Thromboembolic Disorder

INR

Duration

Clinical Comments

Venous thromboembolism

Prophylaxis (eg, high-risk surgery)

Perioperative

Perioperative use of LMW heparin or adjusted-dose unfractionated heparin is appropriate in most patients

Target 2.5; range 2.0–3.0

≤ 3 months or until ambulatory

Warfarin may be considered for use until patients become ambulatory

Treatment: single episode (DVT or PE)

Target 2.5; range 2.0–3.0

Reversible or time-limited risk factor: 3–6 months

Idiopathic DVT or PE: ≥ 6 months

At or above the knee

Initial treatment with LMW heparin or adjusted dose unfractionated IV heparin for at least 5 days and to overlap warfarin at a therapeutic level for 2–4 days

Treatment: recurrent DVT or PE or continuing risk factor (cancer, congenital thrombophilic states, antiphospholipid antibody, etc.)

Target 2.5; range 2.0–3.0

Indefinite

At or above the knee

Initial treatment with LMW heparin or adjusted dose unfractionated IV heparin for at least 5 days and to overlap warfarin at a therapeutic level for 2–4 days

Prevention of Systemic Embolism

AF

Target 2.5; range 2.0–3.0

Indefinite

Age < 65, no risk factors (ie, no prior TIA, systemic embolus or stroke, hypertension, poor LV function, rheumatic mitral valve disease): ASA recommended

Age 65–75, no risk factors: aspirin or warfarin recommended

Age 65–75 with risk factors or > age 75: warfarin recommended

AF: cardioversion

Target 2.5; range 2.0–3.0

3 weeks prior for patients in AF > 48 hours; continue until NSR stable for 4 weeks

Indefinite anticoagulation as above for those who do not return to NSR

Acute MI

Target 2.5; range 2.0–3.0

≤ 3 months

ASA (160–325 mg enteric) daily indefinitely

When no thrombolytics given, give heparin followed by warfarin to patients at increased embolic risk (anterior Q-wave MI, severe LV dysfunction, CHF, prior emboli, 2D echo evidence of mural thrombus, AF)

Cardiomyopathy

Target 2.5; range 2.0–3.0

Indefinite

Consider for patient with ejection fraction = 25%

Recurrent systemic embolism

Target 2.5; range 2.0–3.0

Indefinite

Criteria for recurrence: events, temporal and etiologic relationships

Valvular heart disease

Target 2.5; range 2.0–3.0

Indefinite

Consider patients with a history of SE, AF, or LA diameter ≥ 5.5 cm

If recurrent SE occurs on warfarin, add ASA (80–100 mg/day) or increase target INR to 3.0 (range 2.5–3.5)

Tissue prosthetic heart valve

Target 2.5; range 2.0–3.0

3 months (absent AF)

Prosthetic mitral or aortic valve or positions without AF; then ASA (162 mg/day)

If history of SE or LA thrombus at surgery, consider treating indefinitely

Mechanical heart valve

Target 3.0; range 2.5–3.5

Indefinite

If high embolic risk, add ASA (81 mg/day)

INR 2.0–5.0

No bleeding or minor bleeding

Withhold warfarin or lower dosage if above the therapeutic range and monitor INR

Resume at same or lower dosage as INR approaches the desired range

INR 5.0–9.0

No bleeding

Withhold warfarin for one to two doses

Monitor INR frequently

Restart warfarin at lower dosage when INR falls into therapeutic range

No bleeding but increased risk

Withhold one dose of warfarin

Vitamin K (1.0–2.5 mg) po

Minor bleeding

Withhold warfarin, monitor INR

Vitamin K (1.0–2.5 mg) po or SC

INR > 9.0

No bleeding or minor bleeding

Withhold warfarin, monitor INR

Vitamin K (3–5 mg) po or SC

Severe bleeding

Discontinue warfarin

Vitamin K (5–10 mg, slow IV infusion as increased risk of anaphylaxis)

Administer fresh frozen plasma

May repeat vitamin K every 12 hours

Life-threatening bleeding

Discontinue warfarin

Vitamin K (10 mg, slow IV infusion as increased risk of anaphylaxis)

Administer fresh frozen plasma (prothrombin complex concentrate can be considered if insufficient time to thaw fresh frozen plasma)

1. A baseline INR (and APTT if on heparin) should be obtained.

■      In acute thrombotic episodes, warfarin treatment should be initiated during therapy with unfractionated or low-molecular-weight heparin. Dosing can begin with an estimated average maintenance dose, often 2.5 to 5.0 mg in the elderly patient. The two treatments should overlap for 2 to 4 days following a therapeutic INR.

■      In non-urgent situations, such as chronic stable AF, warfarin treatment can begin in the absence of heparin treatment, following the above regimen.

2. The INR should be monitored daily until a stable and therapeutic level is achieved (usually 5 to 7 days).

3. The INR can be monitored 2 to 3 times weekly for 1 to 2 weeks, then weekly for 1 month, and monthly thereafter. More frequent monitoring may be required in some patients and is indicated during antibiotic therapy, during diet changes, or during changes affecting medications that interact with warfarin binding or metabolism.

Hold warfarin for 3 days prior to planned procedure

INR < 2.0

Consider heparin until 4 hours prior to procedure

Procedure at INR < 1.5

Post-procedure, consider heparin until INR is therapeutic

INR 5.0–9.0

Withhold warfarin, monitor INR until < 2.0

Consider vitamin K (1.0 mg) po if rapid correction of INR required

Consider heparin when INR < 2.0 until 4 hours prior to procedure

Procedure at INR < 1.5

Post-procedure, administer heparin until INR is therapeutic

INR > 9.0

Withhold warfarin, monitor INR until < 2.0

Vitamin K (2.0–4.0 mg) po; may repeat in 24 hours if INR still high

Consider heparin when INR < 2.0 until 4 hours prior to procedure

Procedure at INR < 1.5

Post-procedure, administer heparin until INR is therapeutic

Post-procedure—Restart warfarin at regular maintenance dosage