Warfarin in General Practice

Warfarin in General Practice QUALITY IN PRACTICE COMMITTEE AUTHORS Dr Philippa Kildea-Shine Dr Margaret O Riordan Disclaimer and Waiver of Liabilit...
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Warfarin in General Practice QUALITY IN PRACTICE COMMITTEE

AUTHORS Dr Philippa Kildea-Shine Dr Margaret O Riordan

Disclaimer and Waiver of Liability Whilst every effort has been made by the Quality in Practice Committee to ensure the accuracy of the information and material contained in this document, errors or omissions may occur in the content. This guidance represents the view of the ICGP which was arrived at after careful consideration of the evidence available. The guide does not however override the individual responsibility of healthcare professionals to make decisions appropriate to the circumstances of individual patients in consultation with the patient and/or guardian or carer.

Original Publication: Revised Publication: Next Review Date:

2006 2010 2013

Warfarin in General Practice, Published April 2006, © ICGP 2006, Reviewed December 2009

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Key to Evidence Statements and Grades of Recommendations1

Statements of Evidence la lb lla llb lll IV

Evidence obtained from meta-analysis of randomised controlled trials Evidence obtained from at least one randomised controlled trial Evidence obtained from at least one well designed controlled study without randomization Evidence obtained from at least one other type of well designed quasi-experimental study. Evidence obtained from well designed non-experimental descriptive studies, such as comparative studies, correlation studies and case studies. Evidence obtained from expert committee reports or opinions and/or clinical experiences of respected authorities.

Grades of Recommendations A

Requires at least one randomised controlled trial as part of a body of literature of overall good quality and consistency addressing the specific recommendation. (Evidence levels Ia,Ib)

B

Requires the availability of well conducted clinical studies but no randomised clinical trials on the topic of recommendation.(Evidence levels IIa, IIb, III)

C

Requires evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities. Indicates an absence of directly applicable clinical studies of good quality. (Evidence level IV)

ICGP Quality in Practice Committee Dr Michael Boland, Dr Sorcha Dunne, Mr Dermot Folan, Dr Jason McMahon, Dr Ailis ni Riain, Dr Seamus O’Baoighill, Dr Raymond O’Connor, Dr Margaret O’Riordan, Dr Ben Parmeter, Dr Sheila Rochford (Chair), Dr Andree Rochfort.

Warfarin in General Practice, Published April 2006, © ICGP 2006, Reviewed December 2009.

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Table of Contents Disclaimer and Waiver of Liability .........................................................................................................................i Key To Evidence Statements And Grades Of Recommendations ....................................................................ii How To Use This Document .................................................................................................................................. 1 Introduction .............................................................................................................................................................1 New editions to revised document .......................................................................................................................1 Starting Warfarin In The GP Setting .....................................................................................................................1 Loading Dose Regime ...........................................................................................................................................1 Check List For Patient Advice At Initial Consultation.............................................................................................3 Practice Organisation ............................................................................................................................................3 Indications and Targets .........................................................................................................................................4 Duration Of Therapy ..............................................................................................................................................5 Stopping Warfarin Therapy ....................................................................................................................................5 Follow Up Visits ......................................................................................................................................................5 Excessive Anticoagulation .....................................................................................................................................6 General Management Issues .................................................................................................................................6 Suspected Non-Adherance....................................................................................................................................6 Change In Patient Medication................................................................................................................................6 Pain Relief For Gout ..............................................................................................................................................6 Low Dose Aspirin ...................................................................................................................................................7 Swelling And Pain In Legs After Deep Vein Thrombosis ......................................................................................7 Minor Bleeding And Bruising .................................................................................................................................7 Elective Surgery .....................................................................................................................................................7 Dental Extraction ...................................................................................................................................................7 Near Patient Testing ..............................................................................................................................................7 Recent developments in anticoagulation ............................................................................................................8 References ..............................................................................................................................................................9 Appendix 1: Common Drugs, Herbs And Supplements: Potential Interaction With Warfarin .................... 10 Appendix 2: Vitamin K Content Of Foods And Beverages .............................................................................. 11 Appendix 3: Warfarin Flow Chart ....................................................................................................................... 12 Appendix 4: Step By Step Guide For Coaguchek ............................................................................................ 13 1. Performing Quality Control ............................................................................................................................. 13 2. Performing INR Test ....................................................................................................................................... 13 3. Trouble Shooting ............................................................................................................................................ 13

Warfarin in General Practice, Published April 2006, © ICGP 2006, Reviewed December 2009.

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How to Use This Document It is intended that this document will encourage reflection on the current warfarin prescribing system in your practice with consequent benefits for both practice personnel and patients. It has been developed to assist you in analysing your current warfarin prescribing methods and for ongoing review. It is not intended to be the definitive text on prescribing warfarin in general practice. A laminated sheet highlighting key areas of warfarin management accompanies this document for use as an aide memoir for your desk. A step by step approach has been taken so that you can start to make a difference today in your practice. Hopefully having taken that first step you will be inspired to continue!

New editions to revised document 3,4,5

As the international guidelines on which the original impact document was based have not been updated recently there are relatively few revisions in this version. These include more information on the use of warfarin in patients with mechanical heart valves (page 4), management of patients with head injury (page 6), dental extraction (page 7) and the use of warfarin and newer anticoagulents post operatively (page 8).

Introduction It is estimated that approximately 950,000 people take warfarin in the UK and this number is set to increase rapidly in 1 the next decade . Warfarin is increasingly prescribed and monitored in the general practice setting. Warfarin acts as an anticoagulant by antagonising the effects of vitamin K and it takes 48 -72 hours for the anticoagulant effect to 2 develop fully . The main indications for warfarin are deep vein thrombosis, pulmonary embolism, atrial fibrillation in patients at risk of embolism and those with mechanical prosthetic heart valves. The prothrombin time reported as the international normalised ratio (INR) is used to monitor patients on warfarin therapy. Due to its narrow therapeutic index and high risk: benefit ratio careful consideration is needed prior to initiation of warfarin – balancing the risk of thromboembolism versus major haemorrhage.

Starting Warfarin in the GP Setting Warfarin is usually started in the hospital setting but it is increasingly initiated in primary care. The first consultation is often after the patient has been discharged from hospital or attended the medical out patients department. Contraindications should be checked and include peptic ulcer, severe hypertension, bacterial endocarditis and 2 pregnancy . Caution should be exercised in patients with hepatic or renal impairment, those with a history of recent 2 surgery and breastfeeding mothers .

Loading Dose Regime Ten milligrams is the usual starting dose in the hospital setting where rapid anticoagulation is often required. Table one shows the regime developed by Fennerty et al in 1984 (Grade B level 11b) recommended by the British 3 Haematology Society (BHS) guidelines and used in hospital settings for the past twenty years. The BHS guidelines state that a slow loading regimen (2mg -5mg) is safe in patients who do not need rapid anticoagulation and achieves therapeutic anticoagulation in the majority of patients within 3-4 weeks (grade B, level 11b). This helps to reduce the risk of overcoagulation and bleeding. Extra care (and therefore a lower starting dose e.g. 5mg) should be taken with patients that are at increased risk of side effects with warfarin especially if aged over 65 and underweight (5

See excessive anticoagulation below 4

Table 5 If the INR is outside the desired range (Grade C) Warfarin in General Practice, Published April 2006, © ICGP 2006, Reviewed December, 2009 5

Excessive Anticoagulation The risk of bleeding increases significantly with an INR > 5.0. Patients at increased risk of bleeding are those on their first year of warfarin therapy, aged over 65 years of age, with 4 hypertension or alcoholism or liver disease and those with a past history of gastrointestinal bleeding or stroke . 3

In the case of an elevated INR proceed as follows

Consider the possibility of laboratory or coaguchek error. Check if there is an obvious cause for the fluctuation e.g. compliance, new medication and correct this underlying cause first. If they have a high INR but it is still