Preprocedure Administration of Oral Vitamin K1: Lessons Learned from 2 Experiences in the Same Patient

Abstract

INTRODUCTION

The management of patients undergoing invasive procedures while taking oral anticoagulant therapy can be complex and requires careful evaluation of several risk factors, including the urgency of the surgery, the risk of thrombosis in the absence of warfarin, and the risk of procedure-related bleeding. Lowering the international normalized ratio (INR) before an invasive procedure may involve the following steps: withholding warfarin for about 4 days before the procedure,1 administering vitamin K1 (phytonadione) either orally or intravenously 24–48 h before the procedure,1-3 and infusing fresh frozen plasma or clotting factor concentrate for patients with life-threatening bleeding or an urgent need for surgery.3,4 For ambulatory patients, vitamin K1 by oral administration is commonly used to rapidly reduce critical INR values (defined as INR above 5.0) to therapeutic values (2.0–3.5).1 Small doses (1.0–2.5 mg) of oral vitamin K1 are suggested if INR is between 5.0 and 9.0, whereas 5–10 mg of oral vitamin K1 is recommended if INR is 10.0 or above.1 IV administration of vitamin K1 is also efficacious for this indication, but use of this route for outpatients is limited, because the drug must be administered slowly. The use of oral vitamin K1 to completely reverse a therapeutic INR in ambulatory patients in preparation for elective invasive procedures is not routine, and to our knowledge has not been reported. We proposed that the use of oral vitamin K1 might reduce the number of preprocedure days over which a patient would require subtherapeutic anticoagulation. Current practice for periprocedural management of ambulatory patients who are receiving oral anticoagulant therapy and who have an INR range of 2.0–3.0 is to discontinue warfarin 4 or 5 days before the procedure and then to reintroduce it after the procedure.1 Patients at greater risk of thromboembolism are often given “bridging therapy” with heparin while oral anticoagulation is temporarily reversed.1 In patients with elevated INR (above 3.0) withholding warfarin for a longer period before an invasive procedure is recommended5,6; this implies, for patients at high risk of a thromboembolic event, an extended period before the procedure when full-dose heparin or full-dose low-molecular-weight heparin (LMWH) must be administered.2 We describe a patient at high risk of thrombosis (INR range 3.5–4.0) who was treated with oral vitamin K1 before each of 2 invasive procedures. Despite the abundant literature evaluating the use of oral vitamin K1 for critical INR management, to our knowledge this is the first report of the use of this drug to normalize the INR on an ambulatory basis before an elective procedure.