Transcript INR for warfarin monitoring

INR for
warfarin
monitoring
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©bpacnz, October 2006
Key Messages
• A systematic and methodological approach is
needed for managing warfarin therapy
• Patient education is an important part of
achieving good INR levels
• For most people once the INR is stable, the rate
of testing can be extended 4 to 6 weekly
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Introduction
Good management of INR levels requires a
systematic approach involving the whole
practice team
• Warfarin is the most widely used anticoagulant in
NZ
• Use of warfarin is associated with serious risks
• A systematic and methodological approach is
needed for warfarin therapy
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The role of INR
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What is INR?
INR = (
Patient PT
_________
Control PT
) ISI
Some people are at particular risk
from warfarin therapy
•
The large number of variables in controlling INR levels
•
There is no standard response to warfarin
•
Elderly people often require lower doses of warfarin
•
Poor literacy or numeracy skills are associated with poor INR
control
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Low-dose initiation
protocols
• Suitable for outpatients
• Safe
• Achieves therapeutic anticoagulation within 3 to
4 weeks
• Reduces the risk of over-anticoagulation
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Transfer of care across the
primary – secondary interface
High risk due to:
• Poor communication on discharge
• Tablet strengths may be inappropriate for
maintenance therapy.
• Other medications, e.g antibiotics, may
interact with warfarin.
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Transfer of care across the primary
– secondary interface…..contd
New Zealand hospitals must effectively transfer
the following essential details of warfarin
therapy:
•
Condition for which warfarin has been prescribed
•
Target INR range
•
Planned duration of treatment
•
Brand and strength of warfarin tablets given
•
Last three doses
•
Last three INRs
•
Date next INR test due
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Pre initiation tests
• Complete blood count including platelets
• INR/PR and APTT
• Liver function tests
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Detailing the plan for
warfarin therapy
The patient notes should contain the following
information:
•
The patient is on warfarin
•
Condition for which prescribed
•
Target INR range
•
Planned duration of treatment
•
Brand of warfarin
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Target INR range
• In most situations the target INR range is 2.0 – 3.0
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Prescribing warfarin
• All clinicians should use the same brand of warfarin
• Warfarin use: Marevan ~ 95%, Coumarin® ~ 5%
• The brands are not interchangeable and come in
different tablet strengths
• Use only 1 mg tablets during initiation to minimise
confusion
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Drug labelling can highlight the
importance of INR monitoring
• Use labelling on warfarin to remind patients of the
need for regular blood tests
• Labels such as “PRN” or “as required” may confuse
• A better option may be “Take the dose advised by
your doctor or nurse. You need regular INR blood
tests to make sure this dose is right for you”
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Patient Education
• Patients who understand
what they are doing, benefit
more from treatment
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Patient education must to
cover:
•
Need for patient to remind their health
professional they are receiving warfarin
•
Requirement for regular blood tests
•
Adherence to dosage changes after blood tests
•
Importance of avoiding other medications
except with medical advise
•
Significance of illness, such as diarrhoea,
infection or fever
•
Ability to recognise the signs of bleeding
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Signs of possible bleeding
Indications to call the doctor immediately:
•
Red or dark brown urine
•
Red or dark brown stool
•
Severe headache
•
Unusual weakness
•
Excessive menstrual
bleeding
•
Prolonged bleeding from
gums or nose
•
Dizziness, trouble breathing
or chest pain
•
Unusual pain, swelling or
bruising
•
Dark, purplish or mottled
fingers or toes
•
Vomiting or coughing up
blood
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“The red book”
•
Facilitates patient education
•
Means of sharing information
•
Patients should always show to
any health professional
•
Clinicians and pharmacists should
asking to see the book
•
The book should be kept up to
date.
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Monitoring INR
• A reasonable standard of warfarin therapy is
an INR within the target range 60% of the time
• Regular testing of INR levels is essential
• Once the INR is stable the rate of INR testing
can be extended to 4 to 6 weekly in most
people
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For patients initiated with low-dose
protocol
(warfarin initial dose 2 – 3mg daily):
Initially:
•
When INR < 4: Weekly
•
When INR > 4: Every 2-3 days until stable for 2
consecutive tests
•
Then: fortnightly until stable for 2 - 3 consecutive tests
•
Maintenance: Most patients can be extended to 4 – 6
weekly testing however a minority may require more
frequent testing.
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For patients initiated with
higher doses:
•
Initially: daily for at least five days until stable
for 2 consecutive tests
•
Then: every 3 – 5 days until stable for 2
consecutive tests
•
Then: weekly until stable for 2 - 3 consecutive
tests
•
Then: fortnightly until stable for 2 - 3
consecutive tests
•
Maintenance: Most patients can be extended
to 4 – 6 weekly testing however a minority may
require more frequent testing.
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Changes in INR levels
Changes in the INR level in a usually stable
patient may be due to a number of reasons:
• Non-adherence to dosage regimen
• Drug interactions (pharmaceutical or herbal)
• Major changes in diet or alcohol intake
• Systemic or concurrent disease
• Unknown causes
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Managing alterations
in the INR
• Changes in weekly doses are usually not
required for minor fluctuations.
• For more significant fluctuations in the INR use
a standard guide to assist dose modification.
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Managing
Overanticoagulation
INR 5 – 8 without bleeding
1.
Stop warfarin
2.
Restart in reduced dose when INR < 5
3.
Test INR daily until stable
4.
Given Vitamin K 0.5 – 1 mg oral/sc if INR
fails to fall, or reversal required within 24 –
48 hours
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Managing
Overanticoagulation….contd
INR > 8 with minor bleeding
1.
Stop warfarin
2.
Consider admission if clinical appropriate
3.
Restart in reduced dos when INR < 5
4.
Given Vitamin K 1 – 2 mg oral/sc
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Managing
Overanticoagulation….contd
High INR and major bleeding
1.
Stop warfarin
2.
Give Vitamin K 10 mg sc
3.
Admit stat
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Sample collection for
INR
•
Collect blood into a light blue top tube
•
The tube must be filled completely
•
View the patient handbook
•
Ask questions specific to warfarin control, for
example:
 Adherence to the dosing regimen,
 Any changes in diet
 Any medications the patients may have
stopped or started
 Signs of bleeding
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Ceasing warfarin therapy
• Warfarin therapy can be discontinued abruptly
at the end of treatment period
• Prospective studies have not indicated a
rebound prothrombotic state
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Dental extractions and
preoperative warfarin doses
• For minor surgical procedures aim for a target
INR of approx 2.0 on the day of surgery
• Stop warfarin at least three days prior to major
surgery
• When INR < 3.0 warfarin does not need to be
stopped for dental extractions
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Warfarin and pregnancy
• Pregnant women should never take warfarin, as it
is teratogenic
• Women on warfarin should contact their doctor
urgently if they think they are pregnant.
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Managing warfarin in rest
homes
• In rest homes there may be several health
professionals involved in the prescribing, dose
adjustment and administration of warfarin.
• Clear written instructions are necessary to guide
rest home staff.
• Verbal instructions should be avoided whenever
possible.
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Near patient testing
• Near patient testing (NPT) of INR levels is
effective for selected patients
• NPT is risky for patients who are unmotivated
or do not understand the process
• NPT requires high standard of quality
assurance procedures
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Resources available from
bpacnz for INR monitoring
• Evidence based guide “INR monitoring”
• Interactive online quiz
• Quiz feedback
• Clinical audit pack for general practice
visit
www.bpac.org.nz
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