Warfarin reversal with Prothrombinex

When a warfarinised patient presents with an intracranial haemorrhage, do you automatically think “prothrombinex”? In our ED there is no stock of fresh frozen plasma (FFP), so the administration of prothrombinex has become more common of late. This post touches on some of the critical nursing care considerations surrounding the administration of prothrombinex.

With increasing numbers of patients on warfarin for atrial fibrillation (AF), it’s wise to know how to handle INR reversal in the ED. Warfarin is a vitamin K antagonist, which reduces blood clotting by inhibiting conversion of inactive vitamin K epoxide to its reduced active form. If that last sentence makes no sense to you either, don’t worry – the point is, warfarin is an anticoagulant.

INR: blood clotting time (coagulation) is measured using the international normalised ratio (INR). For patients on warfarin a reasonable target range for INR is 2 to 3 seconds. Bleeding risk increases exponentially from INR 5 to 9. However, significant bleeding episodes still occur at INR 4, therefore INR should be used as a guide only. All patients with an INR >5 require close monitoring.

Onset and duration: prothrombinex is said to reach peak plasma levels in 5 minutes post-infusion, and INR reversal in 15 minutes. When given together with vitamin K (to sustain the reversal), the duration of INR effects = 12-24 hours.

Administration: reconstituted promthrombinex should be administered within 3 hours. The recommended infusion rate is 3 ml per minute, OR as tolerated by the patient. For example, a dose of 25 units/kg for a 100kg patient requires 5 vials (500 units per 20ml vial). To give the resulting 100ml dose at 3ml per minute would take about half an hour.

Contraindications: heparin allergy, active thrombosis, disseminated intravascular coagulation (DIC). Overdose increases the risk of DIC, thrombosis, myocardial ischaemia and pulmonary embolism. High or repeat doses increase the risk of thrombotic adverse effects.

Monitoring: a patient with a clinically significant bleed + warfarin should be continuously monitored until their INR drops below 5 and the bleeding stops. There is some controversy about INR as a monitoring tool post-warfarin reversal, therefore INR results should be interpreted in light of clinical signs.

What about Dabigatran (aka Pradaxa)? At present, there is no specific way to reverse the anticoagulant effect of dabigatran in the event of a major bleed. More on this in future posts.

Further information can be found via CSL Limited, Bioplasma Division

 

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About tamarahills

ED nurse working on the beautiful Sunshine Coast, Australia.
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