Warfarin Guidelines

Howden Warfarin Protocol

Initiation of Warfarin in Primary Care (West Lothian)

NHS Lothian Guidelines for Warfarin

Howden Warfarin Protocol

Patient Group

Patients on oral anticoagulants (Warfarin)
New patients after referral from hospital or GP

Individual Responsibilities

Patients

• Carrying anticoagulant record book which states:
      Target INR
      Contact numbers
      Referring doctors
      Doctor managing treatment
• Attend for blood tests, as instructed.
• Alter dose as instructed.
• Keep a personal record of dose and INR in book.

Practice Nurses

• Perform blood tests
• Ensure that each patient has an anticoagulant book
• Ensure patients are aware of the risks of Warfarin in relation to alcohol consumption etc.
• Teach identification of side effects etc

GP

• Workflow for INR results
• Result received from laboratory via electronic link (GP initiates link).
• GP records INR, dose and review interval on GPASS SPICE Warfarin screen.
• GP completes letter template with result & dosing instructions for patient.
• GP only contacts patient by telephone if dose change needed, or if retesting required within 2 weeks.
• Letter posted with instructions to all patients.

Office staff

Fortnightly search is performed on computer to identify patients who are late for repeat INR checks, and they are contacted by phone or letter.

GUIDELINE FOR THE INITIATION OF WARFARIN IN PRIMARY CARE

West Lothian Healthcare NHS Trust

General Practitioners are being asked with increasing frequency to initiate warfarin in the community, often in older patients with atrial fibrillation where there is no need for rapid warfarinisation. This guideline for the gradual introduction of warfarin has been modified from one developed and tested in secondary care in patients similar to those seen in general practice.

This guideline is only for initiating warfarin in non-acute situations
e.g. in patients with pre-existing atrial fibrillation.

Before commencing treatment, it is important to consider whether the patient might be especially sensitive to warfarin (see BNF).

· Is the patient on drugs, which interact with warfarin e.g. analgesics, amiodarone, some antibacterials, St John’s Wort, antiepilectics, antifungals, lipid regulating drugs, some ulcer healing drugs? (See BNF for more extensive information).

· Do they have a pre-existing abnormal liver function or INR, heart failure, low weight or age >80?

· Is the patient's alcohol intake of concern?

· If concerned about sensitivity, consider more frequent monitoring or start at lower dose/seek specialist advlce*.

The guideline is intended to give an INR of 2.0-3.0 at 6 weeks. People with different target ranges could still start this way and further adjustments made after 6 weeks. INRs only have to be done at weekly intervals and the dose of Warfarin only changes if the INR is >3.0 or persistently <1.5. Note that the INR at 14 days predicts the maintenance dose. In weeks 3-6, adjust dose according to the INR, which is routinely checked once a week.

ADJUST DOSE DURING THIS PHASE AS FOLLOWS:

IN THIS CASE THE GUIDELINE BECOMES INVALID. FURTHER ADVICE IS AVAILABLE FROM CONSULTANT HAEMATOLOGIST, ST JOHN'S HOSPITAL.

PREDICTED MAINTENANCE DOSE TABLES

TABLE 1 -MALES

TABLE 2- FEMALES

Target values are now recommended rather than ranges, except for prophylaxis of DVT where a range is still recommended. (Guidelines on Oral Anticoagulation – British Society of Haematology).

Target Values:

                                INR 2.0-2.5 prophylaxis of DVT

INR 2.5 DVT and pulmonary embolism. Recurrence of venous thromboembolism when no longer on warfarin therapy, atrial fibrillation, cardioversion, dilated cardiomyopathy, rheumatic mitral valve disease, mural thrombus following myocardial infarction.

INR 3.5 recurrent DVT or pulmonary embolism while on warfarin, mechanical prosthetic valves, symptomatic antiphospholipid antibody syndrome.

ACKNOWLEDGEMENT

Grateful thanks to Dr Bruce Guthrie, MRC Training Fellow in Health Services Research, Strathbrock Partnership Centre, 189a West Main Street, Broxburn, who initially adapted this guideline from that developed by Oates A, Jackson PR, Austin Ac, Channers KS. A new regimen for starting warfarin therapy in outpatients. British Journal of Clinical Pharmacology 1998: 46:157-161. Thanks also to the haematologists in Lothian for reviewing the guideline, to Dr John Donald, Primary Care Referral Advisor, for his advice, and to Dr Cook, Consultant Haematologist, St John’s Hospital, who has further adapted the guideline for use in West Lothian.

Date approved for use: December 2002