A person receiving warfarin as an oral anticoagulant may develop a coagulopathy if excessive drug is taken or a significant change in diet occurs. Administration of vitamin K1 (phytonadione) can reverse the coagulopathy but may result in under-anticoagulation for a period of time. The proper intervention depends on the patient's clinical status and situation.
Parameters:
(1) seriousness of the underlying reason necessitating anticoagulation
(2) prolongation of the INR
(3) risk for bleeding or presence of bleeding
(4) urgency for surgery or other intervention
|
INR |
Clinical Status |
Intervention |
|
> 3 and <= 5 |
no significant bleeding and no urgent surgery |
skip the next dose or use a smaller dose; if the INR is only slightly increased, then no dose adjustment may be needed, else consider reducing future doses |
|
> 3 and <= 5 |
bleeding or urgent surgery |
<not covered by Hirst et al> skip the next dose and give 0.5-1.0 mg vitamin K1 po |
|
> 5 and <= 9 |
no significant bleeding and no urgent surgery |
skip the next 1-2 doses and reduce future coumadin doses, adjusting the INR to the therapeutic range |
|
> 5 and <= 9 |
at risk for bleeding |
skip the next dose of coumadin and give Vitamin K1 1.0 – 2.5 mg po |
|
> 5 and <= 9 |
urgent surgery or dental extraction |
skip the next dose of coumadin and give Vitamin K1 2.0 – 4.0 mg po |
|
> 5 and <= 9 |
bleeding |
<not covered by Hirst et al> skip the next dose of coumadin and give Vitamin K1 2.0 – 4.0 mg po; consider FFP or prothrombin complex if bleeding serious |
|
> 9 and <= 20
|
no significant bleeding |
skip the next dose of coumadin and give Vitamin K1 3.0 – 5.0 mg po |
|
> 20 |
no serious bleeding |
Vitamin K1 10 mg by slow infusion |
|
> 9 |
serious bleeding |
Vitamin K1 10 mg by slow infusion, consider FFP or prothrombin complex |
after Hirsh et al, page 458S
If the patient is seriously bleeding, then infuse fresh frozen plasma (FFP) or prothrombin complex concentrate.
If the patient has received a large dose of vitamin K for correction of the INH, then there may be interference with coumadin anticoagulation and administer heparin may need to be given until the patient is once again responsive to the coumadin.
Route of administration for vitamin K:
(1) oral: preferred route
(2) subcutaneous: may be used as an alternative to the oral route.
(3) intravenous: Use only when rapid reversal of the INR is critical. Since infusion of intravenous vitamin K may result in an anaphylactic response with cardiovascular collapse and death, give only by slow infusion. While an anaphylactic response may still occur during slow infusion, it usually is not as severe as that following rapid infusion.
|
Route |
Dose |
Time to Reversal |
Additional Dose if not reversed |
|
oral |
low dose: 1.0 to 2.5 mg higher dose: 3.0 to 5.0 mg |
24 to 48 hours |
at 24 hours |
|
intravenous |
10 mg by slow infusion |
depends on the INR |
at 12 hours |
where:
• A slow infusion of vitamin K involves dilution with D5W and administration over 30 minutes.
• A high oral dose of vitamin K does not improve efficacy but does increase the period before coumadin is once again effective.
• Hung et al found that a dose of 0.5 mg vitamin K1 given IV corrected most patients who were overanticoagulated to a therapeutic INR, while higher doses resulted in an INR < 2. However, most people recommend no vitamin K1 or oral vitamin K1 for the group of patients studied.
Specialty: Hematology Oncology, Clinical Laboratory, Pharmacology, clinical, Clinical Laboratory
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