Discontinuation of warfarin prior to elective invasive procedures

INTRODUCTION. Patients on warfarin are normally required to interrupt treatment for a fixed number of days prior to an invasive procedure. This study aimed to investigate the potential influence of the warfarin maintenance dose and the initial international normalised ratio (INR) level on the duration of the break required to achieve the planned target INR. METHODS. A total of 120 patients on self-managed warfarin treatment measured INR once daily for five days before the intervention and were guided by the anticoagulation clinic on when to discontinue warfarin. Depending on the bleeding risk of the planned intervention, the target INR on the day of the intervention was ≤ 1.4, ≤ 2.5 or ≤ 3.0. RESULTS. From day 1 to day 5 after interruption of warfarin, the INR ratio (INR_dayX/INR_day0) decreased exponentially, with wide interpatient variation in the rate of decrease. Patients with a maintenance warfarin dose < 25 mg/week decreased significantly less in INR during the first day after stopping warfarin than patients who received a higher maintenance dose (9% vs 15%; p < 0.04). The INR half-life after day 1 was 113 hours for patients receiving < 25 mg/week and 101 hours for patients receiving ≥ 25 mg/week. CONCLUSIONS. The duration of pre-interventional discontinuation of warfarin can be individualised by knowing the maintenance dose, baseline INR and target INR for the planned procedure.