What is the critical therapeutic level of heparin in patients with pulmonary embolism (PE)?

Updated: Sep 18, 2020
  • Author: Daniel R Ouellette, MD, FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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The critical therapeutic level of heparin is 1.5 times the baseline control value or the upper limit of normal range of the activated partial thromboplastin time (aPTT).

This level of anticoagulation is expected to correspond to a heparin blood level of 0.2-0.4 U/mL by the protamine sulfate titration assay and 0.3-0.6 by the anti-factor X assay.

Each laboratory should establish the minimal therapeutic level for heparin, as measured by the aPTT, to coincide with a heparin blood level of at least 0.2 U/mL for each batch of thromboplastin reagent being used.

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