Letters to the Editor
Warfarin: balancing the benefits and harms
- Aust Prescr 2004;27:138-41
- 1 December 2004
- DOI: 10.18773/austprescr.2004.115
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Editor, – As an eye surgeon I was surprised to read that warfarin was contraindicated when eye surgery was contemplated (Aust Prescr 2004;27:88-92). Given that cataract surgery is one of the most common elective surgical procedures performed in this country and most patients are aged over 65, this advice was somewhat at odds with accepted practice. A number of papers have looked at this issue and a study from New Zealand suggested that there was no greater risk of adverse events in patients undergoing surgery being maintained on warfarin, provided their INR was between 2.0 and 2.5.1
Mount Gambier, SA
Dr M. Borosak, Ms S. Choo and Professor A. Street, the authors of the article, comment:
The contraindications to warfarin indicated in the article were obtained primarily from the product information. The relevant paragraph indicates that any circumstance where the 'hazard of haemorrhage might be greater than the potential clinical benefit of anticoagulation' may constitute a contraindication. It goes on to say that examples of these circumstances may be haemorrhagic tendencies and blood dyscrasias, recent or contemplated surgery of the central nervous system, the eye or traumatic surgery resulting in large open surfaces. The risk:benefit analysis is the key to the decision making related to what is considered a contraindication.
This view is also supported by a study of the management of anticoagulation before and after elective surgery, which presented figures pertaining to such a risk:benefit analysis. The absolute risk of thromboembolism associated with a few days of perioperative subtherapeutic anticoagulation is generally very low while the risk of bleeding if anticoagulated may be relatively high.2
The study quoted by Dr Hodson describes a retrospective review of 28 cataract patients being treated with warfarin (outcomes were available for 23 eyes) who had INRs ranging from 1.0 to 2.4 (median 1.5). There were four haemorrhages, all of which were visually not significant, and there were no thromboembolic phenomena. The conclusion was that with modern techniques cataract extraction can safely and effectively be performed in patients taking warfarin who have an INR of approximately 2.0.
It is our opinion that in all perioperative circumstances the patient's individual risk factors for thrombosis and haemorrhage should be considered before a decision is made to maintain warfarin therapy and the INR level above 2.0.