Microsoft word - pat t 22 v.2 - bridging anticoagulation - final.doc

PAT/T 22 v.2
Bridging Anticoagulation:
The Peri-procedural Management of
Patients on
Oral Vitamin K Antagonists (e.g. Warfarin)

This procedural document supersedes: PAT/T 22 v.1 – ‘Bridging
Anticoagulation’ Peri-opertive Management of Patients on Oral Anticoagulation
Therapy.

WARNING: Always ensure that you are using the most up to date approved procedural
document. If you are unsure, you can check that it is the most up to date version by looking on
the Trust Website: www.dbh.nhs.uk under the headings → ‘Freedom of Information’ →
‘Information Classes’ → ‘Policies and Procedures’

PAT/T 22 v.2
Amendment Form
To be completed when reviewing an existing approved procedural document

Please record brief details of the changes made alongside the next version number.
If the procedural document has been reviewed without change, this information will
still need to be recorded although the version number will remain the same.
Brief Summary of Changes
• Updated in accordance with the British Committee for Standards in Haematology (BCSH) guidance, incorporating the switch-over to Dalteparin. PLEASE READ IN FULL
PAT/T 22 v.2
Table of Contents
INTRODUCTION………………………………………………………………………………………4 SITUATIONS COVERED BY THIS GUIDELINE….…………………………………………….4 PRE-OPERATIVE ASSESSMENT AND MANAGEMENT……………………………………….4 Pre-op assessment…………………………………………………………………………………4 determine whether a patient is in the Standard risk or High risk category………………….4 Patients who are at particularly high risk of thrombosis……………………………………….5 Procedures which carry a very high bleeding risk………………………………………………5 Epidurals / spinals for high risk patients………………………………………………………….5 Renal impairment………………………………………………………………………………….5 Patients weighing more than 150kg………………………………………………………………5 Pre-operative management of emergency patients…………………………………………….5 POST-OPERATIVE MANAGEMENT……………………………………………………………….6 Monitoring for heparin-induced thrombocytopenia (HIT)………………………………………6 Spinal or epidural anaesthesia or analgesia…………………………………………………….6 Re-starting warfarin post-procedure…………………………………………………………….6 DISCHARGING PATIENTS………………………………………………………………………….7 BACKGROUND AND RATIONALE FOR RECOMMENDATIONS………………………………7 Introduction………………………………………………………………………………………….7 Bleeding risk associated with procedures……………………………………………………….8 Assessment of thrombotic risk……………………………………………………………………8 Low molecular weight heparin (LMWH) bridging anticoagulant therapy…………………….9 Timescale for peri-operative anticoagulation………………………………………………….10 Stopping warfarin………………………………………………………………………………10 Stopping other Vitamin K antagonists……………………………………………………….10 Other oral anticoagulants (e.g. rivaroxaban, dabigatran, apixaban).……………………10 Restarting anticoagulation and bleeding risk……………………………………………….10 REFERENCES……………………………………………………………………………………….11 Appendix 1 - Procedures which may be performed with an INR less than 3.0……………….13 Appendix 2 - Assessment of thrombotic risk…………………………………………………….14 Appendix 3 - Treatment guidelines for Standard risk patients………………………………….15 Appendix 4 - Treatment guidelines for High risk patients……………………………………….16 Appendix 5 - Cancellation of surgery………………………………………………………………17 PAT/T 22 v.2

INTRODUCTION
When patients on anticoagulation require surgery or an invasive procedure, the risks and
benefits of stopping or continuing anticoagulation must be considered. In many cases it is
necessary to stop the oral anticoagulant (most commonly warfarin) and replace it with low
molecular weight heparin (LMWH) until after the procedure. This is known as “bridging
anticoagulation”.

SITUATIONS COVERED BY THIS GUIDELINE

This guideline provides recommendations for the management of peri-procedural
anticoagulation for patients on warfarin who need interruption of anticoagulant therapy
(with an INR of less than 1.5) for a procedure.
This guideline may also be used as guidance for the management of patients who are on
acenocoumarol (Sinthrome®) or phenindione (Dindevan®), but additional advice should be
sought from a haematologist regarding the timescales for stopping these drugs prior to the
procedure.
This guideline may also be used as guidance for the management of patients who are on
long term treatment with low molecular weight heparin (LMWH).

This guideline does not cover the management of the following groups of patients:
• Patients on other oral anticoagulants such as dabigatran (Pradaxa®), rivaroxaban
(Xarelto®), or apixaban (Eliquis®). Advice on the management of these patients should always be sought from a haematologist and a senior anaesthetist. • Pregnant patients: advice should always be sought from a Obstetrician/
This document provides guidance only. In all cases, the risks of stopping anticoagulant therapy to prevent procedure related bleeding must be balanced against the risk of a further thromboembolic event. Throughout this guideline, the terms “Standard risk” and “High risk” refer to a
patient’s thrombotic risk.
PRE-OPERATIVE ASSESSMENT AND MANAGEMENT
Assessment of elective patients should be carried out at pre-operative assessment. Where
the procedure does not warrant a formal pre-operative assessment, the clinician ordering the
procedure should ensure that the guidance is followed.
If anticoagulation is to be interrupted, patients will need to be given clear instructions to take
their last dose of warfarin 5 days pre-operatively (i.e. 4 clear days) and attend for INR checks
as appropriate (if the patient is taking an anticoagulant other than warfarin, advice should be
sought from a haematologist regarding when to stop.). Patients should be advised that they
may need to continue receiving injections of dalteparin after discharge from hospital until
their INR is therapeutic. Patients or carers should be trained to inject dalteparin wherever
possible.

1. Pre-op assessment: assess whether anticoagulation needs to be interrupted for
the procedure. Certain procedures may be done whilst on warfarin with an INR of less
than 3.0 – see appendix 1.
2. If anticoagulation needs to be interrupted, determine whether a patient is in the
Standard risk or High risk category (see appendix 2 for criteria for stratification of
thrombotic risk).
PAT/T 22 v.2
3. Pre-operative investigations
3.1. A full blood count must be taken in the week prior to surgery (this may be performed at the same time as the pre-op INR). If the patient has acute or chronic thrombocytopenia (platelets less than 150 x 109/L) then discussion with a haematologist is recommended. 3.2. A U&E must be taken within 6 weeks prior to surgery. Ideally this should be repeated in the week prior to surgery for accurate assessment of renal function (i.e. eGFR). 3.3. Obtain an accurate weight for the patient so that dosing can be carried out correctly. 3.4. An INR will be required on day -2 (High risk patients) or day -1 (Standard risk 4. Certain patients should be discussed with senior clinicians before commencing
bridging:
4.1. Patients who are at particularly high risk of thrombosis should be discussed with
the senior clinician and anaesthetist involved: 4.1.1. patients with a venous thrombosis in the last 3 months 4.1.2. patients with recent stroke (within the previous 6 months) 4.1.3. patients with a history of prosthetic valve thrombosis 4.2. Procedures which carry a very high bleeding risk: these patients can follow the
pre-operative bridging guideline but post-operative bridging may need to be individualised (e.g. spinal surgery, radical prostatectomy). 4.3. Where there is uncertainty about the management of any patient, discuss with the senior clinician and anaesthetist involved.
5. “High risk” patients who are expected to require epidural/spinal anaesthesia or
analgesia for more than 48 hours post-operatively should be considered for an
alternative method of analgesia, as high dose dalteparin is incompatible with safe
removal of epidural catheters. If no other mode of anaesthesia/analgesia is suitable, the
patient must be discussed with a Anaesthetist/ Haematologist.

6. Patients with renal impairment
6.1. Standard risk patients should have doses reduced if eGFR is less than
20ml/min/1.73m2. High risk patients should use IV unfractionated heparin if
eGFR is less than 20ml/min/1.73m2.
Click here to access the online eGFR calculator

7. In patients weighing more than 150kg, discussion with a haematologist may be
considered as dose adjustments and monitoring of anti-Xa activity may be required.
8. Pre-operative management of emergency patients
8.1. For emergency life threatening procedures consider warfarin reversal with vitamin K and prothrombin complex concentrate (Beriplex™) pre-operatively. 8.2. For non life threatening emergency procedures, IV Vitamin K 2-5mg with a INR 8.3. For patients on low molecular weight heparin, discuss with a haematologist. 8.4. Post-procedure follow the guidance below. 9. If surgery is cancelled see advice in appendix 5. It is the responsibility of the person
cancelling the patient to inform pre-assessment clinic staff as patients will need advice regarding their bridging therapy. PAT/T 22 v.2

POST-OPERATIVE MANAGEMENT
1. Follow the appropriate treatment plan according to the patient’s thrombotic risk.
1.1. Treatment should be reviewed daily. Doses should only be escalated when haemostasis is secure. Pay particular attention if the patient is at high bleeding risk and seek advice if there are any concerns. If overt bleeding is present, stop dalteparin and discuss with a haematologist. 1.2. Doses should be adjusted according to the patient’s weight and renal function – 2. Monitoring for heparin-induced thrombocytopenia (HIT)
2.1. All patients receiving dalteparin must have a full blood count performed in the week 2.2. Full blood counts must be repeated every 3 to 4 days (i.e. twice weekly) for the first two weeks of treatment with dalteparin, including after discharge from hospital where applicable. 2.3. If the platelet count falls by 30-50% or to less than 150x109/L, and/or the patient develops new signs of thrombosis, suspect HIT: contact a haematologist for advice.
3. Spinal or epidural anaesthesia or analgesia
The risks of spinal haematoma with spinal/epidural anaesthesia are greatest at times of
needle/catheter insertion and removal.
3.1. Patients on low dose dalteparin (i.e. any “standard risk” patients, or “high
risk” patients receiving treatment on days 0, 1 or 2 post-operatively):
3.1.1. Spinal/epidural catheters must be inserted or removed at least 12 hours after 3.1.2. The next dose of dalteparin must be given at least 4 hours after inserting or 3.1.3. If a patient is on twice daily dosing of low dose dalteparin, a dose should be delayed by 4 hours to allow removal of the spinal/epidural catheter 3.2. Patients on high dose dalteparin (i.e. “high risk” patients from day 3 post-
operatively)
If a “high risk” patient is expected to require spinal/epidural analgesia for more than 48 hours post-operatively then an alternative route of analgesia should be considered. High dose dalteparin is incompatible with safe removal of spinal/epidural catheters. For further information, discuss with a Consultant Anaesthetist. 3.2.1. If a patient receiving high dose dalteparin still has a spinal/epidural catheter in situ, advice should be sought from an anaesthetist regarding management of the patient. 3.2.2. Spinal/epidural catheters must be inserted or removed at least 24 hours after 3.2.3. High dose dalteparin must not be administered within 12 hours of insertion or 3.3. INR should be less than 1.5 when epidural catheters are inserted or removed.
3.4. Be vigilant for the signs of spinal cord compression due to spinal haematoma:
backache, leg weakness, loss of perineal and leg sensation, loss of bladder control. These must be acted upon promptly with urgent referral to the on-call anaesthetist 4. Warfarin should be re-started at the patient’s usual dose on the first day post-
procedure
It will take up to 2 weeks for the INR to become therapeutic. Additional loading or boost
doses of warfarin are not recommended. Dalteparin should be continued until the INR is
greater than 2 for all patients including those with a higher INR target range.
5. Patients or their carers should be trained to inject dalteparin whilst they are in
hospital
Many patients are capable of self-injecting dalteparin after discharge, and failure to train
them appropriately places an unnecessary burden on the district nursing service.
PAT/T 22 v.2

DISCHARGING PATIENTS
1. Patients should remain on dalteparin treatment until INR is greater than 2.
• If INR is greater than 2 at the time of discharge, patients should be referred back to their usual anticoagulation provider. • It is essential that the anticoagulation hand held record (yellow book) is completed with details of discontinuation of the drug to enable safe further dosing. • Patients must have an INR check within 7 days of discharge (sooner if clinically • If INR is 2 or less, suitable discharge arrangements should be made. • Ensure supply of dalteparin is prescribed on the TTO • Train patient/carer to administer dalteparin wherever possible, or refer to a District • Monitoring requirements (INR and HIT monitoring) should be considered.
BACKGROUND AND RATIONALE FOR RECOMMENDATIONS
Introduction
The purpose of this document is to provide recommendations for the management of peri-
procedural anticoagulation for patients on oral anticoagulant therapy who require an INR of
less than 1.5 prior to the procedure. They are part of a Trust wide initiative to implement
NPSA guidance for safer anticoagulation and are adapted from the guidelines by the
American College of Chest Physicians (Douketis et al, 2008) and the British Committee for
Standards in Haematology (Keeling et al, 2011).
There are an estimated 500,000 patients in the UK using oral anticoagulants (warfarin,
acenocoumarol and phenindione), the majority for atrial fibrillation (AF) and mechanical heart
valves (Baglin et al, 2007). In the USA approximately 10% of patients on oral anticoagulants
are thought to require surgery or invasive procedures annually (Douketis et al, 2008) making
peri-operative bridging anticoagulation a common occurrence. A risk assessment by the
National Patient Safety Agency demonstrated wide variation in practice of the peri-operative
management of patients on oral anticoagulation both between and within hospital trusts as
well as deficiencies in training of staff dealing with anticoagulation issues (National Patient
Safety Agency, 2006). This can lead to potentially unnecessary admissions for pre-
procedural anticoagulation, delays in discharge because of unstable anticoagulation, and
unsafe anticoagulation management with potentially increased morbidity and mortality.
For patients on oral anticoagulant therapy requiring invasive procedures, the risk of a
thromboembolic event in the peri-operative period when anticoagulation is interrupted must
be balanced against the risk of bleeding when these are continued. If the risk of procedure
related bleeding whilst continuing oral anticoagulation is thought to be small, anticoagulation
may be continued. This applies to some minor dental (Douketis et al, 2008;Perry et al, 2007),
ophthalmic (Douketis et al, 2008) and dermatological (Douketis et al, 2008) procedures and
should be discussed with the relevant team. Recent guidelines from the British Society of
Gastroenterology suggest that diagnostic endoscopic procedures with or without biopsy,
biliary or pancreatic stenting and diagnostic endoscopic ultrasound can also be performed
whilst the patient is on therapeutic anticoagulation (Veitch et al, 2008). Similarly, patients
requiring invasive cardiology procedures may be at low risk of bleeding and can be done
whilst anticoagulated. These patients should be discussed with the cardiology team before
anticoagulation is altered. Patients requiring diagnostic angiography also have a low risk of
bleeding and procedures can generally be done on warfarin provided the INR is less than 3
PAT/T 22 v.2
and the guidance as given by vascular radiology should be followed. A list of procedures
that may be undertaken whilst a patient’s INR is less than 3 is given below, and in appendix
1 of this document.
If the risk of procedure related bleeding is thought to outweigh the risk of thromboembolic
events, anticoagulation should be stopped and bridging anticoagulation considered
depending on the thrombotic risk. If bridging anticoagulation is instituted, this should be done
in a manner whereby both the time without anticoagulation and the bleeding risk are
minimised. The peri-procedural management therefore depends on individual patient
characteristics and the type of procedure done.

Bleeding risk associated with procedures
Note that this list is not comprehensive and is intended as guidance only.
Very high risk1
High risk
Low risk2
Procedures which may be
performed on warfarin 3
Biliary or pancreatic stenting (Veitch et Diagnostic EUS (Veitch et al, 2008) Minor dental surgery (Perry et al, 2007) (cataract extraction) (Douketis et al, abdominal and thoracic surgery renal biopsy. 1 Procedures with very high bleeding risk can follow this guideline pre-operatively. Post operative
dalteparin should not be escalated before day +3 and some may need an individualised decision.
2 Minor procedures at low risk of bleeding but where warfarin needs to be stopped should be identified
by the treating physician or surgeon. In patients with a high thrombotic risk undergoing a low risk
procedure high dose dalteparin may be restarted at earliest 24 hours after the procedure. Caution
may be needed with procedures that appear to have a low bleeding risk but have been associated
with higher bleeding rates. These include resection of large pedunculated polyps or broad based flat
(sessile) polyps requiring EMR and pacemaker or defibrillator implantation.
3 Guidelines on selected procedures that may be done whilst on warfarin are available from the British
Society for Gastroenterology (Veitch et al, 2008), ACCP (Douketis et al, 2008) and British Committee
for Standards in Haematology (Perry et al, 2007) (Keeling et al, 2011). Other minor vascular and
cardiological procedures may also be possible whilst on warfarin but should be discussed with the
relevant team.
Assessment of thrombotic risk
This guideline recommends stratification of thrombotic risk as Standard risk or High risk.
Mechanical heart valves
The risk of thrombosis is highest in mechanical mitral valve prosthesis and aortic valve
prosthesis using caged ball or tilting disc devices. The risk is lower in modern bileaflet aortic
valves. Most studies assessing the use of low molecular weight heparin (LMWH) as bridging
anticoagulation have used therapeutic dose regimens (for a review see Douketis et al, 2008).
Two studies have used low dose LMWH (including patients with mitral valve prosthesis) but it
is not clear if this is sufficient as it can be argued that higher doses of LMWH are needed for
the prevention of arterial thrombosis. The latter however is also not established.
PAT/T 22 v.2

This guideline therefore classifies all patients with mechanical valve prosthesis as high risk
except those with bileaflet aortic valves without any other risk factors for stroke.
Atrial Fibrillation
Patients at highest risk for stroke are those with a previous stroke or rheumatic valvular heart
disease. These patients should be bridged according to the high risk guideline. For others,
the optimal bridging regimen is unclear. The BCSH guidelines (Keeling et al, 2011) suggest
using prophylactic doses of LMWH in patients without prior stroke or TIA, whereas the ACCP
guidelines suggest that either prophylactic or higher doses are acceptable in patients with a
CHADS2 score up to 4 (Douketis et al, 2008).
This guideline recommends using prophylactic doses of LMWH in all patients with AF except
those with previous stroke, TIA or rheumatic valvular heart disease. If there is any
uncertainty as to which category a patient should be assigned, this should be discussed with
the cardiology team/relevant medical team prior to admission.

Previous venous thrombotic events (VTE)
In contrast to arterial thrombotic events, there is evidence that prophylactic dose LMWH
therapy decreases the post-operative thrombotic risk. Therefore there is a clear role for the
use of prophylactic dose LMWH in patients with a previous VTE who are on long term
anticoagulation with warfarin and have a target INR of 2 – 3.
Patients with VTE in the previous 2 – 3 months are at high risk of recurrence and any
procedures (for which interruption of anticoagulation is necessary) should preferably be
delayed for 2 – 3 months. If this is not possible, a temporary IVC filter should be considered.
Patients with antiphospholipid syndrome (who have had either arterial or venous thrombotic
events) and those with recurrent thrombosis whilst on warfarin (who are managed with a
target INR of 3.5) are at high risk of recurrence: they should be managed according to the
high risk guideline.

The use of low molecular weight heparin (LMWH) for bridging anticoagulant therapy
LMWH given subcutaneously has a 90 – 100% bioavailability and a more predictable
anticoagulant response than unfractionated heparin (UFH). It has a half life of approximately
4 hours and is given in weight adjusted doses. Dosage monitoring is generally not necessary
except in patients with renal failure, extremes of body weight, and during pregnancy.
Compared to unfractionated heparin, it has a favourable benefit to risk ratio in animal models
and when used to treat VTE (Hirsh et al, 2008). In addition LMWH can be given in the
outpatient setting. Because of these advantages LMWH is recommended in preference to
unfractionated heparin (UFH) for anticoagulation bridging.
Standard risk patients should receive prophylactic doses of LMWH until oral anticoagulation
has become therapeutic.
High risk patients should receive LMWH with the dose increasing at increments post-
operatively until full therapeutic doses have been achieved. LMWH should continue until oral
anticoagulation has become therapeutic (INR greater than 2.0)
Dose adjustments are necessary for patients with renal impairment. Patients requiring low
“prophylactic” doses of dalteparin should have doses reduced if their eGFR is less than
20ml/min/1.73m2
For patients with renal impairment (calculated eGFR less than 20 ml/min) requiring high dose
(“therapeutic dose”) LMWH, unfractionated heparin infusion may be preferable. High risk
patients should use IV unfractionated heparin if eGFR is less than 20ml/min/1.73m2.
PAT/T 22 v.2

Timescale for peri-operative anticoagulation
Stopping warfarin
Prospective cohort studies stopped warfarin 5 – 6 days prior to surgery (for a review see
Douketis et al, 2008). One study stopping anticoagulation 5 days before surgery found that
7% of patients had an INR greater than 1.5 the day before surgery which was corrected with
1mg oral vitamin K (Kovacs et al, 2004). In another retrospective study including 43 patients
with an INR of 1.5 – 1.9, administration of 1mg oral vitamin K resulted in INR normalization in
91% of the patients (Woods et al, 2007). An INR greater than 1.5 on the day of operation is
more likely in patients with a higher INR target (e.g. mechanical heart valves and patients
with recurrent VTE whilst on warfarin) and elderly patients. This guideline recommends
stopping warfarin 5 days prior to surgery (4 clear days), checking the INR the day prior to
surgery and giving 1mg oral vitamin K if INR greater than 1.5. Patients at high thrombotic risk
should have their INR checked on day -2 and started on LMWH. Advice on starting LMWH is
detailed below.
Stopping other Vitamin K antagonists
Other vitamin K antagonists (i.e. phenindione and acenocoumarol) have shorter half-lives
and a shorter duration of action. They should be stopped closer to the date of surgery:
advice should be sought from a haematologist about the management of patients on these
anticoagulants.
They should be re-started later after surgery due to their short half-lives and more rapid
onset of action.
Other oral anticoagulants (e.g. rivaroxaban, dabigatran, apixaban)
The newer oral anticoagulants have a different mode of action to vitamin K antagonists, and
require different management. They are renally excreted and therefore the timescale for
stopping and re-starting peri-operatively is partly dependent on renal function. It is difficult to
assess the degree of anticoagulant effect in patients who are on these drugs as a clotting
screen may appear normal. Advice should always be sought from a haematologist and a
senior anaesthetist regarding the management of these patients.
Restarting anticoagulation and bleeding risk
When to anticoagulation is restarted after a procedure depends on the bleeding risk
associated with the type of procedure and the proximity of surgery. The ultimate dose is
dependent on the thrombotic risk of the patient. The risk of bleeding is highest in patients
who receive therapeutic doses of anticoagulation in the immediate post-operative period. The
ACCP guidelines suggest that therapeutic-dose LMWH should not be restarted within 24
hours of minor procedures with a low bleeding risk and not within 48 – 72 hours of surgery
with a high bleeding risk.
Very little data are available on surgery with a very high bleeding risk. There continue to be
concerns about potential high bleeding rates in patients where therapeutic anticoagulation
has been started post-operatively. Studies are underway randomising patients with high risk
AF and mechanical heart valves to bridging with low molecular weight heparin versus no
bridging [The BRIDGE study (http://clinicaltrials.gov/ct2/show/NCT00786474) and PERIOP-2
study (http://clinicaltrials.gov/ct2/show/NCT00432796).]
Provided surgical haemostasis is secure, low dose prophylactic LMWH can usually be
restarted 6 – 8 hours after surgery. Patients at high risk of thrombosis should initially be
started on low-dose LMWH and the dose can subsequently be escalated over the following
48-72 hours provided haemostasis is secure.
Warfarin can be restarted at the patient's usual dose on the day after surgery provided
haemostasis is secure. Loading or boost doses of warfarin should be avoided as these
increase the risk of over-anticoagulation. It will take 1 to 2 weeks for the patient’s INR to
become therapeutic. LMWH should be continued until the INR is greater than 2.0.
PAT/T 22 v.2

Other vitamin K antagonists (i.e. phenindione and acenocoumarol) should be re-started later
after surgery due to their short half-lives and more rapid onset of action.
REFERENCES
Baglin,T.P., Cousins,D., Keeling,D.M., Perry,D.J., & Watson,H.G. (2007) Safety indicators for inpatient and outpatient oral anticoagulant care: [corrected] Recommendations from
the British Committee for Standards in Haematology and National Patient Safety
Agency. Br.J.Haematol., 136, 26-29.
Douketis,J.D., Berger,P.B., Dunn,A.S., Jaffer,A.K., Spyropoulos,A.C., Becker,R.C., & Ansell,J. (2008) The perioperative management of antithrombotic therapy: American
College of Chest Physicians Evidence-Based Clinical Practice Guidelines (8th
Edition). Chest, 133, 299S-339S
http://chestjournal.chestpubs.org/content/133/6_suppl/299S.full?sid=596b3771-d915-
4539-b288-91379836acae
Hirsh,J., Bauer,K.A., Donati,M.B., Gould,M., Samama,M.M., & Weitz,J.I. (2008) Parenteral anticoagulants: American College of Chest Physicians Evidence-Based Clinical
Practice Guidelines (8th Edition). Chest, 133, 141S-159S
http://chestjournal.chestpubs.org/content/133/6_suppl/141S.long
Keeling,D., Baglin,T., Taite,C. et al (2011) Guidelines on oral anticoagulation with warfarin – fourth edition. British Journal of Haematology doi:10.1111/j.1365-2141.2011.08753.x http://www.bcshguidelines.com/documents/warfarin_4th_ed.pdf Kovacs,M.J., Kearon,C., Rodger,M., Anderson,D.R., Turpie,A.G., Bates,S.M., Desjardins,L., Douketis,J., Kahn,S.R., Solymoss,S., & Wells,P.S. (2004) Single-arm study of
bridging therapy with low-molecular-weight heparin for patients at risk of arterial
embolism who require temporary interruption of warfarin. Circulation, 110, 1658-1663.
National Patient Safety Agency (2007) Actions that can make anticoagulant therapy safer. http://www.nrls.npsa.nhs.uk/resources/?EntryId45=59814 Pengo,V., Cucchini,U., Denas,G., Erba,N., Guazzaloca,G., La,R.L., De,M., V, Testa,S., Frontoni,R., Prisco,D., Nante,G., & Iliceto,S. (2009) Standardized low-molecular-
weight heparin bridging regimen in outpatients on oral anticoagulants undergoing
invasive procedure or surgery: an inception cohort management study. Circulation,
119, 2920-2927.
Perry,D., Nokes,T., & Helliwell,P. (2007) Guidelines for the management of patients on oral anticoagulants requiring dental surgery. http://www.bcshguidelines.com/documents/WarfarinandentalSurgery_bjh_264_2007.
pdf Singer,D.E., Albers,G.W., Dalen,J.E., Fang,M.C., Go,A.S., Halperin,J.L., Lip,G.Y., & Manning,W.J. (2008) Antithrombotic therapy in atrial fibrillation: American College of
Chest Physicians Evidence-Based Clinical Practice Guidelines (8th Edition). Chest,
133, 546S-592S
http://chestjournal.chestpubs.org/content/133/6_suppl/546S.full?sid=269090ce-e1de-
4474-93f0-01f3272563c6
VanVeen,J.,Ellis,R (2012) Bridging Anticoagulation- The periporcedural management of patients on oral anticoagulants. STHFT guideline Veitch,A.M., Baglin,T.P., Gershlick,A.H., Harnden,S.M., Tighe,R., & Cairns,S. (2008) Guidelines for the management of anticoagulant and antiplatelet therapy in patients PAT/T 22 v.2
undergoing endoscopic procedures. Gut, 57, 1322-1329.
http://gut.bmj.com/content/57/9/1322.full.pdf (Athens password required)
Woods,K., Douketis,J.D., Kathirgamanathan,K., Yi,Q., & Crowther,M.A. (2007) Low-dose oral vitamin K to normalize the international normalized ratio prior to surgery in patients
who require temporary interruption of warfarin. J.Thromb.Thrombolysis., 24, 93-97.
PAT/T 22 v.2
Appendix 1
PROCEDURES WHICH MAY BE PERFORMED WITH AN INR LESS THAN 3.0
Surgery without interruption of oral anticoagulation
• Dermatological
• Joint and soft tissue injections or aspirations • Endoscopy without biopsy
• Dental surgery (single or multiple extractions) see below

Endoscopic procedures with high bleeding risk requiring bridging anticoagulation.
• Endoscopy with biopsy
• Polypectomy
• Pneumatic or bougie dilation
• Endosonographic guided fine needle aspiration.

Dental surgery
• Oral
should not be discontinued in patients with a stable INR in the
therapeutic range 2.0-4.0 requiring out patient dental surgery. • Stably anticoagulated patients who are prescribed a single dose of antibiotics as prophylaxis against endocarditis do not need alteration of their anticoagulant regimen. • A check INR is recommended within 72 hours prior to dental surgery. • Risk of bleeding maybe minimised by use of 5% tranexamic acid mouthwashes, oxidised cellulose or collagen sponges and sutures. • Patients on oral anticoagulants with co-existing medical problems e.g. liver disease, renal disease, thrombocytopenia or who are taking anti platelet drugs are at an increased
risk of bleeding and should NOT have their procedure in the primary care setting.

Diagnostic angiographic procedures by vascular radiology:
Check INR in pre-assessment clinic If INR less than 3.0, check the INR on the day-ward, proceed with angiography and discharge on usual dose of warfarin If the INR is greater than 3.0 and the patient is non-urgent, adjust dose accordingly and proceed when the INR is less than 3.0 If the INR is greater than 3.0 and the patient is urgent discuss with Radiologist and a haematologist
Some invasive cardiology procedures may be done whilst the patient is
anticoagulated on warfarin: these patients should be discussed with the cardiology team
before anticoagulation is altered.
PAT/T 22 v.2
Appendix 2
ASSESSMENT OF THROMBOTIC RISK

Reason for being on oral
STANDARD RISK
HIGH RISK
anticoagulants
Mechanical heart valve
Bileaflet aortic valve and no other risk factors Bileaflet prosthetic aortic valve and
hypertension diabetes prior stroke or TIA Chronic atrial fibrillation
Atrial fibrillation without prior stroke/TIA or Atrial fibrillation with previous stroke/TIA Atrial fibrillation with rheumatic valvular heart disease Venous thromboembolism or
Recent episode of VTE (within 3 months) – discuss with senior clinician antiphospholipid syndrome
and anaesthetist: consider postponing surgery or placing an IVC filter Antiphospholipid syndrome with a history of venous or arterial Recurrence of VTE on oral anticoagulation (target INR 3.5) PAT/T 22 v.2
Appendix 3
TREATMENT GUIDELINES FOR STANDARD RISK PATIENTS
Use eGFR to assess renal function.
Click here to access the online eGFR calculator TREATMENT PLAN FOR STANDARD RISK PATIENTS
with eGFR 20ml/min/1.73m2 or greater
less than 46kg
46 – 120kg
120 – 150kg
greater than 150kg
Last dose of warfarin/ Vitamin K antagonist (4 clear days) Check INR:
if greater than 1.5: give vitamin K 1mg orally stat. Re-check INR on day 0 Start dalteparin if INR is less than 2.0 (give last dose at least 12 hours before procedure) once daily
once daily
units once daily
twice daily
Restart warfarin at patient’s usual dose. Continue dalteparin as per day +1 until INR is greater than 2.0 Dalteparin must only be started post-operatively when haemostasis is secure.
TREATMENT PLAN FOR STANDARD RISK PATIENTS
with eGFR less than 20 ml/min/1.73m2
Day Recommended
treatment
Last dose of warfarin/ Vitamin K anatagonist (4 clear days) if greater than 1.5: give vitamin K 1mg orally stat. Re-check INR on day -1. Start dalteparin 2,500 units OD if INR is less than 2.0 (give last dose at least 12 hours before Dalteparin 2,500 units 6 – 8 hours post-operatively Dalteparin 2,500 units once daily
+1 onwards
Restart warfarin at patient’s usual dose. Continue dalteparin as per day +1 until INR is greater than 2.0 PAT/T 22 v.2
Appendix 4
TREATMENT GUIDELINES FOR HIGH RISK PATIENTS
Click here to access the online eGFR calculator
TREATMENT PLAN FOR HIGH RISK PATIENTS
with calculated eGFR 30ml/min or greater
greater than
less than 46kg
100-120 kg
121-150 kg
Last dose of warfarin / vitamin K antagonist (4 clear days) Check INR: if greater than 1.5: give Phytomenadione (vitamin K) 1mg orally stat and re-check INR Start dalteparin if INR is less than 2.0 Restart warfarin at patient’s usual dose on day +1. Continue dalteparin until the INR >2.0 on 2 consecutive days. Dalteparin must only be started or increased post-operatively when haemostasis is
Dalteparin dosing for high risk patients
with calculated eGFR less than 30 ml/min
PAT/T 22 v.2
Appendix 5
CANCELLATION OF SURGERY

Cancellation of surgery will lead to an increased period of bridging (even if warfarin is restarted). There
is the potential for patients to receive inadequate anticoagulation or no anticoagulation during this time.
This would put them at increased risk of thromboembolic events.
• Cancellation should be avoided if at all possible. • If cancellation is unavoidable, postpone the surgery or procedure for a maximum of 1 week. • Teach patients or carers to inject dalteparin wherever possible, to avoid unnecessary district Dalteparin dosing for HIGH RISK PATIENTS who have been cancelled
with calculated eGFR 30ml/min or greater
greater than
less than 46kg
100-120 kg
121-150 kg
The last dose should be given in the morning on the day prior to procedure/surgery Dalteparin dosing for high risk patients
with calculated eGFR less than 30 ml/min

Source: http://www.jmaskill.co.uk/web_documents/pat_20t_2022_20v.2_20-_20bridging_20anticoagulation_20-_20final.pdf