Published in:
01-02-2008
Utilization of vitamin K in an outpatient anticoagulation clinic
Published in: Journal of Thrombosis and Thrombolysis | Issue 1/2008
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Background The options for management of elevated INRs in the outpatient setting include holding and/or reducing the dose of warfarin, administering oral vitamin K or sending the patient to the emergency department. Since these various options have not been directly compared, the optimal management of excessive anticoagulation remains somewhat controversial. Objectives To investigate the efficacy and safety of vitamin K administration compared to holding/reducing the dose of warfarin in patients with INR levels >6. Efficacy is defined as an INR which returns to a target range of 2.0–4.0 with 72 h. Safety is defined as no occurrence of an adverse event within 30 days of vitamin K treatment. Methods A retrospective analysis of patients with an INR >6 between March 2000 and March 2006 was performed. In total, 152 patients were analyzed; 73 patients received vitamin K and 79 had warfarin held. Results Patients who received vitamin K were more likely to be older and have AF; the INR value was higher while the average weekly warfarin dose was lower. Active cancer was more prevalent in the vitamin K group. Bleeding risk was similar between the two groups while risk of thrombosis was higher in the no vitamin K group. There was a trend towards increased bleeding in the vitamin K group. Patients who received vitamin K had their INR checked sooner than those who did not receive vitamin K. Warfarin resistance was not a significant concern. Conclusion Preliminary results of this study support the American College of Chest Physicians guidelines for the management of elevated INRs. By evaluating the risk factors for bleeding and thrombosis, the patients with an elevated INR were safely and effectively managed with either vitamin K administration or by withholding warfarin in our outpatient clinic.|
Vitamin K (n = 73)
|
No vitamin K (n = 79)
|
P-value
|
|
|---|---|---|---|
|
Age (years)
|
65.8 (±18)
|
58.8 (±18.5)
|
0.017
|
|
A. Fib
|
48%
|
31.7%
|
0.047
|
|
INR
|
9.6 (±2.5)
|
7.1 (±0.8)
|
<0.0001
|
|
Warfarin dose (mg/week)
|
37.9 (±35.3)
|
41.2 (±21.4)
|
0.049
|
|
Vitamin K dose
|
3 mg (±1.5)
|
n/a
|
|
|
Cause of high INR
|
|||
|
Drug interaction
|
38.4%
|
24.1%
|
0.78
|
|
Active cancer
|
11%
|
2.5%
|
0.049
|
|
Bleeding risk*
|
60.3%
|
59.5%
|
1.0
|
|
Thrombosis risk*
|
34.3%
|
59.5%
|
0.002
|
|
Outcomes
|
|||
|
No. of days warfarin held
|
1.67 (±1.1)
|
2.01 (±1.2)
|
0.086
|
|
1st INR
|
2.43 (±1.4)
|
2.79 (±1.3)
|
0.019
|
|
No. of days post
|
2.32 (±1.2)
|
3.49 (±2.4)
|
0.0003
|
|
2nd INR
|
3.07 (±1.6)
|
2.83 (±1.3)
|
0.81
|
|
No. of days post
|
9.5 (±4.9)
|
12.2 (±5.9)
|
0.004
|
|
Warfarin resistance
|
5.3%
|
7.3%
|
0.72
|
|
Minor bleed
|
42.5%
|
30.4%
|
0.13
|
|
Major bleed
|
4.1%
|
1.3%
|
0.35
|
|
Thromboembolic events
|
0
|
0
|
|