used because of predictable pharmacokinetics. This study aims to determine the subcutaneous (SC) dose of enoxaparin that would give the best anti-factor Xa levels in ICU patients.

Methods

The 72 patients admitted to a mixed ICU at Odense University Hospital (OUH) in Denmark were randomised into four groups to receive 40, 50, 60, or 70 mg SC enoxaparin for a period of 24 hours. Anti-factor Xa activity (aFXa) was measured before, and at 4, 12, and 24 hours after administration. An AFXa level between 0.1 to 0.3 IU/ml was considered evidence of effective antithrombotic activity.

Results

Median peak (4 hours after administration), aFXa levels increased significantly with an increase in enoxaparin dose, from 0.13 IU/ml at 40 mg, to 0.14 IU/ml at 50 mg, 0.27 IU/ml at 60 mg, and 0.29 IU/ml at 70 mg (P = 0.002). At 12 hours after administration, median aFXa levels were still within therapeutic range for those patients who received 60 mg (P = 0.02).

Conclusions

Our study confirmed that a standard dose of 40 mg enoxaparin yielded subtherapeutic levels of aFXa in critically ill patients. Higher doses resulted in better peak aFXa levels, with a ceiling effect observed at 60 mg. The present study seems to suggest inadequate dosage as one of the possible mechanisms for the higher failure rate of enoxaparin in ICU patients.

Trial Registration

ISRCTN03037804