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Warfarin/ INR nomogram

Discussion in 'Internal Medicine and IM Subspecialties' started by APACHE3, Aug 8, 2006.

  1. APACHE3

    APACHE3 Senior Member
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    Where is there a good nomogram on dosing Vitamin K for high INR levels? I have cross cover in a couple of days, ...just need to know!! :eek: Thanks
     
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  3. APACHE3

    APACHE3 Senior Member
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  4. Mumpu

    Mumpu Burninator, MD
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    Some key points not mentioned in the card:

    1) You MUST bridge with heparin for 5 days. Even if the INR is therapeutic on day 2 of therapy, the most enduring vitamin K-dependent coagulation factors persist for 5 days.

    2) There are basically no real indications for subcutaneous vitamin K. It creates a depot of the vitamin in the subq tissues and makes it very very difficult to re-anticoagulate the patient. If you are an ER doc and you give someone subq vitamin K, the ward teams will have all sorts of nasty and very well deserved things to say about you -- I have seen a single SC injection produce 2-week-long resistance to warfarin, and at $100/day LMWH is not cheap.

    3) The INR scale is non-linear. 3.2 vs 3.0 is no big deal. 1.8 vs. 2.0 is a big subtherapeutic deal. INRs in the 5-9 range do not increase the risk of bleeding all that much.

    4) Expect to have to do a dose adjustment as your patient leaves the hospital. A change in diet, usually for the worse, will mess with vitamin K levels.
     
  5. VCMM414

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    What's the standard heparin bridge dosing? I've seen 70 IU/kg bolus + 15 IU/kg/hr or 18 IU/kg/hr. Epocrates doesn't provide this information (that I am aware of).
     
  6. AJM

    AJM SDN Moderator
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    There's no standard heparin dosing - you change the dose based on PTT goal, usually 60-80, but the goal depends on your indication for anticoagulation. The boluses and initial drip ranges that you mentioned sound about right, but almost no one stays at that rate.

    BTW, the heparin dosing is listed in epocrates -- separated by indication.
     
  7. Adcadet

    Adcadet Long way from Gate 27
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    This came up on my medicine sub-i, and my attending insisted that bridging therapy is not needed nor supported by evidence. At the time it was a minor point that I was too busy to track down beyond the NEJM review article that insisted on 5-day briding therapy as Mumpu describes (and I really didn't feel like going out of my way to tell her she was wrong). Does anyone have a good reference handy regarding the necessity of bridging therapy for when this comes up again?
     
  8. goredsux

    goredsux Junior Member
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    I am post call so forgive me if this is a bit wordy......It depends on the indication for anticoagulation. The reason for bridging is that Proteins C & S are also vitamin K dependent. However they have the shortest half-lives. Therefore on day one of coumadin you will have lower levels of these relative to the other vitamin K dependent factors. Since proteins C&S inhibit factors V and VIII, you will transiently have more of these factors (V and VIII) lying around on that first day as protein c and s are depleted and their production is inhibited. So in the first couple of days of coumadin you are actually hypercoagulable. Now if you are anticoagulating for AFib, where the risk is around 5% per year, your day to day risk is very low, so there is little reason to bridge with heparin at all (especially when you consider if you start coumadin and heparin simultaneously it will likely be 24 hours before you have reached the right dose of heparin anyway). On the other hand if it is for DVT/PE or an artificial valve, heparin bridging (or LMWH - another topic) is usually done. In addition to the Protein C&S thing, it is true that the other factors, especially those other than factor VII hang around longer. Factor VII though is the one which exerts the greatest influence on PT (the extrinsic pathway). This is why it is recommended that if you intend to wait until therapeutic on coumadin to stop heparin, you wait until 2 consecutive days of therapeutic INR and not just stop at the first bump in PT. So all together this amounts to about the 5 days you have been hearing. Hope that helps.....
     
  9. Adcadet

    Adcadet Long way from Gate 27
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    That helps a lot. Thank you. The article I was reading was for treating DVTs. The refs are:

    Schulman, Care of patients receiving long-term anticoagulant therapy. NEJM 2003;349:675-83

    Bates and Ginsberg, Treatment of deep-vein thrombosis. NEJM 2004;351:268-77.

    These, as indicated by the titles, refer to treating symptomatic DVTs, which as Goredsux points out, is only one reason for anticoagulation.
     
  10. yesh

    yesh Member
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    uptodate has a nice table you can download to your pda.....just remember...give it orally if at all possible....sc before iv given risk of anaphylaxis.
     
  11. binswanger

    binswanger Member
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    I agree with the give Vitamin K orally if at all possible ( no active bleeding, INR <20), but several guidelines do not support IM or SC administration. This just recently came up on the wards....check out the national guideline clearinghouse recommendations (IM, SC have unpredictable absorption which can lead to erratic correction and resistance to warfarin) and advice on giving IV - - slow over 30 minutes in D5W under monitored conditions to avoid anaphylaxis.
     
  12. Mumpu

    Mumpu Burninator, MD
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    It's not just a Protein C and S issue. The most-enduring vitamin K-dependent coag factors take 5 days to go away. You can't do anything to reduce their half-lives, and the patient is not fully anti-coagulated until these factors clear. Whether it's clinically significant is another matter.

    For The Word, you should be looking at the ACCP Conference on Antithrombotic and Thrombolytic Therapy guidelines (there is a bunch for all sorts of situations). In the event of a bad anticoag-related outcome, your level of care will be compared against these guidelines.
     
  13. goredsux

    goredsux Junior Member
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    Agreed, see second half of paragraph I wrote

    [/QUOTE]
    For The Word, you should be looking at the ACCP Conference on Antithrombotic and Thrombolytic Therapy guidelines (there is a bunch for all sorts of situations). In the event of a bad anticoag-related outcome, your level of care will be compared against these guidelines.[/QUOTE]

    I have, here is a direct quote, emphasis added:

    Following the administration of warfarin, an initial
    effect on the PT usually occurs within the first 2 or 3 days,
    depending on the dose administered, and an antithrombotic
    effect occurs within the next several days.138,139
    Heparin should be administered concurrently when a
    rapid anticoagulant effect is required
    , and its administration
    should be overlapped with warfarin until the INR has
    been in the therapeutic range for at least 2 days. .................
    If treatment is not urgent (eg, chronic stable atrial fibrillation),
    warfarin administration, without concurrent heparin administration,
    can be commenced out-of-hospital with an anticipated
    maintenance dose of 4 to 5 mg per day.

    Also for reference on annual risk of thrombosis taken from same:

    Table 7—Annualized Risk of Thrombotic
    Complications in the Absence of Anticoagulant
    Therapy for Selected Conditions179
    Condition
    Annualized
    Thrombosis
    Risk, %
    Lone atrial fibrillation 1
    Average risk atrial fibrillation 5
    High-risk atrial fibrillation 12
    Dual-leaflet (St. Jude) aortic valve prosthesis 10–12
    Single-leaflet (Bjork-Shiley) aortic valve prosthesis 23
    Dual-leaflet (St. Jude) mitral valve prosthesis 22
    Multiple St. Jude prostheses 91
     
  14. CSCheart

    CSCheart Cards Practice Manager

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    Hi everyone, love your posts. PT/INR levels really get out of hand. I work in a large cardiology practice in NJ. We have a PT/INR office clinic and we do this test by finger stick. The results are pretty accurate, we have had a few patients with INR that came in over 10. When this happens we send them for a STAT to have their lab tested at the hospital. When its high like this they have we have ordered Vit K inject, wait a few days and retest.

    There are many patients who are so non compliant with taking their coumadin. We offer a coumadin teaching session and patients can come in as a group or one on one. This seem to be helpful.
    I have a few patients who just love to adjust their own coumadin. :scared:
     
  15. Mumpu

    Mumpu Burninator, MD
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    You should not be giving IM vitamin K. The absorption is erratic and you create a depot of the drug that can make it difficult to manage the INRs.
     

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