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Guidelines for warfarin management inthe communityJanuary 2016 Disclaimer This guideline has been prepared to promote and facilitate standardisation and consistency of practice, using a multidisciplinary approach
Information in this guideline is current at time of publication
Queensland Health and the Royal Flying Doctor Service do not accept liability to any person for loss or damage incurred as a result of reliance upon the material contained in this guideline
Clinical material offered in this guideline does not replace or remove clinical judgement or the professional care and duty necessary for each specific patient case
Clinical care carried out in accordance with this guideline should be provided within the context of locally available resources and expertise
This Guideline does not address all elements of standard practice and assumes that individual clinicians have the responsibility to: Discuss care with consumers in an environment that is culturally appropriate and which enables respectful confidential discussion. This includes the use of interpreter services where necessary
Advise consumers of their choice and ensure informed consent is obtained
Provide care within scope of practice, meet all legislative requirements and maintain standards of professional conduct
Apply standard precautions and additional precautions as necessary, when delivering care
Document all care in accordance with mandatory and local requirements
Guidelines for Warfarin Management in the CommunityPublished by the State of Queensland (Queensland Health) and the Royal FlyingDoctor Service Queensland Section, May, 2016© State of Queensland (Queensland Health) 2016This work is licensed under a Creative Commons Attribution Non-Commercial ShareAlike 3.0 Australia licence. In essence, you are free to copy, communicate and adaptthe work for non-commercial purposes, as long as you attribute Medicines Regulationand Quality, Queensland Health and the Royal Flying Doctor Service, QueenslandSector, you distribute any derivative work only under this licence and you abide by thelicence terms. To view a copy of this licence, visithttp://creativecommons.org/licenses/by-nc-sa/3.0/au/deed.enFor more information contact:Medicines Regulation and Quality, Department of Health, GPO Box 48, Brisbane QLD4001, email [email protected], phone (07)3328 9818
Disclaimer:The content presented in this publication is distributed by the Queensland Government as an information source only
The State of Queensland makes no statements, representations or warranties about the accuracy, completeness orreliability of any information contained in this publication. The State of Queensland disclaims all responsibility and allliability (including without limitation for liability in negligence) for all expenses, losses, damages and costs you mightincur as a result of the information being inaccurate or incomplete in any way, and for any reason reliance was placedon such information
Guidelines for warfarin management in the community - ii - ContentsGuidelines for warfarin management in the community ...................................... 1 Purpose ............................................................................................................... 1 Scope .................................................................................................................. 1 Related documents .............................................................................................. 1 Authorising Policy and Standard/s: ............................................................. 1 Procedures, Guidelines and Protocols: ....................................................... 1 Forms and templates: ................................................................................. 1 Other: ......................................................................................................... 11. Guideline .................................................................................................... 2 1.1 General information .................................................................................... 2 1.2 Indications .................................................................................................. 2 1.3 Risk assessment ........................................................................................ 3 1.3.1 Risk of stroke in patients with atrial fibrillation .................................... 3 1.3.2 Risk of bleeding ................................................................................. 4 1.3.3 Contraindications to warfarin therapy................................................. 5 1.4 Initiation of warfarin..................................................................................... 6 1.4.1 Patients at low risk of thrombosis (i.e. AF) ......................................... 6 1.4.2 Patients at high risk of thrombosis (e.g. DVT) .................................... 7 1.5 Subsequent maintenance dosing using warfarin ......................................... 8 1.6 Frequency of INR monitoring .................................................................... 10 1.6.1 Patients at low risk of thrombosis (i.e. AF) ....................................... 10 1.6.2 Patients at high risk of thrombosis (e.g. DVT) .................................. 11 1.7 Management of high INR .......................................................................... 11 1.8 Perioperative thromboembolism risk stratification ..................................... 13 1.9 Stopping warfarin for procedures .............................................................. 13 1.10 Factors that influence the INR .................................................................. 15 1.11 Patient counselling ................................................................................... 18 1.12 Auditing management of warfarin ............................................................. 19 1.13 Guide for patients non-responsive to warfarin therapy .............................. 192. Review ..................................................................................................... 203. Business Area Contact ............................................................................ 204. Glossary of terms used in the policy and supporting documents ............. 215. Approval and Implementation .................................................................. 216. Version Control ........................................................................................ 227. References............................................................................................... 22Guidelines for warfarin management in the community - iii - Guidelines for warfarin management in thecommunityPurposeThis guideline provides recommendations regarding best practice for initiation andmanagement of warfarin for patients in the community, as well as primary andcommunity health services (e.g. Home Based Acute Care Service or Hospital in theHome). This guideline applies to all Queensland Health patients prescribed warfarin inthe community where a work unit procedure is unavailable
ScopeThis guideline provides information for all Queensland Health employees (permanent,temporary and casual) and all organisations and individuals acting as its agents(including Visiting Medical Officers, Royal Flying Doctor Service and other partners,contractors, consultants and volunteers)
Related documentsAuthorising Policy and Standard/s: Queensland Health List of Approved MedicinesProcedures, Guidelines and Protocols: Queensland Health inpatient Guidelines for Anticoagulation using Warfarin – Adult (available from Medicines Regulation and Quality, Department of Health, Queensland Health, email: [email protected])Forms and templates: Queensland Health Non-Inpatient Rural and Remote Warfarin Record, SW032, Material number (FAMMIS): 10202082Other: Warfarin patient education booklet (e.g. medication manufacturing company, private pathology or other)Guidelines for warfarin management in the community -1- 1. Guideline1.1 General informationWarfarin inhibits the synthesis of vitamin K-dependent clotting factors (II, VII, IX, X) andthe antithrombotic factors, protein C and protein S. The suppression of proteins C andS can create a hypercoagulable state in the first few days of warfarin treatment,especially at doses for conditions with high risk of thrombosis (see section 1.4.2)(Clarke et al. 2006). In patients at high risk of thrombosis, such as venousthromboembolism, another anticoagulant (e.g. heparin) is required to provide adequateanticoagulation cover for the first five days of warfarin initiation therapy
Warfarin is extensively metabolised by the liver, mostly to inactive hydroxylatemetabolites which are predominantly eliminated by the renal system (Micromedex 2.02015). For factors that may impact on the metabolism of warfarin or monitoring of theINR refer to section 1.9 Factors that Influence the INR
The two brands of warfarin available in Australia, Marevan® and Coumadin®, are notinterchangeable and swapping brands may affect INR control. Queensland Healthfacilities generally use the Marevan® brand
1.2 IndicationsDuration of treatment and target INR may vary depending on the indication for warfarintherapy (see Table 1 below)
Table 1 Indications for warfarin therapy with recommendations for target INR and duration Indication Target INR Minimum recommended range duration Valve repairs 2–3 6 weeks post operatively Bioprosthetic valve DVT 2–3 3 months PE AF* Irreversible, clinically hyper-coagulable 2–3 Life long, balanced against risks states # Mechanical AVR with no risk factors High risk mechanical heart valves Mechanical MVR 2.5 – 3.5 Life long, balanced against risks # Mechanical AVR with risk factorsSource: Tran et al. 2013, Guyatt et al. 2012; Kearon et al. 2012; Cardiovascular Expert Group 2012;Ageno et al. 2012; Keeling et al. 2011* Refer also to section 1.3.1 Risk of stroke in patients with AF# Risk factors: AF, previous VTE, hypercoagulable state, left ventricular dysfunction or older generationAVRRisk of bleeding increases if warfarin is combined with antiplatelet therapy. Ifconsidering combination with antiplatelet therapy, discuss options with a specialist. DoGuidelines for warfarin management in the community -2- not add aspirin for patients who have both AF and ischaemic heart disease. Consideraddition of clopidogrel to patients with stents after discussion with a specialist (Blaauw& Crijns 2008). Literature suggests that triple therapy with warfarin, aspirin andclopidogrel is acceptable for short term treatment of up to four weeks in patients withacute coronary syndrome and AF (Camm et al. 2010)
1.3 Risk assessment1.3.1 Risk of stroke in patients with atrial fibrillationThe CHADS2 scoring system (Gage et al. 2001) is a simple system that can be used toassess the annual risk of stroke in AF. In the CHADS2 scoring system (see Table 2)each point increases the annual risk of stroke by a factor of 1.5. Treatment withwarfarin is recommended for a CHADS2 or CHA2DS2VASc scores of equal to orgreater than 2. Whilst the CHADS2 score is simple it does not include many commonstroke risk factors. The CHA2DS2VASc score (see Table 3) is inclusive of the mostcommon stroke risk factors in everyday clinical practice and has been validated inmultiple cohorts; the accumulated evidence shows that CHA2DS2VASc is better atidentifying ‘truly low-risk’ patients with AF and is as good as, and possibly better than,scores such as CHADS2 in identifying patients who develop stroke andthromboembolism (ESC Guidelines 2012)
Table 2 CHADS2 scoring system CHADS2 Clinical Add CHADS2 score Annual risk of characteristic points Stroke C Congestive Heart Failure 1 0 1.9% H History of Hypertension 1 1 2.8% A Age 75 years or older 1 2 4% D Diabetes Mellitus 1 3 5.9% S2 History of Stroke or 2 4 8.5% Transient Ischaemic 5 12.5% Attack TOTAL SCORE (max 6) = 6 18.2%Source: Gage et al. 2001Guidelines for warfarin management in the community -3- Table 3 CHA2DS2VASc scoring system CHA2DS2VASc Clinical Add CHA2DS2VASc score Annual risk of characteristic points Stroke C Congestive Heart Failure 1 0 0% H History of Hypertension 1 1 1.3% A Age 75 years or older 2 2 2.2% D Diabetes Mellitus 1 3 3.2% S2 History of Stroke or 2 4 4.0% Transient Ischaemic 5 6.7% Attack V Vascular disease 1 6 9.8% A Age 65 years or older 1 7 9.6% Sc Sex category, female 1 8 6.7% TOTAL SCORE (max 9) 9 15.2% =Source: ESC Guidelines for the management of atrial fibrillation European Heart Journal (2012)Direct comparison between the effects of Vitamin K Antagonist (VKA) and aspirin hasbeen undertaken in nine studies, demonstrating that VKA were significantly superior,with an RR reduction of 39%
1.3.2 Risk of bleedingThe risk of stroke should be weighed against the risk of bleeding to assessappropriateness of anticoagulant therapy. Warfarin causes major bleeding in one totwo per cent of people treated and intracranial bleeding in 0.1 to 0.5 per cent ofpatients each year of treatment (Gallus et al. 2000). The highest rate of major bleedingoccurs in the first three months of treatment (Clarke et al. 2006). In comparison, aspirincauses major bleeding in 1.3 per cent of patients (van Walraven et al. 2002). Absoluterisk increase for intracranial haemorrhage with warfarin compared to aspirin is only 0.2per cent per year (Hart et al. 2007)
Risk of bleeding can be assessed using the HAS-BLED scoring system (see Table 4)where a bleeding risk score of equal to or greater than 3 indicates high risk. There areother bleeding risk assessment tools available including HEMORR2HAGES (Gage etal. 2006). Assessment may identify reversible risks that can be managed prior toinitiation of warfarin. In general, clinicians should be cautious and conduct regularreview of the patient if initiating warfarin (Camm et al. 2010)
Guidelines for warfarin management in the community -4- Table 4 HAS-BLED scoring system HAS-BLED Clinical characteristic Add points H Hypertension 1 (uncontrolled, greater than 160 mm Hg systolic) A Abnormal renal and liver function (1 point each) 1 or 2 S Stroke (previous history, particularly lacunar) 1 B Bleeding (history or predisposition e.g. anaemia) 1 L Labile International INRs 1 (i.e. time in therapeutic range is less than 60 per cent) E Elderly (older than 65 years) 1 D Drugs (e.g. non-steroidal anti-inflammatory or antiplatelet drugs, 1 or 2 heparin or thrombolysis) OR alcohol (1 point each) TOTAL SCORE (out of maximum 9 points) =Source: Pisters et al. 2010HAS-BLED scores of 0, 1 or 2 correlate to 1.13, 1.02 and 1.88 major bleeds per 100patient-years respectively. This risk significantly increases at higher scores with HAS-BLED scores of 3, 4 and 5 correlating to 3.74, 8.70 and 12.50 major bleeds per 100patient-years respectively (Pisters et al. 2010)
1.3.3 Contraindications to warfarin therapyIn determining whether to start warfarin, there is a need to consider absolute andrelative contraindications. The lists below are not exhaustive (Smith 2011)
Absolute contraindications to warfarin therapy include: known large oesophageal varices significant thrombocytopenia (platelet count less than 50 x 109/L) within 72 hours of major surgery with risk of severe bleeding – defer and reassess post-operatively previously documented hypersensitivity (e.g. priapism or ischaemic necrosis) acute clinically significant bleed – defer and reassess stroke versus bleeding risk within three months decompensated liver disease or deranged baseline clotting screen (initial INR greater than 1.5) pregnancy and within 48 hours postpartum. Warfarin is teratogenic and can cause foetal bleeding. It is also associated with spontaneous abortion and peri-natal bleeding (Australian Drug Evaluation Committee 2015)
Relative contraindications to warfarin therapy include: previous history of intracranial haemorrhage – seek specialist opinion recent major extracranial bleed within the last six months where the cause has not been identified or treated – defer the decision for warfarin therapy peptic ulcer within last three months – defer until peptic ulcer treatment completed
Ensure peptic ulcer preventative therapy is initiated whilst on anticoagulant recent history of recurrent falls in patient at higher risk of bleeding (i.e. HAS-BLED score greater than or equal to 3)Guidelines for warfarin management in the community -5- dementia or marked cognitive impairment with poor medicines adherence and no carer support chronic alcohol abuse, especially if binge drinking untreated or poorly controlled hypertension, consistently greater than 160/90 mm/Hg
Warfarin may be used during breast feeding. It has not been detected in breast milk atdoses up to 12 mg per day. Higher doses may require periodic INR monitoring of theinfant (National Institute of Health, USA 2015; Rossi 2015)
1.4 Initiation of warfarinWhen initiating warfarin, it is important to involve the patient ensuring he or sheunderstands the benefits and potential side effects as well as the monitoring that isnecessary with warfarin therapy. Obtain patient consent and document in the clinicalnotes
Consideration should be given to using 1 mg tablets only, particularly for patients whohave difficulty with reading or with numbers. This may assist in reducing confusion untila stable dose is achieved
There are two methods for initiating warfarin, depending on the patient’s level of risk forthrombotic events: low thrombotic risk patients (i.e. AF) high thrombotic risk patients (e.g. DVT)
Tables 5 and 6 recommend dose changes based on the assumption that the patienthas taken daily doses as recommended. Adherence to therapy should be checked priorto adjusting doses in response to an INR result
Post-operative patients can be restarted with their ‘normal’ pre-operative maintenancedose of warfarin without re-loading. See section 1.8 for information on stoppingwarfarin for procedures
1.4.1 Patients at low risk of thrombosis (i.e. AF)No heparin cover is required for patients at low risk of thrombosis and a low initial doseregimen starting with 3 mg warfarin is recommended. The time taken to reach atherapeutic INR is not critical; for 85 per cent of patients, this is achieved by day 29(Clarke et al. 2006)
The regimen shown in Table 5 is based on weekly INR testing taken on day 1(baseline), day 8 and day 15. Stabilisation of warfarin needs to take into accountfactors that influence the INR or affect the risk of bleeding. Note that older people tendto respond more slowly with changes to the INR. However, rarely, there may also bepatients who are more sensitive to the effects of warfarin. If there are clinical concernsregarding response to warfarin, INR monitoring should be conducted more frequently(e.g. every three to four days). In these instances dose adjustments should be basedon clinical judgement as the recommended protocol in Table 5 would no longer apply
Guidelines for warfarin management in the community -6- Table 5 Regimen for Initiation of Warfarin in Patients at Low Risk of Thrombosis (Target range of INR 2 – 3)Day to take INR test INR Daily Warfarin Dose(Initiation = day 1) (until next INR test)Day 1 Obtain Baseline INR 3 mg (provided baseline INR is 1.4 or less) Increase to 6 mg Less than 1.4 Check INR again on Day 11 or 12 Refer to Section 1.13 for guidance on dosing 1.4 – 1.5 Increase to 5 mg 1.6 – 1.8 Increase to 4 mgDay 8 1.9 – 2.1 Maintain 3 mg 2.2 – 2.5 Reduce to 2.5 mg 2.6 – 2.7 Reduce to 2 mg 2.8 – 3 Omit one to two daily doses, then reduce to 1 mg Stop Warfarin # Greater than 3 Check causes and indication Repeat INR in three to five days If warfarin definitely indicated, restart at 1 mgDay 15 Check INR and adjust dose according to section 1.5 – Subsequentand weekly thereafter Maintenance Dosing Using WarfarinSource: Janes, Challis & Fisher 2004# If INR is abnormally high (i.e. greater than 5), refer to section 1.7 Management of High INR
1.4.2 Patients at high risk of thrombosis (e.g. DVT)For patients at high risk of thrombotic events, heparin cover is required. Start warfarinon the same day as therapeutic heparin or LMWH* and overlap for a minimum of fivedays, until target INR has been reached for at least two consecutive days (Pisters et al
2010; Rossi 2015). For initiation, a starting dose of 5 mg warfarin with daily INRmonitoring for a minimum of five days is recommended
Guidelines for warfarin management in the community -7- Table 6 Regimen for Initiation of Warfarin for High Risk Patients (Target range of INR 2 – 3*) Day to take INR test INR Daily Warfarin Dose (Initiation = day 1) (until next INR test) Day 1 Less than 1.4 5 mg Less than 1.8 5 mg Day 2 1.8 - 2 1 mg # Greater than 2 Nil Less than 2 5 mg 2 - 2.5 4 mg 2.6 - 2.9 3 mg Day 3 3 – 3.2 2 mg 3.3 – 3.5 1 mg # Greater than 3.5 Nil Less than 1.4 10 mg 1.4 - 1.5 7 mg 1.6 – 1.7 6 mg 1.8 – 1.9 5 mg Day 4 2 – 2.3 4 mg 2.4 – 3 3 mg 3.1 – 3.2 2 mg 3.3 - 3.5 1 mg # Greater than 3.5 NilSource: adapted from Kovaks et al. 2003; Gedge et al. 2000* Exercise caution in patients with impaired renal function (calculated creatinine clearance is less than 30mL/min) where LMWH can accumulate and contribute to bleeding
# If INR is abnormally high (i.e. greater than 5), refer to section 1.7 Management of High INR
Note: Dose modification is required for patients with mechanical heart valves as the target INR range ishigher (2.5 – 3.5)
After Day 4 clinicians should continue regular INR monitoring every three to four daysuntil stabilised and if the patient is still on heparin or LMWH review the ongoing needfor these additional anticoagulants. Note that a change in the INR of 0.5 over threedays or 1 over seven days is considered unstable. Dose adjustments during this periodwill need to be based on clinical judgement; if unsure seek advice. After INR resultshave been stabilised, refer to subsequent maintenance dosing recommendations(Section 1.5)
1.5 Subsequent maintenance dosing using warfarinThe following regimen (see Table 7) can be used for ongoing maintenance afterstabilisation. Clinicians should reflect on whether the patient has had INR variations inthe past to guide future adjustments in maintenance doses. Changes arerecommended based on confirmation that regular daily doses have been taken asprescribed and the patient has had a consistent diet. Clinicians should considerGuidelines for warfarin management in the community -8- available tablet strengths and the patient’s ability to break scored tablets whenprescribing future doses
The dose modifications in Table 7 below are based on the total weekly dose ofwarfarin. The weekly dose can be prescribed using a range of dosing regimens (e.g
alternate day dosing or dose regimens with different doses for weekdays compared tothe weekend). Dose modifications based on the total weekly dose also enable doseadjustments for low dose regimens whereas a change would not be recommended ifcalculations were based on the daily dose
Table 7 Regimen for Subsequent Maintenance Dosing Using Warfarin (Target range of INR 2 – 3*) INR Dosage adjustment Less than 1.5 Increase weekly dose by 20% 1.5 – 1.9 No change – recheck in one week If persistent, increase weekly dose by 10% 2–3 No change 3.1 – 3.9 No change – recheck in one week If persistent, decrease weekly dose by 10%–20% Omit one dose 4 – 4.9 Decrease weekly dose by 10%–20% Re-check INR in two to five days Greater than or equal to 5 See section 1.7 – Management of High INRSource: adapted from Guidelines & Protocols Advisory Committee 2010* Note: Dose modification is required for patients with mechanical heart valves as the target INR range ishigher (2.5 – 3.5)
Worked examples of dose modifications:1. Current dose regimen of 1 mg daily (equates to 7 mg weekly). If INR result is 1.6:Recommended dose adjustment is an increase of 7 mg x 10% = 0.7 mg
Example of new dose regimen: Mon Tue Wed Thur Fri Sat Sun Total weekly dose Current 1mg 1mg 1mg 1mg 1mg 1mg 1mg 7mg dose Suggested 1mg 1mg 1mg 1mg 1mg 1mg 2mg 8mg new dose (1) Suggested 1mg 1mg 1.5mg 1mg 1mg 1.5mg 1mg 8mg new dose (2)2. Current dose regimen of 4 mg on Monday, Wednesday and Friday, 3 mg every other day (equates to 24 mg weekly). If INR result is 4.2:Recommended dose adjustment is a dose omission then a reduction of 24 mg x 10%-20% = 2.4-4.8 mg over the week
Example of new dose regimen: omit one dose; then change dose to 3 mg daily
Guidelines for warfarin management in the community -9-
Alike 3.0 Australia licence. In essence, you are free to copy, communicate and adapt the work for non-commercial purposes, as long as you attribute Medicines Regulation and Quality, Queensland Health and the Royal Flying Doctor Service, Queensland Sector, you distribute any derivative work only under this licence and you abide by the licence terms.
Warfarin
Warfarin should usually be started at a dose of 5 mg per day.A 10-mg dose more frequently results in a supratherapeutic international normalized ratio (INR). Amiodarone, fluconazole, metronidazole, trimethoprim- sulfamethoxazole, and many other drugs inhibit the metabolism of warfarin.
consider resumption of prior maintenance dose if factor causing decreased INR is transient [eg: missed warfarin dose (s)] if adosage adjustment is needed, increase maintenance dose by 10%–20% consider a booster dose of 1 ½ – 2 times daily maintenance dose
Warfarin, sold under the brand name Coumadin among others, is a medication that is used as an anticoagulant (blood thinner). It is commonly used to prevent blood clots such as deep vein thrombosis and pulmonary embolism, and to prevent stroke in people who have atrial fibrillation, valvular heart disease or artificial heart valves.