Volume 6, No. 1
October 2012
This Medicines Information Leaflet is produced locally to optimise the use of medicines by encouraging prescribing
that is safe, clinically appropriate and cost-effective to the NHS.
Elective Surgery and Invasive Procedures in Patients Taking Warfarin
he management of patients who are receiving oral
anticoagulation with warfarin and who require
surgery depends on the underlying thrombotic
risk, the intended surgical procedure, and the risk of
bleeding associated with it. This MIL covers the
management of patients on warfarin undergoing
elective surgery (excluding vascular surgery), grouped
into three categories: major surgery, minor surgery and
endoscopy. Dentistry is not performed as an inpatient
at OUH, so has been omitted from this version of the
MIL. For guidelines on managing oral anticoagulation in
patients undergoing routine dental surgery, please see
the OHTC outpatient guidelines. For patients taking
other oral anticoagulants, please contact the Oxford
Anticoagulation Service.
1. Major surgery or procedure which requires the
INR to be normalized.
(i) Pre-operative assessment
The pre-operative assessment team must liaise with the
anticoagulation service (JR bleep 1857).
Warfarin should be stopped 5 days before surgery.
The main decision is whether to give bridging
anticoagulant therapy with full treatment doses of low
molecular weight heparin (LMWH) or, less commonly
with unfractionated heparin (UFH) once the INR is less
than 2.0.
Patients with mechanical heart valves (MHV), patients
with atrial fibrillation (AF) and previous stroke/TIA or
multiple other risk factors and patients who are at high
risk of recurrent venous thromboembolism (VTE)
should be considered for bridging therapy (see table 1).
All patients who do not require full dose
anticoagulation over the operative period should be
risk assessed and considered for VTE prophylaxis as for
any other patient.
There is no need to monitor the INR in patients who are
at home for the 5 days before surgery. The last dose of
warfarin should be taken on the evening of day -6.
LMWH is started on the morning of day -3 and is
continued until day -1 (i.e. 24 hours before surgery). If
the surgery poses a high risk of bleeding, this final dose
Medicines Management and Therapeutics Committee
Oxford University Hospitals
of LMWH on day -1 should only be half the full
anticoagulant dose. NB according to Oxfordshire Shared
Care guidelines, supply of LMWH for patients who need
bridging at home should come from the hospital. This
should be discussed and arranged during the preoperative assessment.
In patients who are in hospital in the run up to surgery
and who are receiving bridging anticoagulation with
therapeutic dose UFH (see MIL vol.5 no.6 “Guidelines on
when to use and how to monitor unfractionated heparin
in adults” for full guidance on the use of UFH) the
heparin should be stopped 4-6 hours before surgery
(discuss timing with the operating surgeon).
In all patients whose warfarin has been stopped 5 days
before surgery, the INR should be measured on the day
before surgery, allowing correction with oral
phytomenadione (vitamin K) if it is greater than or
equal to 1.5 (suggested dose 2mg). If correction with
phytomenadione is required, the INR should be rechecked on the morning of surgery.
Table 1: Risk stratification for bridging therapy
Bridging with
treatment dose
heparin not required
Bridging with
treatment dose
heparin considered
Last episode > 3
months ago
Last episode within
previous 3 months
AF with no prior
stroke/TIA and without
multiple other risk
AF and previous
stroke/TIA or multiple
other risk factors
Bileaflet aortic MHV
with no other risk
Mitral MHV;
Non-bileaflet aortic
Bileaflet aortic MHV
with other risk factors
(ii) Restarting anticoagulation after surgery
In patients who are undergoing a procedure which
carries a low bleeding risk and who were receiving
bridging therapy with full dose UFH or LMWH preoperatively, it should be resumed 24 hours after the
October 2012
Medicines Information Leaflet
procedure assuming adequate haemostasis was
achieved at surgery (discuss with the operating
The recommendations for action following risk
assessment are summarized below:
In patients undergoing a procedure which carries a high
risk of bleeding, the perioperative anticoagulation
depends on a balance between the risk of bleeding and
the risk of thrombosis. The choices are:
Warfarin should be discontinued 5 days before the
procedure. Bridging therapy with heparin (UFH or
LMWH) should be considered for high risk conditions
while the INR is below therapeutic level (especially for
mechanical valve in mitral position)
1. Avoid all heparin after surgery
2. Give prophylactic dose LMWH or UFH after surgery
once haemostasis has been secured.
3. Give therapeutic dose LMWH or UFH no sooner than
48 hours if haemostasis is secured.
i.e. therapeutic dose LMWH or UFH must not be given
for at least 48 hours after high bleeding risk surgery.
Instruction for the provision of post-operative heparin
is the responsibility of the operating surgeon.
Warfarin can be resumes, at the normal maintenance
dose, the evening of surgery or the next day if there is
adequate haemostasis, following discussion with the
operating surgeon.
2. Minor surgery or procedure with low bleeding
For some operations the surgeon may advise that the
INR need only be reduced (to 1.5‐2.0 for example) for
the procedure in which case bridging anticoagulation
may not be required.
In these cases, the surgical team should liaise with the
anticoagulation service in good time to make necessary
dose adjustments and arrange heparin cover (if
required) and arrange an INR test the day before
surgery as described above.
Some procedures, such as joint injections and cataract
surgery, can be carried out without interrupting
warfarin therapy. However the person performing the
procedure may advise that the INR is reduced to
1.5‐2.0. If so they should make the necessary dose
adjustments, assess the need for bridging therapy and
arrange this if it is needed.
3. Endoscopy in anticoagulated patients
In general, low risk diagnostic procedures including
mucosal biopsy can be performed when the INR is up to
and including 3.0 without altering anticoagulation. For
therapeutic procedures, the risk of post-procedure
bleeding is higher and reduction of anticoagulation is
preferred. There are, however, no absolute rules and
the risks and benefits should be discussed with the
patient prior to the procedure and an individual
decision made.
If warfarin is stopped, it is safe to reinstate
anticoagulation on the evening of the procedure unless
the endoscopist advises otherwise.
The risk of thromboembolism and risk of bleeding after
a procedure can be divided into high and low; see table
High Risk Procedure
Low Risk Procedure
No change in anticoagulation is recommended unless
the INR is greater than 3.0.
Table 2: Risk evaluation for endoscopic procedures
High Risk Conditions
Mechanical valve in mitral
AF with valvular heart
Mechanical valve and prior
thromboembolic event
Low Risk Conditions
AF without valvular heart
Biprosthetic valve (xenograft)
Mechanical valve in aortic
High Risk Procedures
Sphincterotomy at ERCP
PEG placement
Treatment of varices
Argon plasma coagulation
Low Risk Procedures
Diagnostic upper endoscopy
or colonoscopy and mucosal
ERCP +/- stent without
sphincterotomy or precut
1. Keeling, D., Baglin, T., Tait, C., Watson, H., Perry, D., Baglin,
C., Kitchen, S. & Makris, M. (2011) Guidelines on oral
anticoagulation with warfarin - fourth edition. Br J Haematol
154, 311-324
2. Dunn, A.S. and A.G. Turpie, Perioperative management of
patients receiving oral anticoagulants: a systematic review.
Arch Intern Med, 2003. 163(8): 901-8.
3. Kearon, C., Managment of anticoagulation before and after
elective surgery, in American Society of Hematology Education
Program Book. 2003. 528-534.
4. Douketis, J.D., et al., The perioperative management of
antithrombotic therapy: American College of Chest Physicians
Evidence-Based Clinical Practice Guidelines (9th Edition).
Chest, 2012. 141 (Suppl).
5. Eisen, G.M., et al., Guideline on the management of
anticoagulation and antiplatelet therapy for endoscopic
procedures. Gastrointest Endosc, 2002. 55(7): 775-779.
Prepared by:
Scott Harrison, Lead Pharmacist – Anticoagulation; Dr. David
Keeling, Consultant Haematologist; Teresa Tripp, Lead
Thrombosis Nurse
With advice from:
Dr. Clare Crowley and Joanne Coleman (Medicines Safety
Team); Dr. John Reynolds (MAC chairman)
Review date: October 2014