Low Molecular Weight Heparins

[La Quokka]

Why do you not need to do coagulation studies when giving low molecular weight heparin SQ for DVT prophylaxis?

[I M 2 BZ 2 P]

Low-molecular-weight heparin is a relatively recent addition to the list of therapies for prophylaxis and treatment of deep venous thrombosis (DVT). As a prophylactic, low-molecular-weight heparin is as effective as standard heparin or warfarin and does not require monitoring of the activated partial thromboplastin time or the International Normalized Ratio. Traditionally, treatment for DVT required patients to be hospitalized for administration of intravenous heparin. With subcutaneous injections of low-molecular-weight heparin, treatment of DVT can be initiated or completed in the outpatient setting with no increased risk of recurrent thromboembolism or bleeding complications. Low-molecular-weight heparin is an attractive option for use in patients with a first episode of DVT, no risk factors for bleeding and the ability to administer injections with or without the help of a visiting nurse or family member.

Monitoring LMWH

• Sample NOT to be taken from a line contaminated with standard heparin. Must be a venous sample placed in a coagulation tube. Do not overfill tube.

• The APTT is irrelevant in LMWH monitoring.

• LMWH can accumulate in the body over time, especially in patients with renal disease, so periodical testing is essential.

• A platelet count should be obtained weekly for the first month. If there is an abrupt decrease in the platelet count (approx. 50%) consideration must be given to the possibility of Heparin Induced Thrombocytopaenia (HIT). Consult Haematology if concerned.

• Avoid the use of aspirin (as this can potentiate the anticoagulant effects of LMWH) unless clearly directed by the primary physician to take the 2 drugs concurrently

• Avoid IM injections and arterial punctures if possible during treatment with LMWH.