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HOSPITAL POLICY - Prescribing and Monitoring of Vitamin K Antagonist Anticoagulants for Inpatients

 Doncaster and Bassetlaw Hospital NHS Foundation Trust

Formulary Guidance Standards for the Prescribing and Monitoring of

Vitamin K Antagonist Anticoagulants for Inpatients

Reviewed by:

Dr Stuti Kaul, Consultant Haematologist

Julie Kay, Consultant Pharmacist

Lee Wilson, Consultant Pharmacist

Sarah Bambrough, Chief Biomedical Scientist, Haematology and Coagulation 

Approved by Drug and Therapeutics Committee: September 2016

Review Date: September 2019

1 INTRODUCTION

1.1   Related documents to be read in conjunction with this guidance

1.2      Training

All staff caring for patients on anticoagulant therapy must have the necessary work competences.

The consultant is responsible for the competence to prescribe of their clinical team. The Ward Manager is responsible for the competence of their nursing staff to administer. The Clinical Director of Pharmacy and Medicines Management is responsible for the competence of the staff providing the clinical pharmacy and dispensing services  

Additional learning can be found via the e- learning modules.

http://learning.bmj.com/learning/search-result.html?moduleId=5004325 http://learning.bmj.com/learning/search-result.html?moduleId=5004429

To access these modules requires registration with the site which has a subscription cost. 

1.3     Patient Information

(Confirm with your patient who is normally responsible for their warfarin dosing and ensure anticoagulant referral form is directed to appropriate service.)

2 PRESCRIBING

2.1     On Admission

All patients admitted on warfarin must have an INR checked on the day of admission before prescribing

2.2     General Guidance On Initiating Warfarin 

Bridging Anticoagulation guidance

DAY

*Patients aged under 65

**Patients aged 65 or over 

INR

(IN MORNING)

WARFARIN DOSE (mg)

(IN EVENING)

INR

(IN MORNING)

WARFARIN DOSE

(mg) (IN

EVENING)

1 (Pre-treatment baseline)

less than1.4

10

less than 1.4

10

2 if INR greater than 1.8, patient may be warfarin sensitive. Monitor frequently.

less than 1.8 1.8 – 2.0 greater than 2.0

10

1

0

less than 1.8 1.8 – 2.0 greater than 2.0

5

1

0

3

less than 2.0

2.0 – 2.2 2.3 – 2.5 2.6 – 2.9 3.0 – 3.2

3.3 – 3.5 greater than 3.5

10

5

4

3

2

1

0

less than 2.0

2.0 – 2.2 2.3 – 2.5 2.6 – 2.9 3.0 – 3.2

3.3 – 3.5 greater than 3.5

5

4

4

3

2

1

0

4

less than 1.4

1.4 – 1.5 1.6 – 1.7 1.8 – 1.9 2.0 – 2.3 2.4 – 3.0

3.1 – 4.0 greater than 4.0

 

Greater than 8

8

7

6

5

4

3

Omit dose until INR is 3.0 or under

less than 1.4

1.4 – 1.5 1.6 – 1.7 1.8 – 1.9 2.0 – 2.3 2.4 – 3.0

3.1 – 3.2

3.3– 3.5

3.6– 4.0 greater than 4.0

Greater than 7

7

6

5

4

3

2

1

0

0

After day 4

Use clinical judgement

Use clinical judgement 

*Modified from British Society for Haematology Guidelines on Oral Anticoagulation: Third Edition. Br J Haematology 1998; 101: 374-87 and Fennerty et al. British Medical Journal 1988; 297: 1285-8.

** Modified from Gedge et al. Age and Ageing 2000; 29: 31-34 

2.3     Warfarin Prescription

Warfarin is prescribed on either the separate ‘Oral Anticoagulant Prescription’ section of the Inpatient Medicines Prescription and Administration chart or the separate warfarin module in the JAC e-prescribing system

There are three different warfarin products described on the e-prescribing system:

More information can be found on the E-Prescribing manual for Warfarin prescribing and Administration 

2.4     Recording the INR

 To enable the Anticoagulant Monitoring Service Referral to be completed at discharge the INR results and dates should be recorded on the JAC e-prescribing  system.

At discharge this document can be printed off and sent with the referral form as a record of doses given and INR results

For instruction on how to record and the print off the INR. See E-Prescribing manual for Warfarin Prescribing and administration (p.7)

2.5     Maintenance Dosing Of Warfarin For Patients

After any dose change, or when starting or stopping an interacting medicine check the INR every 2 to 3 days General principles:

2.6     Recommended Target Ranges for INR

A target INR of 2.5 (range 2.0 - 3.0) is sufficient for most indications EXCEPT:  

• Recurrent or further DVT/PE when fully anti-coagulated. For these patients a target INR of 3.5 is recommended. 

•Certain mechanical prosthetic heart valves:

Valve type

Position

Target INR

Range

Bi-leaflet

Aortic

2.5

2.0-3.0

Tilting Disc

Aortic

3.0

2.5-3.5

Bi-leaflet or Tilting disc

Mitral

3.0

2.5-3.5

Caged ball or caged disc

Aortic/mitral

3.5

3.0-4.0

2.7 Management Of Over-Anticoagulation Or Bleeding On Warfarin

Check INR in all patients and resuscitate as necessary

Adverse effect/INR

Warfarin

Vitamin K

(phytomenadione)

Other actions 

Life/limb threatening/major bleeding (including intra-cerebral, intracavity or critical organ bleeds)

Withhold

5mg IV

Give Beriplex (as per policy) in addition to phytomenadione

(vitamin K)

Clinically relevant non

– Major Bleeding

(INR less than 4.5)

Withhold

**

Investigate underlying cause in the same manner as for patients not taking warfarin.

Clinically relevant non

– Major Bleeding

(INR above 4.5)

Withhold

1-2mg IV or orally*** (IV active within 6-8hrs, oral active within

12-24hrs)

Repeat INR the next day

Head injury (normal CT scan, no bleeding, and INR above 4.5)

Withhold

1-2mg IV*

Following a significant head injury, the INR should be more stringently maintained in the patients’ desired therapeutic range  for 4 weeks following a normal CT scan to minimise the risk of delayed intracranial bleeding

Head injury (normal CT scan, no bleeding, and INR in desired range)

Withhold/continue dependent on patient factorsseek advice

 

Clinical decision – consider factors such as how the head injury occurred, indication for anticoagulation, etc. In some patients it may be appropriate to discontinue the anticoagulant for a period of time. Advice should be taken from the Consultant in charge/Haematologist as needed. If continued follow advice above.

No Bleeding (INR greater than 8)

Withhold

1mg IV or orally***

(IV active within 68hrs oral active within 12-24hrs)

 

No Bleeding (INR between 4.5 and 8.0)

Withhold 

Consider 1mg

orally*** if patient considered at increased risk of bleeding (e.g. age >65 yrs, previous GI or intracranial bleed, renal or liver failure, anaemia, cancer, recent stroke, or recent surgery)

 

*If the risk of utilising vitamin K to bring an INR back into the therapeutic range is felt to be greater than the risk of bleeding for the individual patient concerned then as a minimum prior to discharge the INR should be rechecked.  The patient should only be discharged if the INR is decreasing and arrangements have been put in place to ensure that this continues. **In presence of increased risk factors for bleed (such as age over 65yrs,previous GI bleed or intracranial bleed, renal or liver failure, anaemia, recent stroke, recent surgery, head injury with normal CT etc) clinicians may consider giving Vitamin K 1mg iv or orally if benefit of doing so outweighs the risk

***Use Konakion MM paediatric injection (given orally)

2.8     Special Patient Groups

2.8.1 Elderly Patients

  1. High risk of drug interaction with warfarin due to likelihood of higher comorbidity and polypharmacy. 
  2. Decision to initiate should take into account likely adherence, attendance for INR checks and risk of falling. 
  3. Normal ageing and/or acute ill health may require treatment to be reviewed in light of point 2 above.

2.8.2 Cancer Patients

Patients with active malignancy, particularly if receiving chemo/radiotherapy, should be considered for ongoing treatment with low molecular weight heparin. Discuss with oncology consultant. 

2.8.3 Thromboembolic Disease in Pregnancy and the Puerperium Avoid warfarin therapy during pregnancy. Seek advice from an obstetrician on heparin treatment in pregnancy and warfarin initiation in the puerperium.

3 COUNSELLING

 

4 DISCHARGE

4.1     Prescriber’s responsibilities

The prescriber retains the responsibility to dose the discharged patient until their first appointment with either the DBH Anticoagulant Monitoring Service (AMS) or the Primary Care Provider (GP).

       •    At discharge the prescriber must

4.2     Pharmacy’s responsibilities

All discharge prescriptions for warfarin will receive a clinical check against the inpatient prescription by a pharmacist prior to dispensing.  

4.3 Nurse’s responsibilities •     At discharge the nurse must:

INR test and the arrangements for their next INR test

5 DISCONTINUATION

Appendix 1 Roles of the Prescriber Pharmacist and Nurse

Detailed Warfarin Counselling Checklist