Anticoagulation Using Warfarin, NP Central

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Laboratory Monitoring Guidelines

INR Monitoring based on stability of the patient
1. Check INR 2-3 times a week then,
2. Check INR weekly for two weeks then,
3. Check INR every 4-6 weeks if INR is stable
  1. Patients are considered stable if they have had two consecutive INRs that have not required dosage change.
  2. Re-check INR no more than 2 weeks after a dose change.
Other Laboratory Monitoring
1. CBC should be checked every 6-12 months
2. A urinalysis and hemocult test recommended annually

Reference:
Kania, D. S., Weathermon, R. A.. Anticoagulation monitoring. Notes from clinical skills course 581.

INR Goal 2 - 3

Patient's INR Level	Action	Comment
At desired range	Repeat INR at interval determined by duration of therapeutic INR and underlying condition	Repeat INR in 4-6 weeks with stable condition and long-term therapeutic INR At least weekly when underlying condition can impact coagulation state (malignancy, clotting disorder, use of medications that can influence warfarin effect)
INR< 2	Increase weekly dose by 5-20% Repeat INR 2-3 times/ week until within desired range	Check for adherence to recommended therapy Use of medications or foods that may interfere with warfarin effect
INR 3-3.5	Decrease weekly dose by 5-15% Repeat INR 2-3 times/ week until within desired range	Check for Adherence to recommended therapy Use of medications or foods that may enhance warfarin effect
INR 3.6-4	Consider withholding 1 dose, decrease weekly dose by 10-15% Repeat INR 2-3 times/ week until within desired range	Check for Adherence to recommended therapy Use of medications or foods that may enhance warfarin effect
INR >4 without complications and no indication for rapid reversal of anticoagulation effect	Consider withholding 1 dose, decrease weekly dose by 10-20% Repeat INR 2-3 times/ week until within desired range	Check for Adherence to recommended therapy Use of medications or foods that may enhance with warfarin effect
INR > 4 and need for rapid reversal of anticoagulant effect	Vitamin K 3 mg SC or slow IV	Check INR at 6 and 24 hours May repeat dose

Resource:
Horton, J., Bushwick, B. (1999) Warfarin therapy: Evolving strategies in anticoagulation. American Family Physician. 59 (3) 635-647.

INR 2.5 - 3.5

Patient's INR Level	Action	Comment
At desired range	Repeat INR at interval determined by duration of therapeutic INR and underlying condition Repeat INR 2-3 times/ week until within desired range	Repeat INR in 4-6 weeks with stable condition and long-term therapeutic INR At least weekly when underlying condition can impact coagulation state; malignancy, clotting disorder, use of medications that can influence warfarin effect
INR< 2	Increase weekly dose by 10-20% Repeat INR 2-3 times/ week until within desired range	Check for Adherence to recommended therapy Use of medications or foods that may interfere with warfarin effect
INR 2- 2.4	Increase weekly dose by 5-15% Repeat INR 2-3 times/ week until within desired range	Check for Adherence to recommended therapy Use of medications or foods that may interfere with warfarin effect
INR 3.5-4.6	Decrease weekly dose by 5-15% Repeat INR 2-3 times/ week until within desired range	Check for adherence to recommended therapy Use of medications or foods that may enhance with warfarin effect
INR 4.7-5.2	Consider withholding 1 dose, decrease weekly dose by 10-20% Repeat INR 2-3 times/ week until within desired range	Check for Adherence to recommended therapy Use of medications or foods that may enhance with warfarin effect
INR >5.2 without complications and no indication for rapid reversal of anticoagulation effect	Consider withholding 1-2 doses, decrease weekly dose by 10-20% Repeat INR 2-3 times/ week until within desired range	Check for Adherence to recommended therapy Use of medications or foods that may enhance with warfarin effect
INR > 5.2 and need for rapid reversal of anticoagulant effect	Vitamin K 3 mg SC or slow IV	Check INR at 6 and 24 hours May repeat dose

Resource:
Adapted from: Horton, J., Bushwick, B. (1999) Warfarin therapy: Evolving strategies in anticoagulation. American Family Physician. 59 (3) 635-647.

Reversing Over-Anticoagulation With Warfarin

Vitamin K should be administered in cases of extremely high INRs where the patient is not bleeding or at serious risk of having a serious bleed.
Traditional Vitamin K doses were 10 mg IM as a one-time dose.
Low dose Vitamin K (AquaMephyton) is now preferred therapy.
1. Decreases warfarin resistance
2. Minimizes patient's length of stay
3. Able to re-attain therapeutic INR sooner
Any serious, significant bleeding symptoms with associated excessively prolonged INR -- Refer to ER.

INR Level	Action
INR < 6 (No bleeding)	Hold coumadin
INR 6-10 (No bleeding)	Hold coumadin Vitamin K 0.5 - 3.0 mg sc or 2.5 mg po Recheck INR in 24 - 48 hours
INR 10-18 (No bleeding)	Hold coumadin Vitamin K 2.5 - 5.0 mg sc or po Repeat INR in 6 - 24 hours
INR > 18	Vitamin K 10 mg sc REFER TO ER

For more information

American College of Chest Physicians (ACCP) Guidelines for Oral Anticoagulation Therapy

References:

Horton, J., Bushwick, B. (1999) Warfarin therapy: Evolving strategies in anticoagulation. American Family Physician. 59 (3) 635-647.

Kania, D. S., Weathermon, R. A.. Anticoagulation monitoring. Notes from clinical skills course 581.

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Last updated: October 31, 2000