• Check indication for use of IV unfractionated heparin in relevant guideline. Is this correct regime?
• e.g. use for post thromboembolism but not following post MI thrombolysis
• Check the following:
• no allergy or previous history of heparin-induced thrombocytopenia
• FBC (specially for baseline platelets)
• International Normalised Ratio (INR)
• APTT ratio
• U&E (to check baseline serum potassium)
• If starting a pregnant woman on IV unfractionated heparin, discuss with consultant haematologist to arrange anti-Xa monitoring
• Check need for loading dose
• advice in indication for use of IV unfractionated heparin in relevant guideline

Prescription

• Prescribe in hospital’s prescription chart

• Weigh patient
• Give bolus dose of unfractionated heparin (1000 units/mL) 75 units/kg IV over 5 min

Volume of 1000 units/mL IVUH solution for loading dose of 75 units/kg

Patient unfit to be weighed

• For haemodynamically stable PE, DVT, unstable angina and acute peripheral arterial occlusion, give bolus dose of unfractionated heparin 5000 units (5 mL 1000 units/mL) IV over 5 min 
• For haemodynamically unstable PE, give bolus dose of unfractionated heparin 10,000 units (5 mL 1000 units/mL) IV over 5 min

• Prepare solution of 500 units unfractionated heparin per mL
• take 20 mL unfractionated heparin 1000 units/mL (which therefore contains 20,000 units)
• add 20mL of sodium chloride 0.9% injection to produce a total volume of 40 mL
• start infusion dose at 18 units/kg/hr which is equivalent to 0.036 mL/kg/hr

Maintenance infusion rate of IV heparin 500 units/mL to give 18 units/kg/hr

Warn all staff members

• Check concentration of IV Unfractionated Heparin carefully to avoid risk of overdose and bleeding
• IV heparin therapy without strict monitoring carries high risk of bleeding

APPT ratio

• Check APTT ratio 4 hr (6 hr if no loading dose) after starting infusion
• 4 hr after any dose change
• Adjust rate as dictated by APTT ratio
• patients with renal impairment may have delayed clearance of heparin
• Once APTT ratio lies within target range of 2.0-3.0, check APTT once daily

APTT ratio and corresponding change in infusion rate

Adapted from Fennerty A.G., Renowden S., Scolding N. et al. BMJ 1986; 292: 579-80

Overdose or bleeding

• Contact on-call haematology consultant to advise on urgent reversal of anticoagulant effect

Heparin-induced thrombocytopenia

• If patient post-operative, check platelet count before starting heparin and then on alternate days from day 4 until day 14 of heparin treatment or until heparin is stopped
• if unfractionated heparin, dalteparin or any other low-molecular-weight heparin given within last 100 days, check on alternate days from day 2
• If platelet count falls by >50% during heparin therapy, suspect heparin-induced thrombocytopenia - see Heparin-induced thrombocytopenia guideline

Hyperkalaemia

• Check U&E before starting heparin
• Twice weekly if:
• IV Unfractionated Heparin likely to continue for >7 days
• patient has raised baseline serum potassium, diabetes mellitus, chronic kidney disease or acidosis, or is taking a potassium-sparing agent

• Protamine reverses the IV Unfractionated Heparin anticoagulant effect
• protamine carries significant risk of serious adverse drug reaction
• 1 mg of protamine neutralises 80-100 units unfractionated heparin when administered within 15 min of the heparin dose
• if protamine is required more than 15 mins after heparin dose, less is needed
• 50 mg protamine sulphate is enough for most bleeds
• Report all anticoagulant related bleeding events
• Contact on-call haematology consultant for advice if necessary