Proactive Management Follow-up -- and reasons for a Case

[Protimenow]

Last week, I was worrying about attending a conference where I'd be doing a lot more walking, sweating, and probably less eating than usual. I figured that the extra activity and dietary changes may affect my INR. I even speculated on slightly increasing my dose of warfarin to accommodate for anticipated drop in INR.

I got good advice not to do anything to change my dosing.

I heeded the advice.

I packed my fully charged ProTime 3 meter and brought a test setup for two tests.

It turned out that I wasn't able to do the tests because my meter was packed without a case. Because of this, the button on the front of the monitor was frequently pressed -- and run down the rechargable battery. I left home with a full charge -- at the hotel, the meter was dead. I didn't bring the charger.

I'm thinking that most meters have the same kind of issue -- a front button that turns the meter on and off. I could have had similar dead battery problems with any of the meters (although I realize that the InRatio and CoaguChek also use AA or AAA batteries - and these can be removed for travel and replaced when the time's right for testing).

As it turns out, when I got back, my INR tested just fine. Although I wanted to test during the conference - I never did before - and it probably wouldn't have mattered if I had. I don't think that this five day trip did enough to change my INR drastically to matter.

So - a few thoughts -- if you pack your meter into a suitcase, be sure it's in a case of its own to prevent damage to the buttons, or consider removing the batteries when you aren't using the meter - or bring along the charger.

And don't necessarily expect changes that may not actually happen.

In the words, I think, of Ronald Reagan 'Trust, but verify.' (If you have concerns about changes in INR, feel free to test -- but you probably won't have to)

 

[Bill B]

I feel the need to squash some incorrect assumptions that lead you to worry about your INR unnecessarily.

I have read here before things like:
"exercise will increase your metabolism, and as a result will process the Coumadin at a faster rate"
"The more you exercise the more blood will pump through your organs and be processed. This processing will reduce your INR."

Both are simply not true.

Many people expect that caloric metabolic rate has something to do with the metabolism of drugs like warfarin. It doesn't. Totally unrelated. Warfarin metabolism or its affects on vitamin K or the metabolism of clotting factors are not affected by physical activity or caloric intake. Warfarin is metabolized in the liver. Calories, on the other hand, are primarily consumed by muscle tissue. Hence, no relationship. As to blood flow, there are some drugs whose metabolism is affected by liver blood flow. Liver blood flow is reduced (not increased) by exercise (blood is shunted to the muscles and away from the liver), and this would reduce the elimination of these drugs. These are drugs that are very rapidly and efficiently cleared by the liver (warfarin is very slowly and inefficiently cleared). Propranalol is one example of what are called flow-limited drugs (drugs whose metabolism is limited by liver blood flow), but even then the effects of exercise are not pronounced and are limited to the few hours of strenuous activity and some individuals show no effect at all.

The old pharmacist in me just could not let this go by unnoticed.

 

[Protimenow]

Bill -- thanks for the clariification. I seem to recall earlier posts by others saying that their increased exercise had dropped their INRs.

I didn't consider that the blood flow to the liver would drop in order to accommodate the increased need for fresh blood in the muscles. Makes sense.

In any case -- I guess the real message is to keep your meter in a case if there's a chance that the buttons will be pressed and run down the charge on the meter, or to carry spare batteries (if your battery uses batteries), and not to worry about activities having dramatic impact on INRs.

 

[Eva]

The old pharmacist in me just could not let this go by unnoticed.

Bill, thanks you for the *old pharmacist" in you did *not let this go unnoticed*. Sharing your scientific knolwledge is a gained knowledge to all of us and I hope you always help us learn more facts.

Thanks again. Interesting facts I did not know about exercise and liver.

Protimenow, a good point you brough up...I personally carry my co-agucheck in my carry-on luggage in its case and wrap it with soft clothes I have.

 

[Protimenow]

I don't expect to travel more than a few days at a time, so I probably won't be bringing a meter with me, but if I should happen to wind up with more extensive travel, I'll probably take my InRatio - and will do my best to protect the buttons so it's not turned on multiple times. Of course, because it works with batteries, it's not as big a deal as it is with the ProTime meters that only use internal NiCads.

 

[catwoman]

However, I have seen many, many statements on credible websites that state that increased activity levels can affect the INR.

If not through increased metabolism, how?

I just found several websites (clotcare.com, University of Wisconsin) that caution warfarin patients to tell their anticoagulation manager/doctor when they change their activity level.

 

[Protimenow]

I THOUGHT there may be something to this.

Let me venture a guess -- if not through increased metabolism, what about through dehydration and clearance through the kidneys or, perhaps, even sweating the warfarin out through the skin? I haven't looked for any studies that explored these routes. However, it may stand to reason that with excessive dehydration, the concentration of the warfarin in the blood would be increased -- as would the concentration of clotting factors - and perhaps this (the more concentrated clotting factors effected by warfarin) can account for a reduced INR. Conversely, if a person has TOO MUCH fluid - perhaps the INR will increase because of a reduced concentration of the factors. It would probably be much more difficult to hyperhydrate than it would be to DEhydrate, so the effect on INR would probably be more common in people who are dehydrated than in people who are hyperhydrated because most people would just get rid of extra liquids the usual way.

 

[ALCapshaw2]

Interesting Information Bill, but it does raise the Question

"What causes the not-uncommon drop in INR following Surgery as patients become more active"?

As you are aware, this phenomenon has been reported by several members following surgery and has been attributed to exercise and/or increased metabolism. It would be helpful to many of us to have a better understanding of what is going on during the early weeks/months of recovery.

'AL Capshaw'

 

[realkarl]

I have read here before things like:
"exercise will increase your metabolism, and as a result will process the Coumadin at a faster rate"
"The more you exercise the more blood will pump through your organs and be processed. This processing will reduce your INR."

Both are simply not true.

Many people expect that caloric metabolic rate has something to do with the metabolism of drugs like warfarin. It doesn't. Totally unrelated. Warfarin metabolism or its affects on vitamin K or the metabolism of clotting factors are not affected by physical activity or caloric intake. [...see original post for full text]

What you are explaining sounds perfectly logical, but then I do not understand the following:

Over the soon two years since my surgery, with weekly home testing of INR, for my body, there appears to be a clear relationship between activity level and required Coumadin to maintain my range. I have kept an accurate journal, and as my exercise and activity levels have increased while maintaining a steady diet, so has the required Coumadin dose. My weekly dosage has increased from 27.5mg/week to 43.75mg/week over two years. If a week went by with little activity (rarely), my INR chart shows a spike. The increase has been more rapid over the last 6 months (35 -> 43.75), as I have increased exercise time and intensity significantly. I now exercise ~6 hours weekly, at a high intensity level (4600C last 7 days), considering my post-surgery limitations and medication, relative to perhaps ~2.5 hours low intensity, the first months after surgery.

My anti-coagulation clinic also advises me that there is a relationship between activity level and INR/Coumadin dosage. They may not know what they are talking about - but have been in this business for a long time nonetheless.

If my Coumadin dosage is not related to my exercise and activity level, I am not able to explain it, but please, offer suggestions to correct what I have thought to be the case for a long time.

-Karl