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Anticoagulation: hitting the target after cardiac surgery


A pharmacy led anticoagulant service has recently been introduced to dose and monitor warfarin in all cardiothoracic inpatients at the Leeds General Infirmary. This abstract presents an audit of locally produced guidelines for the induction of warfarin in cardiothoracic patients.


To improve the anticoagulant process for cardiothoracic patients by using the experience of clinical pharmacists to produce guidelines for induction of warfarin.


An audit was undertaken and data was collected on 89 patients. Sixty patients (67%) received a warfarin loading dose according to the local guidelines. Fifteen (71%) of the 21 patients with mechanical valves had an acceptable INR on day four. Only one patient (5%) had a high INR. and 5 (24%) had a low INR. Of the 39 'low risk' patients (tissue valves, coronary endarterectomies and A.F), 21 (54%) were within the acceptable range on day 4 whilst four (10%) were high and 14 (36%) were low.

In a group of 29 patients where guidelines were not followed (dosing decisions were made by junior surgeons), only 8 patients (28%) had an acceptable INR on day four, 16 (55%) had a low INR and 5 (17%) had a high INR.


This study has shown that the locally developed guidelines can be used to safely initiate warfarin in cardiothoracic patients immediately following cardiac surgery. In the future we intend to undertake an analysis to produce maintenance dose guidelines which are specific to cardiothoracic patients. A combination of these two guidelines should optimise the dosing of warfarin in cardiothoracic patients and contribute to an overall improvement in their care.

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Booth, C., Nelson, C. Anticoagulation: hitting the target after cardiac surgery. Crit Care 3 (Suppl 1), P235 (2000).

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