Enoxaparin (Low MW Heparin) Guidelines

The following are guidelines for initiating and monitoring Enoxaparin (Lovenox) therapy.  Modifications for individual circumstances may be necessary.  These guidelines pertain only to Enoxaparin and cannot be extrapolated to other low molecular weight heparins.  Enoxaparin should be ordered by the hematology consult service after a formal consultation on the patient.  The treatment and prophylactic dose of Enoxaparin in children are extrapolated from the adult clinical trials and a cohort study in children.

Indications

• neonates
• any patient requiring anticoagulation and deemed to be at increased risk for hemorrhage
• patients in whom venous access for administration and monitoring of standard heparin therapy is difficult

Low Molecular Weight Heparin Dose (see nomogram below)

Maximum dose is 2.0 mg/kg/dose BID.  If still no response after attaining this dose, consult hematology.  Intravenous therapy is possible but requires a hematology consult.

Ongoing Follow Up

1. Contact the thromboembolism nurse coordinator when the patient is admitted.  A consult from hematology will be arranged and with Hematology Clinic follow-up.
2. Prior to initiation of Enoxaparin therapy, obtain blood for CBC, PT, and aPTT.  If appropriate (as determined by the Hematology Service) do a prothrombotic workup.
3. If treating acute DVT or PE, bedrest with bathroom privileges for 24 hours then reassess.  Mobilization should then be encouraged as tolerated.
4. Avoid aspirin or other antiplatelet drugs during heparin therapy.  If analgesia is required, prescribe acetaminophen.
5. Avoid IM injections and arterial punctures during anticoagulation.
6. Measure platelet counts daily.  If the platelet count drops below 100 x 10⁹/L on day 5 or greater of initial heparin therapy or any day of heparin therapy if the patient received heparin therapy in the last 3 months, please take a red top tube and a blue top tube and send to the coagulation lab for heparin-induced thrombocytopenia (HIT) screen.  In adults, the risk of HIT is greater after 5 days of treatment on the first exposure and anytime if the patient has been treated with heparin in the past.  The epidemiology of HIT in children has not as yet been established.  If a decrease in platelet count occurs, and the total count is less than 100 x 10⁹/L call the hematology consult service, discontinue the Enoxaparin and reinstitute alternate therapy.
7. The duration of heparin therapy is dependent upon the primary problem.  For DVT in children, heparin is usually administered for a minimum of seven days.  Maintenance coumadin should be instituted on day 1 or 2 of heparin therapy.  NOTE:  If the thrombus is extensive or massive PE is present, administer heparin for 7-14 days and begin coumadin therapy on day 5.  NOTE: Newborns may be treated for 10-14 days without coumadin.  This decision should be individualized following consultation with the hematology consult service.
8. If platelet count is less than 150 x 10⁹/L or bleeding occurs, notify M.D. immediately.

Monitoring of Low Molecular Weight Heparin

1. The hematology service should be consulted for all patients receiving Enoxaparin.
2. Bloodwork to be done after drug administration: PLEASE draw blood from fresh venipuncture.  THERE MUST BE NO CONTAMINATION FROM standard heparin; e.g., from arterial line.
3. On day 1 and/or day 2, a blood sample should be drawn 4 hours after the SQ administration of Enoxaparin.  If therapeutic, a weekly check on the anti-factor Xa level is sufficient.
4. The therapeutic anti-Xa level for treatment dose therapy is 0.5-1 units/mL.  The target anti Xa level for prophylactic dose therapy is 0.2-0.4 units/mL.
5. For patients on long term Enoxaparin therapy (> 3 months), consider bone densitometry studies at baseline and then every 6 months to assess for possible osteoporosis.

Enoxaparin Antidote

However, studies in experimental animal models indicated that increased microvascular bleeding produced by very high concentrations of Enoxaparin is neutralized by protamine sulfate.  The dose of protamine sulfate is dependent on the dose of heparin used and the time of administration.  If protamine is given within 3-4 hours of the Enoxaparin, then a maximal neutralizing dose is:  1 mg of protamine sulfate per 100 units (1 mg) of Enoxaparin given in last dose.  The protamine should be administered IV and over a 10 minutes period as rapid infusion can cause hypotension.  Protamine sulfate should only be given after consultation with hematology.

Nomogram for Enoxaparin Treatment

The above nomogram assumes that there is no bleeding.  If any bleeding occurs, contact hematology STAT.

Accumulation of Enoxaparin

Low Molecular Weight Heparin Dilution Procedure

Procedure:

• Withdraw water for injection into 3 ml syringe, almost to 1.5 ml
• Inject contents of the enoxaparin syringe directly into  the water for injection and fill to a total volume of 1.5 ml.  Inject into a sterile vial.
• Fill dose syringe to volume required plus 0.05 ml overfill (for needle) from this vial
• Cap and label syringe.

References

1. Hirsh, J.  Low molecular weight heparins.  Monograph.  Decker Periodicals, Inc.  Hamilton, Ontario, Canada.  1994.
2. Massicotte, P, Adams, M, Marzinotto, V, Brooker, LA, Andrew, M.  Low molecular weight heparin in pediatric patients with thrombotic disease: A dose finding study.  J Ped 128(3):313-318.

These guidelines are adapted from the Children's Thrombophilia Network Exoxaparin Guidelines, April 22, 1996.
 

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