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Indications
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The indications for therapeutic unfractionated heparin (UFH) include the following:
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- treatment of acute venous thromboembolism in the medically unstable patient or in those patients in whom labour or surgery is imminent
- prevention of arterial thromboembolism in medically unstable patients with cardiac arrhythmias and/or presumed embolic stroke
- peripartum or perioperative anticoagulation in women with prosthetic heart valves.
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- The following are guidelines for the commencement and maintenance of unfractionated heparin (UFH) infusions. It may be necessary to modify this protocol according to individual patient requirements.
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Administration
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(UFH) can be administered by intravenous or subcutaneous routes. This protocol applies to the intravenous route only. UFH is compatible with 5% Dextrose and 0.9% sodium chloride (NaCl).
1. Weigh patient.
2. Obtain baseline FBE, APTT and PT.
Any patient with a low platelet count or an abnormal APTT or PT should be discussed with a haematologist prior to starting heparin.
3. Prepare UFH to a concentration of 10 Units/kg/mL in 50mL Normal saline or dextrose
i.e. 60 kg patient = 10x60x50 = 30,000 Units in 50mL
therefore: 1mL/hr =10 Units/kg/hr, 2mL/hr =20 Units/kg/hr
4. Give a loading dose of heparin = 80 Units/kg to a maximum of 5000 Units over 10 minutes.
5. Commence infusion at 18 Units/kg/hr. Monitor APTT after 4 hours.
The loading dose may be omitted in patients considered at increased risk of bleeding. Perform APTT after 6 hours infusion at 18 Units/kg/hr.
Patients with renal failure will require modified doses. Consult with Haematology.
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Loading dose
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Configure the pump to accept the 10mL syringe and set the pump to 60mL/hr for 10 minutes.
Using a 10mL syringe, prepare the required heparin according to the table below based on patient weight.
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| Heparin required to make 10mL=
80unitsxkg to maximum of 5000Units
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| Loading dose give over 10 minutes
80Units/kg to maximum of 5000Units
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Maintenance Dose
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Once the loading dose has been completed, re-set the pump to accept the 50mL syringe and set the pump rate to infuse maintenance dose at 1.8mL/hr.
Using a 50mL syringe, prepare the required heparin infusion according to the table below based on patient weight.
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| Heparin required to make 50mL=
10Unitsxkgx50mL
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| Maintenance rate of infusion
(give after loading dose)
18units/kg/hr
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Nomogram for adjusting heparin dose (dose adjustment to be decided by medical officer)
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* Heparin infusion orders should include the dose written as U/kg/hour and the corresponding mL/hour rate.
* Patients should have a dedicated line for heparin infusions. The infusion must not be stopped or interrupted for other medication. APTT blood samples should be drawn from the contra-lateral arm.
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Monitoring of therapy
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1. Heparin is usually monitored by APTT. The therapeutic range corresponds to 1.5-2.5 times the normal APTT (usually 60-90 sec).
2. The MAXIMUM interval between APTT assays should not exceed 24 hours. The APPT may be inaccurate in certain clinical circumstances. An alternative is an anti Xa assay.The therapeutic range for the UFH anti Xa assay is 0.3 – 0.7units/mL.
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NOTE: this is a different therapeutic range compared to the LMWH assay. Results cannot be interchanged. Request forms must indicate the type of heparin being used.
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3. APTT blood samples can NOT be drawn from the same line as the heparin infusion. Coagulation tubes must be filled exactly to the specified mark.
4. Twice weekly FBEs, (platelet count) are required. If there is an abrupt decrease in platelet count, (e.g. 50%) consider Heparin Induced Thrombocytopaenia (HIT), cease all heparin administration and immediately contact haematologist on call.
5. Avoid IM injections and arterial stabs during anticoagulant therapy. When such procedures are clinically necessary, ensure adequate external pressure is applied post-procedure.
6. The duration of heparin therapy is dependent upon the primary problem. Please consult the Haematology department for guidelines.
7. Avoid aspirin and other anti-platelet medications during heparin therapy.
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Neuroaxial anaesthesia
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Intravenous UFH infusion should be ceased 4-6 hours before epidural catheter insertion or spinal injection. A normal APTT and platelet count should be documented before the procedure occurs.
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Adverse events
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The major adverse event potentially related to standard heparin infusion is bleeding. If a patient on heparin develops bleeding, cease heparin infusion and seek urgent Haematology consult.
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Heparin antidote
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If anticoagulation with heparin needs to be discontinued for clinical reasons, termination of the heparin infusion will usually suffice.
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If an immediate effect is required, consider administering protamine sulfate.
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Protamine is a medication that requires a high level of caution when being prescribed and administered. Protamine sulfate neutralises heparin by virtue of its positive charge. Following IV administration, neutralisation occurs within 5 minutes. The dose of protamine sulfate is based on the amount of heparin received in the previous 2 hours as follows:
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Time since last heparin dose
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| Protamine dose (mg) per 100 Units heparin received
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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.
Obtain blood for PT and APTT 15 min after the administration of protamine sulfate.
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References
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Refer to: References: Anticoagulants.
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Revised and updated: 19 May 2009
Edited to include weight/dose tables: 30 June 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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