Thrombosis Interest Group of Canada

Practical Treatment Guidelines

Treatment of Venous Thromboembolism with Low-Molecular-Weight Heparin
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Background

Full dose subcutaneous low molecular weight heparin has been shown to be at
least as effective and safe as intravenous (IV) heparin in the initial
treatment of proximal venous thrombosis in both in-patients and out-patients.
Ongoing studies indicate that LMWH is effective and safe in the initial
management of acute pulmonary embolism (PE). Cost effectiveness analyses
indicate that LMWH is more cost effective than IV heparin in the treatment of
deep vein thrombosis (DVT) especially in the out-patient setting.

Indications

Subcutaneous LMWH is an alternative to the use of IV heparin in the initial
treatment of DVT and in selected patients with acute PE. The use of LMWH has
made the out-patient treatment of DVT possible.

Dosage and Administration

Low-molecular-weight heparins can be given by weight via once or twice daily
subcutaneous injection utilizing a weight adjusted protocol and do not require
routine anticoagulant monitoring. (Please see individual product monographs
for dosing information.) Other low-molecular-weight heparins are likely to be
approved in the near future. In most patients warfarin therapy should be
commenced simultaneously. LMWH is continued for at least five days and until
the INR is therapeutic for two consecutive days. Home therapy with LMWH must
only be considered with appropriate infrastructure in place.

Precautions

As with all forms of heparin, the most frequent side effect is bleeding.
Intramuscular injections should be avoided. The use of ASA should be avoided
and other non-steroidal anti-inflammatory drugs should be used with caution.

The risk of thrombocytopenia is lower with LMWH than with standard
(unfractionated) heparin. Platelet counts should be monitored as recommended
in the individual product monograph. Prior exposure to unfractionated heparin
increases the risk of thrombocytopenia.

Contraindications

The contraindications for the use of LMWH are similar to those of
unfractionated heparin, i.e. recent cerebral or subarachnoid hemorrhage;
serious active bleeding; recent surgery of the brain, spinal cord or eye;
malignant hypertension, renal failure or a history of heparin induced
thrombocytopenia.

Low-Molecular-Weight Heparin Therapy in Children

The treatment of confirmed deep venous thrombosis (DVT) or pulmonary embolism
(PE) with low molecular weight heparin (LMWH) may be warranted in certain
groups of children as an alternative to intravenous (IV) heparin in initial
therapy as well as an alternate to secondary prophylaxis with Coumadin. The
following groups of children may be considered for LMWH:

1.High risk of bleeding

2.Lack of venous access

3.Difficulty monitoring anticoagulant therapy.

For children, as opposed to adults, it is suggested to monitor LMWH levels
using an anti-Xa factor level. In this situation it is highly advisable to
seek expert advice in the management of these patients.

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References


1.Hirsh J, Levine MN. LMWH. Blood 1992; 79:1-17.

2.Barrowcliffe TN. LMWH(s). Brit. J. Haematol. 1995;90:1-17.

3.Hull RD, Raskob GE, Pineo GF, et al. Subcutaneous LMWH compared with
continuous  intravenous heparin in the treatment of proximal-vein thrombosis.
N Engl J Med  1992;326:975-982.

4.Levine MN, Hirsh J, Gent M, et al. A comparison of LMWH administered
primarily at  home with unfractionated heparin administered in the hospital
for proximal deep-vein  thrombosis. N Engl J Med 1996;334:677-681.

5.Koopman MMW, Prandoni P, Piovella F, et al. Treatment of venous thrombosis
with intravenous unfractionated heparin administered in the hospital as
compared with  subcutaneous LMWH administered at home. N Engl J Med
1996;334:682-689.

6.Massicotte MP, Adams M, Marzinotto V, Brooker L and Andrew M. Low molecular
weight heparin in pediatric patients with thrombotic disease: A dose finding
study. J Peds  128:313, 1996.

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 Publication Fall 1997