Warfarin Institute of America
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MANAGING WARFARIN WHEN A PATIENT REQUIRES A PROCEDURE
People who are taking warfarin require other procedures about as often as people who do not take warfarin. However, people taking warfarin face an additional risk if their warfarin has to be stopped. In my opinion, this risk is often discounted by the physician or dentist who wants to stop the warfarin. They seem to carve the body up into little chunks. "I need to check the (you fill in the blank.). If the patient has a stroke, well that is not in my little chunk, so it is not my problem." I may be biased but it is because one of my favorite patients, a delicate, elderly lady, suffered a stroke and was never able to live alone again after her warfarin was stopped, for what I considered an excessive amount of time, to perform a procedure which turned out to be negative. When I mentioned this to the physician who had stopped the warfarin, the comment was, "Well the (procedure) had to be done." There was little concern for the fact that this had ruined the woman's life. I have also served as consultant in several legal actions and am now convinced that, "The procedure had to be done" is not an adequate defense in a lawsuit. There needs to be careful weighing of both the risks and benefits stopping warfarin, continuing warfarin, using low-molecular weight heparin bridging therapy, the risk of doing the procedure, the risk of not doing the procedure and alternate methods of doing the procedure.
I think that physicians tend to overestimate the risks of bleeding. This probably has a basis in history. Prior to about 1990, warfarin was managed in a manner far different from how it is used today. Many of the test materials were fairly insensitive, but this was not recognized. The procedure was to have a person not taking warfarin go to the lab and have blood drawn to do a pro-time test. The results of this were considered the control. Then all of the people who were taking warfarin that were tested that day were regulated to keep their pro-times at one and one-half to two and one-half times the control. It is now recognized that with the least sensitive materials in use, a pro-time of two and one-half times control was equivalent to an INR of about 8. Today almost everyone should have an INR between 2.0 and 3.5. It is little wonder that people bled when they had procedures done. Almost every doctor in practice today was either trained before 1990 or was in turn trained by someone who schooled in that era. The old perceptions last, but it is time to bring things up to date.
One of the things hindering progress is the lack of controlled studies comparing choices. It is unlikely that these will ever be done. For one thing, it would be unethical to do many of them since we know that they are likely to result in undesirable outcomes. Even if they were ethical, the studies are expensive and unlikely to be sponsored by pharmaceutical companies that will never recoup their expenses. So we have to proceed with the best that we have -- small studies and case reports.
PATIENTS WITH ATRIAL FIBRILLATION
There is a wide variation in the risk of thromboembolism having to do with whether or not the person has other risk factors or has had a stroke. Other risk factors include mitral stenosis, prosthetic heart valves, heart failure, age over 65 years, hypertension, diabetes, previous stroke, previous transient ischemic attack or thyrotoxicosis. If a person has the warfarin stopped two to three days before a procedure and it takes two to three days to have the INR reach a therapeutic level after the procedure, then the approximate risk of stroke during the time the warfarin is discontinued is 0.012% to 0.3%. To put this in another perspective, imagine that there were 10,000 people in the world who had atrial fibrillation and their warfarin was stopped for a procedure today. Among those 10,000 people somewhere between 1 and 30 would have a stroke. For every day over six that the INR remains below the desired range, the number of people having a stroke will increase. You will then have to consider the risk of bleeding. Routine dental procedures, cataract surgery, and most skin surgery present little risk of serious bleeding. For these, the risk of stroke ordinarily outweighs the risk of bleeding so they should be performed without stopping warfarin. As the risk of bleeding increases, the need for stopping warfarin increases. However, the risk of stroke remains the same. Therefore, the use of bridge therapy with low-molecular weight heparin increases in importance.
PATIENTS WITH MECHANICAL HEART VALVES
A wide variation in the risk of thromboembolism exists for patients with mechanical heart valves. Older style, such as caged-ball and Bjork Shiley valves and any valve in the mitral position have increased risk over newer valves such as St. Jude and Medtronics and any valve it the atrial position. If a person has the warfarin stopped two to three days before a procedure and it takes two to three days to have the INR reach a therapeutic level after the procedure, then the approximate risk of stroke during the time the warfarin is discontinued is 0.02% to 0.06%. To put this in another perspective, imagine that there were 10,000 people in the world who had mechanical heart valves and their warfarin was stopped for a procedure today. Among those 10,000 people somewhere between 2 and 6 would have a stroke. For every day over six that the INR remains below the desired range, the number of people having a stroke will increase. You will then have to consider the risk of bleeding. Routine dental procedures, cataract surgery, and most skin surgery present little risk of serious bleeding. For these, the risk of stroke ordinarily outweighs the risk of bleeding so they should be performed without stopping warfarin. As the risk of bleeding increases, the need for stopping warfarin increases. However, the risk of stroke remains the same. Therefore, the use of bridge therapy with low-molecular weight heparin increases in importance.
PATIENTS WITH VENOUS THROMBOEMBOLIC DISEASE
It has been estimated that stopping warfarin in the first month after a deep vein thrombosis (DVT) is associated with a 1% per day chance of recurrence. During the second and third months after a DVT, the risk of recurrence drops to 0.2% per day. After the third month, the risk of recurrent DVT decreases to 0.04% per day risk. Put in other terms, if 1,000 people had their warfarin held for six days for a procedure during the first month after a DVT, about 600 of them would have a recurrent DVT. If the procedure were postponed for a month or two them those 10,000 people would only have 120 recurrent DVTs. Postponed until four or more months after a DVT, then those 10,000 people would likely have only 24 DVTs.
PATIENTS WITH HYPERCOAGULABLE STATES
(Factor V Leiden Mutation, Prothrombin Gene Mutation, Anticardiolipin Antibodies, Protein C Deficiency, Protein S Deficiency, Antithrombin III Deficiency)
The risk of having warfarin stopped with these patients is unknown. Since the most common manifestation of these states is a DVT, it seems logical that the risk would be at least as great as for others who have had DVT and possibly even somewhat higher. These people are more likely to have recurrent events and life threatening events than people who do not have these conditions.
BRIDGE THERAPY
IT MUST BE NOTED THAT THE US FDA HAS NEVER GIVEN APPROVAL TO USING ANY LOW MOLECULAR WEIGHT HEPARIN AS A BRIDGE THERAPY WHEN WARFARIN MUST BE STOPPED.
While not approved, there is a large body of evidence that supports the use of low-molecular weight heparins to prevent thrombotic events when warfarin must be discontinued. The simples protocol to remember involves enoxaparin. Day 1. Discontinue warfarin. Day 2. Start enoxaparin 1 mg/kg every 12 hours. Day 3. Same as day 2. Day 4. Hold the last dose of enoxaparin due before the procedure. Perform the procedure. After the procedure, when it has been determined that the risk of bleeding is low restart enoxaparin and warfarin at their previous doses. Day 5 and until the INR returns to the desired range. Continue enoxaparin and warfarin. It should be noted that not every pharmacy is going to carry enoxaparin and many insurance companies require prior authorization before payment will be made for enoxaparin, so arrangements should be started several days before the enoxaparin will be needed.
ALTERNATE METHODS
Non-invasive imaging such as virtual colonoscopies are becoming much more refined and reliable. This may be a useful screening method for people on warfarin. If there is a finding requiring further investigation, then the risk of stopping warfarin has to be considered. If there was nothing found that requires further investigation, then the risk of stopping warfarin has been avoided. Cost is a problem. Medicare does not cover these procedures and so it is unlikely that other insurance plans will either. Some insurances may pay if the procedure receives prior authorization. You will need to start the process several weeks or months before the procedure is scheduled. The justification might be avoidance of the cost of low-molecular weight heparin and of course the cost of care should someone have a stroke.
The following is some correspondence that I had with a reader of these pages giving her opinion of these methods. It is used with her permission but she wished her name to be withheld.
I
had a virtual colonoscopy after the blood occult stool test showed a
'positive.'
I agree with you so much on the opinions you have of Warfarin/Coumadin and
the tests associated with it. Especially since my colonoscopy was clear as
a bell....It did show a 3 mm kidney stone which my Urologist said is not a
big deal as it appears to be in the 'meat.'
I tracked down a hospital that does the virtuals, called my doc to have
him fax over the order, informed him I needed a script for the stuff you
drink, and set it up with the Radiologist to be done 2 days after I
called... All within the same week...
My Urologist was intrigued with the films of the virtual.....so much that
he called one of his associates over to take a look. They really 'reveal'
a lot! It was the first set of a colonoscopy films that he had seen -- it
is indeed the 'future.'
Also, I printed out your info on not holding warfarin before a dental
procedure and took it to my Dentist. He was very interested and said he
would go along with my cardiologist if he also chose to let me stay on
Coumadin...for an extraction.
Cardiologist said he didn't have any problem with me not holding....In
fact, they said that I was lucky to find a Dentist willing to have me
continue on Coumadin.
I have had one of my warfarin patients undergo a colonoscopy and she had a polyp cut out with an INR of 2.3 and had no noticeable bleeding.
DENTAL PROCEDURES
These are discussed on another page, click here.
SKIN SURGERY
This is discussed on another page, click here.
PROSTATE SURGERY
This is discussed on another page, click here.
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Last updated September 1, 2006
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