audit of warfarin reversal in over-anticoagulated patients d wright and j seal department of...
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Audit of warfarin reversal in over-anticoagulated patients
D Wright and J Seal
Department of Haematology
Pontefract General Infirmary
Nov 2002
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Bleeding during warfarin therapyRisk factors
• Age
• High target INR
• Actual INR
• PMH of bleeding
• CVA
• Hypertension
• Alcohol/liver disease
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Risk of bleeding whilst on warfarin
ISCOAT study
Prospective study of 2745 patients
Bleeding complications: All 7.6 per 100 patient years
Major 1.1 per 100 patient years
Fatal cerebral bleeds 0.25 per 100 patient years
Age > 70 : 10.5 per 100 patient years
< 70 : 6 per 100 patient years
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Risk of bleeding whilst on oral anticoagulation
INR Bleeding events per 100 patient years
2 – 3 4.8
3 – 4.5 9.5
4.5 – 7 40.5
>7 200
ISCOAT study: Lancet 1996
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Aim of study
• Establish a baseline audit of historical practice of warfarin omission in patients with INR>8
• Assess feasibility of using oral vitamin K to reverse anticoagulation in patients with INR>8
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Methods• Patients attend community phlebotomy
clinics for venous blood sampling.
• At this visit patient completes a record sheet detailing warfarin dose, change in medication, clinical condition and any bleeding symptoms.
• Samples are sent to central lab for INR testing, along with record sheet. Results are downloaded to A/C computer. BMS reviews results.
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INR Advice Given5.5 - 7.0 Inclusive Miss 3 days.Repeat INR
In 1 week. Reduce Dose
7.1 - 8.0 Inclusive Miss 3 days. Repeat INR in 3 days. No dose given. See High INR policy.
8.1 and above Unable to calculate dose
See High INR policy
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INR OVER 8.0
• Significant bleeding symptoms – refer to A/E
• No Bleeding – inform Clinical Haematologist
• Give 2mg oral dose Vitamin K (KONAKION)
• See separate SOP for prescription
• Warfarin discontinued temporarily
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INR OVER 8.0
• Arrange for INR next day. Repeat INR daily until INR <6.0
• If INR remains over 8.0 repeat Vitamin K
• If patient unable to receive Vitamin K discontinue for 3 days and re-check INR
• Complete a case report
• Send a fax to inform GP
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INR 7.1 – 8.0
• Significant bleeding symptoms – refer to A/E
• No bleeding proceed as follows
• Stop Warfarin for 3 days and re-check INR
• Advise patient to attend A/E if bleeding develops
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INR 7.1 – 8.0
• Send a fax to inform GP
• Recommence warfarin when INR is back in the therapeutic range
• Complete a case report
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CASE REPORT FOR OUT PATIENTS WITH HIGH INR’S OVER 7.0
SURNAMESeal
DOB16/01/1949
GPDr Waring
FORENAMEJohn
HOSPITAL NO.1234567
TARGET INR2.5
AC REASONAF
MAINTENANCE DOSE5.0mg
CAUSE OF OVER-ANTICOAGULATIONAlcohol
Warfarin start date: 15/07/2001…………………….
Other recent medication:Amoxyxcillin……………………………………..
DATE INR 2MGVITAMIN K
GIVEN
FAXTOGP
WARFARINDOSE
PRESCRIBED
SYMPTOMS
DAY 1 01/11/02 9.9 Nil None
DAY 2 02/11/02 4.7 Nil
DAY 3 Nil
DAY 4 4mg daily
DAY 5
DAY 6
FollowUp
07/11/02 2.7 4mg daily
Patient Outcome:Back in range off alcohol………………………………….
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Restarting Warfarin
• If over anticoagulation is clearly secondary to a transient event, which has now resolved, then restart Warfarin at the previous maintenance dose
• If the reason for over anticoagulation is unknown or due to a continuing risk factor, then restart at a dose between 20% and 25% less than the previous maintenance dose
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Results
• Between Feb - Dec 2001 forty-one patients had an INR>8 in the absence of significant bleeding
• 20 received oral vitamin K
• 21 were managed by Warfarin omission
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Vitamin K (n=20)
Warfarin omission (n=21)
Age: Mean 68 67
Range 34-86 36-94
Duration of therapy:
Median 4.8yrs 5yrs
Range 0.1-19 1-16
Baseline INR:
Mean 12.8 10.2
Range 8.7-22.5 8.1-19.9
Characteristics of high INR patients
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Vitamin K Warfarin omission
AF 8 12
DVT/PE 6 4
Mechanical valve
3 5
PVD 3 0
Indications for warfarin therapy
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Causes of over-anticoagulation
Vitamin K group (n=20)
Warfarin omission
group (n=21)
Wrong dose 3 6
Interacting medication
2 2
Alcohol excess
3 0
Unknown 12 13
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Vitamin K (n=20)
Warfarin omission (n=21)
1st follow up INR:
Mean 4.7 4.8
Range 2-16.6 1.6-18.6
No with INR>4.5 7 10
No with INR >8.0 2 2
No with INR<2.0 0 2
1st follow up INR
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Warfarin omission
0
5
10
15
20
25
INR
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Vitamin K
0
5
10
15
20
25
INR
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Vitamin K Warfarin omission
Day 7 INR
Mean 2.7 2.4
Range 1.1-5.5 1.0-5.1
No with INR>4.5
3 2
No with INR<2.0
5 8
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Clinical events
• One patient from each group admitted with bleeding complications
• One patient in warfarin omission group had a breakthrough PE
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Conclusions
• After omitting warfarin in patients with an INR>8, 50% still had a raised INR after 3 days
• Oral vitamin K at a 2 mg dose achieved at least comparable results within 24 hours
• Both patient groups had unstable INR control for at least 1 week after the event
• Use of oral vitamin K was not associated with warfarin resistance