BACKGROUND

For patients with supratherapeutic international normalized ratio (INR) and no evidence of bleeding, the 2012 guidelines of the American College of Chest Physicians discourage administration of vitamin K. At the study hospital, it was observed that vitamin K was frequently prescribed for patients with INR of 4.5 or higher and no bleeding.

OBJECTIVES

To compare efficacy and safety outcomes between holding warfarin alone and holding warfarin with administration of vitamin K and to compare these outcomes among various doses and routes of vitamin K administration in non-critical care inpatients experiencing supratherapeutic INR without evidence of bleeding.

METHODS

This single-centre retrospective chart review involved noncritical care inpatients with supratherapeutic INR (4.5-8.9) without evidence of bleeding. The primary outcomes were the change in INR 1 day after implementation of supratherapeutic INR management and the time to reach INR less than 3.0. The secondary outcomes were length of stay, frequency of warfarin resistance, incidence and duration of bridging anticoagulation, incidence of thromboembolism and major bleeding, and death.

RESULTS

Regardless of vitamin K dose, the administration of vitamin K combined with holding warfarin, relative to holding warfarin alone, was associated with a greater INR decrease 1 day after the intervention (mean ± standard deviation -3.2 ± 1.9 versus -0.9 ± 1.0, < 0.001) and a shorter time to reach INR below 3.0 (1.9 ± 1.0 days versus 2.6 ± 1.4 days, = 0.003). No statistically significant differences in any other outcomes were observed.

CONCLUSIONS

In hospitalized non-critical care patients with INR between 4.5 and 8.9 without evidence of bleeding, the combination of holding warfarin and administering vitamin K was associated with greater and faster decreases in INR than holding warfarin alone. No significant differences were found in clinically important outcomes. The practice of administering vitamin K in this population warrants further study and re-evaluation.