Monitoring of unfractionated heparin

If given by intravenous infusion, monitor the anticoagulant effect of UFH by measurement of activated partial thromboplastin time (APTT). Measure APTT before starting UFH and every 4 to 6 hours. When 2 consecutive APTT results are in the target range, consider daily monitoring. Revert to 4- to 6-hourly monitoring following dose adjustments.

UFH can cause heparin-induced thrombocytopenia (HIT). If long-term therapy with UFH is planned (eg more than 14 days) measure the full blood count at baseline. If the patient has not previously been treated with heparin, measure the platelet count on day 5 after starting UFH and recheck the platelet count every 2 to 3 days during therapy, until day 14. If the patient has previously been treated with heparin, measure the platelet count on day 2 after starting UFH and recheck the platelet count every 2 to 3 days during therapy, until day 14. Suspect HIT if the absolute platelet count falls by 50% or more from baseline.