Warfarin Protocol

What is a warfarin protocol?
...A way for a care giver to initiate, or maintain, a patient's warfarin by simply ordering "warfarin by protocol." A pharmacist, or other specialist, oversees the daily warfarin using the institution's algorithm to achieve a particular target INR (International Normalized Ratio).

What is the benefit of a warfarin protocol?
A standard approach permits easier quality review and improvement. It may reduce morbidity.

What is a warfarin algorithm?
This is the actual schedule to which the specialist refers when figuring how much warfarin to give. It is a predefined range of doses based on the most recent INR. It takes into account patient parameters like day of dosing, age, other medications (amiodarone, antibiotics), and alcohol history. Algorithms can be tabular printed data or computer based.

(Evidence is thin for endorsement of any particular algorithm. Even the much touted, "you've got to use only 5 mg to start" is based on equivocal evidence.)

Is there a gold standard algorithm?
None has been proven to be the "best" by controlled study.

What is a target?
A target is an INR value or range that the specialist hopes to achieve using warfarin anticoagulation. A supplement published in the journal Chest is cited as an evidenced-based listing of target INRs by diagnosis (atrial fibrillation, pulmonary embolism, heart valve).

Examples of published warfarin protocols?
Most relevant is Toronto Hospital's recent experience. They built a warfarin service in 1996 and now share their superb quality review.

On the other hand, others have created the wheel by publishing guidelines for their practioners without creating a warfarin management service. Univera in New York State has a clearly written guideline, as does Massachussett's Baystate. You could individually get certified online in warfarin management for $1250.00.

Where does patient education fit in?
Important. Would seem to reduce morbidity and improve efficacy. Sources of educational material are abundant.

Is warfarin the only oral anticoagulatant?
Direct thrombin inhibitors, such as AstraZenca's ximelagatran (Exanta) have been trumpeted. Tough to find evidence. Benefit? No protimes needed. Other benefit? Merrill Lynch estimates a billion dollar market by 2005.

How can an institution build a warfarin protocol?
A multidisciplinary task force can build it, as Toronto and others show us.

What is a best next step?
A task force. Read Toronto's experience.

Last update: 8/4/02; 6:54:22 PM.