Low Molecular Weight Heparins (LMWH) are used for the prophylaxis and treatment of venous thromboembolism.
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The following are guidelines only and may need to be adapted in individual circumstances.
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Administration and maintenance of LMWH
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- weigh patient
- obtain baseline FBE , APPT, INR and fibrinogen
- timing of commencement of therapy (especially post-procedural) should be individualised
- duration of therapy is determined on an individualised basis, based upon indication for treatment.
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 | | | | | | | | 1mg/kg BD or 1.5mg/kg daily
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Monitoring of the anti-Xa level is not required except in the following circumstances:
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- pregnancy (note: once daily administration for therapeutic anticoagulation is not recommended in pregnancy)
- extremes of body weight (<50kg, >100 kg)
- impaired renal function
- prosthetic heart valves: desired anti-xa is higher e.g. 0.8-1.2
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Nomogram for Low Molecular Weight Heparin Therapy
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A therapeutic anti-Xa level for LMWH is 0.5-1.0 IU/mL 4 hours after a dose of LMWH.
A prophylactic anti-Xa level for LMWH is 0.1-0.3 IU/mL 4 hours after a dose of LMWH.
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To locate the correct specimen tube refer to the shared Pathology service (RCH and the Women's) Specimen Collection Handbook: Anti-Xa .
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The APTT is irrelevant in LMWH monitoring.
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The table below outlines dose adjustments required for a given anti-Factor Xa result in patients requiring therapeutic anticoagulation with LMWH.
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| | | | | | | 4 hours post next a.m. dose
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| | | | 4 hours post next a.m. dose
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| | | | According to underlying disorder
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| | | | 4 hours post next a.m. dose
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| | | | Trough level pre next dose, then 4 hours post next a.m.dose.
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| | Until aXa level <0.5 Units/mL
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| | Trough level pre next dose and if not <0.5 Units/mL repeat BD
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The above nomogram assumes there is no bleeding.
Doses may be rounded up or down to the nearest commercially available dose size eg calculated dose 7000IU bd, round up to 7500 bd and recheck anti-Xa level after 2 more doses.
A platelet count should be obtained during initial therapy. 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 concurrent use of NSAIDS (as this can potentiate the anticoagulant effects of LMWH)
Avoid IM injections and arterial punctures if possible during treatment with LMWH.
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Adverse events
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The major adverse event related to treatment with LMWH is bleeding. If a patient on LMWH develops a major bleed, withhold further doses and seek an urgent Haematology consult.
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LMWH antidote
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The antidote for LMWH is Protamine sulphate
Protamine is a medication that requires a high level of caution when being prescribed and administered.
Protamine reverses some, but not all, of the effects of LMWH. The dose of protamine sulphate given is dependent upon the dose of LMWH administered and the time of administration. If protamine is given within 8 hours of the LMWH then a maximum neutralizing dose is 1mg Protamine/100units (or 1mg) of LMWH given in the last dose.
If more than 8 hours have passed since the dose of LMWH was given, administer 0.5mg Protamine per 100 Units (or 1mg) of LMWH given. Protamine is administered by slow IV infusion (over 10 mins) to avoid a hypotensive reaction. The maximum dose of protamine sulfate, regardless of the amount of heparin received is 50mg except for reversal of heparin following cardiopulmonary bypass. Protamine sulfate is usually administered in a concentration of 10mg/mL at a rate not to exceed 5mg/minute. If administered too quickly, protamine sulfate may cause cardiovascular collapse. Patients with known hypersensitivity reactions to fish, and those who have received protamine- containing insulin or previous protamine therapy may be at risk of hypersensitivity reactions to protamine sulfate.
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Special note regarding administration of LMWH around the time of procedures
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As with other anticoagulant medications, consideration must be given to the management of LMWH prior to invasive procedures such as spinal injections, epidural anaesthesia and surgery. In general, regional anaesthesia is contraindicated if the patient has received LMWH within the last 24 hrs (for therapeutic doses) or 12 hours (for prophylactic doses).
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The anti-Xa level and/or APTT is not predictive of the risk of neuraxial bleeding.
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If urgent surgery or delivery is required in a therapeutically anticoagulated patient, management advice should be obtained from the haematologist on call and the obstetric and anaesthetic consultants.
LMWH may be given at prophylactic dose 6 hours following spinal injection or removal of the epidural catheter. Traumatic needle or catheter placement increases the risk of spinal haematoma and LMWH should be deferred for at least 24 hours.
Concurrent use of LMWH and NSAIDS increases the risk of spinal haematoma.
Non-steroidal anti-inflammatories (NSAIDs) eg. Aspirin /voltaren, should NOT be administered to patients receiving LMWH who have an epidural insitu. Removal of epidural catheters should be delayed until 12 hours after an injection of LMWH.
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References
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Refer to: References: Anticoagulants.
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Refer to Women's CPGs:
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Revised and updated: 15 May 2009
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Royal Women's Hospital Clinical Practice Guidelines (CPGs) are intended to provide guidance to health care professionals, based on a thorough evaluation of research evidence, on the practical assessment and management of specific clinical issues or situations. The guidelines allow some flexibility on the part of the health care professional based on the needs of the specific patient for whom they are caring.
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