The ABCs of Vitamin K and Coagulation
The most recent version of guidelines for managing antithrombotic
therapy by the American College of Chest Physicians (2004) contains
specific recommendations for handling vitamin K to counterbalance too
much anticoagulation therapy. Here are some highlights:
Monitoring
• Begin international normalized ratio (INR) monitoring after the
initial two or three doses of oral anticoagulation therapy.
• For patients on a stable dose of anticoagulants, monitor at least
every four weeks.
Managing Nontherapeutic INR
• For patients with INRs above the therapeutic range but less than 5.0
and who have no significant bleeding, lower or omit the dose; monitor
more frequently; and resume therapy at a lower dose when the INR is in
the therapeutic range.
• For patients with INRs of 5.0 or above and less than 9 and who have no
significant bleeding, omit the next dose or two, monitor more frequently
and resume therapy at a lower dose when the INR is in the therapeutic
range. Alternatively, omit a dose and administer vitamin K1 orally at 1
to 2.5 mg. The vitamin K1 (phytonadione) dose can be increased to 5 mg
or more if more rapid reversal is required because of imminent surgery.
• For patients with INRs of 9.0 or greater and who have no significant
bleeding, hold anticoagulation therapy and administer a higher dose of
vitamin K1 (5-10 mg orally). Monitor the patient more frequently and use
additional vitamin K1 if necessary.
• In patients with serious bleeding and elevated INRs, the guidelines
recommend holding anticoagulation therapy and administering vitamin K1
(10 mg by slow I.V. infusion) supplemented with fresh plasma,
prothrombin complex concentrate or recombinant factor VIIa, depending on
the urgency of the situation. Vitamin K1 administration can be repeated
every 12 hours.
• In patients with life-threatening bleeding and elevated INRs, the
guidelines recommend holding anticoagulation therapy and administering
prothrombin complex concentrate or recombinant factor VIIa supplemented
with vitamin K1 (10 mg by slow I.V. infusion). Repeat if necessary,
depending on the INR.
Source: Ansell J, Hirsh J, Poller L, et al. The pharmacology and
management of the vitamin K antagonists: the
Seventh ACCP Conference on Antithrombotic and Thrombolytic Therapy.
Chest. 2004;126(3 Suppl):204S-233S.
http://www.chestjournal.org/cgi/content/full/126/3_suppl/204S
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