Management plan for patients on warfarin in the peri-operative period

Introduction

This guideline aims to balance the competing risks - thrombosis versus haemorrhage - that patients anticoagulated with warfarin face in the peri-operative period. Management advice on peri-operative anticoagulation for patients on the newer direct oral anticoagulants (DOACs) can be found on StaffNet, separately for dabigatran and the direct factor Xa inhibitors (apixaban, edoxaban and rivaroxaban) - see NHSGGC StaffNet / Clinical Info / Clinical Guidelines Directory and search in the 'haematology' section of the directory.

In doubtful cases it is usually safer to omit anticoagulant drugs rather than over treat, but each case needs individual assessment and you should consult senior colleagues and/or seek Haematology advice readily.

Emergency Admissions

In warfarinised patients admitted with trauma, major bleeding or for emergency surgery, the risks from haemorrhage generally far outweigh the thrombotic risks (even in high thrombotic risk patients). Full and immediate anticoagulation reversal is required and include:

1. Check INR, full coagulation screen, full blood count and cross match blood.
2. Withhold warfarin
3. Reverse anticoagulation fully and rapidly (see Reversal of Anticoagulation Therapy Guideline)
4. Recheck full coagulation screen and full blood count.
5. If any concerns or uncertainty, discuss with on-call haematologist.
6. Proceed to surgery as appropriate.
7. Only when you are sure the risk of bleeding has abated, re-anticoagulate as appropriate to the patient's thrombotic risk category using the guideline for elective admissions (see below).

Elective admissions - risk stratification

Invasive procedures can be classified as to their risk from bleeding. Patients can be classified as to their risk from thrombosis.

Elective admissions – management strategy

Low risk of bleeding: in general these procedures can be undertaken without interrupting warfarin therapy, however INR should be checked within 48 hours prior to surgery to ensure levels are not supra-therapeutic and are ideally <3.5.

High risk of bleeding: the general strategy for anticoagulant management is laid out in Table 3: Pre-operative management for procedures with a high risk of bleeding. Therapeutic doses of LMWH should not be re-commenced until at least 48h post procedure. If the post-operative bleeding risk will remain high for ≥3 days consider bridging with Unfractionated Heparin (UFH) - see further below.

Very high risk of bleeding (e.g. neurosurgery): consult the appropriate senior colleague (do not apply recommendations from table 3).

Some patients or procedures may not be easily classified into the above categories - if so, they should be discussed with the relevant senior clinician (e.g. haematologist, cardiologist, surgeon).

Cautions and contraindications to heparin / high dose bridging therapy with LMWH

Absolute contraindication:

• History of heparin allergy or heparin-induced thrombocytopenia (HIT), applies to unfractionated heparin (UFH) and low molecular weight heparin (LMWH).

Relative contraindication:

• High bleeding risk (e.g. recent major bleed, stroke, neurosurgery, etc. in previous month)
• Creatinine clearance <30ml/minute. Use of LMWH heparin may be possible with suitable downward dosage adjustment, otherwise consider the use of UFH. See guideline on Heparin dose adjustment in renal impairment in the Haematology section of Clinical Guidelines Electronic Resource Directory on NHSGGC StaffNet.

Surgery with spinal or epidural anaesthesia

• Epidural or spinal anaesthesia should not be initiated or removed unless the INR is ≤1.4 and there is no appreciable heparin effect.
• Avoid insertion or withdrawal of an epidural catheter within 12 hours of 40mg enoxaparin or within 24 hours of a therapeutic (1mg/kg) dose of LMWH.
• Avoid heparin administration (SC or IV) for 4 hours after removal of an epidural.

Bridging therapy with unfractionated heparin, for high thrombotic risk patients, in the peri-operative period

The first principle is do not prescribe any heparin or warfarin if there is evidence of active bleeding. If in doubt seek advice.

Use of UFH may occasionally be preferable to using LMWH e.g. when the ability to ensure rapid and complete reversal of heparin is required, where significant renal impairment exists or where standard monitoring of heparin effect is necessary.

1. On pre-operative day -1 commence UFH according to the schedule detailed in the Drug Therapy section of the Diagnosis and Treatment of Venous Thromboembolism guideline.
2. Monitor APTT ratio and adjust UFH to achieve a result of 1.8-2.8.
3. Stop UFH 6 hours pre-operatively.
4. Recommence UFH 8 hours post-op (assuming haemostatic) at 50% of prior therapeutic dose. N.B. Do not give a loading dose post-operatively.
5. Assess APTT ratio on day +1 and slowly adjust UFH dose to achieve a ratio of 1.5-2.0
6. Only after any epidural has been removed, restart usual dose of warfarin as soon as it is safe and GI tract function is judged adequate.
7. Stop UFH for 6 hours prior to removal of any epidural catheters
8. On day +2 monitor APTT ratio and, only after any epidural has been removed, slowly adjust UFH to achieve a ratio of 1.8-2.8.
9. Continue UFH until INR is ≥2.

If good haemostasis has been secured and maintained for 2-3 days post-procedure it may be reasonable to switch from IV UFH to SC LMWH. Enoxaparin 1mg/kg twice daily should be commenced 4 hours after cessation of the UFH infusion. If exposure to UFH (and LMWH) exceeds 4 days, monitor platelet count every 2-3 days from day 4 to 14, or until heparin is stopped. Be alert for evidence of HIT.