• Generally, cease 5 days prior to surgery.
• If INRs labile or high, cease 7 days prior to surgery.
• Consider bridging therapy with LMWH (clexane/enoxaparin) or heparin infusion (for high-risk patients).

• Commence clexane 1mg/kg BD or 1.5mg/kg daily until 1-2 days prior to surgery.
• Transition to heparin infusion 24 hrs before surgery.
• Heparin IV infusion requires APTT monitoring, and is continued until 6 hrs before surgery. INR should be < 1.5 before commencing major surgery.

Again, consider bleeding vs. thrombosis risk, with guidance from the surgeon.

• Takes several days for warfarin to reach therapeutic INR.
• Generally recommence warfarin within 48 hrs of surgery.

• Important for monitoring.
• Standardisation, as warfarin is dosed on a 24hr schedule.
• Encourages prescription before the day team leaves.

Note: on overtime

Do not just chart warfarin after checking the INR. Also consider the patient’s clinical status and risk of bleeding.

Most commonly, medication interactions:

• Antibiotics – inhibit availability of endogenous vitamin K.
• CYP450 inhibitors – ‘azols’ antifungals, amiodarone.

Check the medication list!

• If INR 3-5, withhold or reduce dose for 1 day.
• If INR > 5, consider giving PO or IV vitamin K (max. 1mg if patient is not bleeding).

The patient is in potentially life-threatening hypovolaemic shock, so the INR needs to be reduced to normal, not the therapeutic range.

• Vitamin K 5-10mg, but only has a significant effect from 12-24 hrs.
• Prothrombinex (factors 2, 9, 10 and some 7) – can be given without complications associated with a high fluid load, faster acting, than FFP but not as durable- dose 25-50 IU/kg.
• FFP (factors 2, 7, 9, 10) – dose at 10-15mls/kg, about 1-2 units if they are able to tolerate the fluid load.

• Warfarin is a difficult medication to manage.
• Always consider bleeding and thrombosis risks when starting or stopping warfarin, and involve the treating team in decisions about what to do.
• If labile or supratherapeutic INR – investigate all causes (esp. the medication list).