Warfarin Peri-op

These guidelines are produced to assist medical staff and other healthcare professionals in managing patients who are receiving warfarin and require elective surgery. These patients require a clear management plan identified at their pre-operative assessment based around their risk group assignment (see Table 1).
The aim of the management is to reduce the patient’s INR to less than 1.5 on the day of surgery, a level deemed to be safe to proceed to surgery in the majority of settings. If a patient either requires an INR <1.3 at operation or has documented poor control with INRs > 5 then their management plan may need to be altered after discussion with a Consultant Haematologist. These patients may require an INR to be checked 7 days prior to the procedure to confirm the number of warfarin doses to be omitted.
Each patient is assigned to a risk group dependent upon his or her indication for anticoagulation. There are 3 possible risk groups – low, intermediate and high – and their management plan takes in consideration the bleeding risk versus the thrombo-embolic risk for that patient during the peri-operative period when the patient’s INR is outside the therapeutic range for that indication.

Please note:

Patients assigned to low and intermediate risk groups do not require hospitalisation solely for the purpose of withdrawal from warfarin.
If the management of the patient’s anticoagulation is not clear from these guidelines then it is important to discuss their care with a Consultant Haematologist.

References:

Kearon C, Hirsh J. Management of anticoagulation before and after elective surgery. N Engl J Med 1997;336:1506-1511.
British Committee for Standards in Haematology. Guidleines on oral anticoagulation: Third Edition. Br J Haem 1998;101:374-387.

Low	Intermediate	High
Atrial fibrillation with no history of embolism or valvular heart disease	Atrial fibrillation with positive history of embolism or valvular heart disease Acute venous thromboembolism (within 2/3 months) Recurrent venous thromboembolism	Mechanical heart valve ± atrial fibrillation Acute venous thromboembolism within last month ^§ Acute arterial embolism within last month
Omit 4 warfarin doses^† Admit as normal Cover with s/c LMWH as inpatient	Omit 4 warfarin doses^† Cover with s/c Clexane 40mg as outpatient Admit as normal Cover with s/c LMWH as inpatient	Omit 3 warfarin doses^† Admit 2 days pre-operatively Start i/v heparin infusion @ 1000 units per hour Check APTT and maintain at 1.5 –2.5 Stop heparin infusion 6 hours prior to surgery
Cover with s/c LMWH Restart warfarin maintenance dose on Day 1* Check INR daily Continue LMWH until INR > 1.8	Cover with s/c LMWH Restart warfarin maintenance dose on Day 1* Check INR daily Continue LMWH until INR > 1.8	Restart iv heparin 4-8 hours post-operatively once haemostasis achieved Check APTT after 12 hours and maintain @ 1.5-2.5 Restart warfarin maintenance dose on Day 1* Check INR daily Continue heparin infusion until INR>2.0

^§ Consider insertion of vena caval filter if elective surgery cannot be avoided^† May require more warfarin doses withheld if INR normally maintained > 3.0 or if requirement for INR < 1.3 on day of procedure.
* Aim to restart warfarin as soon as oral fluids tolerated and once haemostasis achieved