Venous thromboembolism: treatment strategies

Unfractionated heparin

Unfractionated heparin, administered by continuous infusion or subcutaneous injections adjustedto achieve activated partial thromboplastin time (APTT) greater than 1.5, is effective as initial treatment of venous thromboembolism. Initial heparinisation should be followed by long term anticoagulation with oral anticoagulants. APTT is a global coagulation test and not specific for heparin, and it is also influenced by various plasma proteins and clotting factors.Measuring plasma heparin levels is more accurate but it is impractical and expensive. A sensible approach is to standardise the APTT with plasma heparin within each laboratory.

The most common mistake when starting heparin treatment is failure to achieve adequate anticoagulation. APTT ratios of less than 1.5 during the first few days of heparin therapy increase the long term risk of venous thromboembolism recurrence. Hence, the initial bolus dose should be adequate and APTT monitored every six hours during the first 24 hours of heparin infusion.